In a Service-Oriented Architecture (SOA) it becomes imperative for the providers and requestors to communicate meaningfully with each other notwithstanding the heterogeneous nature of the underlying information structures, business artifacts, and other documents. This requirement is termed as semantic interoperability.

Often technology is made out to be the biggest impediment to effective collaboration and integration between requestors and providers; however it is usually the problem of semantic interoperability which is the root cause.

Semantic interoperability can be achieved between heterogeneous information systems (service providers and service requestors) in multitude of ways. On one extreme, development of comprehensive shared information models can facilitate semantic interoperability among the participant applications and businesses.

However, the problem with this approach is its rigidity, which translates to inflexibility when it comes to business processes leveraging SOA. On the other extreme, semantic interoperability can be achieved by providing appropriate semantic mediator (translator) at each participant’s end, to facilitate the conversion to the information format which the participant understands.

Most often systems use a combination of context independent shared information models, coupled with context specific information specialization approaches to achieve semantic interoperability.

In the context of SOA, mainly four practical approaches to semantic interoperability have been proposed and used with different levels of success:

* Vertical Domain Centered Business Vocabularies

* Horizontal Canonical Cross-Vertical frameworks like ebXML, UBL etc.

* Semantic Web based ontological frameworks

* Semantic Mediators

Each vertical domain of business applications has various types of peculiarities specific to the domain warranting the development of a specialized shared vocabulary of business processes and documents.

At the same time, it is also observable that various types of business concepts and data types are common across multiple verticals necessitating the development of cross-domain vocabularies and processes so that they can be captured in a domain-independent manner.

Common artifacts falling into this category are:

* Business concepts, Data and Documents like Purchase Orders, Shipping Handles etc.

* Process, workflow, choreography etc. including exception handling

* Contracts, Trust, Roles, permissions etc.

The third truly dynamic category of business processes in SOA fall under the dynamic category. Dynamic SOA based business processes operate on the “publish—find-bind” paradigm principle, where business processes may dynamically involve business partners and associated applications.

The problem of semantic interoperability is far more acute in such dynamic situations involving service brokers, due to the lack of prior business relationships between the enterprises. Industry practitioners have suggested leveraging work in semantic web to devise comprehensive and open ontologies to address the issue of semantic interoperability for dynamic binding based SOA.

While the aforementioned approaches suggest some form of structured common information modeling, a popular prevalent approach to semantic interoperability is via use of custom semantic mediators, which are custom coded application bridges at each information source that handle the task of conversion to/from the format the information source understands.

About the author

Dr. Srinivas Padmanabhuni is a Principal Researcher with the Web Services Centre of Excellence in SETLabs, and specializes in Web services, Service Oriented Architecture, and Grid technologies alongside pursuing interests in semantic web, intelligent agents, and enterprise architecture. He has authored several papers in international conferences. Prior to Infosys, Dr. Srinivas has worked in multiple capacities in startups out of Canada and USA. Dr. Srinivas holds a PhD degree in computing science from University of Alberta, Edmonton, Canada. Prior to PhD he secured his B.Tech and M.Tech from Indian Institutes of Technology at Kanpur and Mumbai respectively.