1. XML Language Family Detailed Examples Most information contained in these slide comes from: http://www.w3.org/ http://www.w3.org/ These slides are intended to be used as a tutorial on XML and related technologies Slide author: Jürgen Mangler etm@wkv.atetm@wkv.at This section contains examples on: –XML, DTD (Document Type Definition) –XSchema –XPath, XPointer –XInclude –XSLT –XLink

2. The W3C is the "World Wide Web Consortium", a voluntary association of companies and non-profit organizations. Membership is very expensive but confers voting rights. The decisions of W3C are guided by the Advisory Committee, lead by Tim Berners-Lee. The stages in the life of a W3C Recommendation (REC) Working Draft (maximum gap target: 3 months) Last Call (public comment invited; W3C must respond) Candidate Recommendation (design is stable; implementation feedback invited) Proposed Recommendation (Advisory Committee review) The XML recommendation was written by the W3C's XML Working Group (WG), which has since divided into a number of subgroups.

3. An XML document is valid if it has an associated document type definition and if the document complies with the constraints expressed in it. The document type definition (DTD) must appear before the first element in the document. The name following the word DOCTYPE in the document type definition must match the name of the root element. tutorial.dtd: tutorial.xml: This is an XML document

4. An element type has element content if elements of that type contain only child elements (no character data), optionally separated by white space. tutorial.dtd: tutorial.xml: Start End tutorial.xml (with errors, BBB missing): Start

5. If an element name in the DTD is followed by the star [*], this element can occur zero, once or several times tutorial.dtd: tutorial.xml: Start Again End The root element XXX can contain zero or more elements AAA followed by precisely one element BBB. Element BBB must be always present.:

6. If an element name in the DTD is followed by the plus [+], this element can occur once or several times. tutorial.dtd: tutorial.xml: Start Again End tutorial.xml (with errors, AAA must occur at least once): End

7. If an element name in the DTD is followed by the question mark [?], this element can occur zero or one times. tutorial.dtd: tutorial.xml: End This example uses a combination of [ + * ?] How could a valid document look like?

8. With the character [ | ] you can select one from several elements. test.dtd: test.xml: Valid The root element XXX must contain either one element AAA or one element BBB: test.xml: Also Valid Text can be interspersed with elements.

9. Attributes are used to associate name-value pairs with elements. Attribute specifications may appear only within start-tags and empty-element tags. The declaration starts with !ATTLIST followed by the name of the element (myElement) to which the attributes belong to, followed by the definition of the individual attributes (myAttributeA, myAttributeB). Text

10. An attribute of type CDATA may contain any arbitrary character data, given it conforms to well formedness constraints. Type NMTOKEN can contain only letters, digits and point [. ], hyphen [ - ], underline [ _ ] and colon [ : ] NMTOKENS can contain the same characters as NMTOKEN plus whitespaces. White space consists of one or more space characters, carriage returns, line feeds, or tabs. <!ATTLIST taskgroup group CDATA #IMPLIED purpose NMTOKEN #REQUIRED names NMTOKENS #REQUIRED>

11. The value of an attribute of type ID may contain only characters permitted for NMTOKEN and must start with a letter. No element type may have more than one ID attribute specified. The value of an ID attribute must be unique between all values of all ID attributes (in the document!).

12. The value of an attribute of type IDREF has to match the value of some ID attribute in the document. The value of an IDREF attribute can contain several references to elements with ID attributes separated by whitespaces.

13. Permitted attribute values can be defined in the DTD If an attribute is implied, a default value can be provided in case the attribute isn't used. #Required: You must set the attribute #Implied: You can set the attribute

14. An element can be defined as EMPTY. In such a case it may contain attributes only but no text. Hello! Are there errors in this example? Where are they?

15. The purpose of XML Schema is to deploy a standard mechanism to describe and evaluate the datatype of the content of an element. XML examples: 12 correct eT also correct The XML Parser can not distiguish the content of an Element. This is where XML Schema comes in: <name xsi:noNamespaceSchemaLocation="correct_0.xsd" xmlns="" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> Jürgen Mangler

16. If we use the attribute " noNamespaceSchemaLocation ", we tell the document that the schema belongs to an element from the null namespace. Valid document: <name xsi:noNamespaceSchemaLocation="correct_0.xsd" xmlns="" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> Jürgen Mangler correct_0.xsd:

17. If we want the root element to be named "AAA", from null namespace, containing text and an element "BBB", we will need to set the attribute "mixed" to "true" - to allow mixed content. <AAAxsi:noNamespaceSchemaLocation="correct_0.xsd" xmlns="" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> xxx yyy ZZZ aaa

18. We want the root element to be named "AAA", from null namespace, containing one "BBB" and one "CCC" element. Their order is not important. <AAAxsi:noNamespaceSchemaLocation="correct_0.xsd" xmlns="" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

19. We want the root element to be named "AAA", from null namespace, containing a mixture of any number (even zero), of "BBB" and "CCC" elements. We need to use the 'trick' below - we use a "sequence" element with "minOccurs" attribute set to 0 and "maxOccurs" set to "unbounded". The attribute "minOccurs" of the "element" elements has to be 0 too. Give a valid document!

20. We want the root element to be named "AAA", from null namespace, containing a mixture of any number (even zero), of "BBB" and "CCC" elements. You need to use the trick below - use "sequence" element with "minOccurs" attribute set to 0 and "maxOccurs" set to "unbounded", and the attribute "minOccurs" of the "element" elements must be set to 0 too. <AAA xsi:noNamespaceSchemaLocation="correct_0.xsd" xmlns="" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" > 111 YYY 222 333 ZZZ A valid solution!

21. We want the root element to be named "AAA", from null namespace, containing either "BBB" or "CCC" elements (but not both) - the "choice" element. Other valid solutions? <AAAxsi:noNamespaceSchemaLocation="correct_0.xsd" xmlns="" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> aaa

22. In XML Schema, the datatype is referenced by the QName. The namespace must be mapped to the prefix. <rootxsi:noNamespaceSchemaLocation="correct_0.xsd" xmlns="" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> 25

23. Restricting simpleType is relatively easy. Here we will require the value of the element "root" to be integer and less than 25. <rootxsi:noNamespaceSchemaLocation="correct_0.xsd" xmlns="" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> 25 Valid? Use to force element >= 0. You can also combine min/max in !

24. If we want the element "root" to be either a string "N/A" or a string "#REF!", we will use <root xsi:noNamespaceSchemaLocation="correct_0.xsd" xmlns="" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> N/A Other solutions?

25. If we want the element "root" to be either an integer or a string "N/A", we will make a union from an "integer" type and "string" type.

26. Below we define a group of common attributes, which will be reused. The root element is named "root", it must contain the "aaa" element, and this element must have attributes "x" and "y". Give a valid document!

27. Below we define a group of common attributes, which will be reused. The root element is named "root", it must contain the "aaa" and "bbb" elements, and these elements must have attributes "x" and "y". <root xsi:noNamespaceSchemaLocation="correct_0.xsd" xmlns="" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" > Valid document from the previous Schema!

28. The element "A" has to contain a string which is exactly three characters long. We will define our custom type for the string named "myString" and will require the element "A" to be of that type. <Axsi:noNamespaceSchemaLocation="correct_0.xsd" xmlns="" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" > abc