There are different ways to design an engineering architecture for reuse. These levels are not exclusive to one another; they can be mixed and matched and customized for particular needs. Product line development involves three architectural levels:

• Level 1: The fundamental level provides the core mechanism to manage product variants across streams. Configuration management concepts similar to those in source controlmanagement (SCM) systems are applied across all lifecycle disciplines, based on a federated configuration management framework. This capability leverages artifact versions,component configurations, and hierarchical baselines. This level is the foundation for all strategic reuse capabilities in the Rational SSE platform.
• Level 2: The second level adds parameterized assets. A single source of the artifact is maintained rather than separate manual streams. The artifact contains parameters that are instantiated based on parameter configurations. Parameterized assets consist of optional elements and property values for the parameters, which provide the means to instantiate the asset. Parameter configurations define how to instantiate variants from a product line.
• Level 3: The third capability applies feature models. Feature models abstract the variability of the system for external stakeholders, and specify variants based on feature profiles. Features are mapped to parameters so a particular feature profile can drive the feature configurations that can instantiate variants following the capability of level 2. Feature models can be done top-down, so parameters are driven from features, or bottom-up, so features are mapped to existing parameters. Feature modeling is done by interfacing with 3rd party feature modeling tools that integrate with the Rational SSE platform.

For the complete text, see the Strategic reuse and product line engineering article.