XML – An Introduction Structured Data Mark-up James McCartney CSCE 590, Cluster and Grid Computing

Why XML? Allows creation of standardized markup. Separates presentation logic from data. Allows for multiple dynamic client applications. Mandates machine readable, rational tags for describing data. Support for wide ranging industry needs.

XML Requirements Identify all types of information making up the content of your document. Define the structure of each distinct type of information you are including in your document.

Tags, elements, and attributes. Mrs. Mary McGoon 1401 Main Street Anytown A. A tag is a value between the less than ( ) angle brackets. B. An element includes the starting and ending tag, and everything between the two. This includes other (child) elements. C. An attribute is a name value pair that is located in the opening tag of an element

Document States 1. Valid Documents abide by the XML syntax for document markup and follow the rules defined by their DTD and Schema definition. 2. Invalid Documents have syntax errors that don’t conform to XML rules. 3. Well-formed Documents follow XML syntax rules, but don’t have a DTD or Schema definition.

XML Structure General Structure of an XML Document:

XML Rules An XML document must contain a single root element. Elements can’t overlap (jump levels). End tags are required (at least ). Element names are case sensitive. Attributes must have a value and the values must be quoted.

Parts and Pieces Declaration – a parser flag. Comments – between Processing Instructions – Entities – begin with an ampersand, end in semi-colon. <>&"&apos;

Namespaces Namespaces allows developers to include multiple elements of the same name in the same document. <math_test xmlns:mtest=“ xmlns:mml=“ a - b =

Document Type Definition DTD are used to describe the document element, order, and structure. ? Optional + one or more * zero or more | choice

XML Schemas XML Schemas use XML syntax, support datatypes (even user-defined), and have more expressions. …

DOM and SAX 1. Document Object Model – digest the entire document and return a tree (of program objects) to be accessed by the program. 2. Simple API for XML – event based model for parsing that allows program to catch document events as they are needed.

Standards The Security Assertion Markup Language (SAML) is "an XML- based framework for exchanging security information. Simple Object Access Protocol (SOAP) define an XML format for Remote Procedure Call. XML-RPC is another less complex method for doing RPC. The Web Services Description Language (WSDL) makes it possible to “find” a web service and interact with it without prior knowledge about it’s design. Universal Description, Discovery, and Integration (UDDI) protocol defines how to query and publish web services with a registry. SVG, XSL-FO, MATHML, XForms, OpenOffice.org, Extensible Messaging and Presence Protocol (XMPP), etc.

References – O’Reilly Network OASIS IBM tutorial on XML, Doug Tidwell XML, The Complete Reference. Williamson, 2001 McGraw-Hill

Questions? XML Questions?