Declare A DTD File

Declare A DTD Inline File For example, use DTD to restrict the value of an XML document to contain only character data.

Inline DTD Include the text for a DTD inside the XML document For short XML documents For all XML documents during the development process and if you do not intend your DTD to be applied to other XML documents

Inline DTD

Restrict “GREETING” to contain characters only

Types of XML Element

External DTD Save the text for a DTD as a separate file and refer this file inside your XML document Using “DOCTYPE” declaration with the “SYSTEM” keyword Add path name if the DTD file is in different path from the XML file

External DTD

Comment DTD Files

Declare A Container Element Elements that consist of other, predefined elements Can enforce container relationships on XML data at run time The ability to enforce container relationships enables you to model complex relationships between XML data – model relationships between employees, projects, orders, products, retailers, etc.

Declare A Container Element

Contained elements need not to be declared in the same order in the DTD as they are in the XML document Indenting each contained element makes identifying the relationships between elements much easier

Declare A Container Element Elements that belong to namespaces must be referenced in DTDs by their fully qualified names. Example,

Declare A Required Element Required element –Created by validation rule to ensure that a given element is associated with one – and only one – value at runtime –Typically defined as contained elements –E.g., Customer name Social Security number Product Identification number Account number Etc.

Declare A Required Element

Declare A Optional Element Optional elements –Elements contained zero or more values at runtime

Declare A Multiple Occurring Element Multiple Occurring elements –Elements contained at least one or more values at runtime

Declare A Multiple Occurring Element

Declare Multiple Elements Multiple elements must be separated by commons, like this (aRequiredElement+, anotherRequiredElement, anOptionalElement*)

Declare An Character Data Element Use #PCDATA keyword #PCDATA is case-sensitive Cannot contain other predefined elements

Declare An Character Data Element

Declare An Empty Element Empty elements –Elements contained no data at runtime –Use to aggregate data, rather than to define specific values E.g., consider the element named “productDescription”

Declare An Empty Element

Declare Attributes That Hold Characters

Define An Entity Define a validation rule to constrain the value of an XML attribute to a developer-defined external data source Enables you to organize XML code in multiple files and pull the XML code together at runtime Use ENTITY keyword to declare an attribute of external type At runtime, the only data types allowed for an element declared as type ENTITY are those data types defined in the DTD file using declaration

Define An Entity

Declare Attributes As Words Define a validation rule using the NMTOKEN keyword to constrain the value of an XML attribute to a single word, or token To constrain a value to a collection of individual tokens, can use the NMTOKENS keyword

Declare Attributes As Words

Restrict Attributes to Lists of Options Constrain XML attribute value to one in a list of predefined options Can declare an attribute of type enumerates list Helps reduce input errors

Restrict Attributes to Lists of Options

Declare Unique-Identifier Attributes Constrain an attribute to accept unique values

Declare Unique-Identifier Attributes

Reference Existing Identifiers Use IDREF to ensure that the value of an XML attribute matches the value of previously defined attribute

Reference Existing Identifiers

Define and Reuse Text Within DTDs Describe a single of text, called parameter entity Reference the chunk repeatedly inside a DTD file Helps reduce errors introduced by retyping Define entities before using them Use and a sign % with a space on both sides. –The % sign denotes that this entity is a parameter entity

Define and Reuse Text Within DTDs An internal parameter entity An external parameter entity –Use URL what the content is located

Define and Reuse Text Within DTDs