XML and Web Services November 21, 2005 Leo Putra Mardjuki Christopher William Lee Corey Fung Chan

Who Invented XML? Jon Bosak (left) “The father of XML" Sun Microsystems. Organized the W3C XML activity in 1996 Chaired the W3C XML Working Group

What is XML used for? Designed to meet the challenges of large- scale electronic publishing and data exchange Important in the exchange of data across the web. sales data inventory data

What is XML? Biggest break through in the last decade. XML is eXtensible Markup Language Not a fixed format like HTML XML is a ‘meta language’ for describing data It allows you to define your own language and applications Establishes rules about formatting and marking up a document Must provide some schema in order for an application to “understand” the document.

XML example <!DOCTYPE OSU[ ]> Business Don Won Demarko

What is Schema? A schema is a conceptual framework that describes the underlying structure of your collection of elements. Define the “vocabularies” of element types and attributes for a given class of documents and allows you to share those documents with other applications. Play a role in information retrieval. These schemas can be formally defined as DTDs.

What is DTD? Document Type Declaration Defines the legal building blocks of an XML document. Defines the document structure with a list of legal elements.

External DTD XML Business Don Won Demarko DTD <!DOCTYPE OSU[ ]>

Internal DTD <!DOCTYPE OSU[ ]> Business Don Won Demarko

XML Parser Database Program HTTP- Server Apache HTTP – Client Browser Client OS Server HTTP – Client Browser OS Client DTD OSI Internet XMLHTTP/XML Open XML Read DTD Loc. Req. DTD Reads DTD Reads Doc Web Service

Advantages Simple (like HTML) Open standard (W3C standard) Endorsed by software industry market leader Extensible (no fix set of tags) Separation of content and presentation Support of Multilingual documents and Unicode Allowing multiple data types Rapid adoption by industry

Disadvantages XML can make very large database unwieldy to maintain Lack of integrated security It is a verbose language therefore the documents require: More disc space to save data More RAM to hold data More bandwidth to carry data More processing power to parse, transform, and extract information from XML files

Prospects of XML XML should be straightforwardly usable over the Internet It shall be easy to write programs that process XML documents XML documents should be human-legible and reasonably clear XML standard should be prepared quickly The design of XML should be formal and concise XML documents shall be easy to create Terseness in XML markup is of minimal importance

Examples of XML Applications Exchanging data (within databases or computer systems) among incompatible system Business-to-Business (B2B) applications – product, sales, financial information exchange over the Internet Storing and sharing plain text data Creating new XML-based languages (XHTML, MathML, XBRL, etc)

Web Services UDDI, WSDL, SOAP

Introduction to Web Services “..a new breed of web application” –xml.com “provides simplicity” XML is a web service standard, communicates through different languages Integrated into Microsoft.Net platform (2000)

Elements of Web Services SOAP (remote invocation) RPC messages UDDI (trader, directory service) WSDL (expression of service characteristics) XML+HTTP  XML+SOAP, UDDI, WSDL Those elements are all incorporated with XML

What Web Services Offer Component services that people use to build bigger services They are modular applications that can be published, located, and invoked across the web Once a web service is launched, other applications can discover and invoke the process

SOAP Simple Object Access Protocol SOAP is a lightweight protocol for exchange of information in a decentralized, distributed environment Sends messages through protocol and receives on the other end Calls object by making Remote Procedure Call (RPC) (Synchronous request/response message passing) XML based

WSDL Web Services Description Language WSDL describes what a web service can do, where it resides, hot to invoke it A WSDL definition contains all of the information necessary to invoke a web service A definition is just an XML document (WSDL schema) Developers can use the WSDL definition to generate code to act with the web service it describes

UDDI Universal Description, Discovery, and Integration It is a SOAP based web service for locating web services and programmable resources on a network provides developers and administrators to share information about internal services across businesses on the Internet

Bibliography Jake Sturm. Developing XML Solution. Microsoft Press, WA, Sean McGrath. XML: Processing with Python. Prentice Hall, NJ, Michael Floyd. Building Web Sites with XML. Prentice Hall, NJ, specs/default.aspx specs/default.aspx ntal.html ntal.html