CSE 636 Data Integration

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CSE 636Data Integration
XML Schema
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XML Schemas

• W3C Recommendation http//www.w3.org/XML/Schema
• Generalizes DTDs
• Uses XML syntax
• Two documents structure and datatypes
• http//www.w3.org/TR/xmlschema-1
• http//www.w3.org/TR/xmlschema-2
• XML-Schema is very complex
• often criticized
• some alternative proposals

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XML Schemas

• lt?xml version"1.0"?gt
• ltxsdschema xmlnsxsd"http//www.w3.org/2001/XMLS
  chema"gt
• ltxsdelement namepaper typepapertype/gt
• ltxsdcomplexType namepapertypegt
• ltxsdsequencegt
• ltxsdelement nametitle
  typexsdstring/gt
• ltxsdelement nameauthor
  minOccurs0/gt
• ltxsdchoicegt
• ltxsdelement namejournal/gt
• ltxsdelement nameconference/gt
• lt/xsdchoicegt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt
• lt/xsdschemagt

DTD lt!ELEMENT paper (title, author?,
(journalconference))gt
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XML Namespaces

• http//www.w3.org/TR/REC-xml-names (1/99)
• Solve the problem of tag name conflicts
• name prefixlocalpart

ltbook xmlnsisbnwww.isbn-org.org/defgt
lttitlegt lt/titlegt ltnumbergt 15 lt/numbergt
ltisbnnumbergt . lt/isbnnumbergt lt/bookgt
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XML Namespaces

• Syntactic ltnumbergt , ltisbnnumbergt
• Semantic provide URL for schema

lttag xmlnsmystyle http//gt
ltmystyletitlegt lt/mystyletitlegt
ltmystylenumbergt lt/taggt
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Elements vs. Types in XML Schema
ltxsdelement nameperson
typepType/gt ltxsdcomplexType namepTypegt
ltxsdsequencegt ltxsdelement namename
typexsdstring/gt
ltxsdelement nameaddress
typexsdstring/gt lt/xsdsequencegtlt/xsdcom
plexTypegt
ltxsdelement namepersongt ltxsdcomplexTypegt
ltxsdsequencegt ltxsdelement namename
typexsdstring/gt
ltxsdelement nameaddress
typexsdstring/gt lt/xsdsequencegt
lt/xsdcomplexTypegtlt/xsdelementgt
DTD lt!ELEMENT person (name,address)gt
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Elements vs. Types in XML Schema

• Types
• Simple types (integers, strings, ...)
• Complex types (regular expressions, like in DTDs)
• Element-type-element alternation
• Root element has a complex type
• That type is a regular expression of elements
• Those elements have their complex types...
• ...
• On the leaves we have simple types

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Local vs. Global Types in XML Schema

• Local type
• ltxsdelement namepersongt define
  locally the persons typelt/xsdelementgt
• Global typeltxsdelement nameperson
  typepType/gtltxsdcomplexType namepTypegt
  define here the type pTypelt/xsdcomplexTy
  pegt

Global types can be reused in other elements
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Local vs. Global Elementsin XML Schema

• Local element
• ltxsdcomplexType namepTypegt
  ltxsdsequencegt ltxsdelement nameaddress
  type.../gt... lt/xsdsequencegtlt/xsdcomplexTy
  pegt
• Global elementltxsdelement nameaddress
  type.../gtltxsdcomplexType namepTypegt
  ltxsdsequencegt ltxsdelement refaddress/gt
  ... lt/xsdsequencegtlt/xsdcomplexTypegt

Global elements like in DTDs
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Regular Expressions in XML Schema
Recall the element-type-element alternation
ltxsdcomplexType name....gt
regular expression on elementslt/xsdcomplexType
gt Regular expressions ltxsdsequencegt A B C
lt/...gt A B C ltxsdchoicegt A B C lt/...gt A
B C ltxsdgroupgt A B C lt/...gt (A B
C) ltxsd minOccurs0
maxOccursunboundedgtlt/gt (...) ltxsd
minOccurs0 maxOccurs1gtlt/gt
(...)?
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Local Names in XML Schema
ltxsdelement namepersongt ltxsdcomplexTypegt
ltxsdelement namenamegt
ltxsdcomplexTypegt ltxsdsequencegt
ltxsdelement namefirstname
typexsdstring/gt ltxsdelement
namelastname typexsdstring/gt
lt/xsdsequencegt lt/xsdcomplexTypegt
lt/xsdelementgt lt/xsdcomplexTypegtlt/xsd
elementgt ltxsdelement nameproductgt
ltxsdcomplexTypegt ltxsdelement
namename typexsdstring/gt
lt/xsdcomplexTypegtlt/xsdelementgt
name has different meanings in person and in
product
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Subtle Use of Local Names
ltxsdelement nameA typeoneB/gt ltxsdcomplexT
ype nameonlyAsgt ltxsdchoicegt
ltxsdsequencegt ltxsdelement nameA
typeonlyAs/gt ltxsdelement nameA
typeonlyAs/gt lt/xsdsequencegt
ltxsdelement nameA typexsdstring/gt
lt/xsdchoicegtlt/xsdcomplexTypegt ltxsdcomplexType
nameoneBgt ltxsdchoicegt
ltxsdelement nameB typexsdstring/gt
ltxsdsequencegt ltxsdelement nameA
typeonlyAs/gt ltxsdelement nameA
typeoneB/gt lt/xsdsequencegt
ltxsdsequencegt ltxsdelement nameA
typeoneB/gt ltxsdelement nameA
typeonlyAs/gt lt/xsdsequencegt
lt/xsdchoicegtlt/xsdcomplexTypegt
Arbitrary deep binary tree with A elements, and
a single B element
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Attributes in XML Schema
ltxsdelement namepaper typepapertype/gt ltxsd
complexType namepapertypegt ltxsdsequencegt
ltxsdelement nametitle typexsdstring/gt
lt/xsdsequencegt ltxsdattribute
namelanguage" type"xsdNMTOKEN"
fixedEnglish"/gt lt/xsdcomplexTypegt

• Attributes are associated to the type,not to the
  element
• Only to complex types
• More trouble if we want to add attributes to
  simple types

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Adding Attributes to Simple Types

• ltxsdelement name"B"gt
• ltxsdcomplexTypegt
• ltxsdsimpleContentgt
• ltxsdextension base"xsdstring"gt
• ltxsdattribute name"testAttr
  type"xsdstring"/gt
• lt/xsdextensiongt
• lt/xsdsimpleContentgt
• lt/xsdcomplexTypegt
• lt/xsdelementgt

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Mixed Content, Any Type

• Better than in DTDs can still enforce the type,
  but now may have text between any elements
• Means anything is permitted there

ltxsdcomplexType mixed"true"gt
ltxsdelement name"anything" type"xsdanyType"/gt

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All Group
ltxsdcomplexType name"PurchaseOrderType"gt
ltxsdallgt ltxsdelement name"shipTo"
type"USAddress"/gt ltxsdelement
name"billTo" type"USAddress"/gt
ltxsdelement ref"comment" minOccurs"0"/gt
ltxsdelement name"items" type"Items"/gt
lt/xsdallgt ltxsdattribute name"orderDate"
type"xsddate"/gt lt/xsdcomplexTypegt

• Restrictions
• Only at top level
• Has only elements
• Each element occurs at most once
• E.g. comment occurs 0 or 1 times

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Derived Types by Extensions
ltcomplexType name"Address"gt ltsequencegt
ltelement name"street" type"string"/gt
ltelement name"city" type"string"/gt
lt/sequencegt lt/complexTypegt ltcomplexType
name"USAddress"gt ltcomplexContentgt
ltextension base"ipoAddress"gt
ltsequencegt ltelement name"state"
type"ipoUSState"/gt ltelement
name"zip" type"positiveInteger"/gt
lt/sequencegt lt/extensiongt
lt/complexContentgt lt/complexTypegt

• Corresponds to inheritance

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Derived Types by Restrictions

• may restrict cardinalities, e.g. (0,infty) to
  (1,1)
• may restrict choices
• other restrictions
• Corresponds to set inclusion

ltcomplexContentgt ltrestriction
base"ipoItemsgt rewrite the entire
content, with restrictions lt/restrictiongt
lt/complexContentgt
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Simple Types

• string
• token
• byte
• unsignedByte
• integer
• positiveInteger
• int
• larger than integer
• unsignedInt
• long
• short
• ...

• time
• dateTime
• duration
• date
• ID
• IDREF
• IDREFS

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Facets of Simple Types

• Facets additional properties restricting a
  simple type
• 15 facets defined by XML Schema

• Examples
• length
• minLength
• maxLength
• pattern
• enumeration
• whiteSpace

• maxInclusive
• maxExclusive
• minInclusive
• minExclusive
• totalDigits
• fractionDigits

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Facets of Simple Types

• Can further restrict a simple type by changing
  some facets
• Restriction subset

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Not so Simple Types

• List types
• Union types
• Restriction types

ltxsdsimpleType name"listOfMyIntType"gt
ltxsdlist itemType"myInteger"/gt lt/xsdsimpleTypegt
ltlistOfMyIntgt20003 15037 95977 95945lt/listOfMyIntgt
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Summary of XML Schema

• Formal Expressive Power
• Can express precisely the regular tree languages
  (over unranked trees)
• Lots of other stuff
• Some form of inheritance
• A null value
• Large collection of data types

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References

• Lecture Slides
• Dan Suciu
• http//www.cs.washington.edu/homes/suciu/COURSES/5
  90DS/12xmlschema.htm
• BRICS XML Tutorial
• A. Moeller, M. Schwartzbach
• http//www.brics.dk/amoeller/XML/index.html
• W3C's XML Schema homepage
• http//www.w3.org/XML/Schema
• XML School
• http//www.w3schools.com