XML Extensible Markup Language

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XMLExtensible Markup Language

• Kaj A. Jørgensen
• Aalborg University, Department of Production

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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

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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

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HTML Example lt!-- The original html recipe
--gt ltHTMLgt ltHEADgtltTITLEgtLime Jello Marshmallow
Cottage Cheese Surpriselt/TITLEgtlt/HEADgt ltBODYgt ltH3gt
Lime Jello Marshmallow Cottage Cheese
Surpriselt/H3gt ltPgtMy grandma's favorite (may she
rest in peace).lt/Pgt ltH4gtIngredientslt/H4gt ltTABLE
BORDER"1"gt ltTR BGCOLOR"308030"gt ltTHgtQtylt/THgtltTH
gtUnitslt/THgtltTHgtItemlt/THgtlt/TRgt ltTRgtltTDgt1lt/TDgtltTDgtbo
xlt/TDgtltTDgtlime gelatinlt/TDgtlt/TRgt ltTRgtltTDgt500lt/TDgtlt
TDgtglt/TDgtltTDgtmulticolored tiny marshmallowslt/TDgtlt/
TRgt ltTRgtltTDgt500lt/TDgtltTDgtmllt/TDgtltTDgtcottage
cheeselt/TDgtlt/TRgt ltTRgtltTDgtlt/TDgtltTDgtdashlt/TDgtltTDgtTab
asco sauce (optional)lt/TDgtlt/TRgt lt/TABLEgt ltH4gtInstr
uctionslt/H4gt ltOLgt ltLIgtPrepare lime gelatin
according to package instructions...lt/LIgt lt!--
and so on --gt lt/BODYgt lt/HTMLgt
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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
  browserexample Recipe.html

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XML tags User Definable

• Start tag

End tag
Empty tag
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lt?xml version"1.0"?gtltRecipegt   ltNamegtLime
Jello Marshmallow Cottage Cheese
Surpriselt/Namegt   ltDescriptiongt My grandma's
favorite (may she rest in peace).lt/Descriptiongt  
 ltIngredientsgt      ltIngredientgt         ltQty
unit"box"gt1lt/Qtygt         ltItemgtlime
gelatinlt/Itemgt      lt/Ingredientgt      ltIngredie
ntgt         ltQty unit"g"gt500lt/Qtygt         ltIte
mgtmulticolored tiny marshmallowslt/Itemgt      lt/In
gredientgt      ltIngredientgt         ltQty
unit"ml"gt500lt/Qtygt         ltItemgtCottage
cheeselt/Itemgt      lt/Ingredientgt      ltIngredien
tgt         ltQty unit"dash"/gt         ltItem
optional"1"gtTabasco saucelt/Itemgt      lt/Ingredie
ntgt   lt/Ingredientsgt   ltInstructionsgt      ltSte
pgtPrepare lime gelatin according to package
instructionslt/Stepgt      lt!-- And so on...
--gt   lt/Instructionsgtlt/Recipegt
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Characteristics of XML

• Simple rules
• No unclosed tags
• No overlapping tags exampleltTomatogtLet's call
  ltPotatogtthe whole thing offlt/Tomatogtlt/Potatogt
• Attribute values must be enclosed in quotes
• The text characters (lt), (gt), and (") must be
  represented by 'character entities' (lt),
  (gt), and (quot)
• 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

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Document Type Definition (DTD)

• DTD example
• lt!ELEMENT Recipe (Name, Description?,
  Ingredients?, Instructions?)gt
• lt!ELEMENT Name (PCDATA)gt
• lt!ELEMENT Description (PCDATA)gt
• lt!ELEMENT Ingredients (Ingredient)gt
• lt!ELEMENT Ingredient (Qty, Item)gt
• lt!ELEMENT Qty (PCDATA)gt
• lt!ATTLIST Qty unit CDATA REQUIREDgt
• lt!ELEMENT Item (PCDATA)gt
• lt!ATTLIST Item optional CDATA "0" isVegetarian
  CDATA "true"gt
• lt!ELEMENT Instructions (Step)gt

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XML Schema example ltxsdschema
xmlnsxsd"http//www.w3.org/1999/XMLSchema"gt ltxsd
element name"shipOrder" type"order"/gt ltxsd
complexType name"order"gt ltxsdelement
name"shipTo" type"shipAddress"/gt
ltxsdelement name"items"
type"cdItems"/gt lt/xsdcomplexTypegt ltxsdcomplexTy
pe name"shipAddress"gt ltxsdelement
name"name" type"xsdstring"/gt
ltxsdelement name"street"
type"xsdstring"/gt ltxsdelement
name"address" type"xsdstring"/gt
ltxsdelement name"country"
type"xsdstring"/gt lt/xsdcomplexTypegt ltxsdcomple
xType name"cdItems"gt ltxsdelement
name"item" type"cdItem"/gt lt/xsdcomplexType
gt ltxsdcomplexType name"cdItem"gt ltxsdelement
name"title" type"xsdstring"/gt
ltxsdelement name"quantity"
type"xsdpositiveInteger"/gt ltxsdelement
name"price" type"xsddecimal"/gt lt/xsdcomple
xTypegt lt/xsdschemagt
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XML document conforming to the XML Schema lt?xml
version"1.0"?gt ltshipOrdergt ltshipTogt
ltnamegtTove Svendsonlt/namegt ltstreetgtRagnhildvei
2lt/streetgt ltaddressgt4000 Stavangerlt/addressgt
ltcountrygtNorwaylt/countrygt lt/shipTogt
ltitemsgt ltitemgt lttitlegtEmpire
Burlesquelt/titlegt ltquantitygt1lt/quantitygt
ltpricegt10.90lt/pricegt lt/itemgt ltitemgt
lttitlegtHide your heartlt/titlegt
ltquantitygt1lt/quantitygt ltpricegt9.90lt/pricegt
lt/itemgt lt/itemsgt lt/shipOrdergt
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Exchanging XML Documents
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Exchanging XML Documents, cont.
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Application Integration
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New Internet Technologies and Standards

• An Internet service
• 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)

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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

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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