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XML Extensible Markup Language

XML Extensible Markup Language. Kaj A. Jørgensen Aalborg University, Department of Production. Extensible Markup Language (XML). XML: looks like HTML but is more than HTML XML will not replace HTML – XML will complement HTML XML is extensible – users can define custom tags

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XML Extensible Markup Language

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  1. XMLExtensible Markup Language Kaj A. Jørgensen Aalborg University, Department of Production XML – Extensible Markup Language

  2. Extensible Markup Language (XML) • XML: looks like HTML but is more than HTML • XML will not replace HTML – XML will complement HTML • XML is extensible – users can define custom tags • Data can be formatted for displaying with HTML • With XML, the meaning of data can be represented • XML is a metalanguage • a language for making new markup languages • XML is a simplification of Standard Generalized Markup Language (SGML) • Public software available for XML processing, e.g. i Java XML – Extensible Markup Language

  3. XML – Schema Definition and Style Definition XML Schema and Document Type Definition (DTD) • Separate files defining the structure of XML documents • Well-formed XML documents folows the rules of XML • Valid XML documents are well-formed and conforms with a schema file or DTD file Extensible Style Language (XSL) • Style sheets can be written in XSL • With XSL, XML documents can be formatted, e.g. in HTML • Different XSL style sheets can format XML documents differently XML – Extensible Markup Language

  4. HTML Example: <!-- The original html recipe --> <HTML> <HEAD><TITLE>Lime Jello Marshmallow Cottage Cheese Surprise</TITLE></HEAD> <BODY> <H3>Lime Jello Marshmallow Cottage Cheese Surprise</H3> <P>My grandma's favorite (may she rest in peace).</P> <H4>Ingredients</H4> <TABLE BORDER="1"> <TR BGCOLOR="#308030"> <TH>Qty</TH><TH>Units</TH><TH>Item</TH></TR> <TR><TD>1</TD><TD>box</TD><TD>lime gelatin</TD></TR> <TR><TD>500</TD><TD>g</TD><TD>multicolored tiny marshmallows</TD></TR> <TR><TD>500</TD><TD>ml</TD><TD>cottage cheese</TD></TR> <TR><TD></TD><TD>dash</TD><TD>Tabasco sauce (optional)</TD></TR> </TABLE> <H4>Instructions</H4> <OL> <LI>Prepare lime gelatin according to package instructions...</LI> <!-- and so on --> </BODY> </HTML> XML – Extensible Markup Language

  5. Hypertext Markup Language (HTML) Characteristics of HTML: • isn't extensible • is very display-centric • isn't directly reusable • only provides one 'view' of data • has little or no semantic structure HTML documents are presented with a browser • View the HTML document with the IE browser:example: Recipe.html XML – Extensible Markup Language

  6. XML tags – User Definable End tag: Empty tag: Start tag: XML – Extensible Markup Language

  7. <?xml version="1.0"?><Recipe>   <Name>Lime Jello Marshmallow Cottage Cheese Surprise</Name>   <Description> My grandma's favorite (may she rest in peace).</Description>   <Ingredients>      <Ingredient>         <Qty unit="box">1</Qty>         <Item>lime gelatin</Item>      </Ingredient>      <Ingredient>         <Qty unit="g">500</Qty>         <Item>multicolored tiny marshmallows</Item>      </Ingredient>      <Ingredient>         <Qty unit="ml">500</Qty>         <Item>Cottage cheese</Item>      </Ingredient>      <Ingredient>         <Qty unit="dash"/>         <Item optional="1">Tabasco sauce</Item>      </Ingredient>   </Ingredients>   <Instructions>      <Step>Prepare lime gelatin according to package instructions</Step>      <!-- And so on... -->   </Instructions></Recipe> XML – Extensible Markup Language

  8. Characteristics of XML • Some simple rules must be obeyed: • No unclosed tags • No overlapping tags – example:<Tomato>Let's call<Potato>the whole thing off</Tomato></Potato> • Attribute values must be enclosed in quotes • The text characters (<), (>), (") and (space) must be represented by 'character entities': (&lt;), (&gt;), (&quot;) and (&nbsp;) • The tag names define the meaning of data • Data + meaning = information • The hierarchy of tags define the information structure • The tags don't define how the document is displayed • Browsers can display XML documentes – example: Recipe.xml XML – Extensible Markup Language

  9. Document Type Definition (DTD) DTD example: <!ELEMENT Recipe (Name, Description?, Ingredients?, Instructions?)> <!ELEMENT Name (#PCDATA)> <!ELEMENT Description (#PCDATA)> <!ELEMENT Ingredients (Ingredient)*> <!ELEMENT Ingredient (Qty, Item)> <!ELEMENT Qty (#PCDATA)> <!ATTLIST Qty unit CDATA #REQUIRED> <!ELEMENT Item (#PCDATA)> <!ATTLIST Item optional CDATA "0" isVegetarian CDATA "true"> <!ELEMENT Instructions (Step)+> XML – Extensible Markup Language

  10. XML Schema example: <xsd:schemaxmlns:xsd="http://www.w3.org/1999/XMLSchema"> <xsd:element name="shipOrder" type="order"/> <xsd:complexType name="order"> <xsd:element name="shipTo" type="shipAddress"/> <xsd:element name="items" type="cdItems"/> </xsd:complexType> <xsd:complexType name="shipAddress"> <xsd:element name="name" type="xsd:string"/> <xsd:element name="street" type="xsd:string"/> <xsd:element name="address" type="xsd:string"/> <xsd:element name="country" type="xsd:string"/> </xsd:complexType> <xsd:complexType name="cdItems"> <xsd:element name="item" type="cdItem"/> </xsd:complexType> <xsd:complexType name="cdItem"> <xsd:element name="title" type="xsd:string"/> <xsd:element name="quantity" type="xsd:positiveInteger"/> <xsd:element name="price" type="xsd:decimal"/> </xsd:complexType> </xsd:schema> XML – Extensible Markup Language

  11. XML document conforming to the XML Schema: <?xml version="1.0"?> <shipOrder> <shipTo> <name>ToveSvendson</name> <street>Ragnhildvei 2</street> <address>4000 Stavanger</address> <country>Norway</country> </shipTo> <items> <item> <title>Empire Burlesque</title> <quantity>1</quantity> <price>10.90</price> </item> <item> <title>Hide your heart</title> <quantity>1</quantity> <price>9.90</price> </item> </items> </shipOrder> XML – Extensible Markup Language

  12. Hierarchcical View of XML Documents • Recipe example: Recipe Name Description Ingredients Ingredient Qty Item … Instructions Step … XML – Extensible Markup Language

  13. Xpath • Xpath is an expression language for • Express addresses/links • Navigation in XML documents • Selection of sets of XML elements • XPath is used in • XSL/XSLT • XLink, Xpointer and XQuery • Xpath expression syntax • axes::pathexpression[predicate] • Path expressions are either • Full path expressions or • Relative path expressions XML – Extensible Markup Language

  14. Xpath – Path Expressions • Full Path Expressions • Expresses a full path from the root node of a document • Examples: • /Recipe – selects all nodes • /Recipe/Name – selects the Name node • Relative Path Expressions • Expresses a path from current node • Examples: • //Description – selects the Description node • //Ingredient – selects all Ingredient nodes • //Item – selects Item node in first Ingredient node XML – Extensible Markup Language

  15. Xpath - Predicates • Predicates are expressions to filter selected node sets • Examples: • //Ingredient[2] – Second ingredient node • //Ingredient[last()] Last ingredient node • //Ingredient[3]/Qty/@unit – The unit attribute of Qty node • //Ingredient[Qty>200] Ingredient nodes with Qty>200 • //Ingredient[Qty>200]/Item Item nodes for which Qty>200 XML – Extensible Markup Language

  16. Xpath - Axes • Additional standard path expressions • Reserved words: • child • descendant • parent • ancestor • following • preceding • Attribute • Example with /Recipe/Ingredients as current node: • descendant::Item[@optional=“1”] XML – Extensible Markup Language

  17. Style Sheets in Extensible Style Language (XSL) • XSL style sheets • define how to format XML documents, e.g. HTML, RTF and SQL • input elements can be rearranged with style sheets • are defined by • Cascading Style Sheet language (CSS) • Extensible Style Language (XSL) • are also XML documents • contain special <xsl: ... > tags with pre-defined meaning • Each XSL style sheet contains a series of templates • Different XSL style sheets can transform XML documents for different applications and display equipment XML – Extensible Markup Language

  18. XSL Style Sheet: <?xml version="1.0"?> <xsl:stylesheetxmlns:xsl="http://www.w3.org/TR/WD-xsl"><xsl:template match="/Recipe">. . . </xsl:template><!-- Format ingredients --><xsl:template match="Ingredients">. . . </xsl:template><!-- Format instructions --><xsl:templatematch="Instructions">. . . </xsl:template><xsl:templatematch="Step">. . . </xsl:template><!-- ignore all not matched --> <xsl:template match="*" priority="-1"/> </xsl:stylesheet> XML – Extensible Markup Language

  19. XSL Style Sheet – individual templates: <xsl:template match="/Recipe"> <HTML>  <HEAD>  <TITLE>   <xsl:value-of select="Name"/>  </TITLE>  </HEAD>  <BODY>  <H3>  <xsl:value-of select="Name"/>  </H3>  <STRONG>  <xsl:value-of select="Description"/>  </STRONG>  <xsl:apply-templates/>  </BODY> </HTML></xsl:template> XML – Extensible Markup Language

  20. XSL Style Sheet – individual templates: <!-- Format ingredients --><xsl:template match="Ingredients"> <H4>Ingredients</H4> <TABLE BORDER="1"> <TR BGCOLOR="#308030"><TH>Qty</TH><TH>Units</TH><TH>Item</TH></TR> <xsl:for-each select="Ingredient"> <TR> <!-- handle empty Qty elements separately --> <xsl:if test='Qty[not(.="")]' >   <TD><xsl:value-of select="Qty"/></TD> </xsl:if> <xsl:if test='Qty[.=""]' >   <TD BGCOLOR="#404040"> </TD> </xsl:if><TD><xsl:value-ofselect="Qty/@unit"/></TD> <TD><xsl:value-ofselect="Item"/> <xsl:if test='Item/@optional="1"'>    <SPAN> -- <em><STRONG>optional</STRONG></em></SPAN></xsl:if></TD> </TR> </xsl:for-each> </TABLE></xsl:template> XML – Extensible Markup Language

  21. XSL Style Sheet – individual templates: <!-- Format instructions --><xsl:templatematch="Instructions"> <H4>Instructions</H4> <OL> <xsl:apply-templatesselect="Step"/> </OL></xsl:template><xsl:templatematch="Step"><LI><xsl:value-ofselect="."/></LI></xsl:template> XML – Extensible Markup Language

  22. Exchanging XML Documents XML – Extensible Markup Language

  23. Exchanging XML Documents, cont. XML – Extensible Markup Language

  24. Application Integration XML – Extensible Markup Language

  25. New Internet Technologies and Standards • XML is the basis for Web Services • expose and describe itself to other applications • can be located by other applications via directories • can be invoked by using standard protocols • XML based standards are currently available • Simple Object Access Protocol (SOAP) • Web Services Desription Language (WSDL) • Universal Desription, Discovery, and Integrat. (UDDI)a standard for new ways of publishing services • conform to the basic ”request” and ”response” functionality • supported by the World Wide Web Consortium (W3C) XML – Extensible Markup Language

  26. Internet Technologies and Standards XML – Extensible Markup Language

  27. Internet Technologies and Standards • Discovery and access to an Internet Service (example) • 1.a A Service Provider creates a service • 1.b The service is defined in WSDL • 1.c The service is published in a Service Directory • 2.a A Service Client queries the directory • 2.b The directory creates a reply • 2.c The reply contains a WSDL descriptor of the service • 3.a The Service Client invokes the service using the descriptor • 3.b A SOAP message is structured, built and sent • 3.c The Service Client receives and interprets the response XML – Extensible Markup Language

  28. Simple Object Access Protocol (SOAP) • Lightweight protocol for exchange of information • The protocol is XML based, simple and extensible • The SOAP standard consists of three parts • the SOAP envelope, what message and who should handle it • the SOAP encoding rules, serialisation mechanisms • the SOAP remote procedure call representation • SOAP envelope is an XML document with • SOAP header, optional • SOAP body, the message body, a set of body entries XML – Extensible Markup Language

  29. Web Services Desription Language (WSDL) • XML format for describing Internet services • Abstract description of network endpoints operating on messages containing either document-oriented or procedure-oriented information • Types, data type definitions, e.g. with XSD • Message, definition of the data being communicated • Port Type, set of supported operations by one or more endpoints • Binding, protocol and data format for a particular port type. • Port, single endpoint defined as binding and network address • Service, a collection of related endpoints XML – Extensible Markup Language

  30. Conclusion • XML – Extensible Markup Language • Meta language – users kan define specific languages, custom tags • The tag names define the meaning of data • XML Schema – definition of the structure of XML documents • Extensible Style Language (XSL) – document formatting • Style sheets are XML documents written in XSL • Product data models can be formulated in XML • Data exchange can be based on XML and XML Schema • International solutions: E-business XML, WEB services XML – Extensible Markup Language

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