Duane
I think that, in principal, a stakeholder 'knows' what he/she owns! But, in general, it is normal for a stakeholder to know about owning things. On the other hand, that is not the case for a resource: it is not the normal case for a resource to be able to be aware of who owns it.
When I looked to see what people defined identity as, the one that seemed closest was:
Identity is the collection of individual characteristics by which a thing or person is recognized or known.
This suggests identity is an aggregate. For us, we needed both the concept of identity and identifier in different parts of the architecture. Hence the inclusion. It is a slight specialization of this definition to focus on identifiers; doing it primarily because we needed to focus on the relationship between a resource, its identity and identifiers. Certainly, identifiers can and do exist independently of the things that they identify.
AFAIK, roles in an association are simply another way of giving a name to the association -- it does not imply transitivity.
In the diagram, the arrow goes from description to identifier, not the other way around. That implies (to me) that you can expect to navigate from descriptions to identifiers but not vice-versa. Similarly from identity to resource and from description to resource.
The overall theme of navigability is that resources are the ultimate target of many associations; but that resources do not imply navigability back to their descriptions, identifiers, stakeholders etc.
Frank
On Jan 18, 2008, at 9:30 AM, Duane Nickull wrote:
Frank (Jeff - please read too).
I think you should remove the traversibility indicators all together.
1. Between Stakeholder and resource:
They might (not in all cases) be aware of each other. Just a straight line,
no arrows.
2. Between Resource and Identity and Identity - Identifier
If you have labels at both ends (embodies, denoes) this implies a binary
transitive relationship. Remove arrow. Also - if it is 1:1, I think by
convention you might not have to explicitly note this. Regardless, is there
any reason why a resource might not have two identities? I'd get rid of the
cardinality indicators.
I am not sure if we need both identity and identifier but might be wrong. I
am also wanting to ask why an identity is aggregated from multiple
identifiers. Is it possible that the identifier exists without the thing it
identifies? IMO - perhaps no.
3. Between Description and Identifier
Are we implying that identifiers (which are items that act as descriptors,
referencers) have a description themselves? Also - if the description
references the identifier, you do not have to explicitly draw the line
between the two as there is already an indirect connection via the
Description-Resource-Identity-Identifier path.
CAVEAT:
This is based on my understanding of UML. Jeff and others should proof
this.
Duane
This one has more cardinalities, and perhaps more careful navigation
Frank
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