WSMO-Lite, which describes a lightweight service ontology and annotation mechanism for Web Service Description Language (WSDL), has been accepted for the European Semantic Web Conference 2008 (you can download the paper here).

WSMO-Lite which is currently under the review process in the CMS WG, has been co-authored by Tomas Vitvar, Jacek Kopecky, Jana Viskova and Dieter Fensel. In the paper we define the service ontology describing constructs for services’ information model (ontology) as well as functional services’ descriptions (i.e., categorization, conditions and effects). Using the W3C Semantic Annotations for WSDL and XML Schema (SAWSDL), we define a mechanism for annotation of various WSDL components with WSMO-Lite semantic descriptions. In addition, we define the algorithm to derive the behavioral service descriptions in a form of Abstract State Machines (ASM) from functional annotations (i.e. conditions and effects) of WSDL interface operations and we outline a usage of semantic annotations for a number of services’ use tasks such as service discovery, composition, selection, mediation, etc.

Today, we had a WSMO phone conference where we discussed the semantic annotations for RESTful services. I have presented the work done by Amit Sheth and his group on SA-REST (see the presentation below and my previous post).

RESTful services are usually described in a free-text form in HTML while service descriptions (i.e. service contracts) are not explicitly defined. In addition, when creating Web 2.0 applications (mashups), the problem with integration of data produced or consumed by these services is still a remaining issue. A developer must either implement a mediator or change the implementation of a service (if possible) to conform to integration needs. SA-REST introduces a novel approach to annotation of RESTful service description in a HTML using microformats. Semantic descriptions can significantly improve the data integration and automation of service lifecycle. SA-REST proposes to use W3C recommendation where possible, thus the annotation mechanism is based on RDFa and GRDDL

SA-REST, however, does not define any forms of semantic descriptions but assumes that such descriptions will be reused. In this respect, SA-REST is an analogous approach to semantic annotations of WSDL using SAWSDL. In the WSMO WG, we have recently done the work on WSMO-Lite (see our paper in ECOWS 2007 conference) which defines a minimal lightweight service ontology and which can be used for annotations of WSDL services by means of SAWSDL. This is the new approach to augmenting existing service descriptions already available (within or outside of enterprises) in a bottom-up fashion. However, it is important to note that WSMO-Lite is independent on WSDL (and SAWSDL). In this respect, we plan to use WSMO-Lite as a concrete service ontology for annotation of RESTful services, and possibly build on top of SA-REST. This will introduce the second annotation mechanism for WSMO-Lite allowing to use both, WSDL and RESTful services as mechanisms for invocation and communication. We call this annotation mechanism MicroWSMO.

The MicroWSMO together with WSMO-Lite are the core specifications of the upcoming EU funded project SOA4ALL.The goal of this project is to enable SOA architectures in the large-scale Web environment where semantics will play the central role in service provisioning, automation, and scalability.

IEEE Internet Computing magazine in its November/December issue published the article authored by Amit Sheth et al. entitled SA-REST: Semantically Interoperable and Easier-to-Use Services and Mashups. They discuss how to enable semantic annotations for RESTful services in an analogical way as SAWSDL does (see my previous post and article on SAWSDL). They define a very simple mechanism to mark input, output, lifting, lowering and fault in the REST specification usually available through some XHTML page and by using RDFa and GRDDL. The main point is that since REST providers usually define the services in a textual form on the web there is no explicit and formal form for definition of input, output or fault schema for messages. SA-REST introduces a micro-format style to their semantic description as part of the REST service specification embedded in a XHTML page.

I only wonder why authors define input and output keywords for SA-REST and do not adopt SAWSDL modelReference. SAWSDL modelReference is more generic annotation you can use for any kind of service description including information model (like they do with input and output) as well as functional (capability such as preconditions and effects) or non-functional descriptions. In my opinion, it would also be handy that the annotation framework is the same as the one introduced by SAWSDL as it would allow to work with independent semantic layer on the top of technologies like WSDL and REST.

What I like in this work is the way how semantic annotations for services can be done using micro-format style to definition of meta-data about resources (in this case XHTML describing a RESTful service). They use RDFa and GRDDL for that purpose. This approach very much complements our work on WSMO-Lite and it is inline with what we plan to further introduce in our conceptual models for services around WSMO. This will all happen in the EU FP7 project SOA4ALL and W3C Incubator Group called SWS-Testbed (Amit contributes to this group with semantic annotations for REST too).

The IEEE Software magazine published in the November/December issue our article entitled SESA: Emerging Technology for Service-Centric Environments where we discuss the innovative SOA technology based on the semantic service descriptions. We first outline a number of governing principles for the SESA design, research and implementation such as the service-oriented principle, the semantic principle, and the problem-solving principle. Following these principles, the SESA defines a set of essential functionalities (middleware services) required for the automation of the service provisioning process such as discovery, adaptation, fault handling, monitoring, mediation, and so on. The important aspect of the SESA lies in the semantic description of business services. The SESA adopts the semantic model introduced by WSMO (Web Service Modeling Ontology) extending WSDL service descriptions with semantics for information model, functional service definitions, behavioral descriptions and non-functional properties. We discuss in detail all these service semantics and illustrate their use on number of examples. In addition, we describe the business services integration process facilitated by the SESA middleware services composed of so called late-binding phase and execution phase.

Our work on the SESA has been done in the context of the EU project Knowledge Web, OASIS Semantic Execution Environment Technical Committee, roadmap for the research agenda of the European Technology Platform NESSI (its Semantic Technology working group), and STi2 initiative. The future direction of this work will be to integrate the SESA platform with major enterprise technologies and to expand the SESA towards large-scale SOA on the Web. Both these directions will be subject of research and development in the upcoming Irish and the EU projects, namely Lion, COIN and SOA4ALL.