Monday, August 31, 2009

On conceptual and run-time EPN

Working now in my spare time on completing the second third of the EPIA book, so I'll have several postings related to the next three chapters of the books that are now in the "cleaning phase". The topic I'll discuss today deals with the concept of EPN (Event Processing Network) which is a major concept in our book. The approach we have taken in the book is to explain event processing through a meta-language that provide the various event processing concepts, and the event flow through a model based on event processing network. We are now also competing an editor that will enable the reader to play with the meta-language. However, this meta-language is not an executable language (at least not in this phase), and thus we also show the readers how the same application described in the meta-language is implemented using various executable languages of different language styles. The EPN described by the meta-language is a "conceptual EPN", it consist of logical EPAs, while the run-time EPN consist of run-time artifacts that implement the run-time instances of the EPAs.
The conceptual EPN can be mapped into physical implementation in various ways, as shown in this picture:

The traditional centralized implementation is that the entire EPN is being executed using a single run-time artifact, and the EPN describe the internal flow within this artifact.

When talking about distributed EPN, the EPN can be distributed according to several criteria:

  • Segment partition: All the EPAs that relate to "platinum customers" are being executed by one run-time artifact, all the EPAs that relate to "gold customers" are being executed by another run-time artifact etc...
  • Function partition: All the EPAs that perform a certain function are being executed by a unique run-time artifact
  • Location partition: All the EPAs that relate to events created in a certain location.
These, of course, are just examples. The most distributed example, is, of course, a direct mapping of each EPA instance to run-time artifact.

The conceptual EPN is important for design and validation of the event processing application, while the run-time EPN is useful for control and management of the run-time.

More about EPNs and their components - in later postings.

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