For instance, as an example of a service in SOA,
imagine a user directory that is accessible via Web services. In this example, the interface may
specify functions, or methods, that include searching the directory (searchDirectory), password
resets (resetPassword), updating user information (updateUser), and adding and removing users
(addUser, removeUser). As long as the interface is adequately de?¬? ned, the consumer of the service
does not need to know how the service is implemented to use it. Figure 16.1 illustrates a simpli?¬? ed
SOA.
Company A Intranet
Web site
Public
Web site SOA
based on Web
services
Employee
User
identity
Inventory
Shipping/
receving
Order
processing Accounting
Payment
provider
Credit card
processing
Shipping
provider
Shipping
service
Customer or
business partner
Figure 16.1 Simpli?¬? ed SOA example.
Service-Oriented Architecture and Web Services Security 211
Figure 16.1 shows that each service is reasonably independent and has a well-de?¬? ned purpose.
Th e idea behind SOA is that, provided the services and their interfaces are designed well, they can
be combined together in di?¬? erent ways to build di?¬? erent types of applications. For example, the
order-processing service may be accessible from both the public Web site for placing orders and the
internal Web site for sales and marketing purposes. Services expose their functionality through
industry standard Web service interfaces described using the Web Services Description Language
(WSDL), which is discussed later in this chapter.
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