July 23, 2005
Introduction to DTD
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Document Type Definition (DTD) is a set of markup declarations that define a document type for SGML-family markup languages (SGML, XML, HTML). DTDs were a precursor to XML schema and have a similar function, although different capabilities.
DTDs use a terse formal syntax that declares precisely which elements and references may appear where in the document of the particular type, and what the elements’ contents and attributes are. DTDs also declare entities which may be used in the instance document.
XML uses a subset of SGML DTD.
As of 2009 newer XML Namespace-aware schema languages (such as W3C XML Schema and ISO RELAX NG) have largely superseded DTDs. A namespace-aware version of DTDs is being developed as Part 9 of ISO DSDL. DTDs persist in applications which need special publishing characters such as the XML and HTML Character Entity References, which were derived from the larger sets defined as part of the ISO SGML standard effort.
<P>The purpose of a Document Type Definition is to define the legal
building blocks of an XML document. It defines the document structure with a
list of legal elements.</P>
<P>A DTD can be declared inline in your XML document, or as an
external reference.</P>
<HR>
<H3>Internal DOCTYPE declaration</H3>
<P>If the DTD is included in your XML source file, it should be wrapped in a
DOCTYPE definition with the following syntax:</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0" ID="Table1">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><!DOCTYPE root-element [element-declarations]></PRE>
</TD>
</TR>
</TABLE>
<P>Example XML document with a DTD: (<A href="http://www.w3schools.com/dtd/note_in_dtd.xml" target="_blank">Open it
in IE5</A>, and select view source):</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0" ID="Table2">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><?xml version="1.0"?>
<!DOCTYPE note [
<!ELEMENT note (to,from,heading,body)>
<!ELEMENT to (#PCDATA)>
<!ELEMENT from (#PCDATA)>
<!ELEMENT heading (#PCDATA)>
<!ELEMENT body (#PCDATA)>
]>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend</body>
</note></PRE>
</TD>
</TR>
</TABLE>
<BR>
The DTD above is interpreted like this:<BR>
<B>
<BR>
!DOCTYPE note</B> (in line 2) defines that this is a document of the type <B>note.<BR>
</B><B>!ELEMENT note</B> (in line 3) defines the <B>note</B> element as having
four elements: "to,from,heading,body".<BR>
<B>!ELEMENT to</B> (in line 4) defines the <B>to</B> element to be of the type
"#PCDATA".<BR>
<B>!ELEMENT from</B> (in line 5) defines the <B>from</B> element to be of the
type "#PCDATA"<BR>
and so on.....
<HR>
<H3>External DOCTYPE declaration</H3>
<P>If the DTD is external to your XML source file, it should be wrapped in a
DOCTYPE definition with the following syntax:</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0" ID="Table3">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><!DOCTYPE root-element SYSTEM "filename"></PRE>
</TD>
</TR>
</TABLE>
<P>This is the same XML document as above, but with an external DTD: (<A href="http://www.w3schools.com/dtd/note_ex_dtd.xml" target="_blank">Open
it in IE5</A>, and select view source)</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0" ID="Table4">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><?xml version="1.0"?>
<!DOCTYPE note SYSTEM "note.dtd">
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note> </PRE>
</TD>
</TR>
</TABLE>
<P>And this is a copy of the file "note.dtd" containing the DTD:</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0" ID="Table5">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><!ELEMENT note (to,from,heading,body)>
<!ELEMENT to (#PCDATA)>
<!ELEMENT from (#PCDATA)>
<!ELEMENT heading (#PCDATA)>
<!ELEMENT body (#PCDATA)></PRE>
</TD>
</TR>
</TABLE>
<BR>
<HR>
<H3>Why use a DTD?
</H3>
<P>With DTD, each of your XML files can carry a description of its own format with
it.
</P>
<P>With a DTD, independent groups of people can agree to use a common DTD for
interchanging data.
</P>
<P>Your application can use a standard DTD to verify that the data you receive from
the outside world is valid.
</P>
<P>You can also use a DTD to verify your own data.
</P>
July 23, 2005
DTD - XML building blocks
<P>The main building blocks of both XML and HTML documents are tags like
<body>....</body>.</P>
<HR>
<H3>The building blocks of XML documents</H3>
<P>Seen from a DTD point of view, all XML documents (and HTML documents) are made
up by the following simple building blocks:</P>
<UL type="square">
<LI>
Elements
<LI>
Tags
<LI>
Attributes
<LI>
Entities
<LI>
PCDATA
<LI>
CDATA
</LI>
</UL>
<P>The following is a brief explanation of each of the building blocks:</P>
<HR>
<H3>Elements</H3>
<P>Elements are the <B>main building blocks</B> of both XML and HTML documents.</P>
<P>Examples of HTML elements are "body" and "table". Examples of XML elements could
be "note" and "message". Elements can contain text, other elements, or be
empty. Examples of empty HTML elements are "hr", "br" and "img".</P>
<HR>
<H3>Tags</H3>
<P>Tags are used <B>to markup elements</B>.</P>
<P>A starting tag like <element_name> marks up the beginning of an element,
and an ending tag like </element_name> marks up the end of an element.</P>
<P>Examples:</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table1">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'>body element marked up with body tags:
<body>body text in between</body>.
message element marked up with message tags:
<message>some message in between</message></pre>
</td>
</tr>
</table>
<BR>
<HR>
<H3>Attributes</H3>
<P>Attributes provide <B>extra information about elements</B>.</P>
<P>Attributes are always placed inside the starting tag of an element. Attributes
always come in name/value pairs. The following "img" element has additional
information about a source file:</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table2">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><img src="computer.gif" /></pre>
</td>
</tr>
</table>
<P>The name of the element is "img". The name of the attribute is "src". The value
of the attribute is "computer.gif". Since the element itself is empty it is
closed by a " /".</P>
<HR>
<H3>Entities</H3>
<P>Entities are variables used to <B>define common text</B>. Entity references are
references to entities.</P>
<P>Most of you will know the HTML entity reference: "&nbsp;". This
"no-breaking-space" entity is used in HTML to insert an extra space in a
document. Entities are expanded when a document is parsed by an XML parser.</P>
<P>The following entities are predefined in XML:</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table3">
<TBODY>
<TR>
<TH class="ex" align="left" cellspacing="0">
Entity References</TH>
<TH class="ex" align="left" cellspacing="0">
Character</TH></TR>
<TR>
<TD>&lt;</TD>
<TD><</TD>
</TR>
<TR>
<TD>&gt;</TD>
<TD>></TD>
</TR>
<TR>
<TD>&amp;</TD>
<TD>&</TD>
</TR>
<TR>
<TD>&quot;</TD>
<TD>"</TD>
</TR>
<TR>
<TD>&apos;</TD>
<TD>'</TD>
</TR>
</TBODY>
</table>
<HR>
<H3>PCDATA</H3>
<P>PCDATA means parsed character data.</P>
<P>Think of character data as the text found between the start tag and the end tag
of an XML element.</P>
<P><B>PCDATA is text that will be parsed by a parser</B>. Tags inside the text will
be treated as markup and entities will be expanded.
</P>
<HR>
<H3>CDATA</H3>
<P>CDATA also means character data.</P>
<P><B>CDATA is text that will NOT be parsed by a parser</B>. Tags inside the text
will NOT be treated as markup and entities will not be expanded.</P>
July 23, 2005
DTD - Elements
<P>In a DTD, XML elements are declared with a DTD element declaration.</P>
<HR>
<H3>Declaring an Element</H3>
<P>In the DTD, XML elements are declared with an element declaration. An element
declaration has the following syntax:</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table1">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><!ELEMENT element-name category>
or
<!ELEMENT element-name (element-content)></pre>
</td>
</tr>
</table>
<BR>
<HR>
<H3>Empty elements</H3>
<P>Empty elements are declared with the category keyword EMPTY:</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table2">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><!ELEMENT element-name EMPTY>
example:</pre>
<PRE><!ELEMENT br EMPTY></PRE>
<PRE>XML example:</PRE>
<PRE><br /></PRE>
</td>
</tr>
</table>
<BR>
<HR>
<H3>Elements with only character data</H3>
<P>Elements with only character data are declared with #PCDATA inside parentheses:</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table3">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><!ELEMENT element-name (#PCDATA)>
example:</pre>
<PRE><!ELEMENT from (#PCDATA)></PRE>
</td>
</tr>
</table>
<BR>
<HR>
<H3>Elements with any contents</H3>
<P>Elements declared with the category keyword ANY, can contain any combination of
parsable data:</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table4">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><!ELEMENT element-name ANY></pre>
<PRE>example:</PRE>
<PRE><!ELEMENT note ANY></PRE>
</td>
</tr>
</table>
<BR>
<HR>
<H3>Elements with children (sequences)</H3>
<P>Elements with one or more children are defined with the name of the children
elements inside parentheses:</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table5">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><!ELEMENT element-name
(child-element-name)>
or
<!ELEMENT element-name
(child-element-name,child-element-name,.....)></pre>
<PRE>example:</PRE>
<PRE><!ELEMENT note (to,from,heading,body)></PRE>
</td>
</tr>
</table>
<P>When children are declared in a sequence separated by commas, the children must
appear in the same sequence in the document. In a full declaration, the
children must also be declared, and the children can also have children. The
full declaration of the "note" element will be:
</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table6">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><!ELEMENT note (to,from,heading,body)>
<!ELEMENT to (#PCDATA)>
<!ELEMENT from (#PCDATA)>
<!ELEMENT heading (#PCDATA)>
<!ELEMENT body (#PCDATA)></pre>
</td>
</tr>
</table>
<BR>
<HR>
<H3>Declaring only one occurrence of the same element
</H3>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table7">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><!ELEMENT element-name (child-name)></pre>
<PRE>example:</PRE>
<PRE><!ELEMENT note (message)></PRE>
</td>
</tr>
</table>
<P>The example declaration above declares that the child element message must occur
once, and only once inside the "note" element.</P>
<HR>
<H3>Declaring minimum one occurrence of the same element</H3>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table8">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><!ELEMENT element-name (child-name+)></pre>
<PRE>example:</PRE>
<PRE><!ELEMENT note (message+)></PRE>
</td>
</tr>
</table>
<P>The + sign in the example above declares that the child element message must
occur one or more times inside the "note" element.</P>
<HR>
<H3>Declaring zero or more occurrences of the same element
</H3>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table9">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><!ELEMENT element-name (child-name*)></pre>
<PRE>example:</PRE>
<PRE><!ELEMENT note (message*)></PRE>
</td>
</tr>
</table>
<P>The * sign in the example above declares that the child element message can
occur zero or more times inside the "note" element.</P>
<HR>
<H3>Declaring zero or one occurrences of the same element
</H3>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table10">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><!ELEMENT element-name (child-name?)></pre>
<PRE>example:</PRE>
<PRE><!ELEMENT note (message?)></PRE>
</td>
</tr>
</table>
<P>The ? sign in the example above declares that the child element message can
occur zero or one times inside the "note" element.</P>
<HR>
<H3>Declaring either/or content</H3>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table11">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'>example:</pre>
<PRE><!ELEMENT note (to,from,header,(message|body))></PRE>
</td>
</tr>
</table>
<P>The example above declares that the "note" element must contain a "to" element,
a "from" element, a "header" element, and either a "message" or a "body"
element.</P>
<HR>
<H3>Declaring mixed content</H3>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table12">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'>example:</pre>
<PRE><!ELEMENT note (#PCDATA|to|from|header|message)*></PRE>
</td>
</tr>
</table>
<P>The example above declares that the "note" element can contain zero or more
occurrences of parsed character, "to", "from", "header", or "message" elements.</P>
July 23, 2005
DTD - Attributes
<P>In a DTD, Attributes are declared with an ATTLIST declaration.</P>
<HR>
<H3>Declaring Attributes</H3>
<P>An attribute declaration has the following syntax:</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table1">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><!ATTLIST element-name attribute-name
attribute-type default-value></pre>
<PRE>example:</PRE>
<PRE>DTD example:
<!ATTLIST payment type CDATA "check">
XML example:
<payment type="check" /></PRE>
</td>
</tr>
</table>
<P>The <B>attribute-type</B> can have the following values:</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table2">
<TBODY>
<TR>
<TH align="left" width="25%">
Value</TH>
<TH align="left" width="75%">
Explanation</TH></TR>
<TR>
<TD>
<P>CDATA</P>
</TD>
<TD>
<P>The value is character data</P>
</TD>
</TR>
<TR>
<TD>
<P>(en1|en2|..)</P>
</TD>
<TD>
<P>The value must be one from an enumerated list</P>
</TD>
</TR>
<TR>
<TD>
<P>ID</P>
</TD>
<TD>
<P>The value is a unique id
</P>
</TD>
</TR>
<TR>
<TD>
<P>IDREF</P>
</TD>
<TD>
<P>The value is the id of another element</P>
</TD>
</TR>
<TR>
<TD>
<P>IDREFS</P>
</TD>
<TD>
<P>The value is a list of other ids</P>
</TD>
</TR>
<TR>
<TD>
<P>NMTOKEN</P>
</TD>
<TD>
<P>The value is a valid XML name</P>
</TD>
</TR>
<TR>
<TD>
<P>NMTOKENS</P>
</TD>
<TD>
<P>The value is a list of valid XML names</P>
</TD>
</TR>
<TR>
<TD>
<P>ENTITY</P>
</TD>
<TD>
<P>The value is an entity
</P>
</TD>
</TR>
<TR>
<TD>
<P>ENTITIES</P>
</TD>
<TD>
<P>The value is a list of entities</P>
</TD>
</TR>
<TR>
<TD>
<P>NOTATION</P>
</TD>
<TD>
<P>The value is a name of a notation</P>
</TD>
</TR>
<TR>
<TD>
<P>xml:</P>
</TD>
<TD>
<P>The value is a predefined xml value</P>
</TD>
</TR>
</TBODY>
</table>
<P>The <B>default-value</B> can have the following values:</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table3">
<TBODY>
<TR>
<TH align="left" width="25%">
Value</TH>
<TH align="left" width="75%">
Explanation</TH></TR>
<TR>
<TD>
<P>value</P>
</TD>
<TD>
<P>The default value of the attribute</P>
</TD>
</TR>
<TR>
<TD>
<P>#REQUIRED</P>
</TD>
<TD>
<P>The attribute value must be included in the element</P>
</TD>
</TR>
<TR>
<TD>
<P>#IMPLIED</P>
</TD>
<TD>
<P>The attribute does not have to be included</P>
</TD>
</TR>
<TR>
<TD>
<P>#FIXED value</P>
</TD>
<TD>
<P>The attribute value is fixed</P>
</TD>
</TR>
</TBODY>
</table>
<BR>
<HR>
<H3>Specifying a Default attribute value</H3>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table4">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'>DTD:
<!ELEMENT square EMPTY>
<!ATTLIST square width CDATA "0"></pre>
<PRE>Valid XML:
<square width="100" /></PRE>
</td>
</tr>
</table>
<P>In the example above, 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.</P>
<HR>
<H3>#IMPLIED</H3>
<H3>Syntax</H3>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table5">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><!ATTLIST element-name attribute-name
attribute-type #IMPLIED></pre>
</td>
</tr>
</table>
<H3>Example</H3>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table6">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'>DTD:
<!ATTLIST contact fax CDATA #IMPLIED></pre>
<PRE>Valid XML:
<contact fax="555-667788" /></PRE>
<PRE>Valid XML:
<contact /></PRE>
</td>
</tr>
</table>
<P>Use the #IMPLIED keyword if you don't want to force the author to include an
attribute, and you don't have an option for a default value.</P>
<HR>
<H3>#REQUIRED</H3>
<H3>Syntax</H3>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table7">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'>lt;!ATTLIST element-name attribute_name
attribute-type #REQUIRED></pre>
</td>
</tr>
</table>
<H3>Example</H3>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table8">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'>DTD:
<!ATTLIST person number CDATA #REQUIRED></pre>
<PRE>Valid XML:
<person number="5677" /></PRE>
<PRE>Invalid XML:
<person /></PRE>
</td>
</tr>
</table>
<P>Use the #REQUIRED keyword if you don't have an option for a default value, but
still want to force the attribute to be present.</P>
<HR>
<H3>#FIXED</H3>
<H3>Syntax</H3>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table9">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'><!ATTLIST element-name attribute-name
attribute-type #FIXED "value"></pre>
</td>
</tr>
</table>
<H3>Example</H3>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table10">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'>DTD:
<!ATTLIST sender company CDATA #FIXED "Microsoft"></pre>
<PRE>Valid XML:
<sender company="Microsoft" /></PRE>
<PRE>Invalid XML:
<sender company="W3Schools" /></PRE>
</td>
</tr>
</table>
<P>Use 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.</P>
<HR>
<H3>Enumerated attribute values</H3>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table11">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'>Syntax:
<!ATTLIST element-name
attribute-name (en1|en2|..) default-value></pre>
<PRE>DTD example:
<!ATTLIST payment type (check|cash) "cash">
XML example:
<payment type="check" />
or
<payment type="cash" /></PRE>
</td>
</tr>
</table>
<P>Use enumerated attribute values when you want the attribute values to be one of
a fixed set of legal values.</P>
August 10, 2005
DTD - Entities
<P>Entities are variables used to define shortcuts to common text.<BR>
<BR>
- Entity references are references to entities.<BR>
- Entities can be declared internal, or external</P>
<HR>
<H3>Internal Entity Declaration
</H3>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table1">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'>Syntax: </pre>
<PRE><!ENTITY entity-name "entity-value">
DTD Example:</PRE>
<PRE><!ENTITY writer "Donald Duck.">
<!ENTITY copyright "Copyright W3Schools."></PRE>
<PRE>XML example:</PRE>
<PRE><author>&writer;&copyright;</author></PRE>
</td>
</tr>
</table>
<HR>
<H3>External Entity Declaration
</H3>
<table bgcolor="#ACB6C5" width="100%" border="1" style='color:white;font-weight:800' cellspacing="0"
ID="Table2">
<tr style='color:white;font-weight:800'>
<td>
<pre style='color:white;font-weight:800'>Syntax: </pre>
<PRE><!ENTITY entity-name SYSTEM "URI/URL">
DTD Example:</PRE>
<PRE><!ENTITY writer
SYSTEM "http://www.w3schools.com/dtd/entities.dtd">
<!ENTITY copyright
SYSTEM "http://www.w3schools.com/dtd/entities.dtd"></PRE>
<PRE>XML example:</PRE>
<PRE><author>&writer;&copyright;</author></PRE>
</td>
</tr>
</table>
August 10, 2005
DTD Validation
<P>Internet Explorer 5.0 can validate your XML against a DTD.</P>
<HR>
<H3>Validating with the XML Parser
</H3>
<P>If you try to open an XML document, the XML Parser might generate an error. By
accessing the parseError object, the exact error code, the error text, and even
the line that caused the error can be retrieved:</P>
<P><B>Note:</B> The load( ) method is used for files, while the loadXML( ) method
is used for strings.</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style=‘color:white;font-weight:800‘ cellspacing="0" ID="Table1">
<tr style=‘color:white;font-weight:800‘>
<td>
<pre style=‘color:white;font-weight:800‘>var xmlDoc = new ActiveXObject("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)</PRE>
</TD>
</TR>
</TABLE>
<P><A href="http://www.w3schools.com/dtd/tryit.asp?filename=note_error_three" target="_blank">Try it Yourself</A>
or just <A href="http://www.w3schools.com/dtd/note_dtd_error.xml" target="_blank">look at the XML file</A></P>
<HR>
<H3>Turning Validation off
</H3>
<P>Validation can be turned off by setting the XML parser‘s
validateOnParse="false".
</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style=‘color:white;font-weight:800‘ cellspacing="0" ID="Table2">
<tr style=‘color:white;font-weight:800‘>
<td>
<pre style=‘color:white;font-weight:800‘>var xmlDoc = new ActiveXObject("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)</PRE>
</TD>
</TR>
</TABLE>
<P><A href="http://www.w3schools.com/dtd/tryit.asp?filename=note_error_four" target="_blank">Try it Yourself</A></P>
<HR>
<H3>A general XML Validator</H3>
<P>To help you validate your xml files, we have created this link so that you can <A href="http://www.w3schools.com/dom/dom_validate.asp" target="_blank">
Validate any XML file</A>.</P>
<HR>
<H3>The parseError Object</H3>
<P>You can read more about the parseError object in our XML <A href="http://www.w3schools.com/dom/default.asp" target=_blank>DOM
tutorial</A>.</P>
August 10, 2005
DTD - Examples from the Net
<H3>TV Schedule DTD
</H3>
<P>By David Moisan. Copied from his Web: <A href="http://www.davidmoisan.org/" target="_blank">
http://www.davidmoisan.org/</A></P>
<table bgcolor="#ACB6C5" width="100%" border="1" style=‘color:white;font-weight:800‘ cellspacing="0"
ID="Table1">
<tr style=‘color:white;font-weight:800‘>
<td>
<pre style=‘color:white;font-weight:800‘><!DOCTYPE TVSCHEDULE [</pre>
<PRE><!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)>Â
<!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>
]></PRE>
</td>
</tr>
</table>
<HR>
<H3>Newspaper Article DTD
</H3>
<P>Copied from <A href="http://www.davidmoisan.org/" target="_blank">http://www.vervet.com/</A>
</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style=‘color:white;font-weight:800‘ cellspacing="0"
ID="Table2">
<tr style=‘color:white;font-weight:800‘>
<td>
<pre style=‘color:white;font-weight:800‘><!DOCTYPE NEWSPAPER [Â </pre>
<PRE><!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)>Â </PRE>
<PRE><!ATTLIST ARTICLE AUTHOR CDATA #REQUIRED>
<!ATTLIST ARTICLE EDITOR CDATA #IMPLIED>
<!ATTLIST ARTICLE DATE CDATA #IMPLIED>
<!ATTLIST ARTICLE EDITION CDATA #IMPLIED></PRE>
<PRE><!ENTITY NEWSPAPER "Vervet Logic Times">
<!ENTITY PUBLISHER "Vervet Logic Press">
<!ENTITY COPYRIGHT "Copyright 1998 Vervet Logic Press"></PRE>
<PRE>]></PRE>
</td>
</tr>
</table>
<HR>
<H3>Product Catalog DTD
</H3>
<P>Copied from <A href="http://www.vervet.com/" target="_blank">http://www.vervet.com/</A>
</P>
<table bgcolor="#ACB6C5" width="100%" border="1" style=‘color:white;font-weight:800‘ cellspacing="0"
ID="Table3">
<tr style=‘color:white;font-weight:800‘>
<td>
<pre style=‘color:white;font-weight:800‘><!DOCTYPE CATALOG [</pre>
<PRE><!ENTITY AUTHOR "John Doe">
<!ENTITY COMPANY "JD Power Tools, Inc.">
<!ENTITY EMAIL "jd@jd-tools.com">
<!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)>
]></PRE>
</td>
</tr>
</table>