Page 95 - DCAP405_SOFTWARE_ENGINEERING

Software Engineering

Notes A multi-perspective analysis is important, as there is no single correct way to analyze
system requirements.

Provides a natural way to structure the elicitation process.
Types of Viewpoints

Data sources or sinks: Viewpoints are responsible for producing or consuming data.
Analysis involves checking that assumptions about sources and sinks are valid.
Representation frameworks: Viewpoints represented by different system models (i.e.,
dataflow, ER, finite state machine, etc.). Each model yields different insights into the
system.

Receivers of services: Viewpoints are external to the system and receive services from it.
Natural to think of end-users as external service receivers.

Method-based RE

“Structured methods” to elicit, analyse, and document requirements.
Examples include:

Ross’ Structured Analysis (SA),
Volere Requirements Process (www.volere.co.uk).
Knowledge Acquisition and Sharing for Requirement Engineering (KARE)
(www.kare.org),

Somerville’s Viewpoint-Oriented Requirements Definition (VORD), and
The baut’s Scenario-Based Requirements Engineering (SBRE)˜

Scenarios

Depict examples or scripts of possible system behavior.
People often relate to these more readily than to abstract statements of requirements.

Particularly useful in dealing with fragmentary, incomplete, or conflicting requirements.
Scenario Descriptions

System state at the beginning of the scenario.
Sequence of events for a specific case of some generic task the system is required to
accomplish.

Any relevant concurrent activities.
System state at the completion of the scenario.

Scenario-Based Requirements Engineering (SBRE)

Marcel support environment allows rapid construction of an operational specification of
the desired system and its environment.

Based on a forward chaining rule-based language.

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