The concept of Web services--now familiar to most companies--is sometimes positioned
as a replacement for EAI (enterprise application integration) solutions. This
confusion is maintained, and even supported, by the new vendors of pure
Web services solutions.
Let us start by looking at the definition of the concepts of Web services and
Web services: A Web service is a modular application that can be accessed
by a network (Internet, intranet, extranet) through a standard XML format interface.
Enterprise application integration: EAI is a concept that groups together
a set of methods, technologies and tools used to consolidate and coordinate
different applications, leading to the urbanization of the enterprises
On reading these definitions, we realize that the functional scope of each
notion is quite different. Web services pinpoint a specific focus area, while
EAI addresses a much wider range of issues.
Technical Composition of Web Services and EAI
Let us examine the technical components that make up Web services and EAI.
Technical Composition of Web Services
Web services are made up of a set of standards:
- XML: technology used to describe information
- UDDI: used to find required services
- WSDL: used to describe Web services
- SOAP: for remotely executing Web services
This simple set of components has enabled Web services to build a strong following.
One of the key elements driving Web services is interoperability. Currently,
interoperability between Web services (as described above) can be considered
a valid reality because the related technologies are both simple and mature.
The diagram illustrates another important point: the standards associated with
Web services do not attempt to define how to build a service that is to be published
or Webified. The service may be new or in existence already, and
whatever the implementation technology used, this will not change the way it
is presented in relation to other Web services. The service wrapper
is also proprietary, with no link to the Web services standards.
However, the initial technical composition of Web services displays a number
of shortcomings, as it does not cover the following aspects:
- Encryption: Over HTTP, it is possible to use SSL to encrypt the channel,
and soon XML Digital Encryption will be available for messages.
- Authentication: Two key standardizations are in progress--SAML (Security
Assertion Markup Language) and XKMS (XML Key Management Specification).
- Signature: XML Digital Signature looks promising.
- Transactions: BTP (Business Transaction Protocol), with a first implementation
by HP (HP Web Services Transaction Server 1.0) and XAML (Transaction Authority
- Orchestration: XLANG (Microsoft BizTalk) and WSFL (Web Services Flow