There’s a lot of confusion about Service Oriented Architecture. Some people dismiss it as meaningless jargon because it is so frequently used synonymously with multi-tier or web services. In fact, however, the term encapsulates an important set of concepts relating to the difference between how a system sees its own data and how that data is exposed to the outside world. This conference paper, Data on the Outside vs. Data on the Inside, by Pat Helland is the best explanation I’ve seen. Here’s an excerpt:
Inside of services, three classes of data are found
Reference Data from Other Services
- This reference data is transmitted by one service to another service that reads and stores the data.
- This includes three types of reference data: operands, historic artifacts, and shared collections.
- Periodically, new versions of the reference data are received and stored internally along with the appropriate version identifier.
Messages (Operators and Responses)
- Messages refer to both incoming and outgoing operators (requests) and their responses.
Service-Private Data
- Service-private data is internally maintained data that is never directly exposed outside of the service.
- Note: This data is frequently exposed indirectly through business logic.
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