Monday, August 15, 2005

Extra Special Bitter


- Naturally leads to a document-oriented processing model

- document-oriented vs. RPC: Not separate methods are called, but instead a document is passed around asynchronously between various steps that make up a business process

- Integration on the level of business events (STP) rather than nightly batch file transfers

- Are data services more RPC-oriented, whereas higher-level business services are document-oriented?

- Virtualisation of service endpoints; therefore a more flexible adaptation of business processes. In addition, the connection complexity is reduced to attaching a service to the bus and then defining the message flow declaratively using high-level graphical tools (see screenshot).The ESB mediates all communication between services services never communicate directly (although such optimisations can be used internally, as e.g., in SonicESB).

- ESB is a distributed system in contrast to the hub-and-spoke architecture of typical EAI-products. This offers advantages in terms of reliability and scalability.

- Because of ist distributed nature, ESB deployment can be Step-by-step.

- Disadvantages: unrealistic that a single ESB product can be rolled out across the enterprise. Its likely that there will be multiple ESB products installed (e.g., mergers, fragmented IT strategies, organic development)

Message-Oriented Middleware (MOM)

- guaranteed delivery semantics (e.g., exactly-once, at-most-once, best-effort)

- different messaging domains: point-to-point, publish-subscribe

Possible process steps within the ESB

- intelligent message routing based on message contents (content-based routing)

- transformation (XSLT) between different technical formats

- enrichment of data with additional information

- archival of entry data

- access control verification

- logging

- throughput monitoring

- delegation to existing applications or web services

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