Product Line Scope

The scope of a single software product is defined by the bounds of the capabilities provided in that product. Similarly, the scope of a software product line is determined by the bounds of the capabilities provided by the collection of products in the product line.

According to Joseph Pine in his book Mass Customization (see Books), the scope of the products in any product line can be characterized in terms of six dimensions in product usage scenarios: who, what, when, where, how, and why. Multiplicity along these dimensions leads to multiple products in a product line.

There are two primary approaches to managing scope software product lines, proactive and reactive. In the case of a pure proactive approach, all of the products needed on the foreseeable horizon are supported by the product line. In the case of a pure reactive approach, only the products needed in the immediate term are supported by the product line and new products are incrementally added as the needs change. There is, of course, a continuum between the two.

The reactive approach requires less up-front effort than the proactive approach since the initial scope coverage is smaller. To implement the same scope coverage, the reactive approach incrementally defers the cost and effort over longer period of time compared to the proactive approach. With the proactive approach, the up-front investment for implementing a broader scope is amortized over time when new products within the scope are deployed with little or no effort.

It is possible for early stage artifacts in a software product line, such as the architecture, to have a more proactive scope than later stage artifacts, such as the source code. However, the overall scope of the product line is defined by the scope of the product collection that can be produced, tested, and deployed.

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