XML_Introduction

Introduction to XML Society for Technical Communication Presented by Craig Jordan Senior Software Analyst, Compuware January 12, 2000 Copyright © 2000, Compuware. All rights reserved. XML’s Place in the World Evolution of the Web Web Technologies What is XML Evolution of the Web  Static  Dynamic – Files  Databases – Retrieve  Find  Documents  Applications – Marketing  Selling – Telling  Interacting  Whole  Part – Content & Presentation  Presentation Web Technologies: Presentation  HTML – Mark-up language for formatting static content  DHTML – API to formatted elements so they can be modified dynamically  CSS – Declarative format rules Web Technologies: App Logic  Scripting, Java, ActiveX – Transport for application logic  ASP, CGI – Server-based techniques for creating interactive web sites by obtaining user responses and dynamically generating HTML pages What has been missing?  An intelligent data format that – offers more than simple formatting – is platform independent and portable – isolates information from presentation  A format that can describe: – Data constraints – Complex relationships – Application behavior XML: Extensible Markup Language  A Definition – XML is a language for creating data-description languages.  An Example ]> XML: Key Characteristics     Data-Centric Database/Source-Neutral Open Human-Readable Extensible Generic   XML Components  Document Type Definition (DTD) – Defines data format   Document – Instantiates a data format Parser – Converts a document into an internal treestructure – Confirms that data conforms to DTD XML Benefits XML Benefits Not Just for the Web Conclusion XML Benefits Separates Content from Formatting – Same content can be formatted in several different ways. – Content can be extracted in its raw form. – Content rather than format can be searched. XML Benefits Data Interoperability – Document Type Definition (DTD) acts as an interface agreement between partners – Data is self-describing – Data is independent of original source XML Benefits Supports Stateless Architectures – Provides a transport mechanism for structured state. – Platform independent state representation. – Persistence in any layer is simplified. XML Benefits Supports Isolation in N-Tier Architectures Data Layer Business Logic Presentation Layer Typical n-tier architecture DTD 1 Data Layer XML Xport Business Logic XML Xport DTD 2 Presentation Layer XML enabled n-tier architecture Not Just for the Web Goal: Strengthen Partnership via Shared Information Partner 1 information DTD Partner 2 information XML XML XML Technical Overview Document Object Model XML Syntax Rendering XML XML: Document Object Model  The Document Object Model presents the content of the XML document as a singlyrooted tree structure. c o n ta c ts c o n ta c t c o n ta c t n am e e m a il n am e e m a il J o e S m ith js m ith @ e m a il.c o m M a ry C a rn m c a rn @ ya h o o .c o m XML Syntax: Terminology Review  ELEMENT – A conceptual name for a portion of a document  TAG – The text that delineates an element. – Normally a pair of START and END tags.  CONTENT – The text contained between an element’s start and end tags.  ATTRIBUTE – A qualifier for an element – Value may be    Value Set Free Text Empty XML Syntax: Terminology Review First Option ELEMENT TAGS CONTENT Option (an item in a pick-list) and First Option VALUE=“Option1” SELECTED     ATTRIBUTES – Free Text – Empty XML Syntax: New Terminology  An XML document consists of 2 parts: – prolog - declares element names, attributes, and rules for valid markup of data – document instance - date with markup; similar to in the HTML world; one ROOT element, with all other elements as children of the root; tree representation  A parsed document is either: – well-formed - document need not have a DTD; elements are properly nested and marked up – valid - in addition to being well-formed, document conforms to a DTD (internal or external); all elements, attributes, and entities used in the document are found in the DTD XML Syntax: Putting it all together 12/20/1999 Rick … foo.asp bar.asp … XML Syntax: Putting it all together ]> Rendering XML XML has no native visual representation. Some techniques commonly used to render XML include – Cascading Style Sheets (CSS) – Document Object Model + Script – Data Binding (Microsoft-specific) – eXtensible Style Sheets (XSL) Rendering XML using XSL XSL can be used to transform XML documents in many ways. One use is to transform XML into HTML. Style Sheet Processor XML Document Transformation XSL Style Sheet Resulting Document Conclusions  XML will be a key enabling technology for web applications in the next decade.  XML is a database transport technology in much the same way that ActiveX and Java are application logic transport technologies. XML will form the foundation for inter-partner data exchange and will make EDI available for the general business consumer. 