Page 51 - Software and Systems Requirements Engineering in Practice

24 S o f t w a r e & S y s t e m s R e q u i r e m e n t s E n g i n e e r i n g : I n P r a c t i c e

Taxonomy Attributes
Any taxonomy for requirements engineering work products should,
as a minimum, have the following attributes:

• Complete At the leaf level, include every requirement type
that will be used by the organization or project. The
categorization of requirements is critical when defining
metrics (see Chapter 7). Without a proper categorization, it
may not be possible to do a filtered query of a large
requirements data store and return meaningful information.
• Extensible Companies should be able to take a core
taxonomy and extend it. The sample fragment shown in
Figure 2.3 is an example of a complex extension for security
requirements.
• Navigable The taxonomy should be easy to navigate,
possibly with hyperlinks on web pages.
• Valid There are many potential taxonomy sources; however,
it is important that any such taxonomy used by an organization
or on a product should be validated with other sources such
as textbooks or experts.
• Systematic The categories should be well chosen and be at
the same level.

Creation of an RE Taxonomy
There are many fine references and tools available to assist with
the creation of taxonomies. We recommend the following simple
2
steps (see the starting point suggested by Capers Jones in the
sidebar on the previous page):
• Identify the tooling that will be used and how the taxonomy
will be presented to project staff, keeping in mind that the
taxonomy may have to be updated periodically, and there
may be links to other tools; e.g., the taxonomy and the artifact
model that will be described in the next section are
interrelated.
• Collect all the requirement types that are currently in use or
planned. Group them together.
• If the project is an incremental development, mine the
requirements for classes. Note that Capers Jones estimates
that as many as 75 percent of all new projects are incremental
changes to an existing product.

2 www.loc.gov/flicc/wg/taxonomy.html