The first step in collecting the required data was to
identify all versions of SoftPM that had complete
documentation including source code files. Complete
documentation is required to extract information about the
number of requirements at each level of the requirements
hierarchy. Five versions satisfied this constraint.
Once the relevant versions had been shortlisted, the next
step was to identify the different levels at which
requirements of SoftPM had been expressed in these versions.
These different levels are shown in Table I. To facilitate
visualization of the amount of detail contained in these levels,
a mapping of each requirements level to a level in the
Cockburn altitude metaphor  is also shown in Table I.
Capability goals, for instance, contain the least amount of
detail and are, therefore, mapped to the cloud level of the
Cockburn metaphor. SLOC, on the other hand, map to the
lowest level (i.e. clam) since they cannot be elaborated any
Determining the number of requirements at each of these
five levels for each of the five versions of SoftPM entails
dealing with the fact that there is considerable overlap
amongst versions. Later versions may not only add brand
new CG but may also elaborate the CG added by previous
versions. For example, consider the scenario shown in Fig. 1.
In this simplified hypothetical scenario, a product has only
two versions i.e. V1 and V2. The second version (V2) adds
more functionality to the first (V1). V1 specified two CG i.e.
CG1 and CG2. V2 inherits these two CG and specifies one
additional CG i.e. CG3. Besides this, V2 also adds a new CR
– CR4 – to CG1. These new additions in V2 have been
shown in bold in Fig. 1.
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Requirements for a software development project
are gradually refined as more information becomes available.
This process of requirements elaboration can be quantified
using the appropriate set of metrics. This paper reports the
results of an empirical study conducted to analyze the
requirements elaboration of an industrial software process
management tool – SoftPM – being used by more than 300
Chinese commercial software organizations. After adjusting
for the effects of overlaps amongst different versions of SoftPM,
multi-level requirements data are gathered and elaboration
factors for each version are obtained. These elaboration data
are compared with the data from a previous empirical study
that analyzed requirements elaboration of a set of different
small e-services projects. This comparison reveals that the
elaboration factors of different SoftPM versions have much
less variation confirming the intuition that projects with
similar characteristics have comparable elaboration factors.