XML Schema (W3C)

1
XML Schema (W3C)

• Thanks to Jussi Pohjolainen
• TAMK University of Applied Sciences

2
XML NAMESPACES

• w3schools.com

3
XML Namespaces

• The idea behing XML namespaces is to avoid
  element name conflicts.
• Example of name conflict (w3schools.com)

lttablegt lttrgt lttdgtAppleslt/tdgt
lttdgtBananaslt/tdgt lt/trgt lt/tablegt
lttablegt ltnamegtAfrican Coffee Tablelt/namegt
ltwidthgt80lt/widthgt ltlengthgt120lt/lengthgt lt/tablegt
Same tag-name, different content and meaning!
4
Solving Name Conflict

• lthtablegt
• lthtrgt
• lthtdgtAppleslt/htdgt
• lthtdgtBananaslt/htdgt
• lt/htrgt
• lt/htablegt
• ltftablegt
• ltfnamegtAfrican Coffee Tablelt/fnamegt
• ltfwidthgt80lt/fwidthgt
• ltflengthgt120lt/flengthgt
• lt/ftablegt

Prefix h has xhtml-related elements and prefix f
has furniture-related elements
5
xmlns - attributes

• When using prefixes in XML, a so-called namespace
  for the prefix must be defined.
• The namespace is defined by the xmlns attribute
  in the start tag of an element.

6
xmlns - attribute

• ltrootgt
• lthtable xmlnsh"http//www.w3.org/TR/html4/"gt
• lthtrgt
• lthtdgtAppleslt/htdgt
• lthtdgtBananaslt/htdgt
• lt/htrgt
• lt/htablegt
• ltftable xmlnsf"http//www.w3schools.com/furni
  ture"gt
• ltfnamegtAfrican Coffee Tablelt/fnamegt
• ltfwidthgt80lt/fwidthgt
• ltflengthgt120lt/flengthgt
• lt/ftablegt
• lt/rootgt

7
xmlns - attribute

• ltroot
• xmlnsh"http//www.w3.org/TR/html4/"
• xmlnsf"http//www.w3schools.com/furniture"gt
• lthtablegt
• lthtrgt
• lthtdgtAppleslt/htdgt
• lthtdgtBananaslt/htdgt
• lt/htrgt
• lt/htablegt
• ltftablegt
• ltfnamegtAfrican Coffee Tablelt/fnamegt
• ltfwidthgt80lt/fwidthgt
• ltflengthgt120lt/flengthgt
• lt/ftablegt
• lt/rootgt

8
Namespace name

• The name of namespace should be unique lthtable
  xmlnsh"http//www.w3.org/TR/html4/"gt
• It is just a string, but it should be declared as
  URI.
• Using URI reduces the possibility of different
  namespaces using duplicate identifiers.

9
Example An XHTML MathML SVG Profile

• An XHTMLMathMLSVG profile is a profile that
  combines XHTML 1.1, MathML 2.0 and SVG 1.1
  together.
• This profile enables mixing XHTML, MathML and SVG
  in the same document using XML namespaces
  mechanism.

10

• lt?xml version"1.0"?gt
• lt!DOCTYPE html PUBLIC
• "-//W3C//DTD XHTML 1.1 plus MathML 2.0 plus
  SVG 1.1//EN"
• "http//www.w3.org/2002/04/xhtml-math-svg/xhtm
  l-math-svg-flat.dtd"gt
• lthtml xmlns "http//www.w3.org/1999/xhtml
  "
• xmlnssvg "http//www.w3.org/2000/svg"gt
  
• ltheadgt
• lttitlegtExample of XHTML, SVG and
  MathMLlt/titlegt
• lt/headgt
• ltbodygt
• lth2gtMathMLlt/h2gt
• ltpgt
• ltmath xmlns"http//www.w3.org/1998/Math/Mat
  hML"gt
• ltmfracgt
• ltmigtalt/migt
• ltmigtblt/migt
• lt/mfracgt

11
W3C SCHEMA
12
XML Schema (W3C)

• Language for defining set of rules for XML
  documents.
• W3C Recommendation (2001)
• More specific than DTD
• Datatypes!
• Is XML-language and it uses xml namespaces

13
Schema vs. DTD (W3Schools.com)

• XML Schemas are extensible to future additions
• XML Schemas are richer and more powerful than
  DTDs
• XML Schemas are written in XML
• XML Schemas support data types
• XML Schemas support namespaces

14
DTD Linking
Defines the structure, tag names and order for
all xhtml - documents
W3C has created XML-language "XHTML" by defining
it's rules in DTD.
15
DTD Linking
Defines the structure, tag names and order for
all "book"- documents
TAMK has created XML-language "Book" by defining
it's rules in DTD.
16
Schema Linking
Defines the structure, tag names and order for
all "book"- documents
TAMK has created XML-language "Book" by defining
it's rules in a Schema.
17
Linking?

• The basic idea with linking to Schema
• lt?xml version"1.0"?gt
• ltroot schemaLocation"note.xsd"gt
• ltfoogt...lt/foogt
• lt/rootgt
• The problem with this is that now it is set that
  attribute "schemaLocation" is part of your
  XML-language

18
Linking and Namespace Usage

• Linking with namespace
• lt?xml version"1.0"?gt
• ltroot
• xmlnsxsi"http//www.w3.org/2001/XMLSchema-instan
  ce"
• xsischemaLocation"note.xsd"gt
• ltfoogt...lt/foogt
• lt/rootgt
• Now the "schemaLocation" attribute is in it's
  own namespaces (xsi) and does not belong to the
  "main" language.

19
Simple Schema

• lt?xml version"1.0"?gt
• ltxsdschema xmlnsxsd"http//www.w3.org/2001/XMLS
  chema"gt
• ltxsdelement name"complete_name"
  type"complete_name_type"/gt
• ltxsdcomplexType name"type"complete_name_type
  "gt
• ltxsdsequencegt
• ltxsdelement name"nome" type"xsdstring"/gt
• ltxsdelement name"cognome" type"xsdstring"/gt
  
• lt/xsdsequencegt
• lt/xsdcomplexTypegt
• lt/xsdschemagt

20
Let's remove namespaces...

• lt?xml version"1.0"?gt
• ltschemagt
• ltelement name"complete_name" type"complete_name
  _type"/gt
• ltcomplexType name"complete_name_type"gt
• ltsequencegt
• ltelement name"nome" type"string"/gt
• ltelement name"cognome" type"string"/gt
• lt/sequencegt
• lt/complexTypegt
• lt/schemagt

It doesn't look so confusing after all?
21
The Basics Element

• You define the name for the elements by using
  element-element. ?
• ltelement name"foo" type"bar" /gt
• Type?
• 44 Built-in schema datatypes
• string, double, time, date, etc.
• See all the datatypes

22
Usage of Datatypes

• ltxsdelement name"firstname"
• type"xsdstring" /gt
• ltxsdelement name"ableToSwim"
• type"xsdboolean" /gt
• ltxsdelement name"date"
• type"xsddate" /gt

23
minOccurs and maxOccurs

• The amount of elements
• In DTD , ?,
• In Schema minOccurs, maxOccurs
• Exampleltxsdelement name"date" type"xsddate"
  minOccurs"1" maxOccurs"2" /gt
• Default and special values
• default minOccurs 1
• default maxOccurs same as minOccurs
• maxOccurs"unbounded" unlimited

24
Defining new Datatypes

• If the the built-in datatypes are not enough, you
  can build your own datatypes.
• This does not necessarily work
• ltxsdelement name"grade" type"xsdinteger" /gt
• There are two ways of specifying your own
  datatype
• Named Data Type
• Anonymous Data Type

25
1) Named Data Type

• lt?xml version"1.0"?gt
• ltxsdschema xmlnsxsd"http//www.w3.org/2001/XMLS
  chema"gt
• ltxsdelement name"grade" type"grade_type"
  /gt
• ltxsdsimpleType name"grade_type"gt
• ltxsdrestriction base"xsdpositiveInteger
  "gt
• ltxsdminInclusive value"4"/gt
• ltxsdmaxInclusive value"10"/gt
• lt/xsdrestrictiongt
• lt/xsdsimpleTypegt
• lt/xsdschemagt

26
2) Anonymous Data Type

• lt?xml version"1.0"?gt
• ltxsdschema xmlnsxsd"http//www.w3.org/2001/XMLS
  chema"gt
• ltxsdelement name"grade"gt
• ltxsdsimpleTypegt
• ltxsdrestriction base"xsdpositiveInt
  eger"gt
• ltxsdminInclusive value"4"/gt
• ltxsdmaxInclusive value"10"/gt
• lt/xsdrestrictiongt
• lt/xsdsimpleTypegt
• lt/xsdelementgt
• lt/xsdschemagt

27
Benefits of Named Data Type

• If you want re-use your datatype
• lt?xml version"1.0"?gt
• ltxsdschema xmlnsxsd"http//www.w3.org/2001/XMLS
  chema"gt
• ltxsdelement name"grade" type"grade_type" /gt
• ltxsdelement name"teachers_IQ"
  type"grade_type" /gt
• ltxsdsimpleType name"grade_type"gt
• ltxsdrestriction base"xsdpositiveInteger
  "gt
• ltxsdminInclusive value"4"/gt
• ltxsdmaxInclusive value"10"/gt
• lt/xsdrestrictiongt
• lt/xsdsimpleTypegt
• lt/xsdschemagt

28
SimpleType enumeration

• Alternative content
• ltxsdsimpleType name"car"gt
• ltxsdrestriction base"xsdstring"gt
• ltxsdenumeration value"Audi"/gt
• ltxsdenumeration value"Golf"/gt
• ltxsdenumeration value"BMW"/gt
• lt/xsdrestrictiongt
• lt/xsdsimpleTypegt

29
SimpleType pattern

• Using REGEX
• ltxsdsimpleType name"lowercase_char"gt
• ltxsdrestriction base"xsdstring"gt
• ltxsdpattern value"a-z"/gt
• lt/xsdrestrictiongt
• lt/xsdsimpleTypegt

30
REGEX Examples

• ltxspattern value"A-ZA-ZA-Z"/gt
• ltxspattern value"a-zA-Za-zA-Za-zA-Z"/gt
• ltxspattern value"xyz"/gt
• ltxspattern value"0-90-90-90-90-9"/gt
• ltxspattern value"(a-z)"/gt
• ltxspattern value"malefemale"/gt
• ltxspattern value"a-zA-Z0-98"/gt

31
Structure of the XML-file

• It's possible to define the structure of the
  XML-file using complexType
• If element A has child-elements, then element A's
  type is complexType

32
SimpleType vs. ComplexType

• SimpleType
• ltgradegt7lt/gradegt
• Since grade does not hold other child elements,
  grade's type is simpleType
• ComplexType
• ltstudentsgtltstudentgtJacklt/studentgtlt/studentsgt
• Since student does hold child element(s),
  student's type is complexType

33
Example XML - File

• lt?xml version"1.0"?gt
• ltstudentsgt
• ltfirstnamegtPekkalt/firstnamegt
• ltlastnamegtVirtanenlt/lastnamegt
• lt/studentsgt

34
Example XSD fileNamed ComplexType

• lt?xml version"1.0"?gt
• ltxsdschema xmlnsxsd"http//www.w3.org/2001/XMLS
  chema"gt
• ltxsdelement name"students"
  type"students_type"gt
• ltxsdcomplexType name"students_type"gt
• ltxsdsequencegt
• ltxsdelement name"firstname"
  type"xsdstring"/gt
• ltxsdelement name"lastname"
  type"xsdstring"/gt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt
• lt/xsdschemagt

Use now complexType (vs. simpleType)
35
Example XSD fileAnonymous ComplexType

• lt?xml version"1.0"?gt
• ltxsdschema xmlnsxsd"http//www.w3.org/2001/XMLS
  chema"gt
• ltxsdelement name"students"gt
• ltxsdcomplexTypegt
• ltxsdsequencegt
• ltxsdelement name"firstname"
  type"xsdstring"/gt
• ltxsdelement name"lastname"
  type"xsdstring"/gt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt
• lt/xsdelementgt
• lt/xsdschemagt

36
Example ComplexType

• ltxsdelement name"employee" type"personinfo"/gt
• ltxsdelement name"student" type"personinfo"/gt
• ltxsdelement name"member" type"personinfo"/gt
• ltxsdcomplexType name"personinfo"gt
• ltxsdsequencegt
• ltxsdelement name"firstname"
  type"xsdstring"/gt
• ltxsdelement name"lastname"
  type"xsdstring"/gt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt

37
Deep Structure in XML - File

• lt?xml version"1.0"?gt
• ltstudentsgt
• ltstudentgt
• ltnamegt
• ltfirstnamegtPekkalt/firstnamegt
• lt/namegt
• lt/studentgt
• lt/studentsgt

38
Using Anonymous Data Type The Horror!

• lt?xml version"1.0"?gt
• ltxsdschema xmlnsxsd"http//www.w3.org/2001/XMLS
  chema"gt
• ltxsdelement name"students"gt
• ltxsdcomplexTypegt
• ltxsdsequencegt
• ltxsdelement name"student"gt
• ltxsdcomplexTypegt
• ltxsdsequencegt
• ltxsdelement
  name"name"gt
• 
  ltxsdcomplexTypegt
• 
  ltxsdsequencegt
• 
  ltxsdelement name"firstname" type"xsdstring"/gt
• 
  lt/xsdsequencegt
• 
  lt/xsdcomplexTypegt
• lt/xsdelementgt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt
• lt/xsdelementgt

39
"There is an error in my schema, could you find
it for me?"

• lt?xml version"1.0"?gt
• ltxsdschema xmlnsxsd"http//www.w3.org/2001/XMLS
  chema"gt
• ltxsdelement name"students"gt
• ltxsdcomplexTypegt
• ltxsdsequencegt
• ltxsdelement name"student"gt
• ltxsdcomplexTypegt
• ltxsdsequencegt
• ltxsdelement name"name"gt
• ltxsdcomplexTypegt
• ltxsdsequencegt
• ltxsdelement name"firstname" type"xsdstring"/gt
  
• lt/xsdsequencegt
• lt/xsdcomplexTypegt
• lt/xsdelementgt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt
• lt/xsdelementgt

40
Use Named Datatypes! It's easier to find errors..

• lt?xml version"1.0"?gt
• ltxsdschema xmlnsxsd"http//www.w3.org/2001/XMLS
  chema"gt
• ltxsdelement name"students" type"students_type
  " /gt
• ltxsdcomplexType name"students_type"gt
• ltxsdsequencegt
• ltxsdelement name"student"
  name"student_type" /gt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt
• ltxsdcomplexType name"student_type"gt
• ltxsdsequencegt
• ltxsdelement name"name" name"name_type"
  /gt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt
• ltxsdcomplexType name"name_type"gt
• ltxsdsequencegt

41
Order of the elements

• Sequence Elements appear in same order than in
  Schema
• All Elements can appear in any order
• Choice One element can appear from the
  choice-list
• ltxsdelement name"person"gt
• ltxsdcomplexTypegt
• ltxsdchoicegt
• ltxsdelement name"employee"
  type"employee"/gt
• ltxsdelement name"member" type"member"/gt
• lt/xsdchoicegt
• lt/xsdcomplexTypegt
• lt/xsdelementgt

42
Attribute

• XML
• ltstudent id"A1"gt...lt/studentgt
• Schema
• ltxsdelement name"student" type"student_type"
  /gt
• ltxsdcomplexType name"student_type"gt
• ltxsdsequencegt
• ...
• lt/xsdsequencegt
• ltxsdattribute name"id" type"xsdID"/gt
• lt/xsdcomplexTypegt

43
Empty Element with Attribute

• XML
• ltstudent id"A1" /gt
• Schema
• ltxsdelement name"student" type"student_type"
  /gt
• ltxsdcomplexType name"student_type"gt
• ltxsdattribute name"id" type"xsdID"/gt
• lt/xsdcomplexTypegt

44
PHP5 and Schema

• With PHP5 you do not have to link xml to schema
  files.
• The linking is done in PHP5 code, not in XML.
• Example of schema-validation
• doc new domDocument
• if ( doc-gtload("books.xml") and
• doc-gtschemaValidate("books.xsd') )
•     print "Is WellFormed and Schema-valid!"