Extreme Java G Session 3 - Sub-Topic 5 XML Information Rendering. Dr. Jean-Claude Franchitti

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1 Extreme Java G Session 3 - Sub-Topic 5 XML Information Rendering Dr. Jean-Claude Franchitti New York University Computer Science Department Courant Institute of Mathematical Sciences 1 Agenda Extensible Stylesheet Language Transformation (XSL-T) Extensible Stylesheet Language Formatting Object (XSL-FO) XML and Document/Content Management XML/XSL and JSP/JavaBeans Rendering Technology Internationalization Issues Web Content Accessibility Guidelines (WCAG) 2 1

2 XML-Based Rendering Development XML Software Development Methodology Language + Stepwise Process + Tools Rational Unified Process (RUP) v.s. XML Unified Process XML Application Development Infrastructure Metadata Management (e.g., XMI) XSLT, XPath XSL-FO APIs (JAXP, JAXB, JDOM, SAX, DOM) XML Tools (e.g., XML Editors, Apache s FOP, Antenna House s XSL Formatter, HTML/CSS1/2/3, XHTML, XForms, WCAG XML Applications Involved in the Rendering Phase: Application(s) of XML XML-based applications/services (markup language mediators) MOM, POP, Other Services (e.g., persistence) Application Infrastructure Frameworks 3 XML Data Rendering Patterns Manipulating and Rendering XML Structures Using Java XSL-T Transform Sort Output XSL-T + -FO Format Output Querying will be covered separately 4 2

3 What is XSL? XSL is a language for expressing stylesheets. It consists of two parts: A language for transforming XML documents A XML vocabulary for specifying formatting semantics See 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 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 extensible Style Language (XSL) DSSSL & DSSSL-O CSS 1, 2, 3 XSLT XPath XSL-FO XSLT Processors Stylus Studio XSL development environment IBM XSL Editor Saxon and Xalan XSLT processors XSL-FO Processors Antenna House fop 6 3

4 XSL Processing Processing Alternatives: HTML + CSS -> Presentation XML + CSS -> Presentation XML + XSLT -> XSL-FO -> Presentation XML + XSLT -> XML/HTML + CSS -> Presentation Client or Server Processing? See Session 2 handout on IE5 s implementation of the XSL Spec. Examples See Session 2 Sub-Topic 1 Presentation: Beginning XML See Session 2 handouts on XSL Tree Transformation Language See Session 2 handout on Cascading Stylesheets See Session 2 handout on Styling Documents Using XSL 7 A Language for Mapping XML (LMX) LMX is a sample textbook application LMX can convert a document in one DTD into another DTD and vice versa LMX uses rules to describe bi-directional MOM conversions between two sets of documents Rules have a from-pattern and a to-pattern b to respectively match the source document, and construct the target document Some restrictions exist w.r.t. the LMX patterns in order to simplify the program as much as possible LMX can also be used to convert a XML document to HTML ( POP application) 8 4

5 How Does the LMX Processor Work? LMX makes heavy use of the DOM 1.0 API LMX uses XML4J internally to: Parse a rule file Parse a source document Generate a target document See chapter 4.3 in the XML and Java textbook for a detailed description of the LMX implementation 9 LMX v.s. the extensible Stylesheet Language (XSL) LMX and XSL both provide a syntax to encode Style Sheets Each XML document can be associated with a style sheet that describes how elements should be organized and formatted for presentation XSL style sheets provide custom appearances that give a web site a unified look and feel 10 5

6 How Does XSL Work? A XSL style sheet is an XML document XSL elements in a XSL style sheet correspond to a series of XSL transformation rules (i.e., XML tree transformation and/or formatting rules) XSL rules describe how particular XML tags are to be converted to flow objects as the document is read 11 Part I Extensible Stylesheet Language Transformation (XSLT) 12 6

7 XSL Transformations Assume root element of style sheet is <xsl> Each <xsl> element contains one or more rule elements Each rule has a target and an action Target is a regular expression defining to which XML elements the rule applies Action is the list of flow objects generated when the rule is applied: Actions output a series of HTML tags in combination with the content of the element Actions may output XML tags obtained via transformation of original XML data Actions may output non-markup text, or run simple scripts or programs Actions may use JavaScript to provide more complex, and dynamic behaviors 13 XSL Transformations (continued) Conceptual Representation of XSL Transformations: <xsl> <rule> <target-element type= tagname /> action </rule> <rule> ( ) </rule> </xsl> 14 7

8 XSL-T and Templates XSLT rules are also called Templates There may not be rules to match every element Elements can be reordered on the output. XSL style sheet must be well-formed e.g., a HTML empty tag specified as <br> must be written as <br/> within a XSL style sheet action XSLT elements used as a basis for a simple stylesheet are: <xsl:stylesheet>, <xsl:template match >, <xsl:applytemplates>, <xsl:for-each select...>, and <xsl:sort select > 15 XSLT Elements and Functions Creating Elements and Attributes xsl:element, xsl:attribute Iteration and Sorting (e.g., xsl:sort) Conditional Processing xsl:apply-templates select=, xsl:if, xsl:choose Copying Nodes (e.g., xsl:copy) Combining Stylesheets xsl:import, xsl:include Defining Variables & Parameters (e.g., xsl:variable) Scripting with XPath functions 16 8

9 Parsers with XSLT Support SAX 2.0 or DOM Level Support Required Apache s Xalan XSLT parser org.apache.xalan.processor/templates/transformer org.apache.xpath Saxon XSLT parser JAXP 1.1 (javax.xml.transform) TraXP Supported by Xalan 2.0, and Saxon 6.1 Sun s XSLTC Converts stylesheet s to class files ( translets ) 17 Part II Extensible Stylesheet Language Formatting Object (XSL-FO) 18 9

10 XSL Formatting XSL flow objects are markup text Markup language output flow objects can be HTML, DSSSL, VRML, etc. 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) 19 XSL Formatting Characteristics XSL formatting is simpler than DSSSL (Document Style Semantics and Specification Language, pronounced dissal, ISO std 10179:1996) XSL formatting is more powerful than CSS (Cascading Style Sheets) XSL s basic formatting syntax is understandable by anybody acquainted with DSSSL or CSS 20 10

11 Part III XML and Document/Content Management 21 What is a XSL Processor? A XML document and its associated style sheet are combined by an XSL processor to produce a HTML document The XSL Processor applies the style sheet to the XML document and outputs static HTML The process can be automated with CGI scripts, Java servlets, or ActiveX controls to convert XML to HTML on the fly A XSL processor is a standalone program or is part of a larger XML browser 22 11

12 How Does a XSL Processor Work? The XSL processor consults the style sheet to find the rule that matches the element The XSL processor takes whatever action is associated to the rule: outputs element s content plus assorted markup 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.) 23 How Does a XSL Processor Work? (continued) XSL processor formats each element upon receipt XSL processor may process elements recursively XSL processor receives input from XML processor and outputs formatted data based on the nature of the elements it receives E.g., XSL processor receives <strong> element XSL processor may output same content as bold text If processor is an audio renderer, it may pump up the volume a notch

13 How Does a XSL Processor Work? The XSL processor consults the style sheet to find the rule that matches the element The XSL processor takes whatever action is associated to the rule: outputs element s content plus assorted markup 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.) 25 How Does a XSL Processor Work? (continued) XSL processor formats each element upon receipt XSL processor may process elements recursively XSL processor receives input from XML processor and outputs formatted data based on the nature of the elements it receives E.g., XSL processor receives <strong> element XSL processor may output same content as bold text If processor is an audio renderer, it may pump up the volume a notch

14 Mainstream XSL Processors See Microsoft s XML and XSL Samples and Demos at See IBM s LotusXSL, Apache s xalan, and fop. Look at Appendix E of the class textbook for relevant information on XSL A comprehensive list of XSL formatters, and XSLT engines/editors/utilities is available at http// Includes links to latest product pages Includes Version numbers, Licensing information, 27 and Platform details DOM 1.0 XSL Processing Support The DOM Level 1 specification does not support XSL stylesheets Microsoft s initial version of MSXML DOM included a DOM Level 1 extension that added support for XSL stylesheets The function transformnode( ) was used to apply an XSL stylesheet to an existing XML document Similar extensions were emulated early on by other XSL processors (LotusXSL, xalan, fop, etc.) DOM Level formalizes rendering support 28 14

15 Mainstream XSL Processors See Microsoft s XML and XSL Samples and Demos at See IBM s LotusXSL, Apache s xalan, and fop. Look at Appendix E of the class textbook for relevant information on XSL A comprehensive list of XSL formatters, and XSLT engines/editors/utilities is available at http// Includes links to latest product pages Includes Version numbers, Licensing information, and Platform details 29 Xalan Xalan-J version is the latest Provides XSL-T processing for transforming XML documents into HTML, text, or other XML document types Built on top of SAX 2.0, DOM Level 2 1.0, JAXP 1.1 Implements the TraX subset of JAXP

16 Latest version is 0.19 FOP xml.apache.org/fop, Print formatter driven by XSL-FO objects Formatted output is in PDF format for now Can be embedded in a Java application by instantiating org.apache.fop.apps.driver 31 Cocoon 2 Xang Batik Frameworks 32 16

17 Part IV XML Application Services and XML Rendering Technology 33 Towards XML Application Service Processing DOM Extensions Binding Extensions Component Frameworks (reusable component models) Model-Based Automation (MDA) Rendering DOM 2.1.0, SAX 2.0, JAXP 1.1 & TraX, XSL-FO 1.0 Component Frameworks Querying XQuery 1.0, XSLT 1.1/2.0, XPath 1.0/2.0 Security (signatures encryption/decryption, etc.) Etc

18 Rendering Software Development Languages (XSL) Process ( XUP ) Frameworks (POP/MOM) - See XMLJ2EE Cocoon 2.0 Xang Batik Etc. XSL Infrastructure XSL-T Processors: Saxon 6.1, Xalan-J XSL-FO Processors: fop W3C s New Architecture Slant New W3C UI Domain Structure Document Formats Amaya Graphics Internationalization Math Style Interoperation Device independence SMIL and voice browsers Architecture 36 18

19 Part V XML Internationalization Issues 37 W3C Internationalization Internationalization Activity Statement I18N and L10N features incorporated in (X)HTML, CSS, XML, RDF, SMIL, DOM, MathML, SVG, XPath, XSL(T), and XML Schema, HTTP 1.0 W3C s Jigsaw, Amaya Problem is to document encodings being used W3C Character Model Character Model for the World Wide Web Normalization to Unicode Standard and ISO/IEC Ruby Annotation 38 Unicode in XML and other Markup Languages 19

20 Part VI Web Content Accessibility Guidelines (WCAG 1.0) 39 Current State of XML Standards WCAG 1.0 (5/5/99) - W3C Recommendation WCAG 2.0 (3/28/01) - W3C Working Draft Support wide range of languages Easier to use by authoring tools developers Easier to check conformance Techniques for WCAG 1.0 (3/20/00) 40 20

21 Guidelines Summary Provide Alternatives to Auditory and Visual content Avoid sole reliance on colors Use markup and style sheets Clarify natural language usage Create tables that transform well Make Sure that Pages that Feature New Technologies Transform Well Ensure User Control of Time-Sensitive Content Changes 41 Guidelines Summary (continued) Ensure Direct Accessibility of Embedded UIs Design for Device Independence Use Interim Solutions Use W3C Technologies and Guidelines Provide Context and Orientation Information Provide Clear Navigation Mechanisms Provide Clear and Simple Documents 42 21

22 Part VII Conclusions 43 Summary XSL style sheets describe how individual elements are displayed in HTML A XSL processor like LotusXSL converts an XML document and its associated style sheet into an HTML document that can be read by current web browsers Style instructions are stored in rule elements 44 22

23 Summary (continued) Each rule has a pattern and an action The pattern define the elements to which the rule applies The action specifies the flow objects that the XSL processor outputs when the rule fires When multiple rules apply to one element, only the most specific rule is applied Flow objects usually include the content of the element, along with some combination of HTML markup 45 Summary (continued) XML Application Services support a stepwise approach towards the development of XML-based system architectures W3C Internationalization is moving towards normalization based on a web character model I18N/L10N support needs to keep being added into XSL, and CSS3. XML Query, XML Protocols, XForms, and newer XML technologies Content Accessibility Guidelines are targeted to Web and Authoring Tools developers to ensure that Web content is accessible to people with disabilities 46 23