Cloudware Technologies - Guide to Cloud Computing for Business and Technology Managers - page 319

data and integrating legacy applications and functions into the SOA
environment. This includes the wrapping and service enablement of
legacy functions.

5. Service realizations : This layer is the component realization layer
that uses components for implementing services out of preexisting
applications and systems found in the operational systems layer.
Components comprise autonomous units of software that may pro-
vide a useful service or a set of functionality to a client (business
service) and have meaning in isolation from other components with
which they interoperate.

6. Operational systems : This layer is used by components to implement
business services and processes. Layer 6 is shown to contain exist-
ing enterprise systems or applications, including customer relation-
ship management (CRM) and ERP systems and applications, legacy
applications, database systems and applications, and other packaged
applications. These systems are usually known as enterprise infor-
mation systems.

15.4 Web Services
Web Services are not implemented in a monolithic manner but rather rep-
resent a collection of several related technologies. The minimum infrastruc-
ture required by the Web Services paradigm is purposefully low to help
ensure that Web Services can be implemented on and accessed from any
platform using any technology and programming language. The develop-
ment of open and accepted standards is a key strength of the coalitions that
have been developing the Web Services infrastructure:

1. Enabling technology standards. Although not specifically tied to
any specific transport protocol, Web Services build on ubiquitous
Internet connectivity and infrastructure to ensure nearly universal
reach and support. For instance, at the transport level, Web Services
take advantage of HTTP, the same connection protocol used by
Web servers and browsers. Web Services use Extensible Markup
Language (XML) as the fundamental building block for nearly every
other layer in the Web Services stack.

2. Core services standards. The core Web Services standards comprise
the baseline standards SOAP, WSDL, and UDDI:

a. Simple Object Access Protocol : SOAP is a simple XML-based

messaging protocol on which Web Services rely to exchange