The concept of DTD. DTD(Document Type Definition) Why we need DTD

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Julius Cunningham
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2 Contents Topics The concept of DTD Why we need DTD The basic grammar of DTD The practice which apply DTD in XML document How to write DTD for valid XML document

3 The concept of DTD DTD(Document Type Definition) The form of document To explicitly declare of XML document structure To confirm valid XML document Why we need DTD We can improve readability of document. It is easy to exchange documents. It is trivial to apply different application using one source. It is trivial to create XML document.

4 The concept of DTD How to use DTD Internal DTD, External DTD, Mixed DTD Internal DTD The case of declaration of DTD in XML document It is difficult to use another XML document Form <!DOCTYPE root_element [ <!ELEMENT root_element ]>

5 The concept of DTD External DTD The case of declaration of DTD in DTD file It is easy to use another XML document Form <!DOCTYPE root_element [ <!ELEMENT root_element ]> <!DOCTYPE root_element SYSTEM dtd_file.dtd > <root_element> dtd_file.dtd file.xml

6 The concept of DTD Mixed DTD It is mixed with internal DTD and external DTD Form <!DOCTYPE root_element [ <!ELEMENT root_element ]> <!DOCTYPE root_element SYSTEM dtd_file.dtd [ <!ELEMENT child_element ]> <root_element> dtd_file.dtd File.xml

7 The component of DTD 1. Comment <! This is comment of DTD > 2. The declaration of Element <!ELEMENT NAME (#PCDATA)> 3. The declaration of Attribute <!ATTLIST student grade (1 2 3) #REQUIRED> 4. The declaration of Entity <!ENTITY SCHOOL HIGH SCHOOL >

8 5. Conditional Section <![% PEOPLE; [<!ELEMENT TELEPHONE (HOUSE, OFFICE)>]]> 6. The declaration of procedural command <?xml stylesheet type= text/css href= xml_style.css?> 7. The declaration of Notation <!NOTATION mp3 SYSTEM C:\player.exe >

9 How to write DTD The form of DTD <[!DOCTYPE root_element source location1 location2 [internal DTD]> DOCTYPE: The keyword of DTD root_element: The root element in XML document source: You can use SYSTEM or PUBLIC location#: The location of external DTD file. [internal DTD]: The declaration of internal DTD.

10 Practice 1 <?xml version='1.0' encoding='utf 8'?> <! Simple DTD > <!DOCTYPE students [ <!ELEMENT students (student)+> <!ELEMENT student (name,subject)> <!ELEMENT name (#PCDATA)> <!ELEMENT subject (#PCDATA)> <!ATTLIST student id CDATA #REQUIRED> ]> <students> <student id="100"> <name>jose</name> <subject>xml Programming</subject> </student> <student id="200"> <name>maria</name> <subject>database</subject> </student> </students> 01.xml

11 The basic rule of writing DTD DTD is starting with <?xml and ends with?>. You have to use directives such as DOCTYPE in order to recognize DTD document. DOCTYPE is capital letters. After writing <!DOCTYPE, You have to use root element name DTD declaration is starting with [ and ends with ]> in XML document. DTD definitions can be defined only once in one document. If you are using external DTD document, You have to use a file extension.dtd

12 DTD Elements element: The basic unit of XML document Every data has to be included in element Syntax <!ELEMENT element_name content_name> element_name: The name of element in XML document content_name: The data type of element in XML document

13 Contents distribution(contents model and Contents category) Contents model #PCDATA : Element contains normal text Children : Contain child element Mixed : Contain normal text form(#pcdata) and child element Contents category Empty : Declare an empty elements that have not contents in elements. Any : Element s content can contain all data.

14 What is #PCDATA? PCDATA means parsed character data. Think of character data as the text found between the start tag and the end tag of an XML element. PCDATA is text that WILL be parsed by a parser. The text will be examined by the parser for entities and markup. Syntax <!ELEMENT element_name (#PCDATA)> Example <!DOCTYPE Students[ <!ELEMENT Students (#PCDATA)> ]> <Students> Parsed Character Data!! </Students>

15 Declare child element Declare sub elements that contain in upper element Syntax <!ELEMENT element_name (child_1, child_2, child_3,..., child_n)>

16 The list of operators/syntax rules we can use when defining child elements: Operator Syntax Description + a+ One or more occurences of a * a* Zero or more occurences of a? a? Either a or nothing, a, b a followed by b a b a followed by b () (expression) An expression surrounded by par entheses is treated as a unit and c ould have any one of the followin g suffixes?, *, or +.

17 Declare mixed form Used to declare text data and child elements at the same time to element Form <!ELEMENT element_name (#PCDATA child_1, child_2,..., child_n)> Precautions when use mixed declarations If you defined with text declare (#PCDATA), you can use only symbol text data declaration (# PCDATA) must be first the repeatability of mixed content may only be defined 0 or more times

18 Declare empty Declare to define empty elements that have no data How to define an empty element <element/> : if only one element express <element></element> : only express start element and end element Form <!ELEMENT element_name EMPTY>

19 ANY declaration If you do not put conditions on element used in the Any declaration can use that element not put in the condition Element can contain all data(text data, child element, comments, CDATA section) Form <!ELEMENT element_name ANY>

20 Property declaration Element is defined and use define properties To define property name, property type, property basic valued element associated with element <!ATTLIST element_name attribute_name TYPE DEFAULT_VALUE attribute_name TYPE DEFAULT_VALUE attribute_name TYPE DEFAULT_VALUE...> Start with capital letter ATTLIST" element naeme: The name of root element of XML document property type : Enumeration, String, tokenized types The default properties : declare first value, #FIXED, #IMPLIED, #REQUIRED

21 The value of attribute Value Explanation value #REQUIRED #IMPLIED #FIXED value The default value of the attribute The attribute is required The attribute is not required The attribute value is fixed

22 Property type Enumeration: Using one of the multiful property value defined by DTD developer String type: can have an arbitrary string using by CDATA keyword property value Token type: Use keywords used to attribute Type Description ID IDREF IDREFS NMTOKEN NMTOKENS ENTITY ENTITIES The value is a unique id The value is the id of another element The value is a list of other ids The value is a valid XML name The value is a list of valid XML names The value is an entity The value is a list of entities

23 Enumerated Attribute Values Use enumerated attribute values when you want the attribute value to be one of a fixed set of legal values. Using the symbol which is bar( ) in order to separate values. Syntax <!ATTLIST element_name attribute_name (value1 value2 value3) default_value>

24 The Attribute Type of CDATA You can use any character without special symbols(<, >, &, and ) If you want to use special symbols, You can use entity reference(<, >, $amp;, ', &quot) Syntax <!ATTLIST element_name attribute_name CDATA default_value> CDATA is only available only. PCDATA is not supported. It is differs from a CDATA section in XML document.

25 The Attribute Type of ID We want to recognize element in XML document Syntax <!ATTLIST element_name attribute_name ID default_value> default value is #IMPLIED or #REQUIRED An element has only one ID. The value of attribute in ID type has to follow XML naming convention.

26 The Attribute Type of IDREF The attribute type of IDREF is used for referring to an ID value of another element in the document. ID attribute which is using value must be required in other part in XML ID type and IDREF type is one to one relationship Syntax <!ATTLIST element_name attribute_name IDREF default_value> default value is #IMPLIED or #REQUIRED

27 The Attribute Type of IDREFS The attribute type of IDREFS is used for referring to the ID values of more than one other element in the document. Each value is separated by a space. ID type and IDREFS type is one to many relationship The separation of value is distinguish using space. Syntax <!ATTLIST element_name attribute_name IDREFS default_value> default value is #IMPLIED or #REQUIRED

28 An Internal Entity Declaration The <!ENTITY> declaration for general entities has the following syntax: <!ENTITY name definition> The usage of entity &name; Every entity definition is starting with <!ENTITY There is not allowed blank <! with ENTITY For example <!ENTITY address Panama City in Republic of Panama > &address;

29 The XML Big Picture Need to XML Parser: Apache Xerces, MSXML, etc XPath XPointer SAX DOM Access Document Data XML Well Formed Document Valid Document CSS DTD XML Schema Define Document Structure Valid Document

XML: Introduction. !important Declaration... 9:11 #FIXED... 7:5 #IMPLIED... 7:5 #REQUIRED... Directive... 9:11

XML: Introduction. !important Declaration... 9:11 #FIXED... 7:5 #IMPLIED... 7:5 #REQUIRED... Directive... 9:11 !important Declaration... 9:11 #FIXED... 7:5 #IMPLIED... 7:5 #REQUIRED... 7:4 @import Directive... 9:11 A Absolute Units of Length... 9:14 Addressing the First Line... 9:6 Assigning Meaning to XML Tags...