Towards a formal representation of EMS

)< noun phrase>/

phrase>

(

)
phrase>

: : =

: : = The : : = general : : = manager C-singular verb> : : = spoke : : = loudly

While the BNF grammar illustrated in Example 1 would hardly be sufficient to recognize all sentences in English, or to generate all valid English sentences, it describes a subset of English grammar. The symbol ::= in the example rules indicates that the item to the left can be decomposed into the items to the right. One notes that the names of parts of the sentence such as noun, verb phrase, etc, are enclosed in brackets < > to represent variables whose values are sequences of symbols. The words (or sequences of symbols) are known as ‘terminals’. The relationship that exists between variables and terminals in these rules are called ‘productions’. The symbol / represents the concept OR. For example in the third rule, one might express this as: A noun phase consists of an adjective followed by another noun phrase, OR of an adjective followed by a single noun. The round brackets indicate that a particular symbol is optional. The curly brackets (which were not used in Example 1) can also be used in BNF to denote the possible repetition of the enclosed variable or terminal symbols zero or more times. For example, the syntax for the generation or recognition of an unsigned integer might be as in Example 2. Example

2. BNF representation

integer>

of an unsigned

integer.

: : = < digit > {}

: : = O/I /2/3/4/5/6/7/6/9

One final concept in the specifications of grammars is the ‘start symbol’. This is a variable that is distinguished by the fact that it generates exactly those strings of terminals that are in the language. In the first example, was the start symbol. Formally, we denote a grammar by the variables, terminals, productions, and the start symbol. An example of the use of BNF to describe aspects of a particular EMS may give a flavour for the generalized representation of EMS we have in mind. PLANET, a computer conferencing system offered by Infomedia Corporation, allows two types of entries: the public entry (available to all authorized participants in a conference) and the private entry (available only to the recipient of the message). A BNF representation of the production (rules) governing the structure of a public entry are shown in Example 3. A sample entry generated by these rules is shown in Example 4. TELECOMMUNICATIONS

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Towardsa formal representationof EMS Example

3. BNF representation

of a PLANET

entry.

: : =

< text>

: : =

: : = [] : : = /(ORG)/ anonymous : : = <,time > : : = - - : : = : : : = AM/PM : : = j 1 Example

4. Sample

PLANET

entry generated

by rules of Example

3.

Miller 22-Ott-79 2:43 PM Regarding the BNF Description A full description of the BNF for an entry would specify the alphabet from which one could choose alphanumeric characters, as well as the integer range for days, years, hours, and minutes and the list of names for the months. [34]

Structure andflow of communication Graph theory and network theory are branches of mathematics which have grown greatly in the last half century, and have had significant roles in the development of telecommunications networks and in the discipline of structured programming and program testing and measurement. The networks studied in these disciplines are abstractions of real systems. The analysis is concerned with centres (called nodes) and the links between the centre (called arcs), and one or more arc functions which are arrays of numbers giving some information about the arcs (such as length, time to traverse, capacity, and so on). Network theory is used as a framework for the study of those properties of systems which depend both on form and arc function. Examples include the largest possible flow between two nodes, the capacity of a certain node that is required to provide a certain ‘average flow’ through it, and other problems which depend on the number of nodes, the number of paths between the nodes, the arrangement of paths, and the capacity of the arcs involved to carry the flow. Network theory has become dependent on theories developed in the operation research disciplines, such as queuing theory, and problems of inventory or resources, scheduling and routing, replacement and maintenance, search problems etc. Many of the properties of real systems which are of interest depend only on form. Graph theory concerns itself only with the form of a system, that is, the number of nodes, and the number and arrangement of arcs. Just as networks are abstraction of real systems, graphs can be looked upon as abstractions of networks. Graph theory has been used extensively in the last 15 years to develop metrics and performance measures of computer programs in an effort to develop a discipline of ‘structured’ programming and software engineering. In an EMS theory, graphs can be used to study the organization of group interaction both from a performance standpoint and from a human standpoint. Social interaction tends to develop along certain lines or paths. One can construct a picture of social interaction that reflects the pattern of exchanges among people in a community of subscribers to an EMS. The pattern of interpersonal relations is called ‘group structure’. A particular structure may be relatively enduring or emerge only briefly, TELECOMMUNICATIONS

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Towards a formal representation of EMS

I2 M. Glanzer and R. Glaser, Techniques for the study of group structure and behaviour: I. Analysis of structure’, Psychological Bulletin, Vol 56, pp 317332, 1959: C. Flament. Aoolications of Graph Theory to G;oui Structure, Prentice-Hall, Englewood Cliffs, NJ, 1963: J.H. Davis, ‘The preliminary analysis of emergent group structure’, Psychometrika, Vol 28, pp 189-198, 1963; F. Harary, R.Z. Norman, and 2. Cartwright, Structural Models: An Introduction to the Theory of Directed Graphs. Wiley, New York, 1965; G. Lindzey and D. Byrne, ‘Measurement of social choice and interpersonal attractiveness’, in G. Lindrey and E. Aronson, eds, The Handbook of Social Psychology, Vol Ii. Addison-Wesley, Reading, MA, 1968, pp 452-525. ‘3 Op cit. Ref 9. ‘4 l-l. Legard and M. Marcotty, ‘A generalogy of control structures’, Commun Assoc Comput Mach, Vol 18, NoGember 1975, pp 629-639.

92

depending on a number of factors such as task demands, motivation and communication medium. All groups of communicating individuals display detectable structures that are important determinants of performance. Sociologists, anthropologists, and social psychologists studying the nature of groups have employed a bewildering array of definitions concerning such notions as ‘position ‘, ‘role’, ‘status’, and ‘connections among positions’. However, this state of affairs has led many theorists, especially those favouring an abstract mathematical treatment of structure, to employ the language and conceptual framework of graph theory in which group structure is simply a ‘set of elements’ among which there exists a ‘well-defined relation’. These elements and associated relations may be represented by a graph consisting of points (nodes) and lines (arcs), respectively.r2 The advantage of using graph theory in the study of group structure is the complement of tools available to represent graphs in a form manipulable by computers. Several different matrix representations have been devised to represent graphs on the basis of nodes being endpoints of arcs (incidence matrices), arcs comprising circuits in a graph (circuit matrices), and others. One particular kind of matrix has found great popularity in the study of group structure. This is the ‘sociomatrix’, in which the rows represent the sender or initiator of a communications act, while the columns represent the receiver. An entry in a sociomatrix can represent either the presence or absence of a relation, whether the relation is mutual, or whether it exists in one direction only. Furthermore, these matrices permit a number of analytical operations that can reveal implicit relationships among people, through analysis of the strength or frequency of a relation. These techniques have been used in the administration, facilitation and analysis of computer conferences.13 Another useful attribute of graphs (and networks) is that they are amenable to representing the control structure of a computer program; ie given a program, one can associate with it a directed graph that has unique entry and exit nodes. Each node in the graph corresponds to a series of operations in the program where the flow is sequential and the arcs correspond to branches-taken in the program. This graph is known as the program control graph.14 While the formal representation of EMS is not primarily concerned with the flow of control wihin a program, it is our view that the flow of control via the users-EMS interface can be represented, and thus analyzed through a similar type of graph-theoretic representation. Thus, we find the use of graph and network representations useful in showing the relationships between users of an EMS (the group structure), and in presenting the operation of an EMS (the control structure). The major value of graphs for representing and analyzing these forms of structure comes from their susceptibility to mathematical treatment. Interaction process analysis

As interpersonal and small group communication became the object of study for psychologists, sociologists and communication researchers in the 1940s and 195Os, several forms of systematic observation were developed to aid the construction of theories of communication behaviour. Two approaches were taken in these methodologies: (1) an observer was asked to classify into categories

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Towards a formal representation of EMS

the behaviour he witnessed, or (2) the observer was requested to assign a numerical index to that behaviour. In other words, the observer could count the frequency of occurrence of a specific kind of behaviour, or he could rate that behaviour on a scale. In the literature on teleconferencing, the second approach appears to have been used most often, either by outside observers or participant-observers, in attempts to elicit subjective evaluations or to compare some aspect of a particular medium to face-to-face and other media. One reason for the lack of a general theory of electronically mediated human communication is the inability of researchers to agree on a common system of categorization. The requirements of a category scheme can be abstracted from the structure (and, in some cases, the content) of categorization methods developed by Bales, Carr, Heyns, and Carter, to name a few.15 The characteristics that seem basic to the problem of developing and using a categorization scheme are exhaustiveness, inference, and the number of dimensions utilized. A category scheme must specify the boundaries of the behaviour it seeks to categorize, and then exhaustively classify all behaviour within that ‘universe’. In the case of human interaction via EMS, the categorization scheme must take into account the different forms of ‘utterances’ that will make a difference in the operation of functioning of the EMS system. In the case of the man-machine interface, the categorization scheme is made difficult by the need to distinguish the intent or the context of a message.

Representation

of EMS

In the previous sections we have introduced the tools for a representation of EMS which permit the characterization of events and data, the decomposition of these events and data into basic units, and the specification of sequences. The problem now becomes one of integrating them into a clear method of description. Our solution to this dilemma has been the development of a rather simple coding sheet. In a format analogous to programming forms found in almost every computer application, the sheet is organized into columns to be filled with: 0 0 0 0 0 ‘6R.F. Bales, interaction Process Analysis: A Method for the Study of Small Groups, Addison-Wesley. Reading, MA, 1950; L.J. Carr, ‘Experimental sociology: a preliminary note on theory and method’, Social Forces, Vol 8, 1929, pp 63-74; R.W. Heyns and Ft. Lippitt. ‘Systematic observational techniques’, in G. Lindzey, Handbook of Soci8l Psychology, Vol 1, Addison-Wesley, MA Reading, 1954, p 372; L. Carter, et 81, The relation of ratings in the categorizations and observation of group behavior’, Humen Relations, Vol4.1951, pp 239-254. TELECOMMUNICATIONS

A label designating the current state of the system; The high order event or datum to be decomposed; The operation(s) comprising this state; The restrictions or test which determine the next state; and, A label designating the next state to which the system passes.

Figure 1 presents a sample coding sheet. This format is useful for a number of reasons. First, it is amenable to a description of the EMS at its highest level, and then, using another sheet, allows the events or data elements to be broken down to their most fundamental units. Unlike other methods of description this sheet describes not only what action is taken, but also why it is being done, how it is being done, and when it is being done. Let us see how this coding sheet can be applied to a hypothetical message system which operates as follows. In the initial state, a user terminal is connected to the computer on which the message system operates. The user logs-in by giving the system a name or identifying code which is registered in a master list of valid users. In the next

POLICY June 1980

93

Towards a formal representation of EMS -_--_-

r---I----

--------------

I

WhJ7

I

II

I I

I I I

I

I

I

I

_+--__-------_---_-+--

I

1

------~-------~--~

-_------

T

I A I I ___l_-_-------_;----_--__---_ L LOG IN

REQUEST

’I

(IDENTIFIER)

(STRING)=
NOTIFY

I

I I I I c---a_---_-I

I I

Example

EMS

,

1

,

RESTRICTION

J_----,,---

__---

TEST RESULT

I STATF

+-------•-+-----!

1

CONNECT
------_

---~---_--__rN~,_I

--em-

1

OPERATION(S)

____________

LOGIN

,

sheet.

T--_----‘-----‘r_--_--

EVENT/DATUM

’

O

3

I

coding

I_--_A--_--___--_L--

I-----I--

INVALID)

*

of

-------a--

I-

STATE

I

(PASSWORD

HOW’

1.

-em

?

(ID INVALID)

i-_--_-__---+--__-__________~-_-__--_

Figure

I I

-----I---

I

l- ---

I I

‘f __-,

AUTHENTICATION

NOTIFY

I

____

(invalid identifier 1

--_--_--__-

1

ID U(i))

I

I I I

I

I I

I

I I ’ 7---l

I

I ’

I

L

--(invalid identiiier)

mm-I

’

I

4

I_--_

;

NOTIFY

I

REQUEST (PASSWORDD

I

INPUT

I I +--___-__-_-------

(ID INVALID)

---_-------A--------------,

-f I

AUTHENTICATION

~~~~~-~~~~~_~~~_____~~_~~_~~_

1

NOTIFY

I

I

’ I

l L-l_

’

I---_

I

(LASTMESSAGE

LEl

I

-------_--_

I

11

I

_--_

I

I

I

I

7

(COMMAND)

94

--

--,-__I I

7

1_______J_:_I I

I

U(i))=

I

1(STRING)

=

(STRING)

I

I

1 (LASTSEEN

INPUT

YES

-1-N2_-

I

‘##ALE

U(I)>

’

I

I

I

-_______l_-__-_---_-_,-_---

7

I

YES

,

YkS

I

Yts

+--_---_---_------l

__-_--__-_

I L

T -_--_

2.

I

’ -~_------~--__l

L__-__-_--_----~----_--_--_--_-~_-----_~:-_: I (NEW MESSAGE)

1

Figure

1 6

I

‘1

I

I3

I

I

1

WRITEMESSAGE

1----

-r-

uo0 1 1

-----------_--_

L_-_____-_-_____~-__z_--_~_______l-~~______l_q

, II 1 READ MESSACEISi +--L__-__-______; ___

(LASTMESSAGE

-----------

I

TEST

rI I C__-L__-_--_-__I I

YES

I

(LASTSEEN U(i)) = (LASTMESSACE U(i) + 1)

REQUEST

1

USER ii)) 7

“,I, + 1)

9 I __~_-__-__--_-~-_--_~__-_--__-_,______________-~_~“_____-l_I_~

I

=
I__--____--____

’

1 IDLE

II

i

--_--

. -+-__-

-_--_------_&----------_----

I

0

INVALID)

~----------_--PRlNT

7

(STRING)

, (LASTSFEN w)= -----

I +___~_~~_~_~~~__~_-~~-~~-~_~

I I

I-

(PASSWORD

UPDATE USER (9

A.--_-_--

’

L_______________~______ (STRING)

I I I_ ---_-----_--__-__________-----~--_--_~-~~-~--~--~

p__; 7 I- ---

I

Example

of coding

---_-_-_I___1

I I ~~_~~~~~~~~~~~~~~~~~~~~~~_~~~~~__~_~~-~~~~_~~, NOTIFY

I C-LOX L -_-__-____----Dlscormfn

sheet

I

I
applied

I

I

(END OF SESSION)

--------_-------_-

I

_--_--__-_--_-

I L

to a hypothetical

----_-----a----

high-level

EMS.

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I

Towards a formal representation of EMS

state, the user must authenticate himself by providing a password, which is associated with the identification in the master list. Having identified and authenticated his identity as a valid user of the system, the user is presented with all the messages he has received since his last use of the system. The messages are presented in the order in which they arrived, indicated by the sequence number associated with each message. After the last new message is transmitted to the user, the system goes into an idle state, and is receptive to command inputs from the user, or to the arrival of new messages. As long as the system is in this idle state, it will immediately print arriving messages as soon as they are received. The commands available to the user include the composition and transmittal of a message to a designated recipient, the retrieval of messages from his collection of messages already seen, and the ability to terminate the session with the EMS. Figure 2 presents the top level of the hypothetical EMS as it would be represented using the BNF formulation and the EMS coding sheet. To the standard BNF metalanguage, we have added the plus sign (+) as a means of representing concurrent processes. This is used in state 9 to denote that the system is simultaneously testing to see if there are new messages, and testing to see what command input is being provided by the user. This description of an imaginary EMS enables the description of the hierarchical arrangement of operations, the sequence of these operations and the protocols required for the interaction between the user and the EMS interface. A full description of the EMS would include subsequent pages describing the processes of writing a message and retrieving messages, as well as a full syntax description (written in BNF) to define the data elements and variables such as ‘LASTSEEN USER(i)‘.

Conclusion We have presented an overview of the dimensions that may lead to the formal representation of electronic message systems. By enumerating the features of an EMS along each dimension, it is possible to arrive at a complete model which designers and users will be able to manipulate. In turn, such models can be used to drive large-scale simulations of future EMS networks. At this point in our research, however, we are concerned with the validation of an initial descriptive scheme and coding method which appears to be applicable to a wide range of EMS in current usage. Since our project is continuing, we invite comments and suggestions from our readers.

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Towards a formal representation of EMS

Towards a formal representation of EMS

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