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How to choose a fourth generation system development environment
systems Howto choosea fourthgeneration SystemDevelopmentEnvironment by COLIN BROOKS and JOHN SMITH
I
n our first article (Data Processing, September 1984) we discussed two approaches to the design of a system using fourth generation techniques. The ‘bones’ of a methodology for building systems quickly were also introduced. In this article we take a break from methodology to describe what features and facilities are necessary before a set of products can justifiably be called a System Development Environment (SDE). Several products of interest are listed and advice on selecting an SDE is given.
Model system development environment An SDE has several components: a language for expressing an application and a means of communicating that language to the computer, diagnostic aids to identify errors, a means of organizing data for the application, a means of controlling the hardware to perform the application. Abstract: This second article on fourth generation system building describes the features necessaryfor a set qfproducts to constitutea viable systemdevelopment environment (SDE). The requirementsfor the fburth generation language, diagnostics, database management and hardware management are described. Several products of interestto thosepurchasing an SDE or wishing to learn more about thefourth generation language scene are listed and some advice on selection is given. Keywords: data processing, systemdesign, fourth generation techniques. Cohn Brooks is a managing John Smith is the manager .\dvanced DBMS group.
~0126 no 9
november
consultant and of Data Logic’s
1984
Each of these components has evolved through successive generations and most are now somewhere between third and fifth generations. Some manufacturers not able to offer the whole environment refer to parts of it as if they were the whole, the most common being the fourth generation language (4GL). Whilst each component is individually valuable, that usefulness is amplified greatly when all components are in place and well integrated. The overiding characteristic of the fourth generation is an emphasis on the requirements of the application and much less emphasis on the methods of achieving it; the what rather than the how.
Ideally, a full screen editor with natural insert/delete functions on the keyboard and an embedded compile/ trace command should be available. The improvement in productivity gained by these methods is as dramatic as that achieved in business through the use of the telephone rather than the letter. The terminal/ screen facility should be easy to use (not require 40 lines of JCL to signon) and be free of computer-oriented syntax such as starting each command with ii. (The telephone would not be nearly so useful if to use it one had to speak in Latin.) Several products are offered to completely satisfy the communication requirements. These are: screen painter -
Fourth generation language The language used to communicate with the computer should be devoid of all constructs pertaining to hardware, such as bytes, blocks, binary coded decimal etc., but be clear and concise. It should be English-based such that its purpose can be undernoncomputer-oriented stood by people. The functionality should be high enough to make explicit looping constructs unnecessary but still provide sufficient flexibility to describe most functions without contrived expressions. (Clearly COBOL is not of this generation.) Traditional communication between man and machine has been based upon some form of batch media such as cards, paper tape, or the electronic equivalent. Fourth generation communication should be interactive and conversational, in the style of screen-based interpretive BASIC.
0011-684X/84/090023-03$03.00
0
1984 Butterworth
co physically draw a screen, the computer accepting it and turning it into code, data dictionary - to free the programmer from having to think in terms of record structures, and to allow all data definitions to be referenced by a single entry point, the data item name, report generator to specify the content and presentation of reports, full screen editor - to accept commands for conversing with the computer and to ensure that the interpretations made by the machine are those the programmer intended. Ideally all these should appear in the same style and with the same commands as the 4GL itself.
Diagnostic
aids
Diagnostic aids and error messages should be readily understandable, ie
& Co (Publishers)
Ltd
23
not memory dumps of many pages of hexadecimal. Syntax and data errors should be detected at the time of entry and indicated by inverse video or the like. The diagnostics/trace facility need be no more than an ability to monitor the value of elements at certain points. The whole point of fourth generation environments is that the methods used by the computer should be hidden from the programmer, so that diagnostics are really no more than a means of confirming that one is achieving one’s intentions. When the diaglogue between computer and programmer is conducted at the natural thinking speed of the programmer, the concept of prototyping becomes a reality.
Data management Data management embraces both the way data is stored within the system and the definition of the data. These aspects are often addressed together, but historically they evolved quite separately, Methods of data storage and retrieval evolved from the inadequacies of serially processing very large files and have resulted in what we now understand to be a database management system (DBMS). Applying the fourth generation criteria (&tat rather than how) excludes DBMS that require an understanding of chains and pointers. Thus Codasyl standards relate to third generation products. Relational DBMS, which require only an understanding of the data, are fourth generation products, but some are not very user friendly. Defining a report in terms of projecls and joins is little better than navigating a database by pointers as all that has been achieved is the trading of computer expertise for expertise in relational albegra. The definition of data has only recently moved from ‘paper’ into the machine with the arrival of data dictionaries and meta data languages. From the discussion so far it can be seen that data must be defined to the
24
1. computer if it is to adequately perform the how part of the system building. The data dictionary should be in the same style as that described above, which replaced explicit data definitions in programs. Additionally, the dictionary should document the relationships between data items and hold additional details covering their
use and definition. The dictionary dictates the structure of the database and its use; it is a further development of the third generation database schema.
Hardware management The organization
of the equipment
in
data processing
Environ-beatproducts
l
l l
resolution of contentions caused by concurrent processes the man/machine interface the amount of res0urc.e required
For the nonIl3Mand small system user Oracle Oracle is available for DEC, DG and Unix based systems. As Oracle is implemented as a number of routines written in the c programming language, complemented by a number of routines in the assembler of the target machine, Oracle is relatively easy to port onto new machines. Adabas (VMS) Th& is a version of Adabas for the DEC Vax rahge of computers. It does not have all the facilities of the IBM version but it is still one of the most comprehensive systems avaiiabie. M&Her Mimer was developed in Sweden and is marketed in the UK by Savant E&erprises. Mimer is interesting as it approaches the problem from a different angle. The SDE incorporates all the normal features, and s &p&cations can be built using an interpretive application generator. Once complete, applicatians can be translated into either FORTRAN or COBOL for my pget
machine. Mimer ity is unrivalled..
will run on many
different
mac&es
and its
i&mdata provicks an advanced and user friendly SDE, based on ROMt DBMS and operating system software. The ALL (Applications Liberator) system takes full advantage of the hardware architeca ‘state-of-the-an product,
l&-%x&m
)
&$I.+is pursuing a si&r line, with further developments of the powerful WS equipment expected in the coming months.
a fourth generation SDE poses special problems because only the computer should be concerned with the deployment of resources, but this tends to work against their economic use. of SDEs are availand this reflects the complexity of the single-user
A large number
able for micros lower
~0126 no 9
november
1984
environment, where the typical multiuser mainframe problems either do not exist or exist at a largely insignificant level. The micro user is also assured of a large amount of dedicated processing power. Issues to be addressed are: response times data integrity
Performance m these area\ is dictated by bon well the design of the DBhiS ‘md ‘I‘P momior match the envisaged dpplications Cnvironmen!. Somc suppliers of‘ mair:framc %;I_ optimum hardware SDES ensure management by providine their own TP monitors and driving the operatmg system directlv, cutt:ng out the overhead of communication between several independent item\ of system software t and saving license charges 1. However, at the end of the day it is sensible to expect thar a 4GL SDE will be fairly demanding in computer power.
Products
available
For those interested in either purchasing an SDE or finding out more about the benefits obtained through the use of an SDE, a brief (and not exhaustive‘, list of products is given in the box.
How to buy As SDE vendors promote the productivity gains to be achieved through the use of their products, it is essential to call their bluff and submit their products to a small benchmark test. All that is required is a minimal set of data entry and update screens, a few online enquiries, a report or two and a degree of genuine data processing. Selection of an SDE without hands-on experience is not recommended. Another benefit of a benchmark is that the strength and depth of the vendor’s support organization can be assessed. If presales assistance is not readily forthcoming, the chances of adequate postsales support are slim. If you are new to the fourth generation scene, the assistance of an experienced consultant is recommended. 0 Dara L.ogic Ltd, Westway House, 320 Ruislip Road East. Greenford. IMiddxL’B6 9BH, UK.
25
I
n our first article (Data Processing, September 1984) we discussed two approaches to the design of a system using fourth generation techniques. The ‘bones’ of a methodology for building systems quickly were also introduced. In this article we take a break from methodology to describe what features and facilities are necessary before a set of products can justifiably be called a System Development Environment (SDE). Several products of interest are listed and advice on selecting an SDE is given.
Model system development environment An SDE has several components: a language for expressing an application and a means of communicating that language to the computer, diagnostic aids to identify errors, a means of organizing data for the application, a means of controlling the hardware to perform the application. Abstract: This second article on fourth generation system building describes the features necessaryfor a set qfproducts to constitutea viable systemdevelopment environment (SDE). The requirementsfor the fburth generation language, diagnostics, database management and hardware management are described. Several products of interestto thosepurchasing an SDE or wishing to learn more about thefourth generation language scene are listed and some advice on selection is given. Keywords: data processing, systemdesign, fourth generation techniques. Cohn Brooks is a managing John Smith is the manager .\dvanced DBMS group.
~0126 no 9
november
consultant and of Data Logic’s
1984
Each of these components has evolved through successive generations and most are now somewhere between third and fifth generations. Some manufacturers not able to offer the whole environment refer to parts of it as if they were the whole, the most common being the fourth generation language (4GL). Whilst each component is individually valuable, that usefulness is amplified greatly when all components are in place and well integrated. The overiding characteristic of the fourth generation is an emphasis on the requirements of the application and much less emphasis on the methods of achieving it; the what rather than the how.
Ideally, a full screen editor with natural insert/delete functions on the keyboard and an embedded compile/ trace command should be available. The improvement in productivity gained by these methods is as dramatic as that achieved in business through the use of the telephone rather than the letter. The terminal/ screen facility should be easy to use (not require 40 lines of JCL to signon) and be free of computer-oriented syntax such as starting each command with ii. (The telephone would not be nearly so useful if to use it one had to speak in Latin.) Several products are offered to completely satisfy the communication requirements. These are: screen painter -
Fourth generation language The language used to communicate with the computer should be devoid of all constructs pertaining to hardware, such as bytes, blocks, binary coded decimal etc., but be clear and concise. It should be English-based such that its purpose can be undernoncomputer-oriented stood by people. The functionality should be high enough to make explicit looping constructs unnecessary but still provide sufficient flexibility to describe most functions without contrived expressions. (Clearly COBOL is not of this generation.) Traditional communication between man and machine has been based upon some form of batch media such as cards, paper tape, or the electronic equivalent. Fourth generation communication should be interactive and conversational, in the style of screen-based interpretive BASIC.
0011-684X/84/090023-03$03.00
0
1984 Butterworth
co physically draw a screen, the computer accepting it and turning it into code, data dictionary - to free the programmer from having to think in terms of record structures, and to allow all data definitions to be referenced by a single entry point, the data item name, report generator to specify the content and presentation of reports, full screen editor - to accept commands for conversing with the computer and to ensure that the interpretations made by the machine are those the programmer intended. Ideally all these should appear in the same style and with the same commands as the 4GL itself.
Diagnostic
aids
Diagnostic aids and error messages should be readily understandable, ie
& Co (Publishers)
Ltd
23
not memory dumps of many pages of hexadecimal. Syntax and data errors should be detected at the time of entry and indicated by inverse video or the like. The diagnostics/trace facility need be no more than an ability to monitor the value of elements at certain points. The whole point of fourth generation environments is that the methods used by the computer should be hidden from the programmer, so that diagnostics are really no more than a means of confirming that one is achieving one’s intentions. When the diaglogue between computer and programmer is conducted at the natural thinking speed of the programmer, the concept of prototyping becomes a reality.
Data management Data management embraces both the way data is stored within the system and the definition of the data. These aspects are often addressed together, but historically they evolved quite separately, Methods of data storage and retrieval evolved from the inadequacies of serially processing very large files and have resulted in what we now understand to be a database management system (DBMS). Applying the fourth generation criteria (&tat rather than how) excludes DBMS that require an understanding of chains and pointers. Thus Codasyl standards relate to third generation products. Relational DBMS, which require only an understanding of the data, are fourth generation products, but some are not very user friendly. Defining a report in terms of projecls and joins is little better than navigating a database by pointers as all that has been achieved is the trading of computer expertise for expertise in relational albegra. The definition of data has only recently moved from ‘paper’ into the machine with the arrival of data dictionaries and meta data languages. From the discussion so far it can be seen that data must be defined to the
24
1. computer if it is to adequately perform the how part of the system building. The data dictionary should be in the same style as that described above, which replaced explicit data definitions in programs. Additionally, the dictionary should document the relationships between data items and hold additional details covering their
use and definition. The dictionary dictates the structure of the database and its use; it is a further development of the third generation database schema.
Hardware management The organization
of the equipment
in
data processing
Environ-beatproducts
l
l l
resolution of contentions caused by concurrent processes the man/machine interface the amount of res0urc.e required
For the nonIl3Mand small system user Oracle Oracle is available for DEC, DG and Unix based systems. As Oracle is implemented as a number of routines written in the c programming language, complemented by a number of routines in the assembler of the target machine, Oracle is relatively easy to port onto new machines. Adabas (VMS) Th& is a version of Adabas for the DEC Vax rahge of computers. It does not have all the facilities of the IBM version but it is still one of the most comprehensive systems avaiiabie. M&Her Mimer was developed in Sweden and is marketed in the UK by Savant E&erprises. Mimer is interesting as it approaches the problem from a different angle. The SDE incorporates all the normal features, and s &p&cations can be built using an interpretive application generator. Once complete, applicatians can be translated into either FORTRAN or COBOL for my pget
machine. Mimer ity is unrivalled..
will run on many
different
mac&es
and its
i&mdata provicks an advanced and user friendly SDE, based on ROMt DBMS and operating system software. The ALL (Applications Liberator) system takes full advantage of the hardware architeca ‘state-of-the-an product,
l&-%x&m
)
&$I.+is pursuing a si&r line, with further developments of the powerful WS equipment expected in the coming months.
a fourth generation SDE poses special problems because only the computer should be concerned with the deployment of resources, but this tends to work against their economic use. of SDEs are availand this reflects the complexity of the single-user
A large number
able for micros lower
~0126 no 9
november
1984
environment, where the typical multiuser mainframe problems either do not exist or exist at a largely insignificant level. The micro user is also assured of a large amount of dedicated processing power. Issues to be addressed are: response times data integrity
Performance m these area\ is dictated by bon well the design of the DBhiS ‘md ‘I‘P momior match the envisaged dpplications Cnvironmen!. Somc suppliers of‘ mair:framc %;I_ optimum hardware SDES ensure management by providine their own TP monitors and driving the operatmg system directlv, cutt:ng out the overhead of communication between several independent item\ of system software t and saving license charges 1. However, at the end of the day it is sensible to expect thar a 4GL SDE will be fairly demanding in computer power.
Products
available
For those interested in either purchasing an SDE or finding out more about the benefits obtained through the use of an SDE, a brief (and not exhaustive‘, list of products is given in the box.
How to buy As SDE vendors promote the productivity gains to be achieved through the use of their products, it is essential to call their bluff and submit their products to a small benchmark test. All that is required is a minimal set of data entry and update screens, a few online enquiries, a report or two and a degree of genuine data processing. Selection of an SDE without hands-on experience is not recommended. Another benefit of a benchmark is that the strength and depth of the vendor’s support organization can be assessed. If presales assistance is not readily forthcoming, the chances of adequate postsales support are slim. If you are new to the fourth generation scene, the assistance of an experienced consultant is recommended. 0 Dara L.ogic Ltd, Westway House, 320 Ruislip Road East. Greenford. IMiddxL’B6 9BH, UK.
25