Tim Bass
07-20-2008 06:57 AM
A blackboard architectureis a distributed computing architecture where*distributed applications, modelled as intelligent agents,*share a*common data structure called*the “blackboard”* and a scheduling/control process.* The blackboard can be either centeralized or distrbuted, depending on the requirements and constraints of the application(s).

To solve a complex problem*in the blackboard-style, the intelligent agents cooperate as functional specialists, observing updates to the blackboard and self-actualizing in an event driven process)*when there is new information to process.* Agents continually*update the blackboard with partial solutions when the agents capabilities for processing*match the state of the blackboard.*

The blackboard architecture is a distributed computing model for a*metaphor*describing how people work together to collaboratively*solve a problem around a blackboard (whiteboard in todays lingo).** For example, one person is standing at the whiteboard working on a solution while three other people are sitting (or standing) around watching.** One of the observers sees new information*on the whiteboard, thinks of how*he (or she) can*contribute,*and then jumps up, takes the whiteboard marker from the person working, and*adds to the solution.* This process is repeated in various scenarios.**

The blackboard*architecture can be very effective in solving complex distributed computing problems, including event processing problems; however, scheduling the self-actuating agents*can be*a key challenge.** Another core challenge is how to model and manage the blackboard itself, especially in distributed blackboard architectures.** John McManus, former CTO of NASA, wrote an excellent PhD dissertation in 1992,* Design and Analysis Techniques for Concurrent Blackboard Systems, at the College of*William and Mary,*these addressing challenges in BB systems.

The table below lists two books that focus on blackboard archtecture:

Date Editor(s) Publisher ISBN Title 1989 V. Jagannathan et al Academic Press 0123799406 Blackboard Architectures and Applications 1988 Robert Engelmore and Tony Morgan Addison-Wesley 0201174316 Blackboard Systems One of the though leaders in blackboard architecture is Daniel D. Corkill a professor at the University of Massachusetts Amherst.*

Blackboard architecture is*relevant to the field of event processing, and in particular complex event processing.** I will go into more details in future blog posts on this topic, including how blackboard architectures relate to grid computing, distributed object caching (of the blackboard), and CEP.



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