2. Basic concepts
Sessions (log in / log out)
Transactions
- atomic units of work which is insulated from others (do / undo)
- require user commits to propagate changes
- no automatic commits unless specified in the process model
Locks (can see but cannot manipulate)
- various locks (read, write, exclusive locks)
- locks must be obtained by requests and they are released by commits, usually only write locks are used
- lock can be defined at different levels of granularity graphs, objects, versions etc...)
Types of data:
- conceptual objects, conceptual graphs, representational graphs, projects (db:s), metamodels