Subject: Survey report

From: Surekha Ghantasala <[email-masked]>
Date: Fri, 27 Jan 1995 11:07:05 -0800 (PST)

SUMMARY OF E-MAIL RESPONSES:

The survey on the usage of LOTOS based on the e-mal responses I got from several LOTOS users all over the world is as follows:

The question asked on the survey are as follows:

1.Why did you select LOTOS as your specification language?
2.What are the applications you found in LOTOS that were better than other specification Languages?
3.What are the advantages you found?
4.What are the disadvantages/limitations you found in this language?
5.What is your personal opinion about LOTOS so far and what would you like to see being included in future?

Responses I got for the above questions are as follows:

Reasons for selecting LOTOS as a specification language:

1.precisely defined syntax and semantics.
2.Good applicability to many real-life problems.
3.It is an International Standard.
4.Useful tools developed all over the world.
5.LOTOS applications are more abstract than Estelle and SDL.
6.LOTOS uses synchronous foundation that allows formal reasoning.
7.LOTOS uses synchronous communication.
8.It has strong mathematical foundation that allows fromal reasoning.
9.Verification, analysis, testing and refinement, synthesis and validation can be easily mechanized.
10.It has a powerful set of operators that allows the construction of very concise specs, with different levels of abstraction and in different styles.
(constraint oriented, resource-oriented, status-oriented, monolithic styles)
11.Formal semantics are defined in LOTOS.
12.It has a well defined design methodology supported with a set of tools that covers almost all the phase of the software life cycle.
13.Specifications can be executable which allows rapid prototyping.
14.In the implementation phase "C code" can be generated automatically from LOTOS specifications.
15.LOTOS has good semantical abstraction capabilities which enable a proper design approach based on stepwise refinement.

Advantages of LOTOS:

1.The main competition is SDL, which is much less precisely defined and much more clumsy to use.
2.LOTOS is abstract, has concise specs, has a very formal model, has tool support, has many specifications already done.
3.It has shown to cover many distributed applications.
4.LOTOS is able to capture a relatively complex temporal pattern of events, involving nondeterminism, concurrency and synchronization, by means of small algebraic expression built by using few conceptually simple operators.
5.Realistic communication protocol can be described in LOTOS, whereas descriptions in Estelle and SDL proved capable of expressing oly a subset of the entities.
6.LOTOS is excellent for describing concurrent systems behaviour.
7.If LOTOS and Z were compared for describing an architecture for distributed systems it was found that LOTOS has much wider capabilities than Z.
8.Behavioural aspects are very relevant, even predominent.

Disadvantages of LOTOS:

1.LOTOS is difficult ot learn, especially the data part.  As there are no predefined data types one must always construct all the operations and related equations for any type.
2.It does not support real-time specs.
3.It has problems in specifying distributed systems - it does not support dynamic reconfiguration which is an important
nteresting characteristics in those systems.
4.Its model of concurrency is based in the known "interleaved semantics" in which an observer can see one event a time and concurrency is represented sequentially.  Many models based on "true concurrency semantics" have been proposed although it seems that none of them will be present in the next version of LOTOS.  This is a weak point in represent distributed processing where in many situations things happen simultaneously and no ordering between events can be established.
5.Derivation of efficient implementations from a given specificatin is not clear
6.Modularity could be improved.
7.LOTOS has weak data specification mechanisms and cannot express time explicitly.
8.Inheritance representation in LOTOS is not perfect.  Polymorphism and inheritaance are not supported.  It would be much better if LOTOS supported OO constructs directly.

Applications of LOTOS:

1.Protocol specification.
2.Specification of Data communication systems.
3.Specification of Tele communication systems.
4.Specification of Hardware systems.
5.Specification Distributed Systems.
6.Application to the specification of security mechanisms.
7.LOTOS can be used as a graphical language for the formal specification of concurrent systems.
8.Specification of multimedia applications - lipsync protocol.
9.LOTOS has validation techniques on sourcelanguage level so that one is able to analyse ahbstract specs and get useful feedback without going through the burden of building an implementation and finding that the design is wrong.
10.LOTOS can be used to represent database oriented problems.

Future Extension:

1.Better data typing facilities, modules, and behavioural extensions have to be included in the future
2.Time and probability aspects and dynamic gate configurations will prove to be highly useful if included in future.
3."Shorthand"ed mechanism of specifying gates is needed which would make LOTOS an easily writable and readable language at the same time.
4.Better safety requirements are needed for a more formal design.
5.Data structures__ high level as well as the basic ones like booleans and integers are required.
6.Distinction between operationally specified ADTs and axiomatically specified ADTs is needed.
7.OO constructs need to be included.
8.LOTOS is a relatively hard language to be taught to engineers and the basic need to step outside the language framework and work with logic for properties is extremely necessary.

People who responded to the survey:

Name                           e-mail
----                           -----
Juan Quemada                  [email-masked]
Richard Sinnott               [email-masked]
Richard H.Carver              [email-masked]
Henk Eertink                  [email-masked]
Luigi Logrippo                [email-masked]
Tommaso Bolognesi             [email-masked]
Harro Kremer                  [email-masked]
Ana Moreira                   [email-masked]
Ken Turner                    [email-masked]
Andreas Vogel                 [email-masked]
Jeroen van de Lagemaat        [email-masked]
Gualberto Rabay Filho         [email-masked]
  
-- 
it is a miracle that curiosity survives formal education. -Albert Einstein
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Surekha Ghantasala                 |   e-mail:[email-masked]
Department of Computer Science     |   tel.  :(208) 885-5562 
University of Idaho                |
Moscow, ID 83843, USA              |
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