Abstract
It is expected that virtual factories and enterprises of the future will be able to self-organize in distributed, autonomous, interoperable, non-hierarchical, innovation ecosystems and be dynamically delivered as services, end-to-end along the global value chain. In this scenario, services and service ecosystems become central artifacts, and it is necessary to model and manage them appropriately for automation and scalability. Two main popular architectural approaches for realizing service orientation are WSDL-based SOA and the RESTful style. The level of automation offered by these approaches is limited, and human intervention is required in order to achieve most of the service-related tasks such as discovery, ranking, invocation, and monitoring. In order for service-oriented technologies to scale, they need to offer a significant degree of automation. To address the scalability issues in service composition, this chapter proposes a semantically enabled service-oriented architectural approach (SESA) and its implementation in the form of a platform. The authors detail the principles, models, architecture, and implementation underlying the approach in which lightweight semantics play a central role.
TopBackground
The Web service technology stack allows for exchanging messages between Web services (SOAP) (Box et al., 2000), describing the technical interface for consuming a Web service (WSDL) (Box et al., 2000), and advertising Web services in registries (UDDI) (Fernandez, Gomez-Perez, & Juristo, 1997). However, in traditional Web service implementations, the lack of information to express the meaning of the data and of the vocabulary referenced by the interface, as well as the lack of formalization of the Web service behavior implies the requirement of human intervention in tasks such as Web service discovery, composition, and ranking and selection, thus severely hindering the automation of the envisioned tasks. The emergence of the Semantic Web (W3C, 2011) envisions an extension of the current Web in which information is given well defined meaning, thus better enabling computers and people to work in cooperation (Berners-Lee et al., 2001). This meaning is represented by the structured collections of information and sets of inference rules that can be used by machines to conduct automated reasoning. The same formalization techniques can form a foundation to introduce semantics to Web service architectures.
Key Terms in this Chapter
Semantic Web Services (SWS): A technology that combines Web services and Semantic Web technologies in order to allow for a higher level of automation when dealing with Web services.
Web Service Modeling Ontology (WSMO): A conceptual model which defines the basic concepts of Semantic Web Services.
Web Service Modeling Ontology Lite (WSMO-Lite): A lightweight service ontology inspired by WSMO, which builds on the newest W3C standards and allows bottom-up, lightweight semantic annotation of services.
Service-Oriented Architectures (SOA): A methodology for reorganizing and building software applications and infrastructure into a set of meaningful interacting services.
Semantically Enabled Service-Oriented Architectures (SESA): A comprehensive framework that augments existing SOA frameworks to incorporate semantic solutions to address the SOA semantic gap.
Web Service: A computational entity that is accessible over the Internet, using Web service standards and protocols.
Service Delivery Platform: A software platform which provides automatic support for service related tasks including discovery, ranking, invocation, and monitoring.
Representational State Transfer (REST): An architecture style for designing networked applications. Rather than using complex mechanisms such as CORBA, RPC, or SOAP to connect between machines, simple HTTP is used to make calls between machines. RESTful applications use HTTP requests to post data (create and/or update), read data (e.g., make queries), and delete data, thus using HTTP for all four CRUD (Create/Read/Update/Delete) operations.
Web Service Description Language (WSDL): An XML format for describing network services as a set of endpoints operating on messages containing either document oriented or procedure oriented information. The operations and messages are described abstractly, and then bound to a concrete network protocol and message format to define an endpoint.