Document Type Definitions Kanda Runapongsa ([email protected])[email protected] Dept. of Computer Engineering Khon Kaen University

Document Type Definitions

Kanda Runapongsa ([email protected])

Dept. of Computer EngineeringKhon Kaen University

mailto:[email protected]

168493: XML and Web Services (II/2546)

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DTD: Document Type Definition

Define the structure of XML documents with a list of legal elements

Why use a DTD? Different groups of people can

agree to use a common set of tags for interchanging data

To verify that the data received from others is valid


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A DTD of the Sample Document

<!ELEMENT Note (To, From, Course*)>

<!ELEMENT To (#PCDATA)><!ELEMENT From (#PCDATA)><!ELEMENT Course (Name, Time+,

Place?)><!ATTLIST Course id ID

#REQUIRED>


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Building Blocks of XML Elements Attributes Entities: define common text PCDATA: parsed character data

Text that will be parsed by a parser Tags inside the text are treated as

markup CDATA: character data

Text is not parsed by a parser. Text is kept as it is


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Element Type Declarations

Each element type declaration starts with <!ELEMENT Followed by the name and a

content specification Its structure

<!ELEMENT elementName (contentSpec)>

Example <!ELEMENT Note (To, From,

Course*)>


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Empty Elements Empty elements are declared

with keyword EMPTY DTD example: <!ELEMENT br EMPTY> XML example: <br></br> or <br/>


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Elements with Only Character Data

Elements with only character data are declared with #PCDATA inside parentheses DTD example:<!ELEMENT To (#PCDATA)> XML example:

<To>Students</To>


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Elements with any contents

Declared with keyword ANY Can contain any combination of

parsable data DTD example: <!ELEMENT Misc ANY> XML example:

<Misc>Hello there</Misc>


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Elements with Sequence Children

Defined with the name of the children inside parentheses

Children are declared in a sequence separated by commas

Children must appear in the same sequence in the document

DTD example: <!ELEMENT Note (To, From,

Course*)>


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Occurrence Types

Element with only one occurrence No symbol after the element Ex: <!ELEMENT Note (To, From, Course*)>

Element with the minimum of one occurrence Symbol + after the element Ex: <!ELEMENT Course (Name, Time+,

Place?)>


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Occurrence Types (Cont.)

Element with zero or more occurrences Symbol * after an element Ex: <!ELEMENT Note (To, From, Course*)>

Element with zero or one occurrence Symbol ? after an element <!ELEMENT Course (Name, Time+, Place?)>


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Elements with Content Options

Provide an alternative with symbol |

DTD example: <!ELEMENT n (fn|nn)> XML example:<n><fn>Duangporn</fn></n><n><nn>Nok</nn></n>


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Elements with Mixed Content

Mixed with children and parsed character data

Declared with symbol | DTD example<!ELEMENT MixedE (#PCDATA|n)*> XML example<MixedE><n><nn>joy<nn></n>

is a person</MixedE>


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Attributes Declarations Attribute declarations

Start with the string “<!ATTLIST” Followed with an element name A list of the information of attributes

The general structure <!ATTLIST elementName (attName

attType default)+>


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Attribute Declarations ID: Identifier

DTD: <!ATTLIST Course id ID #REQUIRED>

XML: <Course id=“168493”> CDATA: “character data”: not

parsed DTD: <!ATTLIST ARTICLE DATE

CDATA #REQUIRED> XML: <ARTICLE DATE=“January 1,

2000”>


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Attribute Defaults Attributes can have default values. For some attributes, the XML author

does not need to specify an attribute value The processor can supply the

default value if it exists But there are some attributes that

the attribute values need to be specified


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Attribute Defaults (Cont.) Default values

The DTD author specifies the default value Implied attributes

The processor specifies the default value Required attributes

The XML author specifies the default value Fixed attributes

The attribute value is fixed and specified by the DTD author


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Default Values Include the default value after the

type or list of allowed values in the attribute list declaration

Examples: DTD: <!ATTLIST SHIRT SIZE (SMALL|

MEDIUM|LARGE) MEDIUM> XML:

<SHIRT><color>red</color></SHIRT>


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Impliable Attributes Allow the user to omit a value for a

particular attribute without forcing a particular default

Examples: some shirts are “one size fits all” DTD: <!ATTLIST SHIRT SIZE NMTOKEN

#IMPLIED> XML:

<SHIRT><color>red</color></SHIRT> Leave the values to be assigned by a

processor or to be ignored


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Required Attributes The XML author is required to

specify the attribute values A value for an attribute is

important and cannot reliably be defaulted

Examples DTD: <!ATTLIST Course id ID

#REQUIRED> XML: <Course id=“168493”>


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Fixed Attributes Attribute values cannot be

overridden at all For the purpose of easy integration

between documents <!ATTLIST CHAPTER TITLE-LEVEL CDATA

#FIXED “FIRST”> <!ATTLIST SECTION TITLE-LEVEL CDATA

#FIXED “SECOND”> <!ATTLIST SUBSECTION TITLE-LEVEL

CDATA #FIXED “THIRD”>


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Attribute Types Attribute value normalization CDATA and name token

attributes Enumerated and notation

attributes ID and IDREF attributes ENTITY attributes


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Attribute Values and Types

The value of an attribute is not necessary the exact character string that you enter between the quotation marks

The string first go through a process called attribute-value normalization

Attribute types apply to the normalized value


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Attribute Value Normalization

XML processors normalize values to make authors’ lives simpler

If it were not for normalization, The XML authors must be very

careful where and how they put white spaces in an attribute value

All XML attribute values are entered as quoted strings


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Normalization Process 1. Strip off the surrounding

quotes 2. Character and entity

references are replaced 3. Newline characters are

replaced by spaces Examples:

|“ token “| |token|


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CDATA Attributes CDATA stands for “character

data” DTD: <!ATTLIST ARTICLE DATE CDATA

#REQUIRED> XML:<ARTICLE DATE=“January 1, 2000”>

…</ARTICLE>


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NMTOKEN Attributes NMTOKEN: Name Token attributes Similar to CDATA but restricted in the

characters that name tokens allow Name tokens are composed of strings

made up of letters, numbers, and a select group of special characters Period (.), Dash (-), Underscore (_), and

colon (:)


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NMTOKEN Examples DTD:<!ATTLIST TABLE NAME NMTOKEN

#REQUIRED FIELDS NMTOKENS #REQUIRED>

XML:<TABLE NAME=“SECURITY”

FIELDS=“USERID PASSWORD DEPARTMENT”>

…</TABLE>


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Entity Declarations Allow you to associate a name with a

fragment which can be A piece of common text A reference to an external file

containing either text or binary data Three kinds of entities

Internal entities External entities Parameter entities


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Internal Entities Associate a name with a string of

literal text Examples: DTD: <!ENTITY KKU “Khon Kaen U.”> XML: &KKU; is in Thailand


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External Entities Allow an XML document to refer to

the contents of another file If another file contains text,

Its content is inserted at the point of reference and parsed as part of the document

If another file contains binary data, Its content is not parsed May only be referenced in an attribute


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External Entities (Cont.) Another file is a text file<!ENTITY sample SYSTEM

“/standard/sample.xml”> Another file contains binary data,

such as figures<!ENTITY logo SYSTEM

“/standard/logo.gif” NDATA GIF87A>


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Parameter Entities Can only occur in the DTD A parameter entity declaration is

identified by placing % (percent-space) in front of its name in the declaration

The percent sign is also used in references to parameter entities, instead of the ampersand


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Parameter Entities (Cont.)

Examples: Without parameter entities<!ELEMENT mixed (#PCDATA | t)*><!ELEMENT misc (#PCDATA | t)*> With parameter entities<!ENTITY % m “#PCDATA | t”><!ELEMENT mixed (%m;)*><!ELEMENT misc (%m;)*>


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Notation Declarations Provide a name for the notation

Which may allow an XML processor to locate an application capable of processing data in the given notation

Example:<!NOTATION GIF87A SYSTEM

“GIF.EXE”><!NOTATION HTML SYSTEM

http://www.w3.org/Markup>


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Declaring a DTD Two ways that a DTD can be

declared Inline in an XML document(Internal DOCTYPE declaration) As an external reference(External DOCTYPE declaration)


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Internal DOCTYPE declaration

<?xml version=“1.0” encoding=“ISO-8859-1”?>

<!DOCTYPE Note [<!ELEMENT Note (To, From, Course*)>…]><Note>…</Note>


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External DOCTYPE Declaration

<?xml version=“1.0” encoding=“ISO-8859-1”?>

<!DOCTYPE Note SYSTEM “Note.dtd”>

<Note>…</Note>

Documents

Document Type Definitions Kanda Runapongsa ([email protected])[email protected] Dept. of Computer Engineering Khon Kaen University