Cache add operation should automatically create its child resources

There is effectively no difference between the behavior of a cache that does not contain a given child resource (e.g. transaction, locking, etc) and one that contains the child resource, but with default attribute values.
Consequently, the cache add operation should automatically create these resources (and the cache remove operation should automatically remove them). We can treat the child add operations as no-ops, and the child remove operations as a series of undefine-attribute operations.