[glue-wg] Endpoints and ComputingService, relationships between services. Some thoughs

[stephen.burke at stfc.ac.uk]

Florido Paganelli [mailto:florido.paganelli at hep.lu.se] said:
> Besides, the comment I made about UML inheritance might be wrong.
> Looking at the schema in page 22 I am not sure if an instance of an
> Endpoint object can be related to a ComputingService or not.

Conceptually an Endpoint can only have a relation to a Service, not to any derived class, because you can't know what classes may be derived in the future. For example if we decide to derive a new class FileTransferService, Endpoint can't possibly have a relation to it because we didn't know it existed when the schema was defined. Perhaps we could have defined the schema in a different way, but it was a decision right at the start to do it like this. And it does have some advantage for type checking, i.e. you can check that a reference points to the right kind of object in a more specific way.

  In LDAP that isn't really a natural way to do it because LDAP objects can easily have multiple types and it makes more sense to extend the base type than redefine it, so in LDAP the GLUE2ComputingEndpoint objectlass only has the additional attributes and not the inherited ones. In XML I don't know which way is best.

> So to come back to the initial problems, if I have

?

Stephen