Loosely coupled, reusable software components that semantically encapsulate discrete functionality and are
distributed and programmatically accessible over standard Internet protocols.
Let’s examine this definition and deconstruct its meaning.
· First, web services are reusable software components. Web services continue the long
ascension of object-oriented design in software development. Rather than requiring
programmers to write one start-to-finish set of instructions after another, the
component-based model allows developers to reuse the building blocks of code created
by others to assemble and extend them in new ways.
· Second, these software components are loosely coupled. Traditional application design
depends upon a tight interconnection of all subsidiary elements. The complexity of
these connections requires that developers thoroughly understand and have control over
both ends of the connection; moreover, once established, it is exceedingly difficult to
extract one element and replace it with another. Loosely coupled systems, on the other
hand, require a much simpler level of coordination and allow for more flexible
reconfiguration.
· Third, web services semantically encapsulate discrete functionality. A web service is a selfcontained
“applet” that performs a single task. The component describes its own inputs
and outputs in a way that other software can determine what it does, how to invoke its
functionality, and what result to expect in return.
· Fourth, web services can be accessed programmatically. Unlike web sites and desktop
applications, web services are not designed for direct human interaction, and they do not
have a graphical user interface. Rather, web services operate at the code level; they are
called by and exchange data with other software. Web services certainly will be
incorporated into software designed for human interaction, however.
· Finally, web services are distributed over the Internet. Web services make use of existing,
ubiquitous transport protocols like HTTP. By piggybacking on the same, wellunderstood
transport as web content, web services leverage existing infrastructure and
can comply with current corporate firewall policies.
distributed and programmatically accessible over standard Internet protocols.
Let’s examine this definition and deconstruct its meaning.
· First, web services are reusable software components. Web services continue the long
ascension of object-oriented design in software development. Rather than requiring
programmers to write one start-to-finish set of instructions after another, the
component-based model allows developers to reuse the building blocks of code created
by others to assemble and extend them in new ways.
· Second, these software components are loosely coupled. Traditional application design
depends upon a tight interconnection of all subsidiary elements. The complexity of
these connections requires that developers thoroughly understand and have control over
both ends of the connection; moreover, once established, it is exceedingly difficult to
extract one element and replace it with another. Loosely coupled systems, on the other
hand, require a much simpler level of coordination and allow for more flexible
reconfiguration.
· Third, web services semantically encapsulate discrete functionality. A web service is a selfcontained
“applet” that performs a single task. The component describes its own inputs
and outputs in a way that other software can determine what it does, how to invoke its
functionality, and what result to expect in return.
· Fourth, web services can be accessed programmatically. Unlike web sites and desktop
applications, web services are not designed for direct human interaction, and they do not
have a graphical user interface. Rather, web services operate at the code level; they are
called by and exchange data with other software. Web services certainly will be
incorporated into software designed for human interaction, however.
· Finally, web services are distributed over the Internet. Web services make use of existing,
ubiquitous transport protocols like HTTP. By piggybacking on the same, wellunderstood
transport as web content, web services leverage existing infrastructure and
can comply with current corporate firewall policies.
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