Version and Product Model Structures
Because product model only considers the software structure of a single version model, and the version model does not take software structure in to consideration, methods to integrate the two models will be discussed in this section. In particular, we will investigate which items are put under version control and how versions of different items are interrelated with each other.
According to the selection order during the configuration process, we can classify the structures into 3 categories, product first, version first and intertwined:
Product first means that the product structure is selected before the version models of components. This approach is followed, for example, by SCCS and RCS. But this method suffers from the restriction that structural versioning can not be expressed (it is because the product structure is fixed for all configurations).
Version first means the version of product is selected first and uniquely determines the component versions. Different product versions may be structured in different ways. For example, a version of a component is contained only in the product version 1.0 but not 2.0. PCTE is an example of an SCM system using this organization.
Intertwined means that the selections of version model and component structure are performed in alternating order. Intertwined structure is relatively more flexible than the two methods mentioned above, because when a new change happens or a new component need to be added in the configuration, for most of time it is not necessary to change the whole configuration structure.
In addition, version first and intertwined both take in to account that different versions of a certain object may vary with respect to their relationships of other objects. This means that in addition to objects, relationships are versioned as well.
Read more about this topic: Component Repository Management
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