When real-time or embedded systems use a database, it is very important that client applications can quickly know when data had changed. Of course, one could use an external event mechanism - but this puts the onus on those updating the database to broadcast the fact that they have just changed a particular table, and those interested in the table will then have to go and refresh their query. Polyhedra's Active Queries™ offer a scalable, low-latency solution that automatically keeps a client application up to date without the need for special code in the application that is feeding changes into the database. There is a 3-part introduction to Active Queries on YouTube:

• part 1: why active queries are needed:

• part 2: a description of active queries:

• part 3: a quick demo of active queries in action, an a look at the code that was used to launch the active query and process deltas:

There is also a white paper on the topic which you can access from the Polyhedra page on Enea web site: www.enea.com/polyhedra (look in the 'Resources' section at the bottom of the page).

Dr. Nigel Day Polyhedra Product Manager www.enea.com/polyhedra