I provide a conclusion but first briefly,
eTOM categorized the business processes that are used by service providers. it does nto define the process, but only categorize them. it allows you to elimitae duplicate functionalities among the enterprise and relate the related processed into one or more set of class or processes. NGOSS at the same time it defining core elements of this process map in a technilogy neutrial architecture and this architecture is based on managed entities that their relationship is defined using abstract information model SID (shared information data). OSSJ has implemented these architecture based on J2EE and is providing set to APIs for different telecomm functional areas such as PM, FM and other processes defined by the abstract definition. SID implementation can be found in OSSJ Common API.
I agree that some of the APIs are not fully aligned together, but work is in progress to make this resolved.
Conclusion: As you see based on above, you can not find any requirements for telecomm enterprise applications because in general you need CM, FM and PM areas but then features that you are providing is up to yourself and you can not find such level of requirements in eTOM in another words it is not defined in this concept.
I recommend you to join the forum to have access to whatever you need also all the training that you might require.
some companies have already implemented their OAM based on OSSJ even though some are still in implementation phase and a couple still in design discussion.
I have one document form Sun Microsystems that explains the use of J2EE in network managemen systems, but I need to find it in my documents.
Nokia has also provided an OAM which is partially based on OSSJ and it is opensource if you are interested
http://www.nokia.com/link?cid=PLAIN_TEXT_6406
I am afraid you need to become a member to have access to the forum's documents and I recomment you to do so. but above was for helping you to go to the right direction.
eTOM and OSSJ is the correct way to do it and it is emerging quickly and lot of effort has been put into it.