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XML for Java Developers G22.3033-002 Session 7 - Main Theme XML Information Rendering (Part I) Dr. Jean-Claude Franchitti New York University Computer Science Department Courant Institute of Mathematical Sciences 1 Agenda n Summary of Previous Session n Extensible Stylesheet Language Transformation (XSL-T) n Extensible Stylesheet Language Formatting Object (XSL-FO) n XML and Document/Content Management n Assignment 4a+4b (due in two week) 2 Summary of Previous Session n Advanced XML Parser Technology n JDOM: Java-Centric API for XML n JAXP: Java API for XML Processing n Parsers comparison n Latest W3C APIs and Standards for Processing XML n XML Infoset, DOM Level 3, Canonical XML n XML Signatures, XBase, XInclude n XML Schema Adjuncts n Java-Based XML Data Processing Frameworks n Assignment 3a+3b (due next week) 3 1 XML-Based Rendering Development n XML Software Development Methodology n Language + Stepwise Process + Tools n Rational Unified Process (RUP) v.s. “XML Unified Process” n XML Application Development Infrastructure n Metadata Management (e.g., XMI) n XSLT, XPath XSL -FO APIs (JAXP, JAXB, JDOM, SAX, DOM) n XML Tools (e.g., XML Editors,Apache’s FOP, Antenna House’s XSL Formatter, HTML/CSS1/2/3, XHTML, XForms, WCAG n XML Applications Involved in the Rendering Phase: n Application(s) of XML n XML-based applications/services (markup language mediators) n MOM, POP, Other Services (e.g., persistence) 4 n Application Infrastructure Frameworks What is XSL? n XSL is a language for expressing stylesheets. It consists of two parts: n A language for transforming XML documents n A XML vocabulary for specifying formatting semantics n See http://www.w3.org/Style/XSL for the XSLT 1.0/XPath 1.0 Recs, the XSL-FO 1.0 candidate rec, and working drafts of XSLT 1.1/2.0 and XPath 2.0 n A XSL stylesheet specifies the presentation of a class of XML documents. It describes how an instance of the class is transformed into an XML document that uses the formatting vocabulary 5 XML Data Rendering Patterns n Manipulating and Rendering XML Structures Using Java n XSL-T n Transform n Sort n Output n XSL-T + -FO n Format n Output n Querying will be covered separately 6 2 eXtensible Style Language (XSL) n DSSSL & DSSSL-O n CSS 1, 2, 3 … n http://www.w3.org/Style/CSS/ n XSLT n XPath n XSL-FO n XSLT Processors n Stylus Studio XSL development environment n IBM XSL Editor n Saxon and Xalan XSLT processors n XSL-FO Processors n Antenna House 7 n fop XSL Processing n http://www.w3.org/Style/XSL/ n Processing Alternatives: n HTML + CSS -> Presentation n XML + CSS -> Presentation n XML + XSLT -> XSL-FO -> Presentation n XML + XSLT -> XML/HTML + CSS -> Presentation n Client or Server Processing ? n See Session 2 handout on IE5’s implementation of the XSL Spec. n Examples n See Session 2 Sub-Topic 1 Presentation: Beginning XML n See Session 2 handouts on XSL Tree Transformation Language n See Session 2 handout on Cascading Stylesheets 8 n See Session 2 handout on Styling Documents Using XSL A Language for “Mapping XML” (LMX) n LMX is a sample textbook application n LMX can convert a document in one DTD into another DTD and vice versa n LMX uses rules to describe bi-directional “MOM” conversions between two sets of documents n Rules have a “from-pattern” and a “to-pattern”b to respectively match the source document, and construct the target document n Some restrictions exist w.r.t. the LMX patterns in order to simp lify the program as much as possible n LMX can also be used to convert a XML document to HTML (“POP” application) 9 3 How Does the LMX Processor Work? n LMX makes heavy use of the DOM 1.0 API n LMX uses XML4J internally to: n Parse a rule file n Parse a source document n Generate a target document n See chapter 4.3 in the XML and Java textbook for a detailed description of the LMX implementation 10 LMX v.s. the eXtensible Stylesheet Language (XSL) n LMX and XSL both provide a syntax to encode “Style Sheets” n Each XML document can be associated with a style sheet that describes how elements should be organized and formatted for presentation n XSL style sheets provide custom appearances that give a web site a unified look and feel 11 How Does XSL Work? n A XSL style sheet is an XML document n XSL elements in a XSL style sheet correspond to a series of XSL “transformation” rules (i.e., XML tree transformation and/or formatting rules) n XSL rules describe how particular XML tags are to be converted to “flow objects” as the document is read 12 4 Part I Extensible Stylesheet Language Transformation (XSLT) 13 XSL Transformations n Assume root element of style sheet is <xsl> n Each <xsl> element contains one or more rule elements n Each rule has a target and an action n Target is a regular expression defining to which XML elements the rule applies n Action is the list of flow objects generated when the rule is applied: n Actions output a series of HTML tags in combination with the content of the element n Actions may output XML tags obtained via transformation of original XML data n Actions may output non-markup text, or run simple scripts or programs n Actions may use JavaScript to provide more complex, and dynamic behaviors 14 XSL Transformations (continued) n Conceptual Representation of XSL Transformations: <xsl> <rule> <target-element type=“tagname”/> action </rule> <rule> (…) </rule> </xsl> 15 5 XSL-T and Templates n XSLT rules are also called “Templates” n There may not be rules to match every element n Elements can be reordered on the output. n XSL style sheet must be well-formed n e.g., a HTML empty tag specified as <br> must be written as <br/> within a XSL style sheet action n XSLT elements used as a basis for a simple stylesheet are: n <xsl:stylesheet>, <xsl:template match …>, <xsl:apply- templates>, <xsl:for-each select ...>, and <xsl:sort select …> 16 XSLT Elements and Functions n Creating Elements and Attributes n xsl:element, xsl:attribute n Iteration and Sorting (e.g., xsl:sort) n Conditional Processing n xsl:apply-templates select=“ … “, xsl:if, xsl:choose n Copying Nodes (e.g., xsl:copy) n Combining Stylesheets n xsl:import, xsl:include n Defining Variables & Parameters (e.g., xsl:variable) n Scripting with XPath functions 17 Parsers with XSLT Support n SAX 2.0 or DOM Level 2 1.0 Support Required n Apache’s Xalan XSLT parser n org.apache.xalan.processor/templates/transformer n org.apache.xpath n Saxon XSLT parser n JAXP 1.1 (javax.xml.transform) n TraXP n Supported by Xalan 2.0, and Saxon 6.1 n Sun’s XSLTC n Converts stylesheet’s to class files (“translets”) 18 6 Part II Extensible Stylesheet Language Formatting Object (XSL-FO) 19 XSL Formatting n XSL flow objects are markup text n Markup language output flow objects can be HTML, DSSSL, VRML, etc. n We will focus on HTML output flow objects (simpler, more widely understood, better supported by current tools, and do not require an extra level of translation) 20 XSL Formatting Characteristics n XSL formatting is simpler than DSSSL (Document Style Semantics and Specification Language, pronounced “dissal”, ISO std 10179:1996) n XSL formatting is more powerful than CSS (Cascading Style Sheets) n XSL’s basic formatting syntax is understandable by anybody acquainted with DSSSL or CSS 21 7 Part III XML and Document/Content Management 22 What is a XSL Processor? n A XML document and its associated style sheet are combined by an XSL processor to produce a HTML document n The XSL Processor applies the style sheet to the XML document and outputs static HTML n The process can be automated with CGI scripts, Java servlets, or ActiveX controls to convert XML to HTML on the fly n A XSL processor is a standalone program or is part of a larger XML browser 23 How Does a XSL Processor Work? n The XSL processor consults the style sheet to find the rule that matches the element n The XSL processor takes whatever action is associated to the rule: n outputs element’s content plus assorted markup n performs more complicated operations (sorting XML data before outputting it, running a Javascript program on the XML data, adding missing content to XML data, etc.) 24 8 How Does a XSL Processor Work? (continued) n XSL processor formats each element upon receipt n XSL processor may process elements recursively n XSL processor receives input from XML processor and outputs formatted data based on the nature of the elements it receives n E.g., XSL processor receives <strong> element n XSL processor may output same content as bold text n If processor is an audio renderer, it may pump up the volume a n otch...2 25 How Does a XSL Processor Work? n The XSL processor consults the style sheet to find the rule that matches the element n The XSL processor takes whatever action is associated to the rule: n outputs element’s content plus assorted markup n performs more complicated operations (sorting XML data before outputting it, running a Javascript program on the XML data, adding missing content to XML data, etc.) 26 How Does a XSL Processor Work? (continued) n XSL processor formats each element upon receipt n XSL processor may process elements recursively n XSL processor receives input from XML processor and outputs formatted data based on the nature of the elements it receives n E.g., XSL processor receives <strong> element n XSL processor may output same content as bold text n If processor is an audio renderer, it may pump up the volume a n otch..