Tuesday, October 31, 2006

SAWSDL Reaches Last Call for Comments

The Semantic Annotations for WSDL WG has promoted the SAWSDL specification to "Last Call for Comments".

Specification :- http://www.w3.org/TR/2006/WD-sawsdl-20060928/
Usage Guide :- http://www.w3.org/TR/2006/WD-sawsdl-guide-20060928/

Semantic Discovery and BPEL

BPEL is leading standard, co-authored by Oracle, IBM, Microsoft, BEA, SAP et all , for business process language to orchestrate Web services.It enables manual composition of services to create complex business process flow. But it lacks semantic expressiveness, which limits the automatic discovery, composition and customization of partner services required to address the growing need for highly dynamic IT environment. Also it is still far from fulfilling the SOA promise of “really” loosely coupled systems.

Semantic discovery can provide the missing functionalities with the help of semantic web and inference technologies. Semantic Web technologies will enable description of services in computer interpretable format and that will make it possible to perform automatic selection, composition and customization of services.

For a real implementation of a semantic discovery service, please refer to ksl.Stanford.edu/sds

Sunday, October 29, 2006

Semantic Integration - integration of data semantics

Visionaries [really farsighted] envision semantic integration as next step of SOA and application integration. EAI/SOA provides integration of technologies, but semantic integration provides integration of data and service behaviors or functionalities.

(Stretched) goal of Semantic Integration is to enable:

- automated service discovery
- automated service composition
- resilient or adaptive system
- automated service customization …etc.

Before we dive into the ways to achive these goals through usage of semantics in enterprise integration, let's look into the meaning of semantics [ sply. semantics of service ].

- Data Semantics: Formal definition of data in input and output messages of a web service which can be used for discovery and interoperability
- Functional Semantics: Formally representing capabilities of a web service which help to automatic discovery and composition
- Execution Semantics: Formally representing the execution or flow of services in a process or operations in a service to enable verification, simulation and exception handling
- QoS based Semantics: Formally describing operational metrics of a web service/process: cost, time, reliability etc. which is used for service optimization or to finding most suitable webservice for given SLA]

Three step process for moving from normal service to semantically enabled service - Semantic registration of services, which allows semantic discovery and composition to higher-level semantic service.

For semantic registration of services, there should be a way to capture semantic information of the service input/output, operations, functionality and QoS. Mainly two separate approaches are considered; by WSDL annotation or keeping separate metadata like WS-Policy etc.

Semantic discovery means selecting services from any specialized registry based on the functional requirements using semantic information of the operation and similarity based on input/output semantics of candidate services using information about the message parts.

And last but not least, semantic composition helps to achieve the most important goal of SOA based systems: reducing the complexity of creating composite services by choosing the optimal combination among possible options.