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Figure 3.3 shows another characteristic of the relation between the type layers. One complete type can be the sub-type of an arbitrary number (0..*) of provides types and one implementation type can be sub-type of an arbitrary number of complete types.
The m:1-relation between provides type and complete type is possible, because a complete type can provide interfaces that are not specified by a concrete provides type. These interfaces, which are not provided by the first concrete provides type still can be provided by another provides type. After all, the complete type is a sub-type of m provides types.
Example 3.4 (m:1)
A short example illustrates the m:1-relation. Assume a complete type that provides I1 and I2. Then there can be two provides types of which the first provides I1 and the second I2. This causes two super-types for one complete types; in general m super-types are possible.
The m:1-relation between complete type and implementation type originates from the same reasons.
Snowball
2007-03-16