Using an Document DTD I did the following:
file.xsl:
<!DOCTYPE xsl:stylesheet[
<!ENTITY red "rgb(255,0,0)">
]>
<xsl:stylesheet>
[...]
<xsl:attribute name="color">&red;</xsl:attribute>
[...]
</xsl:stylesheet>
I wanted to change everything to XML-Schema. So I tried:
file.xsd:
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<xsd:element name="red" type="xs:token" fixed="rgb(255,0,0)" />
</xsd:schema>
file.xsl:
<xsl:stylesheet
xmlns:defs="http://www.w3.org/2001/XMLSchema-instance"
defs:noNamespaceSchemaLocation="file.xsd">
[...]
<xsl:attribute name="color"><defs:red/></xsl:attribute>
[...]
</xsl:stylesheet>
Now parsing the file via Xalan red is not translated like in the DTD version. Where is my error? Are Schema files not read during the parsing process?
XML schemas are written in XML while DTD are derived from SGML syntax. XML schemas define datatypes for elements and attributes while DTD doesn't support datatypes. XML schemas allow support for namespaces while DTD does not. XML schemas define number and order of child elements, while DTD does not.
The purpose of a DTD is to define the legal building blocks of an XML document. It defines the document structure with a list of legal elements. A DTD can be declared inline in your XML document, or as an external reference.
If an entity is declared within a DTD it is called as internal entity. entity_name is the name of entity followed by its value within the double quotes or single quote. entity_value holds the value for the entity name.
The fixed
attribute in an element definition does not tell a parser to do a text substitution. It simply means that the value of the element must always be the same.
In fact, I believe your XSLT is producing XML that will not validate against your schema, since the value of the <defs:red>
element is not "rgb(255,0,0)
". Even if you used default
instead of fixed
, this is not a text substitution. It just means that, if no value is specified, when the value is queried in a DOM instance, you'll find the value set to "rgb(255,0,0)
".
Using schemas to declare your structural rules (rather than DTD) does not preclude you from using entities.
The manner in which you use entity references to substitute the declared content does not change.
Entity references do not need to be declared only within DTD files. You can declare them inline in your XML files.
<?xml version="1.0"?>
<!DOCTYPE foo [
<!ENTITY red "rgb(255,0,0)">
]>
<foo>
<bar color="&red;" />
</foo>
http://www.ibm.com/developerworks/xml/library/x-tipentref.html
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