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Development of an interoperability model for different construction drawing standards based on ISO 10303 STEP
Automation in Construction 14 (2005) 633 – 649 www.elsevier.com/locate/autcon
Development of an interoperability model for different construction drawing standards based on ISO 10303 STEP Inhan KimT, Soonjung Lee1 School of Architecture and Civil Engineering, Kyung-Hee University, Yong-In Si, 449-701, Kyung-Gi Do, Korea Accepted 17 December 2004
Abstract The purpose of this study is to develop an exchange model for the interoperability of various national standards based on the international standard ISO 10303 in construction. Several countries like Germany, Japan, and Korea have developed the drawing standards STEP-CDS, SCADEC, and KOSDIC, respectively, for the neutral drawing data exchange mechanisms among various applications. However, these standards are not naturally exchangeable due to the differences resulting from the national flavors representing the drawing elements defined in their standards. These problems can be solved using the exchange methodology, EXPRESS-X, defined in ISO 10303. In this study, an exchange model applying the standard exchange methodology has been developed by analyzing the three different drawing standards. The developed exchange model demonstrates that the interoperability among the drawing standards is feasible. In addition, the model shows that the use of the standard exchange methodology based on international standards is beneficial in many ways for the data exchange between schemata. D 2005 Elsevier B.V. All rights reserved. Keywords: STEP; Construction drawing standards; Drawing elements; EXPRESS-X
1. Introduction In construction, drawings are used to communicate to the experts of various disciplines through the life cycle of a building, from the conceptual design stage to the construction and maintenance stage. However, experts have generated these drawings using various T Corresponding author. Tel.: +82 31 201 2926; fax: +82 31 202 8854. E-mail addresses: [email protected] (I. Kim)8 [email protected] (S. Lee). 1 Tel.: +82 31 201 2955; fax: +82 31 202 8854. 0926-5805/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.autcon.2005.01.003
applications appropriate to their domains. Thus, data exchange mechanism among the various stages of applications has been recognized as a very important issue [8]. Several countries like Germany, Japan, and Korea have developed drawing standards based on the international standard ISO 10303 for an efficient and neutral drawing exchange among various applications. In the case of Germany, the drawing standard STEP-CDS2 has been developed on the initiative of private companies. In Japan and Korea, on the other 2
Acronym for STEP-Construction Drawing Subset.
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Fig. 1. AP202 data models.
hand, the drawing standards SCADEC3 and KOSDIC4, respectively, have been developed on the initiative of the government. Nonetheless, the developed drawing standards have differences resulting from the objectives of developments and the national flavors representing the drawing elements. The development purpose of STEP-CDS is the exchange and sharing of drawing data, whereas the development purpose of SCADEC is the electronic delivery of drawings to the government [5,6]. KOSDIC has been developed with the purpose of creating a national standard for the electronic delivery of construction drawings like SCADEC in Japan [11]. Later, however, the scope of KOSDIC has been extended to accommodate the uniform exchange and sharing of drawing data [12]. Therefore, these three standards are not naturally exchangeable due to the differences resulting in objectives and national flavors, although the standards have been developed based on the same STEP international standard. For the interoperability of the standards, a mapping methodology converting the instance of one schema to the others shall be applied to them [9]. The application of a mapping methodology among the standards is more efficient for the interoperability than the use of interface-based methodology in generating and maintaining exchange models. In case of STEP, 3
Acronym for Standard for CAD Data Exchange in Japanese Construction Field. 4 Acronym for Korea Standard of Drawing Information in Construction.
the mapping methodology called EXPRESS-X has been developed as the exchange standard [3]. Consequently, this paper suggests the development of an exchange model applying the standard exchange methodology to the interoperability between the standards by analyzing the drawing structure and the representation of the drawing elements used.
2. Construction drawing models based on ISO 10303 2.1. AP202 As part of ISO 10303, AP202 is the basis for the development of the exchange standard of CAD data in construction. It consists of data models used to define a product as well as project the drawings of the product. The data models of AP202 are classified in Fig. 1 [4]. STEP-CDS, SCADEC, and KOSDIC, which can be evaluated as subsets of AP202, have borrowed only the necessary parts from the AP202 data models according to the needs of the individual countries’ development scope. The models shaded in Fig. 2 mean that they are included in the respective construction drawing standards. 2.2. STEP-CDS STEP-CDS has been developed on the initiative of private companies in Germany as the standard for
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AP202
STEP-CDS
SCADEC
KOSDIC
Product Relation
Product Relation
Product Relation
Product Relation
Drawing Structure
Drawing Structure
Drawing Structure
Drawing Structure
Drawing
View Admin
Geometric Shapes 2D
3D
Drawing
View
Admin
Geometric Shapes 2D
3D
Drawing View
Admin
Geometric Shapes 2D
3D
Drawing
View Admin
Geometric Shapes 2D
3D
Annotation
Annotation
Annotation
Annotation
Associativity
Associativity
Associativity
Associativity
Grouping
Grouping
Grouping
Grouping
Fig. 2. Model structure of the drawing models.
CAD data in construction. The objectives of STEPCDS are not only the development of the standard for 2D drawing, but also the exchange and sharing standard of construction information based on STEP in the whole domain of construction and other engineering industries [5]. 2.2.1. Model structure in STEP-CDS With the purpose of exchange and sharing of drawing data, STEP-CDS includes the viewing pipeline5 and associativity6 models for an efficient exchange of drawing data and for an effective preservation of association between them in exchanging the drawing data among the various applications in construction (see Fig. 2). Therefore, within the model structure of STEP-CDS, the model space7 is supported. 2.2.2. Representation of drawing elements in STEP-CDS In STEP-CDS, the drawing elements are represented separately as shape data and annotation data. The shape data is used to define the model of products and the annotation data used to describe the
5
A viewing process to project drawings from a product. Preservation of related information between geometric elements. 7 Working space which is used to generate a product without scale factor.
products. Consequently, within the STEP-CDS drawing elements, curves such as a line, poly-line, circle, arc, etc., which forms the graphical shape and subfigures, are defined as shape data. On the other hand, text, leader, hatch, dimension, etc., which are used to describe the abstraction of the graphical shape in drawings, are defined as annotation data. All drawing elements of STEP-CDS are represented in the draughting_model entity and mapped into the drawing_sheet_revision entity through the mapped_item entity. The draughting_model consists of shape data and annotation data representing the model and the description of the product, respectively. The shape data are defined using the geometric_ curve_set entity and then mapped into the draughting_ model through the mapped_item. The annotation data can be defined as a styled_item entity or complex entity8 according to the characteristics of these data. The representation process of the drawing elements in STEP-CDS can be depicted using the main entities in Fig. 3. In applying the representation methodology of the drawing elements of STEP-CDS, a line can be illustrated as seen in Fig. 4. The line is represented separately as shape data and annotation data according to the representation methodology of STEP-CDS. The shape data defines the geometric information of
6
8
An entity inheriting multi-characteristics from several entities.
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mapped_item
items S[1 : ?]
drawing_sheet_revision
(Drawing sheet) mapping_source
(viewing pipeline) elements S[1 : ?]
mapping_source presentation_view
geometric_curve_set
mapped_item
items S[1 : ?]
trimmed_curve
(Shape data)
camera_image_2d_with_ scale
(Visualization data of shape)
styled_item
Circle
mapping_source
(Visualization data of annotation)
annotation_occurrence (complex entity)
camera_usage
polyline
mapped_representation draughting_model
polyline
.......
items S[1 : ?]
(many entities)
(including the whole drawing elements) .......
Fig. 3. Representation of drawing elements in STEP-CDS.
the line entity and the annotation data defines the visual information of the line entity, e.g., color and line type. The line is then linked to the drawing sheet through the draughting_model entity that contains all drawing elements.
mapped_item
mapping_source
items S[1 : ?]
2.3. SCADEC SCADEC has been developed on the initiative of the Japanese government for the electronic delivery and exchange standard of 2D CAD in the construction
drawing_sheet_revision
(viewing pipeline) mapping_source
presentation_view
geometric_curve_set
mapped_item items S[1 : ?]
elements S[1 : ?]
camera_image_2d_with_ scale
styled_item
item
trimmed_curve
basis_ curve
line
mapping_source
(shape information)
styles S[1 : ?]
pnt
camera_usage presentation_style_assignment
catesian_point
mapped_representation draughting_model
items S[1 : ?]
styles S[1 : ?]
(visual inf ormation)
curve_style
(Line)
Fig. 4. Line in STEP-CDS.
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drawing_sheet_revision
637
(drawing_sheet)
items S[1 : ?]
annotation_occurrence (complex entity) . . .
annotation_subfigure_occurrence (complex entity)
.......
(many entities)
. . .
Fig. 5. Representation of drawing elements in SCADEC.
CALS environments. One of its main objectives is to apply international standards to the public service in construction. The development schedule of SCADEC is divided into four levels. Currently, only level two has been completed [6]. 2.3.1. Model structure in SCADEC With the purpose of exchanging drawing data under construction CALS, SCADEC comprises data models used to represent mainly the visual information of drawing elements in drawings rather than the exchange and sharing of drawing information (illustrated in Fig. 2). Therefore, within the model structure of SCADEC, only the paper space9 can be supported. 2.3.2. Representation of drawing elements in SCADEC In SCADEC, there is no separate representation methodology depicting the drawing elements, whereas STEP-CDS use the representation methodology supported in AP202 by representing the drawing elements as shape data and annotation data according to the property of the drawing data. Therefore, in SCADEC, all drawing elements are represented as annotation data using the uniform representation methodology. In addition, all drawing elements are linked directly to the drawing sheet without the draughting_model because there is no viewing pipeline model. The drawing elements of SCADEC are defined as a complex entity, linked directly to the drawing sheet or linked to the drawing sheet through the subfigure in
9
Working space used to generate drawings with scale factor.
accordance with their intent. The representation process of the drawing elements in SCADEC is depicted with the main entities in Fig. 5. With the representation methodology of the drawing elements in SCADEC, a line can be illustrated as in Fig. 6. The line is defined as a complex entity that inherits the multi-characteristics of several entities representing the geometric and annotative property. It is linked directly to the drawing sheet without the viewing pipeline process. This is the main difference between STEP-CDS and SCADEC in representing the drawing elements. 2.4. KOSDIC KOSDIC has been developed as the drawing exchange standard and part of the Korean government’s initiative in construction CALS/EC plan to facilitate an electronic government [7]. 2.4.1. Model structure in KOSDIC KOSDIC has been developed as the exchange standard supporting the efficient delivery of electronic drawing in the construction CALS/EC environment in Korea since 2000. However, the scope of KOSDIC has been extended to accommodate the exchange and sharing of drawing information in construction. Consequently, KOSDIC includes a viewing pipeline model and an associativity model to maintain the information between the drawing elements. The model structure of KOSDIC is similar to STEP-CDS illustrated in Fig. 2. Nonetheless, there are some differences between the standards in the application of the data model. Therefore, within the model structure of KOSDIC, the model space implementation is supported.
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drawing_sheet_revision
(drawing_sheet)
basis_curve line
trimmed_curve
Representation_item
(shape information) pnt items S[1 : ?]
Geometric_representation_item
styles S[1 : ?] (visual information)
item styled_item
catesian_point
presentation_style_assignment
curve_style
styles S[1 : ?]
Draughting_annotation_occurrence
Annotation_occurrence
Annotation_curve_occurrence
(Line)
Fig. 6. Line in SCADEC.
2.4.2. Representation of drawing elements in KOSDIC In KOSDIC, the drawing elements are represented separately as shape data and annotation data like STEP-CDS. The drawing elements are then linked to the draughting_model entity. The differ-
items S[1 : ?]
mapped_item
ence between the two standards is that in STEPCDS, complex entities are used only to represent the annotation data, on the other hand, in KOSDIC, they are used to represent all the drawing data whether shape data or annotation data [10]. The representa-
drawing_sheet_revision
(Drawing sheet) mapping_source
(viewing pipeline)
elements S[1 : ?]
mapping_source presentation_view
geometric_curve_set
mapped_item
items S[1 : ?]
trimmed_curve
(Shape data)
camera_image_2d_with_ scale
annotation_occurrence (complex entity)
(visualization data of Shape/Annotation)
Circle
mapping_source polyline
camera_usage
.......
(many entities)
mapped_representation ....... draughting_model
items S[1 : ?]
(including the whole drawing elements)
Fig. 7. Representation of drawing elements in KOSDIC.
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camera_image_2d_with_ scale
items S[1 : ?]
mapping_source mapped_item
presentation_view
639
items S[1 : ?]
drawing_sheet_revision
(Drawing sheet)
mapping_source
(viewing pipeline) mapped_representation
camera_usage
items S[1 : ?]
draughting_model
mapping_source geometric_curve_set
mapped_item
elements S[1 : ?] basis_ curve trimmed_curve
line
Representation_item
(shape information) items S[1 : ?]
presentation_style_assignment
Geometric_representation_item
styles S[1 : ?]
item styled_item
catesian_point
(visual information)
curve_style
styles S[1 : ?]
Annotation_occurrence
pnt
Draughting_annotation_occurrence
Annotation_curve_occurrence
(Line)
Fig. 8. Line in KOSDIC.
tion process of the drawing elements in KOSDIC is depicted in Fig. 7. With the representation methodology of drawing elements in KOSDIC, a line can be illustrated as in Fig. 8. The line is represented as a complex entity with shape data and annotation data. The defined line is then linked to the draughting_model including all drawing elements in drawing and represented in the drawing sheet through the viewing pipeline process.
3. Interoperability among the construction drawing models 3.1. Differences in the construction drawing models STEPC-CDS, SCADEC, and KOSDIC have different applying criteria according to the needs of the individual countries’ development scope. Therefore,
among them, there are some differences in representing the drawing elements and in applying the AP202 data models. The main differences in applying the data models are shown in Table 1. 3.1.1. Differences in representing drawing structure In AP202, which is the basis of the drawing exchange standards in STEP, the drawing data can be represented separately as shape data and annotation data. It is the selection of the representation methodologies of drawing data in AP202 according to the
Table 1 The differences of the standards in applying data models AP202
STEP-CDS
KOSDIC
SCADEC
Viewing pipeline Separating Shape and appearance Applying associativity
O O
O O
X X
O
O
X
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drawing_sheet_revision
(drawing_sheet)
(viewing_pipeline)
items S[1 : ?] mapped_item
mapped_item
mapping_ source
mapping_source item presentation_view
styled_item
geometric_curve_set
elements S[1 : ?]
(Sfig_locate)
NULL
items S[1 : ?] mapped_item
camera_image_2d_with_ scale
draughting_model
mapping_source
items S[1 : ?]
(sfig_org elements)
camera_usage
geometric_curve_set
mapped_representation
(sfig_org)
mapping_ source
items S[1 : ?]
mapping_ source
mapped_item
elements S[1 : ?]
(subfigure)
draughting_model trimmed_curve
Circle
polyline
Fig. 9. Representation of subfigure in STEP-CDS and KOSDIC.
applying objectives and the scope of standards. For the exchange and sharing of drawing information, the separate representation methodology shall be chosen. For the delivery of electronic drawing, however, the uniform representation methodology representing all the drawing elements as annotations shall be chosen. Therefore, the main difference among the three standards is in the representation methodologies of the drawing structure. For example, in case the drawing elements are represented separately as shape data and annotation data, the viewing pipeline process is used. Consequently, the draughting_model entity, which includes all the drawing elements, is made and then linked to the drawing_sheet_revision entity through the viewing pipeline process. In case the drawing elements are only represented as annotation data, however, all drawing data are linked directly to the drawing_sheet_revision without the viewing pipeline process. In STEP-CDS and KOSDIC, the viewing pipeline and the separate representation methodology of drawing elements are applied to maintain the drawing
information. Likewise, the associativity model is applied to increase the practical usability of the drawing data in editing and modification after exchanging them. In SCADEC, however, the uniform representation methodology is supported to represent the drawing elements as annotation data and the associativity model is not applied. These are the main differences among the three standards in representing the drawing structure. 3.1.2. Differences in representing drawing element The differences of the representation methodology of the drawing elements, except the drawing representation structure within the drawing exchange standards, are analyzed on the basis of the KOSDIC common entities. While STEP-CDS and KOSDIC have a similar representation methodology of the drawing elements, SCADEC has a different representation methodology in several main entities compared to KOSDIC. There are major differences among the standards in the definition of the subfigure elements and the dimension elements within the drawing elements.
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drawing data from STEP-CDS to KOSDIC have been analyzed on the basis of the common entities of KOSDIC. When exchanging the drawing elements from STEP-CDS to KOSDIC, some elements are required to reform their data structure with respect to the differences by applying the representation methodology. These elements are the ones used for shape data in STEP-CDS. Entities such as line, arc, circle, etc., in STEP-CDS are only represented as a single entity, styled_item entity. In KOSDIC, however, they are represented as a complex entity that reserves complex characteristics of the super-type entities. Therefore, additional entities such as the geometric_representation_item, annotation_occurrence, etc., used to represent the complex entity shall be added when exchanging drawing elements.
In case of representing the subfigure, STEP-CDS and KOSDIC define the subfigure as a single model the draughting_model entity and use the mapped_item entity to insert it into the drawing. However, SCADEC uses a uniformed representation methodology and also defines it as annotation. The representation methodology process of the subfigure and the subfigure locate of STEP-CDS, KOSDIC, and SCADEC are illustrated in Figs. 9 and 10. In case of representing dimension in STEP-CDS and KOSDIC, dimensions can be represented as the object reserving associativity between a measured value and the dimensioning target by the virtue of the residing associativity model. On the other hand, in SCADEC, there is no associativity between the measured value and the dimensioning target because the associativity model is not included in the SCADEC definition. The absence of the associativity model in dimensions introduces some problems. One problem is the separation of dimension in each drawing element, e.g., line, symbol, text, etc., after the exchange. Consequently, the exchanged dimension is no longer a dimension. Thus, for the correct exchange and sharing of drawing information, the associativity model shall be contained.
3.3. Analysis for exchanging data from SCADEC to KOSDIC In Table 3, the necessary and additional data for individual drawing elements to convert drawing data from SCADEC to KOSDIC have been analyzed on the basis of the common entities of KOSDIC. As shown in the analyzed results, it is necessary to define the additional data related to a viewing pipeline for the data conversion from SCADEC to KOSDIC because of the mutually different representation structure. These data shall be additionally assigned to the KOSDIC presentation view when
3.2. Analysis for exchanging data from STEP-CDS to KOSDIC In Table 2, the necessary and additional data for individual drawing elements of STEP-CDS to convert
drawing_sheet_revision
(drawing_sheet)
items S[1 : ?]
annotation_occurrence (complex entity:2D entity)
.......
annotation_subfigure_occurrence (complex entity) item mapping_source
annotation_occurrence (complex entity:2D entity)
annotation_symbol
items S[1 : ?] draughting_subfigure_representation
.......
641
(many entities)
Fig. 10. Representation of subfigure in SCADEC.
(subfigure)
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Table 2 The comparison of the entities converted from STEP-CDS to KOSDIC KOSDIC common entity
STEP-CDS
Remarks
Drawing_sheet Presentation_view Layer Pre_defined_line_font User_defined_line_font Pre_defined_colour_type User_defined_colour_type Point_marker Line
O O O O O O O O O
Polyline
O
Circle
O
Arc
O
Ellipse
O
Ellipse_arc
O
Spline
–
Text_string Multi_text_string Subfigure_organization Subfigure_locate Externally_defined_symbol Linear_dimension Angular_dimension Radius_dimension Diameter_dimension Balloon Label Externally_defined_hatch
O – O O – O O O O – O –
Fill_are_colour Fill_area_style_hatch Fill_area_style_tiles
O O –
Composite_curve
O
representation method is same representation method is same representation method is same representation method is same representation method is same representation method is same representation method is same representation method is same Represented as styled_item but it is represented as complex entity in KOSDIC Represented by styled_item and supporting single thickness (multi thickness supported in KOSDIC) Represented as styled_item but it is represented as complex entity in KOSDIC Represented as styled_item but it is represented as complex entity in KOSDIC Represented as styled_item but it is represented as complex entity in KOSDIC Represented as styled_item but it is represented as complex entity in KOSDIC Represented as poly-line but it is represented as bezier curve in KOSDIC Present some problems in text fonts Not supported representation method is same representation method is same Insufficient information about external defined symbol representation method is same representation method is same representation method is same representation method is same Not supported Difference by linking entity into draughting_model Represented as fill_area_style_hatch but represented as externally_defined_hatch_style in KOSDIC representation method is same representation method is same Represented as fill_area_style_hatch but represented as fill_area_style_tiles in KOSDIC Only used in hatch boundary, but used in hatch boundary and to represent poly-line with multi-thickness
they are converted. In addition, the associativity model, which is included in KOSDIC to define associativity in representing dimensions, is not included in SCADEC. Hence, the additional data such as the dimension measured value, dimension location, and tolerance shall be created for associativity at the same time as exchanging dimensions like linear dimension, angular dimension, radius dimension, and diameter dimension.
4. Development of exchange model 4.1. EXPRESS-X As a mapping language, EXPRESS-X has been developed with the objective of data exchange between schemata defined in EXPRESS that integrates and improves the existing mapping languages such as EXPRESS-V (ISO/TC184/SC4/WG5/N251) and
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Table 3 The comparison of the entities converted from SCADEC to KOSDIC KOSDIC common entity
SCADEC
Remarks
Drawing_sheet
O
Presentation_view
–
Layer Pre_defined_line_font
O O
User_defined_line_font Pre_defined_colour_type
O O
User_defined_colour_type Point_marker Line Polyline
O O O O
Circle Arc Ellipse Ellipse_arc Spline Text_string Multi_text_string Subfigure_organization
O O O O O O – O
Subfigure_locate
O
Externally_defined_symbol Linear_dimension
O O
Angular_dimension
O
Radius_dimension
O
Diameter_dimension
O
Balloon Label Externally_defined_hatch Fill_are_colour Fill_area_style_hatch Fill_area_style_tiles Composite_curve
O O O O O O O
Difference by linking drawing elements into drawing_sheet_revision Not supported, but certainly needs in KOSDIC additional entities for viewing pipeline process must defined with fixing value) representation method is same Converting draughting_pre_defined_curve_font to pre_defined_curve_font representation method is same Converting draughting_pre_defined_colour to pre_defined_colour representation method is same representation method is same representation method is same Supporting single thickness but multi thickness supported in KOSDIC representation method is same representation method is same representation method is same representation method is same representation method is same Entity representation method is same Not supported Difference in definition structure, additional entity must be defined. Represented as annotation but draughting_model used in KOSDIC Difference in definition structure, represented as annotation_symbol but represented as mapped_item in KOSDIC representation method is same Having no associativity, additional entity, for example, dimension measured value, dimension location, and tolerance, must be defined to represent associtativity Having no associativity, additional entity must be defined to represent associtativity Having no associativity, additional entity must be defined to represent associtativity Having no associativity, additional entity must be defined to represent associtativity representation method is same representation method is same representation method is same representation method is same representation method is same representation method is same Only used in hatch boundary, but used in hatch boundary and to represent poly-line with multi-thickness
EXPRESS-M (ISO/TC184/SC4/WG5/N253) [1]. Currently, EXPRESS-X is not a formal ISO 10303 standard yet; however, a Committee Draft (CD) proposal has been submitted for ballot.
There are some difficulties in interoperating between applications with a different schema for each other. For the interoperability between the applications, the data conversion mechanism should be
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Source schema
Target schema Mapping schema
(describes)
(describes) Converter (tools)
Source model
Target model
Instances
Instances
Fig. 11. Data exchange using mapping schemata.
item
styled_item
trimmed_curve
basis_ curve
line
(shape information) pnt
styles S[1 : ?]
presentation_style_assignment styles S[1 : ?]
catesian_point
(visual information)
curve_style
(Line)
trimmed_curve
basis_ curve
line
Representation_item
(shape information) pnt Geometric_representation_item
styles S[1 : ?]
item styled_item styles S[1 : ?]
Annotation_occurrence
presentation_style_assignment
catesian_point
(visual information)
curve_style
Draughting_annotation_occurrence
Annotation_curve_occurrence
Fig. 12. Mapping line from STEP-CDS to KOSDIC.
(Line)
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GLOBAL DECLARE src INSTANCE OF SOURCE_SCHEMA cds; DECLARE trg INSTANCE OF TARGET_SCHEMA kosdic END_GLOBAL ; MAP ON_CALL_ONLY Map_styled_item_curve FOR t_s_i:trg::annotation_curve_occurrence&draughting_annotation_occurrence&geometric_representation_item; FROM(s_s_i:src::styled_item) WHEN(TRUE); BEGIN_MAP REPEAT index := 1 TO HIINDEX(s_s_i.styles); t_s_i.styles[index] := Map_presentation_style_assignment(s_s_i.styles[index]); END_REPEAT; IF('CDS.POLYLINE' IN TYPEOF(s_s_i.item)) THEN t_s_i.item:= Map_polyline(s_s_i.item); ELSE IF('CDS.TRIMMED_CURVE' IN TYPEOF(s_s_i.item)) THEN t_s_i.item := Map_trimmed_curve(s_s_i.item); ELSE END_IF; END_MAP;
Fig. 13. Mapping schema to convert from STEP-CDS to KOSDIC.
developed using an input and output interface of the source schema and target schema, respectively. This is difficult, however. EXPRESS-X has been developed to resolve these interoperable difficulties and to create the instance of the target schema from the instance of the source schema. Data mapping between different schemata requires the mapping schema that can convert the instance from the source schema to the target schema and the input and output tools that can access the instance data of schema defined in EXPRESS [2]. The mapping schema shall be made using the mapping languages defined in EXPRESS-X. In this study, Express Data Manager(EDM) is used for the input and output schema tool defined in EXPRESS (Fig. 11).
4.2. Exchange model applying EXPRESS-X The data mapping schemata between the drawing exchange standards with EXPRESS-X is created using the results analyzed in Tables 2 and 3. In case the representation method between entities is the same, one-to-one mapping is performed between the standards. In case additional definition of entities is needed, however, one-to-many mapping is performed between the standards. The data conversions between STEP-CDS and KOSDIC, which have a similar drawing structure, are mostly done by one-to-one mapping; however, between SCADEC and KOSDIC that have different drawing structures, data conversions are mostly done by one-to-many mapping.
Fig. 14. Data conversion from STEP-CDS to KOSDIC.
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performed through one-to-many mapping for the generation of additional data necessary for the representing line in KOSDIC. Fig. 13 illustrates the exchange module definition used in line mapping within the exchange modules, which have been developed for mapping between the standards. As the exchange module, the map_styled_item_curve converts line, arc, circle, ellipse, polyline, etc., used for data model in STEP-CDS to correspond to those in KOSDIC. With the developed conversion model, the drawing data made according to STEP-CDS can be converted into data that are compatible with KOSDIC. The converted result is shown in Fig. 14. It depicts the drawing data before and after conversion by the viewer of STEP-CDS and KOSDIC, respectively.
4.2.1. Development of exchange model from STEP-CDS to KOSDIC As the standards have similar drawing structures, the drawing sheet and presentation view as the drawing elements representing the drawing structure, are exchanged by one-to-one mapping as conversion entities between them. However, entities such as line, arc, circle, ellipse, poly-line, etc., which are used for model data in STEP-CDS, are represented as complex entities in KOSDIC. Therefore, in case of conversion of the model data defined in STEP-CDS, one-to-many mapping is done for the generation of additional data. The shaded entities in Fig. 12 are additional entities used to represent the complex entities in KOSDIC. As depicted in Fig. 12, the data mapping from the line data in STEP-CDS to the line data in KOSDIC is
drawing_sheet_revision
(drawing_sheet)
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(The whole drawing elements are represented to annotation data)
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Circle
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polyline
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mapped_representation ....... draughting_model
items S[1 : ?]
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Fig. 15. Mapping drawing sheet from SCADEC to KOSDIC.
I. Kim, S. Lee / Automation in Construction 14 (2005) 633–649 GLOBAL DECLARE src INSTANCE OF SOURCE_SCHEM Aassociative_draughting; DECLARE trg INSTANCE OF TARGET_SCHEMA kosdic END_GLOBAL; MA P ON_CALL_ONLY Map_drawing_sheet_revision FOR t_d_s_r:trg::drawing_sheet_revision; FROM(s_d_s_r:src::drawing_sheet_revision) WHEN(TRUE); BEGIN_MAP t_d_s_r.name := s_d_s_r.name; t_d_s_r.revision_identifier:= s_d_s_r.revision_identifier; t_d_s_r.context_of_items:= Map_geometric_global_context (s_d_s_r.context_of_items); t_d_s_r.items[1] := Map_drawing_items_to_draughting_model (s_d_s_r); END_MAP; MAP ON_CALL_ONLY Map_drawing_items_to_draughting_model FOR t_m_i:trg::mapped_item; FROM(s_d_s_r:src::drawing_sheet_revision) MAP ON_CALL_ONLY Map_camera_usage_to_make_draughting_model FOR t_c_u:trg::camera_usage; FROM(s_d_s_r:src::drawing_sheet_revision) MAP ON_CALL_ONLY Map_presentation_view_to_make_draughting_model FOR t_p_v:trg::presentation_view; FROM(s_p_v:src::drawing_sheet_revision) MAP ON_CALL_ONLY Map_camera_image_2d_with_scale_to_make_draughting FOR t_c_i_s:trg::camera_image_2d_with_scale; FROM(s_c_i_s:src::drawing_sheet_revision) MAP ON_CALL_ONLY Map_draughting_model_to_make_draughting_model FOR t_d_m:trg::draughting_model; FROM(s_d_s_r:src::drawing_sheet_revision)
Fig. 16. Mapping schema to convert SCADEC to KOSDIC.
4.2.2. Development of exchange model from SCADEC to KOSDIC SCADEC and KOSDIC have a similar representation methodology in the representation of the drawing element rather than in the representation
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of the drawing structure as opposed to STEP-CDS. The major difference between SCADEC and KOSDIC, as analyzed in Table 3, lies in the representation methodology of the drawing structure. Therefore, to map data from the drawing structure of SCADEC to that of KOSDIC, it is necessary to add some models such as a viewing pipeline model, an associativity model, etc., which are used to represent the KOSDIC drawing structure. The mapping process of a drawing sheet data from SCADEC to KOSDIC is illustrated in Fig. 15. The shaded entities are the additional entities used to represent the drawing structure in KOSDIC. Likewise, to map the drawing elements, it is necessary to add several entities. Although the drawing elements in SCADEC are only represented as annotation data, in KOSDIC, the drawing elements are represented separately as model data and annotation data. The drawing elements, which need additional definition of the entities in SCADEC as converted into the corresponding entities of KOSDIC, are subfigure, subfigure locate, dimension, etc. The exchange module used in the mapping drawing sheet is defined in Fig. 16, within the exchange module developed for mapping between the standards. The exchange module comprises an entity creation module for converting the drawing sheet of SCADEC, which is only defined as the drawing_sheet_revision, into the drawing sheet of KOSDIC, which is applied to the viewing of pipeline model.
Fig. 17. Data conversion from SCADEC to KOSDIC.
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In Fig. 17, SCADEC drawing data is converted into KOSDIC compatible data through the developed exchange model. It illustrates the drawing data before and after conversion by a SCADEC and KOSDIC viewer.
5. Conclusion Several countries like Germany, Japan, and Korea have developed drawing standards based on the international standard ISO 10303 for an efficient and neutral drawing exchange among applications used in the various stages of construction. However, the developed drawing standards have differences resulting from the development objectives and scope and the national flavors in representing the drawing elements. Therefore, the three standards are inherently not exchangeable, although the standards have been developed based on the same STEP international standards. To solve these exchange problems, the authors of this paper suggest using the standard exchange methodology called EXPRESS-X. It is an ISO standard for interoperability among the standards written based on EXPRESS. For the development of the exchange model applying the standard exchange methodology, the schemata of the drawing standards such as STEP-CDS, KOSDIC, and SCADEC are analyzed, with the similarities and differences between the standards in the representation methodology of the drawing elements investigated. In addition, the exchange model applying EXPRESS-X is developed focusing on KOSDIC. In this paper, the exchange model developed for the interoperability between the drawing standards demonstrates that the standard exchange methodology EXPRESS-X is more useful than the conventional data exchange methodology and the interface-based exchange model in exchanging drawing data mutually. The data conversion between the data models whether or not based on the standards is very important for communication but difficult and timeconsuming because of separation of the analysis of the data models for exchange and the implementation of the conversion models based on the analysis. In the conventional methodology, first the source and target model are conceptualized for conversion, and
then the conversion programs are implemented using the particular program interfaces. That is, the exchange models are made and then the conversion programs are made based on the exchange models. These conversions are difficult and time-consuming process. Therefore the conventional methodology could not cope efficiently with the change of application platforms and the revision of their models as it has depended on the particular programming applications. In contrast, in the standard methodology, the conceptualization of the source and target model is identical with the implementation of conversion programs because the exchange models made based on EXPRESS-X are directly used for data conversion between the data models. Therefore the standard methodology can cope flexibly with those situations as it is based on STEP, which is platform-independent. With the developed exchange model, the drawing information in construction shall be exchanged easily between the standards based on STEP. The communication among the experts who participated in the project shall also be improved fairly. Besides, the developed exchange model presents that the application of the standard exchange methodology in the data conversion can be more efficient alternative than the interface-based exchange methodology. However, the developed exchange model is a oneway exchange model focusing on KOSDIC. Therefore, the development of a two-way exchange model between the standards and the harmonization of the three drawing standards with other non-STEP standards, e.g., the IFC model, which is expected to have a 2D extension, are recommended for future research.
References [1] ISO/TC184/SC4, Industrial automation systems and integration—product data representation and exchange—Part 11: Descriptive Methods: The EXPRESS Language Reference Manual (1992). [2] ISO/TC184/SC4, Industrial automation systems and integration—product data representation and exchange—Part 21: Clear Text Encoding of the Exchange structure (1994). [3] ISO/TC184/SC4/WG11 N088, EXPRESS-X Language Reference Manual (1999). [4] ISO/TC184/SC4, Industrial automation systems and integration—product data representation and exchange—Part 202: Application protocol: Associative Draughting (1996).
I. Kim, S. Lee / Automation in Construction 14 (2005) 633–649 [5] [6] [7] [8]
STEP-CDS Homepage, http://www.step-cds.de (2002). SCADEC Homepage, http://www.cad.jacic.or.jp (2002). KOSDIC Homepage, http://www.kosdic.or.kr (2002). I. Kim, A study on current technology analysis for digitalized architectural/construction drawings in Korea, Journal of the Architectural Institute of Korea 15 (6) (1999) 131 – 140. [9] I. Kim, K. Kim, A study on construction drawing data exchange model for information interoperability based on international standards, Transactions of the Society of CAD/ CAM Engineers 6 (3) (2001) 147 – 156.
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[10] I. Kim, S. Lee, A study on standardized information model for the sharing of architectural drawing information using STEP, Journal of the Architectural Institute of Korea 17 (12) (2001) 13 – 20. [11] Ministry of Construction and Transportation, A study of 2D CAD data exchange based on STEP, KICT (2001). [12] Ministry of Construction and Transportation, A study for establishment of an exchange system for the drawing information in construction field, KICT (2002).
Development of an interoperability model for different construction drawing standards based on ISO 10303 STEP Inhan KimT, Soonjung Lee1 School of Architecture and Civil Engineering, Kyung-Hee University, Yong-In Si, 449-701, Kyung-Gi Do, Korea Accepted 17 December 2004
Abstract The purpose of this study is to develop an exchange model for the interoperability of various national standards based on the international standard ISO 10303 in construction. Several countries like Germany, Japan, and Korea have developed the drawing standards STEP-CDS, SCADEC, and KOSDIC, respectively, for the neutral drawing data exchange mechanisms among various applications. However, these standards are not naturally exchangeable due to the differences resulting from the national flavors representing the drawing elements defined in their standards. These problems can be solved using the exchange methodology, EXPRESS-X, defined in ISO 10303. In this study, an exchange model applying the standard exchange methodology has been developed by analyzing the three different drawing standards. The developed exchange model demonstrates that the interoperability among the drawing standards is feasible. In addition, the model shows that the use of the standard exchange methodology based on international standards is beneficial in many ways for the data exchange between schemata. D 2005 Elsevier B.V. All rights reserved. Keywords: STEP; Construction drawing standards; Drawing elements; EXPRESS-X
1. Introduction In construction, drawings are used to communicate to the experts of various disciplines through the life cycle of a building, from the conceptual design stage to the construction and maintenance stage. However, experts have generated these drawings using various T Corresponding author. Tel.: +82 31 201 2926; fax: +82 31 202 8854. E-mail addresses: [email protected] (I. Kim)8 [email protected] (S. Lee). 1 Tel.: +82 31 201 2955; fax: +82 31 202 8854. 0926-5805/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.autcon.2005.01.003
applications appropriate to their domains. Thus, data exchange mechanism among the various stages of applications has been recognized as a very important issue [8]. Several countries like Germany, Japan, and Korea have developed drawing standards based on the international standard ISO 10303 for an efficient and neutral drawing exchange among various applications. In the case of Germany, the drawing standard STEP-CDS2 has been developed on the initiative of private companies. In Japan and Korea, on the other 2
Acronym for STEP-Construction Drawing Subset.
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Fig. 1. AP202 data models.
hand, the drawing standards SCADEC3 and KOSDIC4, respectively, have been developed on the initiative of the government. Nonetheless, the developed drawing standards have differences resulting from the objectives of developments and the national flavors representing the drawing elements. The development purpose of STEP-CDS is the exchange and sharing of drawing data, whereas the development purpose of SCADEC is the electronic delivery of drawings to the government [5,6]. KOSDIC has been developed with the purpose of creating a national standard for the electronic delivery of construction drawings like SCADEC in Japan [11]. Later, however, the scope of KOSDIC has been extended to accommodate the uniform exchange and sharing of drawing data [12]. Therefore, these three standards are not naturally exchangeable due to the differences resulting in objectives and national flavors, although the standards have been developed based on the same STEP international standard. For the interoperability of the standards, a mapping methodology converting the instance of one schema to the others shall be applied to them [9]. The application of a mapping methodology among the standards is more efficient for the interoperability than the use of interface-based methodology in generating and maintaining exchange models. In case of STEP, 3
Acronym for Standard for CAD Data Exchange in Japanese Construction Field. 4 Acronym for Korea Standard of Drawing Information in Construction.
the mapping methodology called EXPRESS-X has been developed as the exchange standard [3]. Consequently, this paper suggests the development of an exchange model applying the standard exchange methodology to the interoperability between the standards by analyzing the drawing structure and the representation of the drawing elements used.
2. Construction drawing models based on ISO 10303 2.1. AP202 As part of ISO 10303, AP202 is the basis for the development of the exchange standard of CAD data in construction. It consists of data models used to define a product as well as project the drawings of the product. The data models of AP202 are classified in Fig. 1 [4]. STEP-CDS, SCADEC, and KOSDIC, which can be evaluated as subsets of AP202, have borrowed only the necessary parts from the AP202 data models according to the needs of the individual countries’ development scope. The models shaded in Fig. 2 mean that they are included in the respective construction drawing standards. 2.2. STEP-CDS STEP-CDS has been developed on the initiative of private companies in Germany as the standard for
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AP202
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Product Relation
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View Admin
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3D
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Annotation
Annotation
Annotation
Associativity
Associativity
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Fig. 2. Model structure of the drawing models.
CAD data in construction. The objectives of STEPCDS are not only the development of the standard for 2D drawing, but also the exchange and sharing standard of construction information based on STEP in the whole domain of construction and other engineering industries [5]. 2.2.1. Model structure in STEP-CDS With the purpose of exchange and sharing of drawing data, STEP-CDS includes the viewing pipeline5 and associativity6 models for an efficient exchange of drawing data and for an effective preservation of association between them in exchanging the drawing data among the various applications in construction (see Fig. 2). Therefore, within the model structure of STEP-CDS, the model space7 is supported. 2.2.2. Representation of drawing elements in STEP-CDS In STEP-CDS, the drawing elements are represented separately as shape data and annotation data. The shape data is used to define the model of products and the annotation data used to describe the
5
A viewing process to project drawings from a product. Preservation of related information between geometric elements. 7 Working space which is used to generate a product without scale factor.
products. Consequently, within the STEP-CDS drawing elements, curves such as a line, poly-line, circle, arc, etc., which forms the graphical shape and subfigures, are defined as shape data. On the other hand, text, leader, hatch, dimension, etc., which are used to describe the abstraction of the graphical shape in drawings, are defined as annotation data. All drawing elements of STEP-CDS are represented in the draughting_model entity and mapped into the drawing_sheet_revision entity through the mapped_item entity. The draughting_model consists of shape data and annotation data representing the model and the description of the product, respectively. The shape data are defined using the geometric_ curve_set entity and then mapped into the draughting_ model through the mapped_item. The annotation data can be defined as a styled_item entity or complex entity8 according to the characteristics of these data. The representation process of the drawing elements in STEP-CDS can be depicted using the main entities in Fig. 3. In applying the representation methodology of the drawing elements of STEP-CDS, a line can be illustrated as seen in Fig. 4. The line is represented separately as shape data and annotation data according to the representation methodology of STEP-CDS. The shape data defines the geometric information of
6
8
An entity inheriting multi-characteristics from several entities.
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mapped_item
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polyline
.......
items S[1 : ?]
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(including the whole drawing elements) .......
Fig. 3. Representation of drawing elements in STEP-CDS.
the line entity and the annotation data defines the visual information of the line entity, e.g., color and line type. The line is then linked to the drawing sheet through the draughting_model entity that contains all drawing elements.
mapped_item
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2.3. SCADEC SCADEC has been developed on the initiative of the Japanese government for the electronic delivery and exchange standard of 2D CAD in the construction
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Fig. 4. Line in STEP-CDS.
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(drawing_sheet)
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annotation_occurrence (complex entity) . . .
annotation_subfigure_occurrence (complex entity)
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. . .
Fig. 5. Representation of drawing elements in SCADEC.
CALS environments. One of its main objectives is to apply international standards to the public service in construction. The development schedule of SCADEC is divided into four levels. Currently, only level two has been completed [6]. 2.3.1. Model structure in SCADEC With the purpose of exchanging drawing data under construction CALS, SCADEC comprises data models used to represent mainly the visual information of drawing elements in drawings rather than the exchange and sharing of drawing information (illustrated in Fig. 2). Therefore, within the model structure of SCADEC, only the paper space9 can be supported. 2.3.2. Representation of drawing elements in SCADEC In SCADEC, there is no separate representation methodology depicting the drawing elements, whereas STEP-CDS use the representation methodology supported in AP202 by representing the drawing elements as shape data and annotation data according to the property of the drawing data. Therefore, in SCADEC, all drawing elements are represented as annotation data using the uniform representation methodology. In addition, all drawing elements are linked directly to the drawing sheet without the draughting_model because there is no viewing pipeline model. The drawing elements of SCADEC are defined as a complex entity, linked directly to the drawing sheet or linked to the drawing sheet through the subfigure in
9
Working space used to generate drawings with scale factor.
accordance with their intent. The representation process of the drawing elements in SCADEC is depicted with the main entities in Fig. 5. With the representation methodology of the drawing elements in SCADEC, a line can be illustrated as in Fig. 6. The line is defined as a complex entity that inherits the multi-characteristics of several entities representing the geometric and annotative property. It is linked directly to the drawing sheet without the viewing pipeline process. This is the main difference between STEP-CDS and SCADEC in representing the drawing elements. 2.4. KOSDIC KOSDIC has been developed as the drawing exchange standard and part of the Korean government’s initiative in construction CALS/EC plan to facilitate an electronic government [7]. 2.4.1. Model structure in KOSDIC KOSDIC has been developed as the exchange standard supporting the efficient delivery of electronic drawing in the construction CALS/EC environment in Korea since 2000. However, the scope of KOSDIC has been extended to accommodate the exchange and sharing of drawing information in construction. Consequently, KOSDIC includes a viewing pipeline model and an associativity model to maintain the information between the drawing elements. The model structure of KOSDIC is similar to STEP-CDS illustrated in Fig. 2. Nonetheless, there are some differences between the standards in the application of the data model. Therefore, within the model structure of KOSDIC, the model space implementation is supported.
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Draughting_annotation_occurrence
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(Line)
Fig. 6. Line in SCADEC.
2.4.2. Representation of drawing elements in KOSDIC In KOSDIC, the drawing elements are represented separately as shape data and annotation data like STEP-CDS. The drawing elements are then linked to the draughting_model entity. The differ-
items S[1 : ?]
mapped_item
ence between the two standards is that in STEPCDS, complex entities are used only to represent the annotation data, on the other hand, in KOSDIC, they are used to represent all the drawing data whether shape data or annotation data [10]. The representa-
drawing_sheet_revision
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mapped_representation ....... draughting_model
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Fig. 7. Representation of drawing elements in KOSDIC.
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Fig. 8. Line in KOSDIC.
tion process of the drawing elements in KOSDIC is depicted in Fig. 7. With the representation methodology of drawing elements in KOSDIC, a line can be illustrated as in Fig. 8. The line is represented as a complex entity with shape data and annotation data. The defined line is then linked to the draughting_model including all drawing elements in drawing and represented in the drawing sheet through the viewing pipeline process.
3. Interoperability among the construction drawing models 3.1. Differences in the construction drawing models STEPC-CDS, SCADEC, and KOSDIC have different applying criteria according to the needs of the individual countries’ development scope. Therefore,
among them, there are some differences in representing the drawing elements and in applying the AP202 data models. The main differences in applying the data models are shown in Table 1. 3.1.1. Differences in representing drawing structure In AP202, which is the basis of the drawing exchange standards in STEP, the drawing data can be represented separately as shape data and annotation data. It is the selection of the representation methodologies of drawing data in AP202 according to the
Table 1 The differences of the standards in applying data models AP202
STEP-CDS
KOSDIC
SCADEC
Viewing pipeline Separating Shape and appearance Applying associativity
O O
O O
X X
O
O
X
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(viewing_pipeline)
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elements S[1 : ?]
(Sfig_locate)
NULL
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draughting_model trimmed_curve
Circle
polyline
Fig. 9. Representation of subfigure in STEP-CDS and KOSDIC.
applying objectives and the scope of standards. For the exchange and sharing of drawing information, the separate representation methodology shall be chosen. For the delivery of electronic drawing, however, the uniform representation methodology representing all the drawing elements as annotations shall be chosen. Therefore, the main difference among the three standards is in the representation methodologies of the drawing structure. For example, in case the drawing elements are represented separately as shape data and annotation data, the viewing pipeline process is used. Consequently, the draughting_model entity, which includes all the drawing elements, is made and then linked to the drawing_sheet_revision entity through the viewing pipeline process. In case the drawing elements are only represented as annotation data, however, all drawing data are linked directly to the drawing_sheet_revision without the viewing pipeline process. In STEP-CDS and KOSDIC, the viewing pipeline and the separate representation methodology of drawing elements are applied to maintain the drawing
information. Likewise, the associativity model is applied to increase the practical usability of the drawing data in editing and modification after exchanging them. In SCADEC, however, the uniform representation methodology is supported to represent the drawing elements as annotation data and the associativity model is not applied. These are the main differences among the three standards in representing the drawing structure. 3.1.2. Differences in representing drawing element The differences of the representation methodology of the drawing elements, except the drawing representation structure within the drawing exchange standards, are analyzed on the basis of the KOSDIC common entities. While STEP-CDS and KOSDIC have a similar representation methodology of the drawing elements, SCADEC has a different representation methodology in several main entities compared to KOSDIC. There are major differences among the standards in the definition of the subfigure elements and the dimension elements within the drawing elements.
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drawing data from STEP-CDS to KOSDIC have been analyzed on the basis of the common entities of KOSDIC. When exchanging the drawing elements from STEP-CDS to KOSDIC, some elements are required to reform their data structure with respect to the differences by applying the representation methodology. These elements are the ones used for shape data in STEP-CDS. Entities such as line, arc, circle, etc., in STEP-CDS are only represented as a single entity, styled_item entity. In KOSDIC, however, they are represented as a complex entity that reserves complex characteristics of the super-type entities. Therefore, additional entities such as the geometric_representation_item, annotation_occurrence, etc., used to represent the complex entity shall be added when exchanging drawing elements.
In case of representing the subfigure, STEP-CDS and KOSDIC define the subfigure as a single model the draughting_model entity and use the mapped_item entity to insert it into the drawing. However, SCADEC uses a uniformed representation methodology and also defines it as annotation. The representation methodology process of the subfigure and the subfigure locate of STEP-CDS, KOSDIC, and SCADEC are illustrated in Figs. 9 and 10. In case of representing dimension in STEP-CDS and KOSDIC, dimensions can be represented as the object reserving associativity between a measured value and the dimensioning target by the virtue of the residing associativity model. On the other hand, in SCADEC, there is no associativity between the measured value and the dimensioning target because the associativity model is not included in the SCADEC definition. The absence of the associativity model in dimensions introduces some problems. One problem is the separation of dimension in each drawing element, e.g., line, symbol, text, etc., after the exchange. Consequently, the exchanged dimension is no longer a dimension. Thus, for the correct exchange and sharing of drawing information, the associativity model shall be contained.
3.3. Analysis for exchanging data from SCADEC to KOSDIC In Table 3, the necessary and additional data for individual drawing elements to convert drawing data from SCADEC to KOSDIC have been analyzed on the basis of the common entities of KOSDIC. As shown in the analyzed results, it is necessary to define the additional data related to a viewing pipeline for the data conversion from SCADEC to KOSDIC because of the mutually different representation structure. These data shall be additionally assigned to the KOSDIC presentation view when
3.2. Analysis for exchanging data from STEP-CDS to KOSDIC In Table 2, the necessary and additional data for individual drawing elements of STEP-CDS to convert
drawing_sheet_revision
(drawing_sheet)
items S[1 : ?]
annotation_occurrence (complex entity:2D entity)
.......
annotation_subfigure_occurrence (complex entity) item mapping_source
annotation_occurrence (complex entity:2D entity)
annotation_symbol
items S[1 : ?] draughting_subfigure_representation
.......
641
(many entities)
Fig. 10. Representation of subfigure in SCADEC.
(subfigure)
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Table 2 The comparison of the entities converted from STEP-CDS to KOSDIC KOSDIC common entity
STEP-CDS
Remarks
Drawing_sheet Presentation_view Layer Pre_defined_line_font User_defined_line_font Pre_defined_colour_type User_defined_colour_type Point_marker Line
O O O O O O O O O
Polyline
O
Circle
O
Arc
O
Ellipse
O
Ellipse_arc
O
Spline
–
Text_string Multi_text_string Subfigure_organization Subfigure_locate Externally_defined_symbol Linear_dimension Angular_dimension Radius_dimension Diameter_dimension Balloon Label Externally_defined_hatch
O – O O – O O O O – O –
Fill_are_colour Fill_area_style_hatch Fill_area_style_tiles
O O –
Composite_curve
O
representation method is same representation method is same representation method is same representation method is same representation method is same representation method is same representation method is same representation method is same Represented as styled_item but it is represented as complex entity in KOSDIC Represented by styled_item and supporting single thickness (multi thickness supported in KOSDIC) Represented as styled_item but it is represented as complex entity in KOSDIC Represented as styled_item but it is represented as complex entity in KOSDIC Represented as styled_item but it is represented as complex entity in KOSDIC Represented as styled_item but it is represented as complex entity in KOSDIC Represented as poly-line but it is represented as bezier curve in KOSDIC Present some problems in text fonts Not supported representation method is same representation method is same Insufficient information about external defined symbol representation method is same representation method is same representation method is same representation method is same Not supported Difference by linking entity into draughting_model Represented as fill_area_style_hatch but represented as externally_defined_hatch_style in KOSDIC representation method is same representation method is same Represented as fill_area_style_hatch but represented as fill_area_style_tiles in KOSDIC Only used in hatch boundary, but used in hatch boundary and to represent poly-line with multi-thickness
they are converted. In addition, the associativity model, which is included in KOSDIC to define associativity in representing dimensions, is not included in SCADEC. Hence, the additional data such as the dimension measured value, dimension location, and tolerance shall be created for associativity at the same time as exchanging dimensions like linear dimension, angular dimension, radius dimension, and diameter dimension.
4. Development of exchange model 4.1. EXPRESS-X As a mapping language, EXPRESS-X has been developed with the objective of data exchange between schemata defined in EXPRESS that integrates and improves the existing mapping languages such as EXPRESS-V (ISO/TC184/SC4/WG5/N251) and
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Table 3 The comparison of the entities converted from SCADEC to KOSDIC KOSDIC common entity
SCADEC
Remarks
Drawing_sheet
O
Presentation_view
–
Layer Pre_defined_line_font
O O
User_defined_line_font Pre_defined_colour_type
O O
User_defined_colour_type Point_marker Line Polyline
O O O O
Circle Arc Ellipse Ellipse_arc Spline Text_string Multi_text_string Subfigure_organization
O O O O O O – O
Subfigure_locate
O
Externally_defined_symbol Linear_dimension
O O
Angular_dimension
O
Radius_dimension
O
Diameter_dimension
O
Balloon Label Externally_defined_hatch Fill_are_colour Fill_area_style_hatch Fill_area_style_tiles Composite_curve
O O O O O O O
Difference by linking drawing elements into drawing_sheet_revision Not supported, but certainly needs in KOSDIC additional entities for viewing pipeline process must defined with fixing value) representation method is same Converting draughting_pre_defined_curve_font to pre_defined_curve_font representation method is same Converting draughting_pre_defined_colour to pre_defined_colour representation method is same representation method is same representation method is same Supporting single thickness but multi thickness supported in KOSDIC representation method is same representation method is same representation method is same representation method is same representation method is same Entity representation method is same Not supported Difference in definition structure, additional entity must be defined. Represented as annotation but draughting_model used in KOSDIC Difference in definition structure, represented as annotation_symbol but represented as mapped_item in KOSDIC representation method is same Having no associativity, additional entity, for example, dimension measured value, dimension location, and tolerance, must be defined to represent associtativity Having no associativity, additional entity must be defined to represent associtativity Having no associativity, additional entity must be defined to represent associtativity Having no associativity, additional entity must be defined to represent associtativity representation method is same representation method is same representation method is same representation method is same representation method is same representation method is same Only used in hatch boundary, but used in hatch boundary and to represent poly-line with multi-thickness
EXPRESS-M (ISO/TC184/SC4/WG5/N253) [1]. Currently, EXPRESS-X is not a formal ISO 10303 standard yet; however, a Committee Draft (CD) proposal has been submitted for ballot.
There are some difficulties in interoperating between applications with a different schema for each other. For the interoperability between the applications, the data conversion mechanism should be
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Source schema
Target schema Mapping schema
(describes)
(describes) Converter (tools)
Source model
Target model
Instances
Instances
Fig. 11. Data exchange using mapping schemata.
item
styled_item
trimmed_curve
basis_ curve
line
(shape information) pnt
styles S[1 : ?]
presentation_style_assignment styles S[1 : ?]
catesian_point
(visual information)
curve_style
(Line)
trimmed_curve
basis_ curve
line
Representation_item
(shape information) pnt Geometric_representation_item
styles S[1 : ?]
item styled_item styles S[1 : ?]
Annotation_occurrence
presentation_style_assignment
catesian_point
(visual information)
curve_style
Draughting_annotation_occurrence
Annotation_curve_occurrence
Fig. 12. Mapping line from STEP-CDS to KOSDIC.
(Line)
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GLOBAL DECLARE src INSTANCE OF SOURCE_SCHEMA cds; DECLARE trg INSTANCE OF TARGET_SCHEMA kosdic END_GLOBAL ; MAP ON_CALL_ONLY Map_styled_item_curve FOR t_s_i:trg::annotation_curve_occurrence&draughting_annotation_occurrence&geometric_representation_item; FROM(s_s_i:src::styled_item) WHEN(TRUE); BEGIN_MAP REPEAT index := 1 TO HIINDEX(s_s_i.styles); t_s_i.styles[index] := Map_presentation_style_assignment(s_s_i.styles[index]); END_REPEAT; IF('CDS.POLYLINE' IN TYPEOF(s_s_i.item)) THEN t_s_i.item:= Map_polyline(s_s_i.item); ELSE IF('CDS.TRIMMED_CURVE' IN TYPEOF(s_s_i.item)) THEN t_s_i.item := Map_trimmed_curve(s_s_i.item); ELSE END_IF; END_MAP;
Fig. 13. Mapping schema to convert from STEP-CDS to KOSDIC.
developed using an input and output interface of the source schema and target schema, respectively. This is difficult, however. EXPRESS-X has been developed to resolve these interoperable difficulties and to create the instance of the target schema from the instance of the source schema. Data mapping between different schemata requires the mapping schema that can convert the instance from the source schema to the target schema and the input and output tools that can access the instance data of schema defined in EXPRESS [2]. The mapping schema shall be made using the mapping languages defined in EXPRESS-X. In this study, Express Data Manager(EDM) is used for the input and output schema tool defined in EXPRESS (Fig. 11).
4.2. Exchange model applying EXPRESS-X The data mapping schemata between the drawing exchange standards with EXPRESS-X is created using the results analyzed in Tables 2 and 3. In case the representation method between entities is the same, one-to-one mapping is performed between the standards. In case additional definition of entities is needed, however, one-to-many mapping is performed between the standards. The data conversions between STEP-CDS and KOSDIC, which have a similar drawing structure, are mostly done by one-to-one mapping; however, between SCADEC and KOSDIC that have different drawing structures, data conversions are mostly done by one-to-many mapping.
Fig. 14. Data conversion from STEP-CDS to KOSDIC.
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performed through one-to-many mapping for the generation of additional data necessary for the representing line in KOSDIC. Fig. 13 illustrates the exchange module definition used in line mapping within the exchange modules, which have been developed for mapping between the standards. As the exchange module, the map_styled_item_curve converts line, arc, circle, ellipse, polyline, etc., used for data model in STEP-CDS to correspond to those in KOSDIC. With the developed conversion model, the drawing data made according to STEP-CDS can be converted into data that are compatible with KOSDIC. The converted result is shown in Fig. 14. It depicts the drawing data before and after conversion by the viewer of STEP-CDS and KOSDIC, respectively.
4.2.1. Development of exchange model from STEP-CDS to KOSDIC As the standards have similar drawing structures, the drawing sheet and presentation view as the drawing elements representing the drawing structure, are exchanged by one-to-one mapping as conversion entities between them. However, entities such as line, arc, circle, ellipse, poly-line, etc., which are used for model data in STEP-CDS, are represented as complex entities in KOSDIC. Therefore, in case of conversion of the model data defined in STEP-CDS, one-to-many mapping is done for the generation of additional data. The shaded entities in Fig. 12 are additional entities used to represent the complex entities in KOSDIC. As depicted in Fig. 12, the data mapping from the line data in STEP-CDS to the line data in KOSDIC is
drawing_sheet_revision
(drawing_sheet)
items S[1 : ?]
annotation_occurrence (complex entity)
(The whole drawing elements are represented to annotation data)
mapped_item
items S[1 : ?]
annotation_subfigure_occurrence (complex entity)
.......
(many entities)
drawing_sheet_revision
(Drawing sheet) mapping_source
(viewing pipeline)
elements S[1 : ?]
mapping_source presentation_view
mapped_item
items S[1 : ?]
geometric_curve_set
trimmed_curve
(model data)
camera_image_2d_with_ scale
annotation_occurrence (annotation data) (complex entity)
Circle
mapping_source
camera_usage
.......
polyline
(many entities)
mapped_representation ....... draughting_model
items S[1 : ?]
(including the whole drawing elements)
Fig. 15. Mapping drawing sheet from SCADEC to KOSDIC.
I. Kim, S. Lee / Automation in Construction 14 (2005) 633–649 GLOBAL DECLARE src INSTANCE OF SOURCE_SCHEM Aassociative_draughting; DECLARE trg INSTANCE OF TARGET_SCHEMA kosdic END_GLOBAL; MA P ON_CALL_ONLY Map_drawing_sheet_revision FOR t_d_s_r:trg::drawing_sheet_revision; FROM(s_d_s_r:src::drawing_sheet_revision) WHEN(TRUE); BEGIN_MAP t_d_s_r.name := s_d_s_r.name; t_d_s_r.revision_identifier:= s_d_s_r.revision_identifier; t_d_s_r.context_of_items:= Map_geometric_global_context (s_d_s_r.context_of_items); t_d_s_r.items[1] := Map_drawing_items_to_draughting_model (s_d_s_r); END_MAP; MAP ON_CALL_ONLY Map_drawing_items_to_draughting_model FOR t_m_i:trg::mapped_item; FROM(s_d_s_r:src::drawing_sheet_revision) MAP ON_CALL_ONLY Map_camera_usage_to_make_draughting_model FOR t_c_u:trg::camera_usage; FROM(s_d_s_r:src::drawing_sheet_revision) MAP ON_CALL_ONLY Map_presentation_view_to_make_draughting_model FOR t_p_v:trg::presentation_view; FROM(s_p_v:src::drawing_sheet_revision) MAP ON_CALL_ONLY Map_camera_image_2d_with_scale_to_make_draughting FOR t_c_i_s:trg::camera_image_2d_with_scale; FROM(s_c_i_s:src::drawing_sheet_revision) MAP ON_CALL_ONLY Map_draughting_model_to_make_draughting_model FOR t_d_m:trg::draughting_model; FROM(s_d_s_r:src::drawing_sheet_revision)
Fig. 16. Mapping schema to convert SCADEC to KOSDIC.
4.2.2. Development of exchange model from SCADEC to KOSDIC SCADEC and KOSDIC have a similar representation methodology in the representation of the drawing element rather than in the representation
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of the drawing structure as opposed to STEP-CDS. The major difference between SCADEC and KOSDIC, as analyzed in Table 3, lies in the representation methodology of the drawing structure. Therefore, to map data from the drawing structure of SCADEC to that of KOSDIC, it is necessary to add some models such as a viewing pipeline model, an associativity model, etc., which are used to represent the KOSDIC drawing structure. The mapping process of a drawing sheet data from SCADEC to KOSDIC is illustrated in Fig. 15. The shaded entities are the additional entities used to represent the drawing structure in KOSDIC. Likewise, to map the drawing elements, it is necessary to add several entities. Although the drawing elements in SCADEC are only represented as annotation data, in KOSDIC, the drawing elements are represented separately as model data and annotation data. The drawing elements, which need additional definition of the entities in SCADEC as converted into the corresponding entities of KOSDIC, are subfigure, subfigure locate, dimension, etc. The exchange module used in the mapping drawing sheet is defined in Fig. 16, within the exchange module developed for mapping between the standards. The exchange module comprises an entity creation module for converting the drawing sheet of SCADEC, which is only defined as the drawing_sheet_revision, into the drawing sheet of KOSDIC, which is applied to the viewing of pipeline model.
Fig. 17. Data conversion from SCADEC to KOSDIC.
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In Fig. 17, SCADEC drawing data is converted into KOSDIC compatible data through the developed exchange model. It illustrates the drawing data before and after conversion by a SCADEC and KOSDIC viewer.
5. Conclusion Several countries like Germany, Japan, and Korea have developed drawing standards based on the international standard ISO 10303 for an efficient and neutral drawing exchange among applications used in the various stages of construction. However, the developed drawing standards have differences resulting from the development objectives and scope and the national flavors in representing the drawing elements. Therefore, the three standards are inherently not exchangeable, although the standards have been developed based on the same STEP international standards. To solve these exchange problems, the authors of this paper suggest using the standard exchange methodology called EXPRESS-X. It is an ISO standard for interoperability among the standards written based on EXPRESS. For the development of the exchange model applying the standard exchange methodology, the schemata of the drawing standards such as STEP-CDS, KOSDIC, and SCADEC are analyzed, with the similarities and differences between the standards in the representation methodology of the drawing elements investigated. In addition, the exchange model applying EXPRESS-X is developed focusing on KOSDIC. In this paper, the exchange model developed for the interoperability between the drawing standards demonstrates that the standard exchange methodology EXPRESS-X is more useful than the conventional data exchange methodology and the interface-based exchange model in exchanging drawing data mutually. The data conversion between the data models whether or not based on the standards is very important for communication but difficult and timeconsuming because of separation of the analysis of the data models for exchange and the implementation of the conversion models based on the analysis. In the conventional methodology, first the source and target model are conceptualized for conversion, and
then the conversion programs are implemented using the particular program interfaces. That is, the exchange models are made and then the conversion programs are made based on the exchange models. These conversions are difficult and time-consuming process. Therefore the conventional methodology could not cope efficiently with the change of application platforms and the revision of their models as it has depended on the particular programming applications. In contrast, in the standard methodology, the conceptualization of the source and target model is identical with the implementation of conversion programs because the exchange models made based on EXPRESS-X are directly used for data conversion between the data models. Therefore the standard methodology can cope flexibly with those situations as it is based on STEP, which is platform-independent. With the developed exchange model, the drawing information in construction shall be exchanged easily between the standards based on STEP. The communication among the experts who participated in the project shall also be improved fairly. Besides, the developed exchange model presents that the application of the standard exchange methodology in the data conversion can be more efficient alternative than the interface-based exchange methodology. However, the developed exchange model is a oneway exchange model focusing on KOSDIC. Therefore, the development of a two-way exchange model between the standards and the harmonization of the three drawing standards with other non-STEP standards, e.g., the IFC model, which is expected to have a 2D extension, are recommended for future research.
References [1] ISO/TC184/SC4, Industrial automation systems and integration—product data representation and exchange—Part 11: Descriptive Methods: The EXPRESS Language Reference Manual (1992). [2] ISO/TC184/SC4, Industrial automation systems and integration—product data representation and exchange—Part 21: Clear Text Encoding of the Exchange structure (1994). [3] ISO/TC184/SC4/WG11 N088, EXPRESS-X Language Reference Manual (1999). [4] ISO/TC184/SC4, Industrial automation systems and integration—product data representation and exchange—Part 202: Application protocol: Associative Draughting (1996).
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STEP-CDS Homepage, http://www.step-cds.de (2002). SCADEC Homepage, http://www.cad.jacic.or.jp (2002). KOSDIC Homepage, http://www.kosdic.or.kr (2002). I. Kim, A study on current technology analysis for digitalized architectural/construction drawings in Korea, Journal of the Architectural Institute of Korea 15 (6) (1999) 131 – 140. [9] I. Kim, K. Kim, A study on construction drawing data exchange model for information interoperability based on international standards, Transactions of the Society of CAD/ CAM Engineers 6 (3) (2001) 147 – 156.
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[10] I. Kim, S. Lee, A study on standardized information model for the sharing of architectural drawing information using STEP, Journal of the Architectural Institute of Korea 17 (12) (2001) 13 – 20. [11] Ministry of Construction and Transportation, A study of 2D CAD data exchange based on STEP, KICT (2001). [12] Ministry of Construction and Transportation, A study for establishment of an exchange system for the drawing information in construction field, KICT (2002).