DTD Notes Page 1

XML Document Type Definition

It Defines the document structure with a list of legal elements

It Can Be Declared Inside the XML File or in an External Reference File

Each of the XML files can carry a separate description of it's own format

Business groups can agree to use a common DTD for interchanging Data

Applications can use a standard DTD to verify the data

Internal Declaration Syntax

              <?xml version = "1.0"?>
              <!DOCTYPE note [
                <!ELEMENT note    (to,from,heading,body)>
                <!ELEMENT to      (#PCDATA)>
                <!ELEMENT from    (#PCDATA)>
                <!ELEMENT heading (#PCDATA)>
                <!ELEMENT body    (#PCDATA)>
              ]>

External Declaration Syntax

Syntax of the XML file

                  <?xml version = "1.0"?>
                  <!DOCTYPE note SYSTEM "note.dtd">
                  <note>
                    <to>Bob</to>
                    <from>Bill</from>
                    <heading>Reminder</heading>
                    <body>Don't forget me this weekend!</body>
                  </note>

Syntax of the DTD file

                  <!ELEMENT note (to,from,heading,body)>
                  <!ELEMENT to      (#PCDATA)>
                  <!ELEMENT from    (#PCDATA)>
                  <!ELEMENT heading (#PCDATA)>
                  <!ELEMENT body    (#PCDATA)>

DTD - XML Building Blocks
All XML and HTML documents are made of the following
1. Elements eg; <body>, <table>... etc.
2. Tags
3. Attributes
4. Entities
5. PCDATA
6. CDATA

Elements

XML Elements are Declared with a DTD Element Declaration

Syntax

              <!ELEMENT element-name category>
                        - OR -
              <!ELEMENT element-name (element-content)>

Empty Element Declaration

Empty Elements are Declared witht the Category KeyWord EMPTY

Example:

                  <ELEMENT element-name EMPTY>

Elements with Only Character Data: (#PCDATA)

Example:

                  <!ELEMENT element-name (#PCDATA)>

Elements with Any Contents

Can contain any combination of parsable data

Example:

                  <!ELEMENT element-name ANY>

Elements with Children (sequences)
Elements with Children are defined with the name of the children

Inside Parentheses

Example:
```
<!ELEMENT element-name (child-element-name, child-element-name...)>
              
```
The children must appear in the correct sequence

Declaring only One Occurance of the same Element

Example:

                <!ELEMENT element-name (child-name)>

Declaring at least One occurance of the Same Element

Example:

                <!ELEMENT element-name (child-name+)>

Declaring Zero or More Occurences of the Same Element

Example:

                <!ELEMENT element-name (child-name*)>

Declaring Zero or One Occurance of the Same Element

Example:

                <!ELEMENT element-name (child-name?)>

Declaring Either/Or Content

Example:

<!ELEMENT element-name (child-name,(child-name|other-child-name))>

Declaring Mixed Content

Example:

<!ELEMENT element-name (#PCDATA|child-name|child-name|child-name)*>

DTD - Attributes

Syntax

<!ATTLIST element-name attribute-name attribute-type default-value>

Attribute-Type can have the following values

Value	Explanation
CDATA	The Value Is Character Data
(en1[en2]..)	The Value Must be One from an Enumerated List
ID	The Value Is A Unique Id
IDREF	The Value is the Id of Another Element
IDREFS	The Value Is A List of Other Id's
NMTOKEN	The Value Is A Valid XML Name
NMTOKENS	The Value Is a List of Valid XML Names
ENTITY	The Value Is is An Entity
ENTITIES	The Value Is a List of Entities
NOTATION	The Value Is a Name of a Notation
xml:	The Value Is a Predefined XML Value

The default-value can have the following values:

Value	Explanation
value	The default value of an Attribute
#REQUIRED	The Attribute Value Must be Included in the Element
#IMPLIED	The Attribute Does Not Have to be Included
#FIXED value	The Attribute Value is Fixed

Specifying a Default Attribute Value

Example:

              DTD:
              <!ELEMENT square EMPTY>
              <!ATTLIST square width CDATA "0">

              Valid XML:
              <square width = "100" />

Explanation:

The square element is defined to be an empty element

with a width attribute of type CDATA

If no width is specified, it has a default value of "0"

#IMPLIED Attributes

Syntax:

              <!ATTLIST element-name attribute-name attribute-type #IMPLIED>

Example:

              DTD:
              <!ATTLIST contact fax CDATA #IMPLIED>

              Valid MXL:
              <contact fax = "555-6687" />

              Valid XML:
              < contact />

Explanation

Use fi you don't want to force the author

to include an attribute and you don't have an option for a default value

#REQUIRED Attributes

Syntax:

               <!ATTLIST element-name attribute_name attribute-type #REQUIRED>

Example:

              DTD
              <!ATTLIST person number CDATA #REQUIRED>

              Valid XML:
              <person number = "5677" />

              Invalid XML:
              <person />

Explanation

Use the #REQUIRED Keyword if you

don't have an option for a default value but want to force

the attribute to be present

#FIXED Attributes

Syntax:

              <!ATTLIST element-name attribute-name attribute-type #FIXED "value">

Example:

              DTD:
              <!ATTLIST sender company CDATA #FIXED "Microsoft">

              Valid XML:
              <sender company = "Microsoft" />

              Invalid XML:
              <sender company = "W3Schools" />

Explanation

Used the #FIXED Keyword when you want an

attribute to have a fixed value without allowing the author to change it

If an author includes another value, the XML parser will return an error

Enumerated Attribute Values

Syntax:

              <!ATTLIST element-name attribute-name (en1|en2|...) default-value>

Example:

              DTD:
              <!ATTLIST payment type (check|cash) "cash">

              XML Example:
              <payment type = "check" />

              Or:
              <payment type = "cash" />

Explanation

Use the Enumerated Attribute Values

when you want the Attribute values to be one of a fixed set of legal values

DTD Entities

Entities are variables used to define shortcuts to common text

- Entity references are references to entities

- Entities can be declared internally or externally

Internal Entity Declaration

Syntax

                  <!ENTITY entity-name "entity-value">

DTD Example:

                  <!ENTITY writer "Donald Duck.">
                  <!ENTITY coopyright "Copyright W3Schools.">

XML Example

                  <author>&writer/&copyright;</author>

External Entity Declaration

Syntax

                  <!ENTITY entity-name SYSTEM "URI/URL">

DTD Example:

<!ENTITY writer SYSTEM "http://www.w3schools.com/entities/entities.xml">
<!ENTITY copyright SYSTEM "http://www.w3schools.com/entities/entities.dtd">

XML Example:

                  <author>&writer;&copyright;</author>

DTD Validation

Validating with the XML Parser

By Accessing the parseError Object

the exact error code, error text and error line can be retrieved

The load() method is used for files

the loadXML() method is used for strings

Example:

                  var xmlDoc = newActiveXObject("Microsoft.XMLDOM")
                  xmlDoc.async = "false"
                  xmlDoc.validateOnParse = "true"
                  xmlDoc.load("note_dtd_error.xml")

                  document.write("<br>Error Code: ")
                  document.write(xmlDoc.parseError.errorCode)
                  document.write("<br>Error Reason: ")
                  document.write(xmlDoc.parseError.reason)
                  document.write("<br>Error Line: ")
                  document.write(xmlDoc.parseError.line)

Turning Validation Off

Example:

                  var xmlDoc = newActiveXObject("Microsoft.XMLDOM")
                  xmlDoc.async = "false"
                  xmlDoc.validateOnParse = "false"
                  xmlDoc.load("note_dtd_error.xml")

                  document.write("<br>Error Code: ")
                  document.write(xmlDoc.parseError.errorCode)
                  document.write("<br>Error Reason: ")
                  document.write(xmlDoc.parseError.reason)
                  document.write("<br>Error Line: ")
                  document.write(xmlDoc.parseError.line)

Examples

TV Schedule DTD

<!DOCTYPE TVSCHEDULE [<!ELEMENT TVSCHEDULE (CHANNEL+)>
<!ELEMENT CHANNEL (BANNER,DAY+)>
<!ELEMENT BANNER (#PCDATA)>
<!ELEMENT DAY (DATE,(HOLIDAY|PROGRAMSLOT+))+>
<!ELEMENT HOLIDAY (#PCDATA)>
<!ELEMENT DATE (#PCDATA)>
<!ELEMENT PROGRAMSLOT (TIME,TITLE,DESCRIPTION?)>
<!ELEMENT TIME (#PCDATA)>
<!ELEMENT TITLE (#PCDATA)>
<!ELEMENT DESCRIPTION (#PCDATA)>

<!ATTLIST TVSCHEDULE NAME CDATA #REQUIRED>
<!ATTLIST CHANNEL CHAN CDATA #REQUIRED>
<!ATTLIST PROGRAMSLOT VTR CDATA #IMPLIED>
<!ATTLIST TITLE RATING CDATA #IMPLIED>
<!ATTLIST TITLE LANGUAGE CDATA #IMPLIED>

]>

Newspaper Article DTD

<!DOCTYPE NEWSPAPER [ <!ELEMENT NEWSPAPER (ARTICLE+)>
<!ELEMENT ARTICLE (HEADLINE,BYLINE,LEAD,BODY,NOTES)>
<!ELEMENT HEADLINE (#PCDATA)>
<!ELEMENT BYLINE (#PCDATA)>
<!ELEMENT LEAD (#PCDATA)>
<!ELEMENT BODY (#PCDATA)>
<!ELEMENT NOTES (#PCDATA)> <!ATTLIST ARTICLE AUTHOR CDATA #REQUIRED>
<!ATTLIST ARTICLE EDITOR CDATA #IMPLIED>
<!ATTLIST ARTICLE DATE CDATA #IMPLIED>
<!ATTLIST ARTICLE EDITION CDATA #IMPLIED><!ENTITY NEWSPAPER "Vervet Logic Times">
<!ENTITY PUBLISHER "Vervet Logic Press">
<!ENTITY COPYRIGHT "Copyright 1998 Vervet Logic Press">]>

Product Catalog DTD

<!DOCTYPE CATALOG [<!ENTITY AUTHOR "John Doe">
<!ENTITY COMPANY "JD Power Tools, Inc.">
<!ENTITY EMAIL "[email protected]">

<!ELEMENT CATALOG (PRODUCT+)>

<!ELEMENT PRODUCT
(SPECIFICATIONS+,OPTIONS?,PRICE+,NOTES?)>
<!ATTLIST PRODUCT
NAME CDATA #IMPLIED
CATEGORY (HandTool|Table|Shop-Professional) "HandTool"
PARTNUM CDATA #IMPLIED
PLANT (Pittsburgh|Milwaukee|Chicago) "Chicago"
INVENTORY (InStock|Backordered|Discontinued) "InStock">

<!ELEMENT SPECIFICATIONS (#PCDATA)>
<!ATTLIST SPECIFICATIONS
WEIGHT CDATA #IMPLIED
POWER CDATA #IMPLIED>

<!ELEMENT OPTIONS (#PCDATA)>
<!ATTLIST OPTIONS
FINISH (Metal|Polished|Matte) "Matte"
ADAPTER (Included|Optional|NotApplicable) "Included"
CASE (HardShell|Soft|NotApplicable) "HardShell">

<!ELEMENT PRICE (#PCDATA)>
<!ATTLIST PRICE
MSRP CDATA #IMPLIED
WHOLESALE CDATA #IMPLIED
STREET CDATA #IMPLIED
SHIPPING CDATA #IMPLIED>

<!ELEMENT NOTES (#PCDATA)>

]>

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