Homework on Active DBs

1. Do Exercise 2.1, a-c, in ADS (skip part d).

2. Write active Oracle rules for version management.

   Thus, there is a Primary relation that remains unchanged, while each user will

   • Specify inserts and deletes on a user_copy (for simplicity forget updates)

   • Read a modified table from a user_view.

   This can be accomplished by letting:

   1. user_copy be an empty relation, and by redirecting every insert or delete to this table to two delta tables called user_PosDelta and user_NegDelta (Oracle's instead rules might become handy here)

   2. Thus user_view is defined as:
      Primary + user_PosDelta - user_NegDelta.

      Observe the similiarity with Example 3.6 in ADS, but remember that a user could here insert a tuple and then delete it, or viceversa.

   3. Derive and write active rules for the efficient (i.e., differential) support of a transitive closure of a graph stored as a binary relation.