Context Free Grammars课件.ppt

Example 2: XML - What is it? XML = eXtensible Markup Language Technology for web applications - 1997 World Wide Web Consortium (W3C) standard that lets you create your own tags. Implications for business-to-business transactions on the web. 精品文档 HTML and XML Why do we need XML? We have HTML today All browsers read HTML Designed for reading by Humans Example on the left 精品文档 HTML Rendered HTML “rendered” as shown to the left Tags describe how the HTML should be displayed, or presented Tags don’t describe what anything is! 精品文档 Sample XML File Same data, but in an XML format Humans, but particularly computers, can understand the meaning of the tags If we want to know the last name, we know exactly where to look! 精品文档 Displaying XML XML can be rendered, or displayed, just like the HTML page if we so desire Rendering instructions aren’t stored in the same file, but in a separate XSL file - exTensible Stylesheet Language 精品文档 Second Rendering With a different style sheet, we can render the data in an entirely different way Same content, just different presentation 精品文档 Second example: Song Lyrics in HTML H1Hot Cop/H1 i by Jacques Morali, Henri Belolo, and Victor Willis/i ul liProducer: Jacques Morali liPublisher: PolyGram Records liLength: 6:20 liWritten: 1978 liArtist: Village People /ul 精品文档 Song Lyrics in XML SONG TITLEHot Cop/TITLE COMPOSERJacques Morali/COMPOSER COMPOSERHenri Belolo/COMPOSER COMPOSERVictor Willis/COMPOSER PRODUCERJacques Morali/PRODUCER PUBLISHERPolyGram Records/PUBLISHER LENGTH6:20/LENGTH YEAR1978/YEAR ARTISTVillage People/ARTIST /SONG 精品文档 Song XSL Style Sheet for Formatting ?xml version=1.0? xsl:stylesheet xmlns:xsl=/TR/WD-xsl xsl:template match=/ html headtitleSong/title/head bodyxsl:value-of select=.//body /html /xsl:template xsl:template match=TITLE h1xsl:value-of select=.//h1 /xsl:template /xsl:stylesheet Style Sheets can be quite complex; most translate to HTML 精品文档 Third Example - News Story New