Abstract
Service-oriented computing (SOC) is a new computing paradigm that uses services as building blocks to accelerate the development of distributed applications in heterogeneous computer environments. SOC promises a world of cooperating services where application components are combined with little effort into a network of loosely coupled services for creating flexible and dynamic business processes that can cover many organizations and computing platforms (Chesbrough & Spohrer, 2006; Papazoglou & Georgakopoulos, 2003). From a technical point of view, the efforts to offer services have focused on the development of standards and the creation of the infrastructure necessary to describe, discover, and access services using the Web. This type of service is usually called a Web service. The availability of an abundant number of Web services defines a platform for distributed computing in which information and services are supplied on demand, and new services can be created (composed) using available services. Nevertheless, the composition of Web services involves three fundamental problems (Sycara, Paolucci, Ankolekar, & Srinivasan, 2003): 1. To elaborate a plan that describes how Web services interact, how the functionally they offer can be integrated to provide a solution to the considered problem. 2. To discover Web services that accomplish the tasks required by the plan. 3. To manage the interaction of the chosen services. Problems 2 and 3 are of responsibility of the infrastructure that supports the composition of services, while the first problem is of responsibility of the (software) agents that use the infrastructure. The discovery and interaction of Web services poses two main challenges to the infrastructure: 1. How to represent Web services capabilities and how to recognize the similarities between service capabilities and the required functionalities. 2. How to specify the information a Web service requires and provides, the interaction protocol, and the low-level mechanisms required to service invocation.
TopIntroduction
Service-oriented computing (SOC) is a new computing paradigm that uses services as building blocks to accelerate the development of distributed applications in heterogeneous computer environments. SOC promises a world of cooperating services where application components are combined with little effort into a network of loosely coupled services for creating flexible and dynamic business processes that can cover many organizations and computing platforms (Chesbrough & Spohrer, 2006; Papazoglou & Georgakopoulos, 2003).
From a technical point of view, the efforts to offer services have focused on the development of standards and the creation of the infrastructure necessary to describe, discover, and access services using the Web. This type of service is usually called a Web service. The availability of an abundant number of Web services defines a platform for distributed computing in which information and services are supplied on demand, and new services can be created (composed) using available services. Nevertheless, the composition of Web services involves three fundamental problems (Sycara, Paolucci, Ankolekar, & Srinivasan, 2003):
- 1.
To elaborate a plan that describes how Web services interact, how the functionally they offer can be integrated to provide a solution to the considered problem.
- 2.
To discover Web services that accomplish the tasks required by the plan.
- 3.
To manage the interaction of the chosen services.
Problems 2 and 3 are of responsibility of the infrastructure that supports the composition of services, while the first problem is of responsibility of the (software) agents that use the infrastructure. The discovery and interaction of Web services poses two main challenges to the infrastructure:
- 1.
How to represent Web services capabilities and how to recognize the similarities between service capabilities and the required functionalities.
- 2.
How to specify the information a Web service requires and provides, the interaction protocol, and the low-level mechanisms required to service invocation.
Current Web service technologies are focused on syntactic interoperability and do not offer adequate support for automatic discovery, composition, and execution of Web services. As a consequence, most available Web service environments support only manual service discovery and composition (Domingue, Galizia, & Cabral, 2006).
The Semantic Web (SW) (Berners-Lee, Hendler, & Lassila, 2001) has the potential to offer the semantic interoperability that an infrastructure for Web services needs in order to support automatic discovery, composition, and execution of Web services. The Semantic Web makes it possible that resources of every type could be localized, retrieved, and processed without human intervention, helping to reduce the information overload of the current Web.
Semantic Web services (SWS) are the result of integrating Web services and Semantic Web technologies (McIlraith, Son, & Zeng, 2001). The SW offers the formal languages and ontologies that enable making relations and inferences among services, message contents, and business rules.
The purpose of this article is to give an overview of the current main proposals for making SWS a reality. This is done by pointing out the main aspects of the relevant specifications currently submitted to the Word Wide Web Consortium (W3C) (http:// www.w3.org), the organization responsible for developing open standards that lead the Web to evolve in a single direction.
TopThe Web Services Architecture
Semantic Web services can be seen as an evolution of the concepts presented in the Web services architecture (WSA), defined in the context of a service-oriented architecture (Booth, Haas, McCabe, Newcomer, Champion, Ferris, et al., 2004).
Key Terms in this Chapter
Bulk Spam: Spammers e-mail in bulk using automatic e-mail-sending programs. Spammers must first obtain e-mail addresses and sources for e-mail addresses include joining mailing lists to gather addresses from the mailing list software, purchasing mail lists from other spammers on CD-ROM (which can contain millions of addresses), and spambots (or harvesters) which scan Internet newsgroups and Web pages for e-mail addresses.
Spam: Spam can be defined as unsolicited e-mail, often of a commercial nature, sent indiscriminately to multiple mailing lists, individuals, or newsgroups.
Spoofing: Spoofing is a technique often used by spammers to make them harder to trace. Trojan viruses embedded in e-mail messages also employ spoofing techniques to ensure the source of the message is more difficult to locate
Computation Time per Message: The key fact is the observation that the solving of a spam deterring puzzle is both an expenditure of actual money (in the form of the amortized yearly cost of a CPU) as well as the expenditure of a certain amount of clock time. As there are only so many seconds in a day, these two ideas can be connected.
Whitelists: Whitelists, along with signatures, are a means of ensuring ease of communication and establishing trust between verified correspondents. EndNote ahttp://www.qovia.com/
SPAM Scams: Mass mailings of fraudulent messages or those designed to con people out of personal information for the purpose of identity theft and other criminal acts.
Trusted E-Mail Open Standard: On April 30, 2003, ePrivacy Group announced the Trusted E-mail Open Standard (TEOS) to fight spam, spoofing, and e-mail fraud (Schiavone et al, 2003). TEOS is a staged approach toward a trusted e-mail system built upon and extending the SMTP protocol.
Domain Certificates: These are a first line of defence for reducing forgery. This is a highly recommended goal in any case. They can be implemented at the SMTP level, separately from the remainder of the filters, which must operate at the message level.