Information Technology Reference
In-Depth Information
0..*
2
CorrespondenceSpecification
ViewpointSpecification
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CorrespondenceRule
CorrespondenceLink
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CorrespondenceEndpoint
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Term
FIGURE 7.2: The elements of a correspondence specification.
Taken from the UML4ODP standard; for copyright, see Preface.
constraint we mentioned earlier about phones with premium service bundles
needing to have a memory capacity above a certain threshold. In UML4ODP,
these constraints are usually expressed in OCL. Correspondence rules can
also serve to provide information about the kind of relationship that links the
elements; a few examples are use, runsOn, affects, implements, realizes and
replicates. These kinds of relationship are not predetermined, but are normally
defined by the system designers. This definition must include their semantics,
indicating what they are to mean in this system specification. For example,
in the PhoneMob specification we use a runsOn constraint to indicate the
technology object types used to run particular BEOs, or replicates to indicate
the correspondence that links a computational object with the set of replicated
BEOs that support it.
7.5
Taking a Formal View
The set of viewpoints defines an associated set of domain-specific lan-
guages. Each of these languages is formally defined in terms of a mapping of
its elements onto some very simple supporting model, often some form of la-
belled transition system representing the way the system's state evolves. If we
are to unify the different viewpoint languages, we must first produce a unified
supporting framework. This brings us back to the importance of unifying the
set of primitive types assumed, and the combination of different languages is
