If you create for an example a big adf application you may want to add all of your entities to one base application for reuse labels, validation and and so on. If you have a big database schema than in short time you have a problem to find your entity. In JDeveloper there is a neat feature to overcome this problem: working sets!
With this you can easily group your entities or other artefacts in logical working set, eg. for a sub application. Unfortunatly working sets are saved per user. There are several description how to share this between your team members. But a better way would to distinct between user and application working sets. Application working set should be saved consequently in the application workspace (jws).
Therefore I have created enhancent request bug 15841657 : SAVE APPLICATION WORKING SETS IN THE APPLICATION WORKSPACE JWS.
If you find this useful too, then create a service request, that you need this feature too. Unfortunatly there seems no other voting function for enhancement requests on oracle.