1. 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

2. 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:

3. 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

4. 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.

5. 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

6. 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

7. 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

8. 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

9. 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!