Notes

Outline

Services Breakout: Expressiveness Challenges & Industry Trends

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1 ( cont’d.) Requirements

1 (cont’d.) Requirements Discovery & Selection Support for yellow pages Preconditions/effects sufficiently expressive Invocation/interoperation Input/outputs (invocation) Execution model Asynchronous messaging Disconnected operation Transactions & integrity Error recovery Rollback vs. “fix”

1 (cont’d.) Requirements Composition Sufficiently expressive preconditions/effects Pervasive computing Dynamic binding User constraints & preferences Semantic brokering Compatibility with existing standards WSDL, uPnP, Corba?, …

1 (cont’d.) Requirements “Web of Services” Compositional architecture API mechanisms supporting modularity, reuse Distinguish API from implementation 1-way reference (via URIs) Business Rules Security Compatibility with existing standards Support composition of multiple approaches

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5 (cont.) Espressiveness challenges Classes of classes E.g., powerset(C) as range of a property Properties of properties, property as range Grounding mappings Need path language, classes of classes, properties of properties Parameter bindings Need path language (for one thing) Processes as classes (not instances) Conditions & effects! Variables, quantifiers, scope State listOfInstancesOf

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