1. FDT Foil no 1 On Methodology from Domain to System Descriptions by Rolv Bræk NTNU Workshop on Philosophy and Applicablitiy of Formal Languages Geneve 15. September 2001

2. FDT Foil no 2 Topics Methods and Methodology Languages for system modelling UML, MSC, SDL, ASN.1, TTCN Approaches Domain and Architecture issues Methods and Methodology Languages for system modelling UML, MSC, SDL, ASN.1, TTCN Approaches Domain and Architecture issues

3. FDT Foil no 3 Methodology and Methods A methodology is a system of methods and principles. A method defines a systematic way to produce given results. A methodology is a system of methods and principles. A method defines a systematic way to produce given results. Which is the way to quality results? Methods provide a kind of “roadmap” with guidelines and rules The main results of systems engineering are target systems and descriptions expressed using languages. Without any methods there would be no systems engineering discipline! The main results of systems engineering are target systems and descriptions expressed using languages. Without any methods there would be no systems engineering discipline!

4. FDT Foil no 4 The systems engineering cycle/spiral Domain System descriptions Develop Install System Manufacture Domain descriptions Model has needs quality = satisfaction of needs

5. FDT Foil no 5 How to describe complex realities? Combine two golden rules: Separation of concerns. Identify aspects that are as independent as possible and describe them separately. Conceptual abstraction. Replace low level concepts representing technical detail by more abstract concepts better suited to describe and study some aspects, i.e. by some kind of model. Combine two golden rules: Separation of concerns. Identify aspects that are as independent as possible and describe them separately. Conceptual abstraction. Replace low level concepts representing technical detail by more abstract concepts better suited to describe and study some aspects, i.e. by some kind of model. Domain descriptions System descriptions First we separate domain from system; then what to separate? Can user aspects be separated from realisation aspects? First we separate domain from system; then what to separate? Can user aspects be separated from realisation aspects?

6. FDT Foil no 6 The main separations Since the purpose of ICT systems is to provide functionality (perform logical behaviour and handle information); and the functionality may be realised in many ways: separate functionality from realisation describe the deployment mapping separately Since the purpose of ICT systems is to provide functionality (perform logical behaviour and handle information); and the functionality may be realised in many ways: separate functionality from realisation describe the deployment mapping separately

7. FDT Foil no 7 Functionality Is a conceptual abstraction intended to describes logical behaviour and information as clearly as possible It should enable users and developers: to communicate precisely to establish a common understanding to ensure that the descriptions of functionality correctly represents the existing domain and/or the system being developed It provides a view where the system may be seen as a whole, independently of realisation and technology Is normally described in terms of structures of active and passive objects with associated object behaviours Is a conceptual abstraction intended to describes logical behaviour and information as clearly as possible It should enable users and developers: to communicate precisely to establish a common understanding to ensure that the descriptions of functionality correctly represents the existing domain and/or the system being developed It provides a view where the system may be seen as a whole, independently of realisation and technology Is normally described in terms of structures of active and passive objects with associated object behaviours

8. FDT Foil no 8 Realisation Is a precise technical definition of the realisation in terms of the technologies used, such as mechanics, electronics and software Is necessary to actually produce a working system The choice of realisation depends on what properties are desired from the realisation itself (often called non-functional properties) Is a precise technical definition of the realisation in terms of the technologies used, such as mechanics, electronics and software Is necessary to actually produce a working system The choice of realisation depends on what properties are desired from the realisation itself (often called non-functional properties)

9. FDT Foil no 9 Deployment and configuration descriptions Describes aspects that come in addition to the functionality, such as distribution, hardware/software allocation and use of middleware and defines a mapping between functionality and realisation by: describing the realisation (the physical system) on a high level identifying the technologies used describing how and where the functionality is realised describes configurations Serves together with functionality as the main documentation. Describes aspects that come in addition to the functionality, such as distribution, hardware/software allocation and use of middleware and defines a mapping between functionality and realisation by: describing the realisation (the physical system) on a high level identifying the technologies used describing how and where the functionality is realised describes configurations Serves together with functionality as the main documentation. –configuration data; –priorities; –versions; –etc.

10. FDT Foil no 10 RM-ODP viewpoints Enterprise Information Computation Information Computation Engineering Technology Engineering Technology

11. FDT Foil no 11 Objects and properties

12. FDT Foil no 12 General description pattern objects properties context content component types (follow same pattern) design specification

13. FDT Foil no 13 Coverage of the ITU-T languages and UML

14. FDT Foil no 14 Two main approaches: Elaboration approach: the functionality description is incomplete and expressed using languages with incomplete semantics => the realisation description ends up as the only complete view of the system and the functionality description is not maintained Most UML use including the Rational Unified Process, RUP, follows the elaboration approach Translation approach: the functionality description is complete and expressed using languages with well-defined and realistic semantics => the functionality description is valid for the realisation, serve as documentation and is maintained Realisation is by (manual or automatic) translation of the functionality description. Deployment is orthogonal to the functionality (using the principle of distribution transparency). Most SDL use follow this approach. Elaboration approach: the functionality description is incomplete and expressed using languages with incomplete semantics => the realisation description ends up as the only complete view of the system and the functionality description is not maintained Most UML use including the Rational Unified Process, RUP, follows the elaboration approach Translation approach: the functionality description is complete and expressed using languages with well-defined and realistic semantics => the functionality description is valid for the realisation, serve as documentation and is maintained Realisation is by (manual or automatic) translation of the functionality description. Deployment is orthogonal to the functionality (using the principle of distribution transparency). Most SDL use follow this approach.

15. FDT Foil no 15 Quality assurance Techniques: Corrective techniques: defect detection, with subsequent correction, e.g. formal verification, simulation, testing and inspection. Constructive techniques: defect avoidance, i.e. to avoid introducing errors in the first place, e.g. synthesis and automatic program generation, languages and methods that help to improve understanding and communication. Aspects Quality of functionality: related to the main purposes, i.e. the needs of the domain. Quality of realisation, i.e. way the functionality is realised. Techniques: Corrective techniques: defect detection, with subsequent correction, e.g. formal verification, simulation, testing and inspection. Constructive techniques: defect avoidance, i.e. to avoid introducing errors in the first place, e.g. synthesis and automatic program generation, languages and methods that help to improve understanding and communication. Aspects Quality of functionality: related to the main purposes, i.e. the needs of the domain. Quality of realisation, i.e. way the functionality is realised. the most effective separated in the translation approach

16. FDT Foil no 16 Which is your preferred approach? Implementation oriented Design oriented The UML approach The ITU-T approach

17. FDT Foil no 17 Languages for functionality should Support human comprehension so that human beings may fully understand and communicate precisely about the functionality => build on concepts that are suitable, well defined, and easy to understand. Provide analytical possibilities so that one may reason about behaviours in order to compare systems, to validate interfaces, and to verify properties. => have a semantic foundation suitable for analysis. Be realistic. Although overlooked in many cases, this requirement is essential for two main reasons: 1.That it shall be possible to implement the functionality 2.That the description of the functionality can serve as valid documentation of the real system. => build on concepts that can be effectively realised in the real world. Support human comprehension so that human beings may fully understand and communicate precisely about the functionality => build on concepts that are suitable, well defined, and easy to understand. Provide analytical possibilities so that one may reason about behaviours in order to compare systems, to validate interfaces, and to verify properties. => have a semantic foundation suitable for analysis. Be realistic. Although overlooked in many cases, this requirement is essential for two main reasons: 1.That it shall be possible to implement the functionality 2.That the description of the functionality can serve as valid documentation of the real system. => build on concepts that can be effectively realised in the real world.

18. FDT Foil no 18 Macro Methodology

19. FDT Foil no 19 Develop system

20. FDT Foil no 20 Features of existing telematics systems Functionality: Highly parallel behaviour Time dependency/real time Sessions – stateful behaviour Object interaction orientation Robust Highly complex Contention for shared resources A lot of operation and maintenance support Adaptability to new contexts and services (partly on-the-fly) Realisation: Physical distribution High performance Scalability Replication/fault tolerance Functionality: Highly parallel behaviour Time dependency/real time Sessions – stateful behaviour Object interaction orientation Robust Highly complex Contention for shared resources A lot of operation and maintenance support Adaptability to new contexts and services (partly on-the-fly) Realisation: Physical distribution High performance Scalability Replication/fault tolerance Adressed by CHILL Adressed by SDL, MSC, TTCN and ASN.1 Quality first!

21. FDT Foil no 21 Some trends Functionality More focus on classes, associations and inheritance More data and object-action-orientation Horizontal integration/interfacing with legacy and 3 rd party More hacker mentality (and quality problems) The classical features remain unchanged! Realisation/technology IP connectivity Web based access Middleware 3rd party service platforms More Java and Mobile code Functionality More focus on classes, associations and inheritance More data and object-action-orientation Horizontal integration/interfacing with legacy and 3 rd party More hacker mentality (and quality problems) The classical features remain unchanged! Realisation/technology IP connectivity Web based access Middleware 3rd party service platforms More Java and Mobile code functionality before quality Addressed by UML Addressed by combining and aligning UML and ITU-T languages

22. FDT Foil no 22 Is it true that: specifications describe implementations? no – they specify properties and functionality, i.e. another view specification languages are modeling approaches? no – they are just languages, but may be used for modeling specification languages are description techniques? yes/no – they may be used to describe a valid view specifications describe implementations? no – they specify properties and functionality, i.e. another view specification languages are modeling approaches? no – they are just languages, but may be used for modeling specification languages are description techniques? yes/no – they may be used to describe a valid view