Web Services

Web Services are SOA enablers of choice. A web service is software designed to support interoperable machine-to-machine interaction over a network. Software applications written in the various programming languages and running on various platforms can use web services to exchange data over computer network like the internet in a manner similar to inter process communication on a single computer. This interoperability (e.g. between Java and python or windows and Linux application) due to the use of open standards. OASIS and W3C are the primary committees responsible for the architecture and standardization of web services. Web Services have an interface that is described in a machine-processable format like WSDL.

XML Web Services is a way to expose .Net classes across a TCP/IP network. It
uses a combination of SOAP, HTTP and XML, and is exposed via a web site
containing the services. The services are accessed via SOAP requests. It
enables the developer to create classes that can be used via web browser or
any other HTTP client application across the Internet. For a simple example,
you could create an XML Web Service Method that returns a .Net DataSet to
the client. The client could call the method, passing the various parameters
it takes, and get back a result set of data from over the Internet

What is WSDL?

The Web Services Description Language (WSDL) is an XML format published for describing Web Services. It is commonly abbreviated as WSDL in technical literature & often pronounced as “Whiz-Dull”. WSDL describes the public interface to the Web services. This is an XML based service description on how to communicate using the web service; namely the protocol bindings and message formats required to interact with web services listed in the directory. The supported operations and messages are described abstractly and then bound to a concrete network protocol and message format.

WSDL is often used in combination with SOAP and XML Schema to provide web service over the internet. A Client (program) connecting to a web service can read WSDL to determine what functions are available on the server. Any special data types used are embedded in the WSDL file in the XML Schema. The Client can then use SOAP to actually call one of the functions listed in WSDL.

What is UDDI?

UDDI is a acronym for Universal Description , Discovery and Integration - platform –independent , XML-based registry for business worldwide to list themselves on the Internet. UDDI is an open industry initiative enabling business to discover each other and define how they interact over the internet. A UDDI business registration consists of three components:

1. White Pages – Address , contact and known identifiers;
2. Yellow Pages – industrial categorizations based on standard taxonomies ; and
3. Green Pages – technical information about services exposed by the business.

UDDI is nominally one of the core Web Services standards It is designed to be interrogated by SOAP messages and provide access to WSDL documents describing the protocol bindings and message formats required to interact with web services listed in its directory.

Seminar on Web Services:

Content:

Section 1:
Look Back,Whats wrong in previous Distributed models like DCOM,CORBA,RPC,RMI

Section 2:
Introduction,Defination,Example,Need for web services,Benefits, Key Features,Challenges faced By WS
Section 3:
SOAP,SOAP-XML Messaging Protocol,HTTP,XML,SOAP Header,WSDL,WSDL Elements ,WSDL header,UDDI,UDDI Components,

Section 4:
WebServices Platform,Web Services Security

Section 5:
WS for Java Developers,WS for .Net Developers

Section 6:
Web Services Application

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The term Web services describes a standardized way of integrating Web-based applications using the XML, SOAP, WSDL and UDDI open standards over an Internet protocol backbone. XML is used to tag the data, SOAP is used to transfer the data, WSDL is used for describing the services available and UDDI is used for listing what services are available. Used primarily as a means for businesses to communicate with each other and with clients, Web services allow organizations to communicate data without intimate knowledge of each other's IT systems behind the firewall.
Unlike traditional client/server models, such as a Web server/Web page system, Web services do not provide the user with a GUI. Web services instead share business logic, data and processes through a programmatic interface across a network. The applications interface, not the users. Developers can then add the Web service to a GUI (such as a Web page or an executable program) to offer specific functionality to users.
Web services allow different applications from different sources to communicate with each other without time-consuming custom coding, and because all communication is in XML, Web services are not tied to any one operating system or programming language. For example, Java can talk with Perl, Windows applications can talk with UNIX applications.
Web services do not require the use of browsers or HTML.
Web services are sometimes called application services.

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XML

The XmlDocument class gives you the ability to load an Xml file. The class implements the DOM, which is an in-memory (cache) tree representation of an XML document, which allows you to navigate and edit the document.

The XmlDocument inherits from the XmlNode class, as seen in the class browser. The XmlNode class in reality provides much of the underlying functionality since it is the base class in the .NET implementation of the DOM.

So the XmlNode represents a single node in the Xml, while the XmlDocument extends the XmlNode class to represent an entire Xml Document (hence the name, XmlDocument).

Once the Xml file is loaded, you can also locate the root node of the document.

DOM

The W3C Document Object Model (DOM) is a platform and language neutral interface that allows programs and scripts to dynamically access and update the content, structure, and style of a document."

The W3C DOM provides a standard set of objects for representing HTML and XML documents, and a standard interface for accessing and manipulating them.

The DOM is separated into different parts (Core, XML, and HTML) and different levels (DOM Level 1/2/3):

Core DOM - defines a standard set of objects for any structured document
XML DOM - defines a standard set of objects for XML documents
HTML DOM - defines a standard set of objects for HTML documents

What is the XML DOM?
The XML DOM is the Document Object Model for XML
The XML DOM is platform and language independent
The XML DOM defines a standard set of objects for XML, and a standard way to access and manipulate XML documents
The XML DOM is a W3C standard.
The XML DOM views XML documents as a tree structure of elements embedded within other elements. All elements, their containing text and their attributes, can be accessed through the DOM tree. Their contents can be modified or deleted, and new elements can be created by the DOM. The elements, their text, and their attributes are all known as nodes.

The Document Object Model (DOM) class is an in-memory representation of an XML document. The DOM allows you to programmatically read, manipulate, and modify an XML document. The XmlReader class also reads XML, however it provides non-cached, forward-only, read-only access. This means that there are no capabilities to edit the values of an attribute or content of an element, or the ability to insert and remove nodes with the XmlReader. Editing is the primary function of the DOM. It is the common and structured way that XML data is represented in memory, although the actual XML data is stored in a linear fashion when in a file or coming in from another object. The following is XML data.

The XmlNode object is the basic object in the DOM tree. The XmlDocument class, which extends XmlNode, supports methods for performing operations on the document as a whole, for instance, loading it into memory or saving the XML to a file. In addition, XmlDocument provides a means to view and manipulate the nodes in the entire XML document. Both XmlNode and XmlDocument have performance and usability enhancements, and have methods and properties to:

Access and modify nodes specific to DOM, such as element nodes, entity reference nodes, and so on.
Retrieve entire nodes, in addition to the information the node contains, such as the text in an element node.

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