Information Technology Reference
In-Depth Information
Another use of replication transparency, this time to increase both avail-
ability and performance, is shown in figure 5.4. This is a refinement of fig-
ure 5.1 in which the original Stock DataMgr basic engineering object has been
decomposed into a supporting object that remains in the PhoneMob node and
coordinates two replicas of the original BEO, each in separate nodes.
Further details of the selection and use of transparencies and migration
functions are given in chapter 9.
5.6
Writing Engineering Viewpoint Specifications
The RM-ODP is agnostic with respect to the methodology used to develop
the system viewpoint specifications. However, in the following list we provide
some guidelines that could be used when writing engineering specifications:
1. Examine the computational viewpoint specification of the system and
identify the computational objects needing support; define BEOs corre-
sponding to each of these computational objects.
2. Analyse the required transparency schemata and identify any necessary
transparencies and the ODP functions required to implement mecha-
nisms for handling them.
3. Identify the nodes and elaborate the node structures.
4. Associate the BEOs with nodes.
5. Associate the ODP functions with nodes.
6. Add engineering objects where needed to support the groupings of ob-
jects identified above (cluster managers, capsule managers and so on).
7. Identify channels and design channel structures.
8. Identify basic conformance points where testing is to be carried out.
The last of these steps forms an important link to the testing process. Con-
formance points are positioned primarily in terms of interfaces in the engineer-
ing viewpoint, although sometimes they may be identified in more abstract
viewpoints. Where this is the case, the abstract model elements concerned
must be linked by a chain of correspondences to engineering interfaces. RM-
ODP defines four kinds of conformance point: interworking, programmatic,
perceptual and interchange conformance points (see section 8.3 for details),
any of which can be nominated and positioned in an engineering viewpoint
specification.
