Learn Web Services
Selected Reading
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Web Services Behavioral Characteristics
Web services have special behavioral characteristics
XML-based
Web Services uses XML at data representation and data transportation layers. Using XML eliminates any networking, operating system, or platform binding. So Web Services based applications are highly interoperable application at their core level.
Loosely coupled
A consumer of a web service is not tied to that web service directly. The web service
interface can change over time without compromising the client's ability to interact
with the service. A tightly coupled system implies that the client and server logic are
closely tied to one another, implying that if one interface changes, the other must also
be updated. Adopting a loosely coupled architecture tends to make software systems
more manageable and allows simpler integration between different systems.
Coarse-grained
Object-oriented technologies such as Java expose their services through individual
methods. An individual method is too fine an operation to provide any useful
capability at a corporate level. Building a Java program from scratch requires the
creation of several fine-grained methods that are then composed into a coarse-grained
service that is consumed by either a client or another service. Businesses and the
interfaces that they expose should be coarse-grained. Web services technology
provides a natural way of defining coarse-grained services that access the right amount
of business logic.
Ability to be synchronous or asynchronous
Synchronicity refers to the binding of the client to the execution of the service. In
synchronous invocations, the client blocks and waits for the service to complete its
operation before continuing. Asynchronous operations allow a client to invoke a
service and then execute other functions. Asynchronous clients retrieve their result at a
later point in time, while synchronous clients receive their result when the service has
completed. Asynchronous capability is a key factor in enabling loosely coupled
systems.
Supports Remote Procedure Calls (RPCs)
Web services allow clients to invoke procedures, functions, and methods on remote
objects using an XML-based protocol. Remote procedures expose input and output
parameters that a web service must support. Component development through
Enterprise JavaBeans (EJBs) and .NET Components has increasingly become a part of
architectures and enterprise deployments over the past couple of years. Both
technologies are distributed and accessible through a variety of RPC mechanisms. A
web service supports RPC by providing services of its own, equivalent to those of a
traditional component, or by translating incoming invocations into an invocation of an
EJB or a .NET component.
Supports document exchange
One of the key advantages of XML is its generic way of representing not only data,
but also complex documents. These documents can be simple, such as when
representing a current address, or they can be complex, representing an entire book or
RFQ. Web services support the transparent exchange of documents to facilitate
business integration.
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