Forum .LRN Q&A: What are relational segments ?

Posted by Peter Alberer on 06/16/03 12:38 PM

While trying to analyze the dotlrn data model, i find that i do not really know about the main idea behind relational segments. These seem to be something like subgroups to me. I am also not sure about the usage of relational segments within dotlrn. There are 5 basic rel-segments created in the beginning (dotlrn_profiles to users, admins, professors, students, externals) and two segments seem to be created when a new community is added. What is the relationship between those two types of segments? Are those only used for permission-checks or are there additional functionalities provided by them?

Are there documents explaining some of those internals where i could find more information?

TIA, peter

2: Re: What are relational segments ? (response to 1)

Posted by Don Baccus on 06/16/03 09:36 PM

Relational segments can be thought of as being subgroups of a group, yes. The basic idea is to define an acs-rel that's derived from membership_rel, say "admin_rel" and then to a relational segment that represents all members of the parent group that also belong to the "admin_rel". Think of this as defining a role and the relseg as the set of all members of a given group who hold that role.

As far as documentation goes ... aD added these close to the end of Tcl ACS 4 and documentation never got written. I'd love to find time to write some but haven't, nor has anyone else who has used them. Sigh.

As far as .LRN goes ... the basic users, admin, etc relsegs created globally have no semantic meaning within the system, they're just used as a way to label people. A professor at an institution might be enrolled as a student of a class, for instance, so perms aren't granted to their global role. Communities and classes each create relsegs specific to themselves which are used to grant permissions (professors are admins in classes, there's admin and plain users in communities, etc)

Does this help?

3: Re: What are relational segments ? (response to 1)

Posted by Peter Alberer on 06/16/03 10:31 PM

Yes, that helps a lot. Thank you for the detailed explanation!