Impact analysis means finding dependencies between objects: which object depends on which other object, or vice-versa: if one object is modified or deleted, which other objects are affected? For example, if a web service interface changes, which callers must be adapted?
In JAXR, dependencies between objects are established via associations.
There are a variety of pre-defined association types, and moreover a JAXR-based
client can create its own association types. Although the names of the
association types - for example HasChild or
HasMember - suggest a certain semantic, JAXR itself does
not imply any semantics with the association types. CentraSite supports the
following conventions for associations.
If there is a dependency between two objects, each of which can exist on
its own, then this dependency should be expressed by a
Uses association. Example: one web service calls another
web service. Remember that JAXR-based associations are directed: the
association's source object should be the caller/user (in general, the object
that depends on another object), and the association's target is the
called/used object.
If there is an object C that cannot exist
without another object P, then
C should have a HasParent
association to P. Example: A table object cannot exist
without a database object, hence there is a HasParent
association from each table to the corresponding database.
The reason for preferring HasParent over the
"inverse" HasChild association is as
follows: CentraSite tries to maintain referential integrity; this means,
among other things, that is not possible to delete an object that is still the
target of an association. Hence associations should be directed in such a way
that an object cannot be deleted if someone else still depends on it: an object
should not be deleted if it still has children, or if it is still in use by
someone else.
