PERE: Evaluation and Improvement of Dependable Processes

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In the development of systems that have to be dependable, weaknesses in the
requirements engineering (RE) process are highly undesirable. Such weaknesses
may either introduce undetected system weaknesses, or otherwise significant costs
may arise in their correction later in the development process. Typically, the RE
process contains a number of individual and group activities and thus is particularly
subject to weaknesses arising from human factors. Our work has concerned the
development of PERE (Process Evaluation in Requirements Engineering), which is
a structured method for analysing processes for weaknesses and proposing process
improvements against them. PERE combines two complementary viewpoints
within its process evaluation approach. Firstly, a classical engineering analysis is
used for process modelling and generic process weakness identification. This initial
analysis is fed into the second analysis phase, in which those process components
that are primarily composed of human activity, their interconnections and
organisational context are subject to a systematic human factors analysis. In this
paper we briefly describe PERE and provide examples of the application experience
to date.


Requirements engineering (RE) is the process within the earlier phases of the
system lifecycle that concerns the discovery, analysis, negotiation and definition of
system requirements, resulting in a specification of what the system must do in
order to satisfy user needs, integrate with other installed systems, satisfy
commercial demands, meet safety regulations and so on. The importance of the RE
process is generally recognised and it is acknowledged that problems originating in
the RE process are hard to detect and expensive to put right later on in the system’s
development. Furthermore, in the context of dependable systems, getting the
requirements wrong may have disastrous consequences.

Within the REAIMS project, we have been developing a number of
improvement strategies to address problems in RE, particularly focusing on the
development of dependable systems. In this paper we report on one aspect of the
REAIMS work that has considered the safety and reliability of the RE process
itself. PERE (Process Evaluation in Requirements Engineering) is a method for
assessing requirements processes, examining them for weaknesses and proposing
protections against those weaknesses. Although PERE has been specifically
developed for the evaluation of requirements processes, the analysis and process
improvement techniques employed are applicable to problems within the broader
process improvement domain. Process evaluation and improvement may be
necessary in any domain where the process is required to be dependable.

In this paper we briefly present an overview of the PERE method and its
background, and give examples of its application.


1.1 Dependable systems
Dependable systems are conventionally those in which failure of one or more
RAMSS (Reliability, Availability, Maintainability, Security and Safety) attributes
would have critical consequences. Within Safety Engineering, numerous techniques
have evolved to aid engineers in safety analysis and risk reduction for safety critical
systems. Such techniques include Fault Tree Analysis, Event Tree Analysis, Failure
Modes and Effect Analysis, and Hazops