Events in an MLS Active Database Systems

Event specifies what causes the rule to be triggered. Possible events that can be supported in an active database system are,

  1. Data modification/retrieval events – the event is raised by an operation (insert, update, delete, access) on some database object.
  2. Transaction event – the event is raised by some transaction command (e.g. begin, abort, commit etc.).
  3. Application-defined event – the application program may signal the occurrence of an event.
  4. Temporal events – events are raised at some point in time. Temporal events may be absolute (e.g., 25th December, 2002) or relative (e.g. 15 minutes after x occurs).
  5. External events – the event is occurring outside the database (e.g. the sensor recording temperature goes above 100 degrees Celsius).

Events can further be classified into primitive and composite events.

a. Primitive event – the event cannot be divided into subparts.

b. Composite event – the event is raised by some combination of primitive events.

Advertisements

, , , , , , , ,

  1. Leave a comment

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: