NTNU Dept of Telematics and SINTEF Telecom and Informatics, Norway Experiences in teaching, learning and introductory use of description techniques Richard Sanders NTNU Dept of Telematics and SINTEF Telecom and Informatics, Norway

Background Description languages taught by Rolv Bræk at university level since the 1980s My own lecturing at university level the last 3 years Holding courses for academics and industry for many years Experience in using the languages since 1985 Use of languages in development methodologies (TIMe - The Integrated Method: www.sintef.no/time)

Learning objectives Seeing the power of abstraction Understanding concepts: state machines, parallelism, synchronisation and asynchronous messages Learning the art of system design of real-time systems Knowing how to analyse designs Managing to turn designs into working systems

Techniques taught and used System modelling with emphasis on logical behaviour Languages for system modelling: UML, MSC, SDL, ASN.1, TTCN, Process Algebra Methods for system modelling Methodology for systems engineering TIMe, Verification and validation Prologue: First let us look at the aspects which must be covered in order to obtain reuse of software Purpose: Reuse is more than just using Points: Design for reuse has to do with the anticipation of future uses Design with reuse has to do with adaptation to existing software Classification is the art of database management and of librarian skills Organization is rewarding, motivating, putting people together, recognition. In many cases organizations oppose reuse.

TIMe at a glance Problem domain problem domain product family UML C++, Java, ... Unified Modeling Language (UML) problem domain Specification product needs product family problems, ideas Application design Framework design Architecture design Implementation Instance configuration system instance needs instance needs Points: First note the three areas of concern: domain, family, instance. There are good reasons for this: The domain helps to understand the problem and to communicate better A company wants to produce many system instances as cost-effectively as possible, this is done in the instance area. In the family area we develop the design and prepare for instantiation. We also maintain and evolve here. This is the core product base - the capital of a company. (some companies do not have a clear picture of this capital, only a series of system instances) Then note the languages. Note that languages are like notes. Knowing notes does not make you a good composer. Knowing the languages does not make you a good designer. Then the parts of the family, and in particular the division into application framework and architecture. Like separating the melody from the arrangement and the orchestra in music: they give you a separation between the essential and the accidental. Analogy: Application = melody; Framework = arrangement; Architecture = orchestra Market needs needs System satisfied needs needs

What parts of the languages University courses: UML: Focus on object modelling MSC: Interaction models SDL: Basic SDL, “OO-SDL”, a selected coverage ASN.1: A brief intro Process Algebra: Introduction (more at Ph.D. level) TTCN: Testing principles and language Industry courses: UML, MSC and SDL - a selected coverage

Use of tools University courses: Students perform compulsory assignments in groups Telelogic TAU for UML, SDL and MSC work Design Simulation Simple validation (MSC against SDL) Implementation platforms JavaFrame from Ericsson Norway: a thread-safe Java environment for FSMs No tools for TTCN

Experiences The languages and tools help to reach the learning goals Students understand parallelism! The languages are good for modelling and analysis An understandable transition to implementation is possible The different languages “sort of” fit together Good tool support Limited availability of adequate teaching material (books) Courses use a selection from books and articles Complex and large languages (esp. UML and SDL) Evolving languages Tools linger Work needed to keep material up-to-date

The Future The selection of languages and tools is evaluated yearly Transition away from SDL/MSC to UML? Not presently If UML 2.0 is “good enough” (= expression, tools, books): probably!