Deliverable: Product Line Requirements Model (PLrequirements_model)
The specification of the requirements for the product line.
Domains: Core Assets
Work Product Kinds: Core Assets
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Main Description

The product line set of requirements is the superset of all requirements that must be satisfied for the products in the product line. The model may take any form that is amenable to analysis and serving as the basis for product building.

For an example look here.

One technique for capturing and analyzing requirements is the use case modeling approach in UML. 

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