Summary of the article “Reasoning with goals to engineer requirements (Colette Rolland)”

Eugenio Mauri

Description

Ingénierie des exigences
Summary of the article “Reasoning with goals to engineer requirements (Colette Rolland)”

Informations

• Publié par: EugenioMauri
• Publié le: 25 juin 2012
• Nombre de lectures: 33
• Langue: English

Extrait

Eugenio MAURI

10/03/2011

MSIC JB 2011 (UE02 - Ingénierie des exigences)

Summary of the article “Reasoning with goals to engineer requirements (Colette Rolland)”

In this article the author gives an overview of various researches on the subject of “goal-

driven approaches”, oriented to requirements engineering field.

She focuses on the “L’Ecritoire” approach to present the state of the art and starts by

reminding that all goal driven approaches, ultimately, aim at building purposeful system

requirements that meet their users’ expectations but also the objectives of different

stakeholders.

Researches pointed out that since requirements arise from the “subject world” (e.g.: the

part of the world on which to provide information) the “usage world” (e.g.: agents’

procedures) and the “system world” (e.g.: the world dictated by system specifications

where requirements coming from the other two worlds must take place) the relationships

that link these systems define different types of requirements.

The “representation relationship” (between subject and system world) address domain-

imposed requirements while “intentional relationship” (between usage world and system

world) address user-defined requirements.

Since the latter explains “why” the system is developed (therefore is the link between the

system and the goals and objectives of the organisation.) all goal-driven approaches focus

on it.

As the author says, this point is quite important since, throughout the whole article, she

stresses the fact that the real purpose of building a system is not to be found inside the

system itself but in the enterprise, which means in a more global context and that all goal-

driven approaches focus on the intentional relationship.

The reading goes on by illustrating some of the advantages of focusing on goals, such as

goals refinement (for exploration of choices), requirements pre-traceability and

justification to stakeholders, conflicts detection, etc..

On the other hand, an overview of drawbacks and issues is also given: problems

mentioned are those such as the definition of the “goal” concept itself, or the fact that

sometimes systems are build with not precise goals in mind, or the fact that sometimes

goals are idealized or not complete or the fact that goal decomposition can be tricky.

An insight is given to the “L’Ecritoire” approach to see how it deals with the above issues

in order to elicit, specify and document requirements.

L’Ecritoire is a tool that produces a requirement document by coupling goals and

scenarios (described as one ore more actions describing a path from two states of agents)

derived by analysing textual scenarios.

The couple goal-scenario (named “requirement chunk”) is the central point if this

approach and represent a possible way to achieve a given goal. By moving from goals to

scenarios, and vice versa, this approach allows for both goals discovery and requirements

elicitation process.

The author then goes a bit into details concerning the mechanism on which goal

formulation is based inside the L’Ecritoire tool: a combinations of verbs and parameters

that can designate a mean, a manner, an agent, etc…

This in order to quickly introduce the concepts of informal, semi-formal and formal

specifications and the reasons behind them (e.g.: automatic analysis) and skim through

some other existing tool and approaches, such as Kaos or Electra.

The concept of composition, alternative and refinements are also detailed, and the

resulting structure organised in “AND”, “OR” and different “granularities” is presented.

A brief panoramic of some possible relationships between goals follows, showing the

possibility for conflict and positive/negative influence.

Relationship between goals and agents is also sketched, and also between other entities,

such as problems, opportunities, threads or obstacles.

The concept of abstractions is presented, with its different types (behavioural, functional,

physical) defining goals at different levels (e.g.: from strategic to technical).

Finally, “goal discovery” and “scenario authoring” strategies are presented but the article

goes into details only on the “discovery rules” implemented by L’Ecritoire (pointing the

reader few other papers that go deeper into the scenario authoring part); an example of a

rule is illustrated, based on refinement strategy and the “WHY/WHAT IF” and “HOW”

techniques are also mentioned.

Few references to other papers on different way to approach this aspect are given to the

reader.

In the end the author summarizes all the benefit from goal-driven RE that lead to the

rationale to the system to be built.

As a conclusion of the article, the author tries to quickly summarise all the advantages

brought by goal-driven RE, namely: provide the rationale for the system to be built,

provide a link between the system and the context, facilitate business changing translation

into features of the system, highlight choices and alternatives, help finding requirements,

facilitates mapping between goals and specs, facilitates goals negotiation, helps finding

conflicts and fixing them.

Some other advantages are also possible and the author points the reader to some other

papers that give more details about them.