FDTFoil no 1

On Methodologyfrom Domain to System Descriptions

byRolv Bræk

NTNU

Workshop on Philosophy and Applicablitiy of Formal Languages

Geneve 15. September 2001

FDTFoil no 2

Topics

Methods and MethodologyLanguages for system modelling

UML, MSC, SDL, ASN.1, TTCNApproachesDomain and Architecture issues

Methods and MethodologyLanguages for system modelling

UML, MSC, SDL, ASN.1, TTCNApproachesDomain and Architecture issues

FDTFoil 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

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!

FDTFoil no 4

The systems engineering cycle/spiral

Domain

Systemdescriptions

DevelopInstall

SystemManufacture

Domaindescriptions

Model

has needs

quality =

satisfaction of needs

FDTFoil 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.

Domaindescriptions

Systemdescriptions

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?

FDTFoil 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

Realisation

sof tware electronics mechanics

Deployment

Functionality

Reality

Descriptions Structure Behaviour

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Realisation

sof tware electronics mechanics

Deployment

Functionality

Descriptions Structure Behaviour

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

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Realisation

sof tware electronics mechanics

Deployment

Functionality

Descriptions Structure Behaviour

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)

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Realisation

sof tware electronics mechanics

Deployment

Functionality

Descriptions Structure Behaviour

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.

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RM-ODP viewpoints

• Enterprise• Enterprise

Realisation

sof tware electronics mechanics

Deployment

Functionality

Domain Descriptions Structure Behaviour

Realisation

sof tware electronics mechanics

Deployment

Functionality

System Descriptions Structure Behaviour

• Information

• Computation

• Information

• Computation

• Engineering

• Technology

• Engineering

• Technology

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Objects and properties

Realisation sof tware electronics mechanics

Deployment

Functionality (Structure Behaviour)

Descriptions

Performance … Dependability ….

Objects Properties

Tests… Measurements

Services …

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General description pattern

objects properties

context

content

•••component types

(follow same pattern)

•••

•••

•••

•••

design

specification

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Coverage of the ITU-T languages and UML

Class, State- Machines

UseCase, Sequence, Collaboration,OCL, Activity

Deployment, Component, Class

Sequence, Collaboration, OCL

Sequence, Collaboration, OCL

Objects Properties

Realisation

Deployment

Functionality

UMLsdl, SDL, ASN.1 ODL

MSC,

TTCN, MSC

CHILL, ASN.1

TTCN, MSC

Objects Properties

I TU-T UML

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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.

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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

FDTFoil no 16

Which is your preferred approach?

Elabortion approach

Translation approach

Functionality

Deployment

Realisation

Initial development

New service

New realisation

Effort spent

Functionality

Deployment

Realisation

Implementation oriented

Implementation oriented

Design orientedDesign oriented

The UML approachThe UML approach

The ITU-T approachThe ITU-T approach

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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.

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Macro Methodology

Develop System

Model Domain

Produce System

Install System

Domain

system

Domaindescription

Systemdescription

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Develop system

Specify functionality

Design deployment

Specify realisation and tests

Design functionality

Specify deployment

Realise and test

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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!

FDTFoil no 21

Some trends

Functionality

•More focus on classes, associations and inheritance

•More data and object-action-orientation

•Horizontal integration/interfacing with legacy and 3rd 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 3rd 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

FDTFoil 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