To mitigate the difficulties that requirements
specifiers face when modeling UCs, several authors
propose the application of resources already used in
other domains to verify their effectiveness in UCM.
Bouzidi (2017) employed business process models to
derive UCs because these models are often available
in a company in the form of work instructions or
administrative manuals in a clear and structured
manner. Conversely, El-Atar and Miller (2012)
presented an antipattern-based strategy for UCM, in
which bad practices are identified to be replaced by
recommended solutions. In a preceding investigation,
we identified other strategies, and their respective
contributions to UCM (Bispo et al., 2019). However,
these studies do not indicate which strategies could
actually mitigate the UCM difficulties.
The difficulty-strategy correlation proposed in
this paper guides the requirements specifier in
selecting the most appropriate strategy to mitigate a
given difficulty. It avoids the adoption of ineffective
practices, and presents various alternatives for
applying tested and evaluated procedures to assist
UCM.
4 CORRELATION BETWEEN
UCM DIFFICULTIES AND UCM
STRATEGIES
The strategies identified in the literature were
proposed to improve the quality of UC models,
instead of indicating which specific difficulties are
mitigated by each strategy. In order to address such a
concern, we defined a two-procedures methodology,
as detailed next.
4.1 Correlation Methodology
The procedures adopted to make the correlation
possible were two-fold: (1) obtaining a precise
definition of the meaning of each difficulty, and then
grouping them into categories; and (2) obtaining a
precise definition of each quality attribute - in order
to gain a deeper understanding of each attribute, in
such a way that it would be possible to identify, in a
UC model, which quality attributes were either met or
not.
4.1.1 Categorizing UCM Difficulties
To categorize the difficulties of UCM, the studies that
present these strategies, earlier presented in Bispo et
al. (2019), were analyzed with the support of
Grounded Theory (GT) (Corbin and Strauss, 2008)
which helps in the construction of data-based
theories.
According to Corbin and Strauss (2008), GT can
be used when there is a need to understand a certain
situation from a volume of information about the
observed phenomenon; how and why the participants
act in a certain way; and how or why a particular
phenomenon or situation unfolds this way or that. An
example, illustrated in Table 1, is an excerpt from one
of the analyzed studies.
Table 1: A piece of text examined using GT.
“The main research question posed by this case study
is whether the proposed strategy can improve the
overall quality of UC models. This is achieved on two
fronts: (a) by restructuring the UC diagrams to adhere
to the notational syntax rules and semantics set by
OMG (OMG, 2010); and (b) by changing UC
descriptions to comply with recommended guidelines
and widely accepted practices (Sect. 2). Therefore, the
effectiveness of using our proposed approach will be
assessed by comparing the resulting UC model with
the original UC model, with respect to the aspects
mentioned in (a) and (b)...” (El-Attar and Miller,
2010).
By using GT procedures, as Figure 1 illustrates,
the highlighted phrase (taken from the example
citation in Table 1) "... restructuring UC diagrams to
adhere to syntax and semantic rules..." was
interpreted as: difficulties that prevent UC diagrams
from being modeled in accordance with syntax and
semantic rules. This interpretation is supported by the
information that the proposed strategy affects those
aspects (syntactic and semantic rules) so that there is
a general improvement in the quality of the UC
models also taken from the example in Table 1.
Another set of studies were examined following
the same approach, and similar interpretations were
made to precisely define a set of difficulties. To this
set the difficulties of UCM reported by Nascimento et
al. (2017), Anda et al. (2009), Bolloju (2006) and Siau
and Loo (2006) were added.
After defining the set of difficulties, they were
grouped into categories, as Figure 2 shows. This is
supported by our finding that a strategy which
supports the identification of an UC, also supports the
identification of actors and relationships. In other
words, the same strategy supports the identification
of the different elements (UC, actor, etc.) in the UC
diagram. Therefore, it was possible to group all these
difficulties in: Difficulty in identifying UCs, actors or
relationships. Furthermore, considering the same
example, for the word identify, some authors used the