XML DTD and Schema

Well formed and valid document
• a valid XML document is a more strict form of
a well-formed XML document .
• well formed if it follows all the preceding syntax rules of XML.
• valid XML documents can improve the quality of document processes.

DTD
• Document type definition.
• Defines a set of rules for an XML document to make it valid.
• Validated & verified using DTD.
• It will define the element like
Optional
No.of times it can occur
Attributes in it

DTD
• Advantage: single DTD can be referenced by many XML documents.
• Types:
Internal
External

Example
<?xml version=“1.0”?>
<!DOCTYPE note [
<!ELEMENT note (to,from,heading,body)>
<!ELEMENT to (#PCDATA)>
<!ELEMENT from (#PCDATA)>
<!ELEMENT heading (#PCDATA)>
<!ELEMENT body (#PCDATA)>
]>
<note>
<to> tove</to>
<from>jani</from>
<heading>remainder</heading>
<body> weekend</body>
</note>

Structure of DTD
• Syntax:
Exclamation mark
DOCTYPE
Root element
SYSTEM|PUBLIC
Internal DTD elements

DTD elements
• Syntax:
• ELEMENT
• Elementname
• Rule
• Elements are processed from top down(order of appearance).

DTD Element rules
• Content rule
• ANY rule
• Empty rule
• #PCDATA rule
• Structure rule
• Element only rule
• Mixed rule

ANY rule
• Element may contain other elements and/or normal character data.
• Syntax:
• Example:

EMPTY rule
• Element contain no data
• Syntax:
• Can contain attributes.
• In HTML, image tag<img> doesn't contain any data nut it has
attributes the describes the location, height,..
• Empty elements can contain diagnostic information for the proessing
of data.

#PCDATA rule
• Indicated that parsed character data will be contained in the element.
• Syntax:
• Example:
• Example for CDATA:

Element-only rule
• Specifies that only elements may appear as children of the current
element.
• If there are to be options for which elements will appear, the listed
elements should be separated by the pipe(|) symbol.

Mixed rule
• Elements that may have both character data and child elements in
the data they contain.
• Options will be separated by the pipe symbol(|).
• Sequential lists will be separated by commas.
• Asterisk symbol(*)

Element symbols
• * -<!ELEMENT children (name*)>
• , -<!ELEMENT address (street, city, state, zip)>
• []() -<!ELEMENT address (street, city, (state |province), zip)>
• | -<!ELEMENT dessert (cake | pie)>
• + - <!ELEMENT appliances (refrigerator+)>
• ? -<!ELEMENT employment (company?)>
• No symbol

DTD attributes
• Metadata to describe XML element.
• Syntax:
<!ATTLIST elementname attributename type defaultbehavior
defaultvalue>
• Eg:<name sex=”male” age=”30” race=”Caucasian”>Michael
Qualls</name>
• <!ATTLIST name
sex CDATA #REQUIRED
age CDATA #IMPLIED
race CDATA #IMPLIED >

Attributes types
1. CDATA: <ATTLIST box height CDATA ”0”>
2. ENTITY:<!ATTLIST img src ENTITY #REQUIRED>
3. ENTITIES:<!ATTLIST imgs srcs ENTITIES #REQUIRED>
4. ID: <!ATTLIST cog serial ID #REQUIRED>
5. IDREF:<!ATTLIST person cousin IDREF #IMPLIED>
6. IDREFS: <!ATTLIST person cousins IDREFS #IMPLIED>

Attribute types
7. NMTOKEN: <!ATTLIST address country NMTOKEN “usa”>
8. NMTOKENS: <!ATTLIST region states NMTOKENS “KS OK” >
9. NOTATION: <!ATTLIST music play NOTATION “mplayer2.exe “>
10. ENUMERATED: <!ATTLIST college grad (1|0) “1”>

Default value types
• #REQUIRED:<!ATTLIST season year CDATA #REQUIRED >
• #IMPLIED:<!ATTLIST field size CDATA #IMPLIED >
• #FIXED:<!ATTLIST bcc hidden #FIXED “true” >
• Default :<!ATTLIST children number CDATA “0”>

DTD Entities
• Storage units.
• well-formed XML, normal text, binary data, a database record, and so
on.
• Syntax:
<!ENTITY entityname [SYSTEM | PUBLIC] entitycontent>

Internal Entity
<?xml version=”1.0”?>
<!DOCTYPE library [
<!ENTITY cpy “Copyright 2000”>
<!ELEMENT library (book+)>
<!ELEMENT book (title,author,copyright)>
<!ELEMENT title (#PCDATA)>
<!ELEMENT author (#PCDATA)>
<!ELEMENT copyright (#PCDATA)>
]>

<library>
<book>
<title>How to Win Friends</title>
<author>Joe Charisma</author>
<copyright>&cpy;</copyright>
</book>
<book>
<title>Make Money Fast</title>
<author>Jimmy QuickBuck</author>
<copyright>&cpy;</copyright>
</book>
</library>

Predefined entities
Entity Content
& &
< <
> >
" “
' ‘

Example
<icecream>
<flavor>Cherry Garcia</flavor>
<vendor>Ben & Jerry’s</vendor>
</icecream>

External entity
<?xml version=”1.0”?>
<!DOCTYPE employees [
<!ENTITY bob SYSTEM “http://srvr/emps/bob.xml”>
<!ENTITY nancy SYSTEM “http://srvr/emps/nancy.xml”>
<!ELEMENT employees (clerk)>
<!ELEMENT clerk (#PCDATA)>
]>
<employees>
<clerk>&bob;</clerk>
<clerk>&nancy;</clerk>
</employees>

Non-text entity and notation
• Example: <!ENTITY myimage SYSTEM “myimage.gif” NDATA gif>
• Notation syntax:
<!NOTATION notationname [SYSTEM | PUBLIC ] dataformat>

External non-text entities
<!NOTATION gif SYSTEM “image/gif” >
<!ENTITY employeephoto SYSTEM “images/employees/MichaelQ.gif”
NDATA gif >
<!ELEMENT employee (name, sex, title, years) >
<!ATTLIST employee pic ENTITY #IMPLIED >
…
<employee pic=”employeephoto”>
…
</employee>

Parameter entities
• Syntax: <!ENTITY % entityname entitycontent>
• Example:
<!ENTITY % pc “(#PCDATA)”>
<!ELEMENT name %pc;>
<!ELEMENT age %pc;>
<!ELEMENT weight %pc;>

Drawbacks of DTD
• Composed of non-XML syntax.
• Single DTD per document.
• Not object oriented.
• Don’t support namespace.
• Weak data typing.

XML Schema Elements
• All
• Any
• anyAttribute
• Annotation
• Appinfo
• Attribute
• attributeGroup
• Choice

• complexContent
• complexType
• Documentation
• Element
• Extension
• Field
• Group
• Import
• Include
• Key
• Keyref
• List

• Notation
• Redefine
• Restrictions
• Schema
• Selector
• Sequence
• simpleContent
• simpleType
• Union
• Unique

Declaring Attribute
<xsd:complexType name=”ProductType”>
<xsd:attribute name=”Name” type=”xsd:string”/>
<xsd:attribute name=”Id” type=”xsd:positiveInteger”/>
<xsd:attribute name=”Price”>
<xsd:simpleType>
<xsd:restriction base=”xsd:decimal”>
<xsd:fractionDigits value=”2”/>
</xsd:restriction>
</xsd:simpleType>
</xsd:attribute>
<xsd:attribute name=”Quantity” type=”xsd:positiveInteger”/>
</xsd:complexType>

Data types
• anyURI
• base64Binary
• Boolean
• Byte
• Date
• dateTime
• Decimal
• Double
• duration

• ENTITIES
• ENTITY
• Float
• gDay
• gMonth
• gMonthDay
• gYear
• gYearMonth
• hexBinary
• ID
• IDREF
• IDREFS

• Int
• Integer
• Language
• Long
• Name
• NCName
• Negative Integer
• NMToken
• NMTOKENS
• Nonnegative integer
• Nonpositive integer
• Normalized string

• NOTATION
• positiveInteger
• Qname
• Short
• String
• Time
• Token
• unsignedByte
• unsignedInt
• unsignedLong
• unsignedShort

• Primitive datatypes
• Derived datatypes
• Syntax:
<attribute name=”” type=”” [use=””] [fixed=””] [default=””] [ref=””]/>
• ‘use’ possible values:
Optional
Prohibited
Required

Declaring element
• Syntax:
<element name=”” [type=””] [abstract=””] [block=””]
➥[default=””] [final=””] [fixed=””] [minOccurs=””]
➥[maxOccurs=””] [nillable=””] [ref=””]
➥[substitutionGroup=””]/>
• Block: all, extension, restriction, substitution.

Declaring Complex Elements
• Syntax:
<xsd:complexType name=’’ [abstract=’’] [base=’’] [block=’’]
➥[final=’’] [mixed=’’]/>
• Block: all, extension, restriction.
• A <complexType>element in the XML Schema Definition Language
may contain only one of the following elements:
all, choice, complexContent, group, sequence, simpleContent.

Declaring Simple Elements
• Syntax:
<xsd:simpleType name=’’>
<xsd:restriction base=’’/>
</xsd:simpleType>

XML DTD and Schema

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