Presentation 19: XML technologies part 2: XSL, XSLT, XSL-FO, XPath & XML Programming

Transcription

1 Presentation 19: XML technologies part 2: XSL, XSLT, XSL-FO, XPath & XML Programming

2 Outline XML recap Formatting CSS or XSL? XPath XSL/XSLT XSL-FO XML Programming Slide 2

3 XML markup recap XML based on SGML (subset of) Like SGML for structure not layout (as HTML) XML targets the Internet but is also being used for application exchange formats (Open Office, XMI) CSVs XML is an W3C Recommendation XML Namespaces for multiply namespaces DTD s or XML Schemas for structure Slide 3

4 Local definitions vs public in XML Schema Instead of using the type system Use local definitions How may this be done using the type approach instead? Another public variant is using ref Slide 4

5 Formatting XSL & CSS XML is only content no formatting Possible to transform the data to XHTML (or other) using JavaScript og server-side The W3C ideal is using CSS or XSL extensible Style Sheets CSS is most common today but XSL has more features Slide 5

6 XSL vs CSS W3C made both XSL and CSS: The Extensible StyleSheet Language XML based language for the formatting of document which by some is regarded as more advantageous compared with the more cryptic CSS XSL consists of XSL-FO (Formatting Objects), the XSL Transformations language (XSLT) and XPath for defining and accessing part of the XML document Exactly the same job may however be solved by using server-side programming but of course XSLT may be used client-side to relief the server (it can also be applied server-side) Slide 6

7 XSL vs CSS II Why both? Why Both (XSL & CSS)? Well of course there are practical reasons If you have already learned CSS & JSP, it takes some efforts to master XSL to the same degree In fact XSL-FO is not fully implemented everywhere but what does the W3C have to say? Slide 7

8 XSL vs CSS III - differences CSS XSL Can be used with HTML? Can be used with XML? Transformation language? yes yes no no yes yes Syntax Proprietary CSS (-) Standard XML (+) Slide 8

9 When to use XSL & CSS (IIII) Why does W3C recommend two different style languages? Which one should you use? Basically, the rule can be summarized very succinctly: Use CSS when you can, use XSL when you must. You may choose to use CSS alongside XSLT when you are dealing with XHTML In fact this is the most common solution today Slide 9

10 The 3 Main Technologies of XSL XSLT, a language for transforming information XSL or XSL-FO, a language for formatting information XPath, a language for defining parts of an XML document and accessing them Each of these elements could fill an entire class. You will only need to be acquainted with the overall functionality of these Slide 10

11 XPath Flexible notation for navigating around trees Resembles notation used in Unix filesystems A basic technology that is widely used uniqueness and scope in XML Schema pattern matching an selection in XSLT relations in XLink and XPointer computations on values in XSLT and XQuery XPath is not written in XML XPath is a W3C Standard Slide 11

12 Location Paths in XPath location path evaluates to a sequence of nodes sequence is sorted in document order sequence will never contain duplicates The location path is a sequence of different steps A location step consists of an axis (a direction of selection successors, descendants) a nodetest (identifies a node within the axis) Some predicates (a statement/expression yielding a boolean) axis :: nodetest [predicate] child::price[price=9.90] (example) Slide 12

13 Evaluating Location Paths Location Paths may consist of several steps A step maps a context node into a sequence This also maps sequences to sequences each node is used as context node and is replaced with the result of applying the step The path then applies each step in turn, using the former step as the sequence to work on It may be absolute or relative (/cd/price or cd/price) Slide 13

14 Example finding all C nodes Slide 14

15 What are we looking for here? Slide 15

16 XPath Axes An axis is a sequence of nodes The axis is evaluated relative to the context node XPath supports 12 different axes child, attribute, descendant, following, parent, preceding, ancestor, self, following-sibling, descendant-or-self, preceding-sibling, ancestor-or-self These all have a direction, either forward, backward or stable (attribute) Slide 16

17 XPath Node Tests text() - child::text() all text nodes of current node comment() - child::comment() processing-instruction() node() - child::node() all children of current node * - attribute::* all attributes of current node More node tests exists Slide 17

18 XPath Predicates General XPath expressions evaluated with the current node as context Result is coerced (translated) into a boolean a number yields true if it equals the context position a string yields true if it is not empty a sequence yields true if it is not empty Example: child::price[price=9.90] - selects all price elements that are children of the current node with a price element that equals 9.90 Example: child::cd[position()<6] Selects the first five cd children of the current node Slide 18

19 XPath Abrivated Syntax Tedious work entering XPath syntax Enter: the abrivated syntax Table from Slide 19

20 XPath Examples Slide 20

21 XPath Advanced This presentation has only shown the basic elements Feel free to explore further Expressions Numerical, Equality, Relational, Boolean, Path, Filter Variable References $test Functions 106 with namespace fn= Examples: fn:avg((1,2,3,4)), fn:round(23.5) Slide 21

22 Slide 22

23 XSLT XSL Transformations Language for transforming a format neutral XML document into another XML document e.g. XHTML or WML for presentation May also add new elements or remove elements XSLT relies heavily on XPath for pattern matching Specifying patterns for template rules Selecting nodes for processing Computing boolean conditions Generating text contents for the output document Slide 23

24 XSLT Template rules An XSLT stylesheet contains template rules The processor finds the most specific rule for the document root It then executes the template body Find the template rules that match the contex node Select the most specific one Evaluate the body (a sequence constructor) Slide 24

25 Applying Templates <xsl:apply-templates> element applies a template rule to the current element or to the current element's child nodes Slide 25

26 Name, Mode, Priority, Sorting & Grouping Templates may have other attributes name: used to call templates like function mode: used to restrict the candidate templates priority: used to determine specificity Other features include: Conditionals (<xsl:if/>, <xsl:choose/>) Control statemetnts (<xsl:for-each/>) Grouping (<xsl:for-each-group/>) Sorting (<xsl:sort/>) Numbering (<xsl:number/>) Functions (<xsl:function/>) Parameters (<xsl:param/>) Slide 26

27 XSL/XSLT example Transforming a XML document using XSLT invovles 2 tree structures Source tree (original XML document) Result tree (the transformed document) AND of course the XSL document! (so totally 3) In this example We take an XML document which could have been generated from a RDBMS database We want to transform this XML document into an XHTML document for browsers And maybe we COULD transform it into a PDF, and a WML document (for mobile phones) or whatever we might need in the future Slide 27

28 1 <?xml version = "1.0"?> 2 <?xml:stylesheet type = "text/xsl" href = "games.xsl"?> 3 4 <!-- Fig : games.xml --> 5 <!-- Sports Database --> 6 7 <sports> 8 9 <game id = "783"> 10 <name>cricket</name> <paragraph> 13 More popular among commonwealth nations. 14 </paragraph> 15 </game> <game id = "239"> 18 <name>baseball</name> <paragraph> 21 More popular in America. 22 </paragraph> 23 </game> <game id = "418"> 26 <name>soccer (Football)</name> <paragraph> 29 Most popular sport in the world. 30 </paragraph> 31 </game> </sports> XML dokument Source tree Games.xml Value type specifies that games.xsl is a text/xsl file. A processing instruction that references the XSL stylesheet games.xsl.. Wait isn t there something wrong here why do we have XSL embedded in the XML documet? We will look at this later Slide 28 af 43

29 1 <?xml version = "1.0"?> 2 3 <!-- Fig : elements.xsl --> 4 <!-- A simple XSLT transformation --> 5 6 <!-- reference XSL stylesheet URI --> stylesheet. 7 <xsl:stylesheet version = "1.0" 8 xmlns:xsl = " <xsl:output method = "html" omit-xml-declaration = "no" 11 doctype-system = 12 " 13 doctype-public = "-//W3C//DTD XHTML 1.0 Strict//EN"/> <xsl:template match = "/"> <html xmlns=" <head> 20 <title>sports</title> 21 </head> <body> <table border = "1" bgcolor = "cyan"> <thead> <tr> 30 <th>id</th> 31 <th>sport</th> 32 <th>information</th> 33 </tr> </thead> Slide 29 af 43 XSL dokument Elements.xsl The stylesheet start tag which begins the XSL Element xsl:output writes an XHTML document type declaration to the result tree. The match attribute to select the document root of the source document (i.e., game.xml).

30 36 37 <!-- insert each name and paragraph element value --> 38 <!-- into a table row. --> 39 <xsl:for-each select = "sports/game"> <tr> 42 <td><xsl:value-of select = "@id"/></td> 43 <td><xsl:value-of select = "name"/></td> 44 <td><xsl:value-of select = "paragraph"/></td> 45 </tr> </xsl:for-each> </table> </body> </html> </xsl:template> </xsl:stylesheet> Elements.xsl Element xsl:for-each iterates through the source XML document and search for game elements. Element value-of retrieves attribute id s value and place it in a td element in the result tree. These three select values are all XPath expressions. Other types of XPath uses include / for navigating to child nodes, and using * wildcards for selecting unknown elements. Other types of usage includes indexing e.g. [1] and selecting attributes Slide 30 af 43

31 XHTML dokument result tree Result of XSLT tranformation Slide 31 af 43

32 More examples? Will only sedate you with boredom and a sad feeling of helplessness Please go try it out yourself instead Plenty of examples at: Assignment (5 min.): Try making an XSL document which will print the following bullet list HTML document Cricket Popular among commenwealth nations (ID: 783) etc Consider the problems when using the XML document with several XSL documents. How may it be done? Slide 32

33 Not nice with embedded XSL? You may use JavaScript to separate gracefully <html> <body> <script type="text/javascript"> // Load XML var xml = new ActiveXObject("Microsoft.XMLDOM") xml.async = false xml.load("cdcatalog.xml") // Load XSL var xsl = new ActiveXObject("Microsoft.XMLDOM") xsl.async = false xsl.load("cdcatalog.xsl") // Transform document.write(xml.transformnode(xsl)) </script> </body> </html> Detect type of browser and load proper XSL doc Slide 33

34 and server-side as well You may also use server-side programming for this <% 'Load XML set xml = Server.CreateObject("Microsoft.XMLDOM") xml.async = false xml.load(server.mappath("cdcatalog.xml")) 'Load XSL set xsl = Server.CreateObject("Microsoft.XMLDOM") xsl.async = false xsl.load(server.mappath("cdcatalog.xsl")) 'Transform file Response.Write(xml.transformNode(xsl)) %> and of course you dont really need XSL then as the same job may be done in Java, C#, VB etc Slide 34

35 Browser Troubles in Paradise History XSLT in Internet Explorer 5 (and 5.5) is NOT compatible with the official W3C XSL Recommendation. Internet Explorer 6 fully supports the official W3C XSLT Recommendation. Netscape 6 isn't fully supporting the official W3C XSLT Recommendation. Netscape 7 supports the official W3C XSLT Recommendation. Slide 35

36 Browser Troubles in Paradise Now Se rowsers#web_technology_support Slide 36

37 Slide 37

38 Cross Browser DOM Handling Slide 38

39 XSL-FO XSL-FO is a language for formatting XML data XSL-FO stands for Extensible Stylesheet Language Formatting Objects XSL-FO is a W3C Recommendation XSL-FO is now formally named XSL XSL-FO is not used extensively with WWW technologies yet, as CSS and XSLT may be used together. This may change however! PDF / Web forms from XSL-FO (Scriptura) Slide 39

40 XSL-FO Formatting instructions: Block Margin, Border, Padding, Background Block Styling Attributes: font-family font-weight font-style font-size font-variant text-align text-align-last text-indent start-indent end-indent wrap-option (defines word wrap) break-before (defines page breaks) break-after (defines page breaks) reference-orientation (defines text rotation in 90" increments) Which in general will handle the same stuff as CSS Slide 40

41 Other XSL-FO elements Areas, Output, Flow, Pages, List, Tables All of which we will not cover here! Slide 41

42 XSL-FO Example Below is a XSL-FO document And the output would be Slide 42

43 XML, XML-FO & XSLT Example Below is a XML document We apply some XSLT including XML-FO And we get a result Slide 43

44 Programmatic XML access? Many API s & framework for XML handling For Java: C#: JDOM: JAXP: SAX: using System.Xml / System.Xml.Xsl; Build-in support for XML, XSD, XSLT, XPATH, SOAP XMLSerializer Object / XML mapping Validating XML document against DTD, XSD, XDR Slide 44

45 C# System.Xml and System.Xml.Schema Validating a Document with DTD in C# Slide 45

46 Mapping Tools Mapping Tools XML to C++/C#/Java XML Spy 2007 Slide 46

47 A JDOM Example: Double Sugar Access all ingredients Get the elements whose attribute name equals sugar Get the amount attribute and double it! Slide 47

48 Other XML Technologies XQuery: Query Language of XML XLink: XML hyperlinks XPointer: named anchors All W3C Recommendations Limited browser support Study these yourselves Slide 48

49 Slide 49