Page 54 - Software and Systems Requirements Engineering in Practice

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C C h a p t e r 2 : R R e q u i r e m e n t s E n g i n e e r i n g A r t i f a c t M o d e l i n g 27 27
h
If templates with the appropriate attributes are filled in for each
artifact, process definition is much simpler (see the section “Extending
an Artifact Model to Augment Process Definition”).
2.3 RE Artifact Model
An RE artifact model (REAM) is a meta-model for the structuring of
requirements engineering work products. A meta-model is an explicit
model of the constructs and rules needed to build specific models
within a domain of interest. An RE artifact model contains all the
artifacts referenced, modified, or created during requirements
engineering activities. The artifacts shown on REAM diagrams are
those that are actually used in a project, and they each have a name
and definition.
Upon first glance, the REAM diagram may appear similar to a
software class diagram. However, there are some significant
differences. A software class diagram may show many different types
of relationships between objects, whereas an RE artifact model only
shows simple associations (a single solid line). For example,
• Classes shown on a class diagram may have methods and
attributes; an RE artifact only has a name and description.
• A class diagram may show abstract classes, or classes for
which there is no physical representation; an artifact model
only shows real objects that will be used or created during a
requirements engineering activity.
An artifact model is different than a taxonomy in that it is a graph
rather than a tree, has many more artifacts than what would be in a
taxonomy, and typically contains many domain specific extensions.
Both a REAM and a taxonomy can be multitiered, so that selecting
an object can open onto a different diagram. However, care must be
taken in that while a taxonomy lends itself well to a hierarchical
approach, artifact models tend to be flatter. For example, an object on
one REAM diagram might have a relationship with an object on a
different diagram.
Elements of an Artifact Model
A fragment of an artifact model is shown in Figure 2.7. It consists of
the following elements:
* Participates in *
Actor 1 Initiates * Use Case
FIGURE 2.7 Simple artifact model