Global Positioning System Reference
In-Depth Information
services composition and some basic assumptions, such as the subdivision
of the involved services into categories, and the use of XML for messages
exchanges, services composition is still a complex task and several facets
must be wisely considered.
The goal of this chapter is to investigate and discuss the issues arising
during the composition of W3C and OGC services, that is how two or more
services can work together in order to obtain a higher level service.
The remainder of this chapter is organized as follows. In the “Service-
oriented Computing” section an overview of SOC and SOA is given. In
“W3C Web services” and “The Open Geospatial Consortium Web Services”
sections the main characteristics and differences of the service platforms
proposed by the W3C and the OGC are discussed. After a brief introduction
to the concept of service composition, the “Services Composition” section
discusses issues related to the Web services and OGC services orchestration,
while the “Web and OGC Services Integration” section reviews some
solutions useful for their integration. “The Representational State Transfer
paradigm” section covers the main characteristics of the Representational
State Transfer (REST) paradigm, as a possible alternative for the development
of distributed systems. Some conclusions are drawn in the last Section.
Service-oriented Computing
A service can be seen as an independent software module that performs
certain (more or less complex) operations, such as an invoicing and a
booking of a plane ticket. One of the key features of a service consists
in the client capability to invoke it through the service public interface,
disregarding details about the service internal implementation. To ensure
such a fundamental characteristic, a service has to meet some basic
requirements (Papazoglou 2003):
being loosely coupled, namely a low level of interconnection among
services;
being technology neutral, which implies that its public interface can
be described by using standard technologies available to anyone in
any operating environment;
supporting location transparency, namely the possibility for a client
to invoke it irrespective of its real location.
A service that meets these characteristics can be then invoked by clients
belonging to different organizations and can be seen as an independent basic
building block to create new types of distributed applications.
The defi nition of service along with the aforementioned features
represent the core of the SOC paradigm whose benefi ts have become clear
in many application domains and in particular in Geographic Information
Search WWH ::
Custom Search