A Document Type Definition (DTD) is a specific document defining and constraining definition or set of statements that follow the rules of the Standard Generalized Markup Language (SGML) or of the Extensible Markup Language (XML), a subset of SGML. A DTD is a specification that accompanies a document and identifies what the funny little codes (or markup) are that, in the case of a text document, separate paragraphs, identify topic headings, and so forth and how each is to be processed. By mailing a DTD with a document, any location that has a DTD "reader" (or "SGML compiler") will be able to process the document and display or print it as intended. This means that a single standard SGML compiler can serve many different kinds of documents that use a range of different markup codes and related meanings. The compiler looks at the DTD and then prints or displays the document accordingly.

As a matter of fact, the document you are looking at is coded in a particular DTD called HTML. In this case, the "compiler" or document handler is your Web browser which is designed to handle text documents encoded with HTML tags. (Other programs could be developed that would handle HTML and other DTDs as well.)

IBM and many large and small corporations are converting documents to SGML or, more recently, to XML, each with its own company document type definition or set of definitions. For corporate intranets and extranets, the document type definition of HTML provides one new "language" that everyone can format documents in and read universally.

Answered by Yash , an ibibo Master, at 11:29 PM on July 06, 2008

DTD is a description in XML Declaration Syntax of a particular type or class of document. It sets out what names are to be used for the different types of element, where they may occur, and how they all fit together. (A question C.16, Schema does the same thing in XML Document Syntax, and allows more extensive data-checking.)
For example, if you want a document type to be able to describe Lists which contain Items, the relevant part of your DTD might contain something like this:
<!ELEMENT List (Item)+>
<!ELEMENT Item (#PCDATA)>
This defines a list as an element type containing one or more items (that's the plus sign); and it defines items as element types containing just plain text (Parsed Character Data or PCDATA). Validators read the DTD before they read your document so that they can identify where every element type ought to come and how each relates to the other, so that applications which need to know this in advance (most editors, search engines, navigators, and databases) can set themselves up correctly. The example above lets you create lists like:
<List>
<Item>Chocolate </Item>
<Item>Music</Item>
< Item>Surfing</Item>
</List>
(The indentation in the example is just for legibility while editing: it is not required by XML.)
A DTD provides applications with advance notice of what names and structures can be used in a particular document type. Using a DTD and a validating editor means you can be certain that all documents of that particular type will be constructed and named in a consistent and conformant manner.
DTDs are not required for processing the tip ‘Rules for well-formedness:’ in question D.2, well-formed documents, but they are needed if you want to take advantage of XML's special attribute types like the built-in ID/IDREF cross-reference mechanism; or the use of default attribute values; or references to external non-XML files (‘Notations’); or if you simply want a check on document validity before processing.
There are thousands of DTDs already in existence in all kinds of areas (see the SGML/XML Web pages for pointers). Many of them can be downloaded and used freely; or you can write your own (see the question on creating your own DTD. Old SGML DTDs need to be converted to XML for use with XML systems: read the question on converting SGML DTDs to XML, but most popular SGML DTDs are already available in XML form.
Some XML editors use a binary compiled format of DTD produced by their own management routines to allow a single person in an organisation to be in charge of modifications, and to distribute only an unmodifiable (binary compiled) version to users.

Answered by Madhurima , an ibibo Master, at 12:59 PM on June 15, 2008

A Document Type Definition (DTD) is a specific document defining and constraining definition or set of statements that follow the rules of the Standard Generalized Markup Language (SGML) or of the Extensible Markup Language (XML), a subset of SGML. A DTD is a specification that accompanies a document and identifies what the funny little codes (or markup) are that, in the case of a text document, separate paragraphs, identify topic headings, and so forth and how each is to be processed. By mailing a DTD with a document, any location that has a DTD "reader" (or "SGML compiler") will be able to process the document and display or print it as intended. This means that a single standard SGML compiler can serve many different kinds of documents that use a range of different markup codes and related meanings. The compiler looks at the DTD and then prints or displays the document accordingly.

As a matter of fact, the document you are looking at is coded in a particular DTD called HTML. In this case, the "compiler" or document handler is your Web browser which is designed to handle text documents encoded with HTML tags. (Other programs could be developed that would handle HTML and other DTDs as well.)

IBM and many large and small corporations are converting documents to SGML or, more recently, to XML, each with its own company document type definition or set of definitions. For corporate intranets and extranets, the document type definition of HTML provides one new "language" that everyone can format documents in and read universally.

Answered by Anju Singh , an ibibo Master, at 8:50 AM on June 12, 2008

A Document Type Definition (DTD) is a specific document defining and constraining definition or set of statements that follow the rules of the Standard Generalized Markup Language (SGML) or of the Extensible Markup Language (XML), a subset of SGML. A DTD is a specification that accompanies a document and identifies what the funny little codes (or markup) are that, in the case of a text document, separate paragraphs, identify topic headings, and so forth and how each is to be processed. By mailing a DTD with a document, any location that has a DTD "reader" (or "SGML compiler") will be able to process the document and display or print it as intended. This means that a single standard SGML compiler can serve many different kinds of documents that use a range of different markup codes and related meanings. The compiler looks at the DTD and then prints or displays the document accordingly.

As a matter of fact, the document you are looking at is coded in a particular DTD called HTML. In this case, the "compiler" or document handler is your Web browser which is designed to handle text documents encoded with HTML tags. (Other programs could be developed that would handle HTML and other DTDs as well.)

IBM and many large and small corporations are converting documents to SGML or, more recently, to XML, each with its own company document type definition or set of definitions. For corporate intranets and extranets, the document type definition of HTML provides one new "language" that everyone can format documents in and read universally.

Answered by Om Prakash , an ibibo Master, at 7:58 PM on June 11, 2008

Hi there

A DTD is a description in XML Declaration Syntax of a particular type or class of document. It sets out what names are to be used for the different types of element, where they may occur, and how they all fit together.

For example, if you want a document type to be able to describe Lists which contain Items, the relevant part of your DTD might contain something like this:

<!ELEMENT List (Item)+>
<!ELEMENT Item (#PCDATA)>

This defines a list as an element type containing one or more items (that's the plus sign); and it defines items as element types containing just plain text (Parsed Character Data or PCDATA).

Validators read the DTD before they read your document so that they can identify where every element type ought to come and how each relates to the other, so that applications which need to know this in advance (most editors, search engines, navigators, and databases) can set themselves up correctly.

The example above lets you create lists like:

<List>
<Item>Chocolate</I tem>
<Item>Music</Item>
<Item>Sur fing</Item>
</List>

A DTD provides applications with advance notice of what names and structures can be used in a particular document type. Using a DTD and a validating editor means you can be certain that all documents of that particular type will be constructed and named in a consistent and conformant manner.

DTDs are not required for processing the tip ‘Rules for well-formedness:’ in question D.2, well-formed documents, but they are needed if you want to take advantage of XML's special attribute types like the built-in ID/IDREF cross-reference mechanism; or the use of default attribute values; or references to external non-XML files (‘Notations’); or if you simply want a check on document validity before processing.

Source :

http://xml.silmaril.ie/au thors/dtds/

Answered by Reeta K , an ibibo Master, at 1:05 PM on June 11, 2008

well rocky, A Document Type Definition (DTD) is a specific document defining and constraining definition or set of statements that follow the rules of the Standard Generalized Markup Language (SGML) or of the Extensible Markup Language (XML), a subset of SGML. A DTD is a specification that accompanies a document and identifies what the funny little codes (or markup) are that, in the case of a text document, separate paragraphs, identify topic headings, and so forth and how each is to be processed. By mailing a DTD with a document, any location that has a DTD "reader" (or "SGML compiler") will be able to process the document and display or print it as intended. This means that a single standard SGML compiler can serve many different kinds of documents that use a range of different markup codes and related meanings. The compiler looks at the DTD and then prints or displays the document accordingly.

Answered by Romi , an ibibo Master, at 6:19 PM on June 10, 2008

A DTD is a description in XML Declaration Syntax of a particular type or class of document. It sets out what names are to be used for the different types of element, where they may occur, and how they all fit together.

For example, if you want a document type to be able to describe Lists which contain Items, the relevant part of your DTD might contain something like this:

<!ELEMENT List (Item)+>
<!ELEMENT Item (#PCDATA)>

This defines a list as an element type containing one or more items (that's the plus sign); and it defines items as element types containing just plain text (Parsed Character Data or PCDATA).

Validators read the DTD before they read your document so that they can identify where every element type ought to come and how each relates to the other, so that applications which need to know this in advance (most editors, search engines, navigators, and databases) can set themselves up correctly.

The example above lets you create lists like:

<List>
<Item>Chocolate</Item>
<Item>Music</Item>
<Item>Surfing</Item>
</List>

A DTD provides applications with advance notice of what names and structures can be used in a particular document type. Using a DTD and a validating editor means you can be certain that all documents of that particular type will be constructed and named in a consistent and conformant manner.

DTDs are not required for processing the tip ‘Rules for well-formedness:’ in question D.2, well-formed documents, but they are needed if you want to take advantage of XML's special attribute types like the built-in ID/IDREF cross-reference mechanism; or the use of default attribute values; or references to external non-XML files (‘Notations’); or if you simply want a check on document validity before processing.

For more visit :

http://xml.silmaril.ie/au thors/dtds/

Answered by Ashish Yadav , an ibibo Wizard, at 3:49 PM on June 10, 2008

well, DTD can be defined as-

A Document Type Definition (DTD) is a specific document defining and constraining definition or set of statements that follow the rules of the Standard Generalized Markup Language (SGML) or of the Extensible Markup Language (XML), a subset of SGML. A DTD is a specification that accompanies a document and identifies what the funny little codes (or markup) are that, in the case of a text document, separate paragraphs, identify topic headings, and so forth and how each is to be processed. By mailing a DTD with a document, any location that has a DTD "reader" (or "SGML compiler") will be able to process the document and display or print it as intended. This means that a single standard SGML compiler can serve many different kinds of documents that use a range of different markup codes and related meanings. The compiler looks at the DTD and then prints or displays the document accordingly.

As a matter of fact, the document you are looking at is coded in a particular DTD called HTML. In this case, the "compiler" or document handler is your Web browser which is designed to handle text documents encoded with HTML tags. (Other programs could be developed that would handle HTML and other DTDs as well.)

IBM and many large and small corporations are converting documents to SGML or, more recently, to XML, each with its own company document type definition or set of definitions. For corporate intranets and extranets, the document type definition of HTML provides one new "language" that everyone can format documents in and read universally.

Answered by Uttam , an ibibo Master, at 1:57 PM on June 10, 2008

A Document Type Definition (DTD) is a specific document defining and constraining definition or set of statements that follow the rules of the Standard Generalized Markup Language (SGML) or of the Extensible Markup Language (XML), a subset of SGML. A DTD is a specification that accompanies a document and identifies what the funny little codes (or markup) are that, in the case of a text document, separate paragraphs, identify topic headings, and so forth and how each is to be processed. By mailing a DTD with a document, any location that has a DTD "reader" (or "SGML compiler") will be able to process the document and display or print it as intended. This means that a single standard SGML compiler can serve many different kinds of documents that use a range of different markup codes and related meanings. The compiler looks at the DTD and then prints or displays the document accordingly.

Answered by Sharad Singh , an ibibo Master, at 1:43 PM on June 10, 2008

well rocky, A DTD is a description in XML Declaration Syntax of a particular type or class of document. It sets out what names are to be used for the different types of element, where they may occur, and how they all fit together. (A question C.16, Schema does the same thing in XML Document Syntax, and allows more extensive data-checking.)
For example, if you want a document type to be able to describe Lists which contain Items, the relevant part of your DTD might contain something like this:
<!ELEMENT List (Item)+>
<!ELEMENT Item (#PCDATA)>
This defines a list as an element type containing one or more items (that's the plus sign); and it defines items as element types containing just plain text (Parsed Character Data or PCDATA). Validators read the DTD before they read your document so that they can identify where every element type ought to come and how each relates to the other, so that applications which need to know this in advance (most editors, search engines, navigators, and databases) can set themselves up correctly. The example above lets you create lists like:
<List>
<Item>Chocolate </Item>
<Item>Music</Item>
< Item>Surfing</Item>
</List>
(The indentation in the example is just for legibility while editing: it is not required by XML.)
A DTD provides applications with advance notice of what names and structures can be used in a particular document type. Using a DTD and a validating editor means you can be certain that all documents of that particular type will be constructed and named in a consistent and conformant manner.
DTDs are not required for processing the tip ‘Rules for well-formedness:’ in question D.2, well-formed documents, but they are needed if you want to take advantage of XML's special attribute types like the built-in ID/IDREF cross-reference mechanism; or the use of default attribute values; or references to external non-XML files (‘Notations’); or if you simply want a check on document validity before processing.
There are thousands of DTDs already in existence in all kinds of areas (see the SGML/XML Web pages for pointers). Many of them can be downloaded and used freely; or you can write your own (see the question on creating your own DTD. Old SGML DTDs need to be converted to XML for use with XML systems: read the question on converting SGML DTDs to XML, but most popular SGML DTDs are already available in XML form.
Some XML editors use a binary compiled format of DTD produced by their own management routines to allow a single person in an organisation to be in charge of modifications, and to distribute only an unmodifiable (binary compiled) version to users.
The alternatives to a DTD are various forms of question C.16, Schema. These provide more extensive validation features than DTDs, including character data content validation.

Answered by satyaiitk , an ibibo Master, at 11:46 AM on June 10, 2008