WSDL – Web Services Description Language
– WSDL is an XML based standard that specifies how a client can interact with a
web service. It tells what methods are present in a web
service, what parameters and return values each method uses, and
how to communicate with them. It specifies what protocol (HTTP GET or HTTP POST
or SOAP (over HTTP)) should be used for transmission over the internet.
WS-Interoperability
Basic Profile – It is a recent standard that sets out a broad
range of rules and recommendations designed to guarantee interoperability
across the web service implementations on the different vendors. It specifies a
recommended sub-set of SOAP 1.1 and WSDL 1.1 specifications and lays out a few
ground rules. WS – Interoperability is strongly backed by all web service
vendors (including Microsoft, IBM, SUN and Oracle).
The WSDL
standard is fairly complex, but its underlying logic is hidden from the
developer in ASP.NET programming. ASP.NET automatically creates WSDL documents
for a web service. It can also create a proxy class based on a WSDL document.
This proxy class allows a client to call a web service without worrying about
networking or formatting issues.
SOAP – Simple Object Access Protocol
– A client can use three protocols to communicate with a web service in .NET:
a) HTTP GET –
It communicates with a web service by encoding information in the query string
and retrieves information as a basic XML document.
b) HTTP POST –
It places parameters in the request body (as form values) and retrieves
information as a basic XML document.
c) SOAP – It
uses XML for both request and response messages. Like HTTP GET and HTTP POST,
SOAP works over HTTP, but it uses a more detailed XML-based language for
bundling information.
SOAP
messages are widely supported by many platforms.
Although
.NET has the ability to support all three of these protocols, it restricts the
first two for better security. By default, it disables HTTP GET, and it
restricts HTTP POST to the local computer.
SOAP
messages are not handled directly by our applications. Instead, .NET will
translate the information in a SOAP message into the corresponding .NET data
types before the data reaches our code. This allows us to interact with web
services in the same way we interact with any other object.
DISCO – Discovery (DISCO is short form
for Discovery) – Disco is a Microsoft specific standard, that is used
for discovering Web Services. A .disco
file specifies the location of a web service on a web server. It provides a
straight forward way to create a repository of web service links that can be
used automatically by .NET.
Benefits of a .disco file:
a) It is only used for web services.
b) We can insert <disco> elements
for as many web services as we want, including the ones that resides on the
other web servers.
UDDI – Universal Description, Discovery
and Integration – The goal of UDDI is to provide repositories where
businesses can advertise all the web services they have. Generally groups of
companies and consortiums band together to set up their own UDDI registries
organized into specific industries. The web services are registered in the UDDI
registry. Many of these UDDI registries are restricted and not publicly available.
The UDDI
registry defines a complete programming interface that specifies how SOAP
messages can be used to retrieve information about a business or register the
web services for a business.
