I got an issue that I suppose it's not possible to do in SD. I hope you can say I'm wrong! :)
A CI can be used by several organizations, right? What I need is for Service Desk to keep in some field the percentage of usage for each organization. Imagine, a CI is used by 3 orgs. Org1 uses the CI 10% of the time, Org2 uses it 50%, and Org3 uses it the remaining 40%.
This is a good example of why it is useful to be able to define attributes of relations, which you cannot do in OVSD.
That being said, the philosophy of a CMDB is to define an approved state for a CI, but not necessarily to track its operational usage. We have monitoring tools for the latter. If you interest is to see the reality of usage, I suggest you try to get that information from monitoring tools, not from the CMDB.
OK so with unlimited custom fields to play with, that is how I would handle it.
Create an attribute for each of the three orgs, and enter the percentage for each on a per-CI basis. Then if you want to do reports per org, you can pull out all CI's that have greater than 0 for each org attribute.
Well I give you an example: imagine that there is a service call with a CI that is used by 20 orgs). I want to be able to define the percentage of responsability for that call among the 20 orgs.. They call it here shared CI's.
In reporting, I could easily build a report that gives me the actual duration of the call and the respective CI. But with a shared CI, that actual duration has to be distributed among the orgs using this CI. For example, if the actual duration of a service call is 2 hours, and we have defined (manually) that this CI is shared through 10 Orgs with 10% each, Org1 will have 12 minutes of the actual duration responsability, Org2 12 minutes, etc, etc, etc.. :)