How to Begin with Requirements

Despite being a recurring topic of discussions, a comprehensive and formalized approach to requirements should not hold back newcomers: given that requirements are the necessary genesis of any project nothing can be assumed about their emergence; as a consequence they are better dealt with as they come.

PopolVuh_Quiché_Maya_Creation

The Genesis of Meanings (Quiché Maya’s view of creation)

For that purpose, and whatever the preferred approach, requirements analysis can be neatly described as an iterative process built from three basic increments: identified individuals, associated features, and classifications.

Individuals

When entering unknown territory, the first thing to do is to set apart recognizable items. Regarding requirements that would be individuals whose identities has to be managed. Such individuals would then further be divided between:

  • Objects (persistent identities) and activities (transient identities).
  • Activities (managed duration) and events (no managed duration).
  • Agents (physical identities) and roles (social identities).
  • Actual (physical identities) and symbolic (social identities) objects.

It must be noted that, except for new standalone applications, most of individuals may have been already defined by existing functional architectures.

Features

Contrary to individuals, features have no identity of their own. As a corollary, they can only be considered as possible attachments to individuals. On that basis, analysts have to answer three basic questions:

  • Can a feature be shared or transferred (functional), or is it bound to the same individual (structural).
  • Does it reflect a state of affairs (attribute) or represent a capability (operation).
  • Is there some overlapping with already known features.

The last question brings about the core of requirements analysis, i.e how to deal with variants, consolidate applications, and manage changes.

Classifications

Categories and rules are the dual facets of requirements purpose, namely how to classify objects and operations and deal with variants.

  • Categories take a declarative approach that relies on static classifications to describe variants. Starting with partitions, analysts will have to distinguish between structural variants (associated with specific features) and functional ones (associated with the state of the same set of features).
  • Rules take a procedural approach with the equivalent of dynamic classifications to deal with variants. As for categories, analysts will have to decide between the equivalent of structural variants (rules to be enforced for the whole of execution paths) and functional ones (rules to be evaluated along execution paths).

Whereas each option may have its benefits depending on the nature of variants, the primary factor when selecting a scheme should be its consistency with regard to existing applications on one hand, between the description of new objects and activities on the other hand.

Further Readings

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s


%d bloggers like this: