This section describes the built-in datatype 'ENTITY' designed to support user defined and unparsed external XML entities. 'ENTITY' datatype is derived from 'NCName'.
In order to support some XML document special features, 3 built-in datatypes are
derived from "NCName": "ENTITY", "ID" and "IDREF".
"ENTITY" is a datatype derived from "NCName" datatype by limiting
its value to names of user defined unparsed external XML entities.
Note that XML entities can not be defined in XSD document.
They must be defined in the DTD (Document Type Definition) format embedded in or assigned to the XML document.
Here is an example of a DTD statement that defines an unparsed external XML entity called "site-logo":
<!ENTITY site-logo SYSTEM "logo.gif" NDATA gif>
Here is a sample XSD document that defines a sub element <ENTITY> to use "ENTITY" values:
Here is a sample XML document that contains <ENTITY> elements to test that definition:
<?xml version="1.1"?>
<!-- ENTITY_datatype_test.xml
- Copyright (c) 2013, HerongYang.com, All Rights Reserved.
-->
<!DOCTYPE ENTITY_Datatype_Test [
<!ENTITY site-logo SYSTEM "logo.gif" NDATA gif>
<!ENTITY cover.photo SYSTEM "sunrise.jpg" NDATA jpeg>
<!ENTITY stdin SYSTEM "input.dat" NDATA data>
<!ENTITY std:out SYSTEM "output.dat" NDATA data>
<!ENTITY footer SYSTEM "/boilerplate/footer.xml">
<!ENTITY quot """>
]>
<ENTITY_Datatype_Test>
<!-- 3 valid "ENTITY" elements -->
<ENTITY> site-logo </ENTITY>
<ENTITY> cover.photo </ENTITY>
<ENTITY> stdin </ENTITY>
<!-- 5 valid "ENTITY" elements -->
<ENTITY> bg-image </ENTITY>
<ENTITY> std:out </ENTITY>
<ENTITY> footer </ENTITY>
<ENTITY> quot </ENTITY>
<ENTITY> amp </ENTITY>
</ENTITY_Datatype_Test>
Notes on this example XML document, entity_datatype_test.xml:
A block of DTD statements is embedded in the document: <!DOCTYPE ENTITYDatatypeTest [...]>.
"bg-image" is not a valid ENTITY, because it is not a defined entity.
"std:out" is not a valid ENTITY, because it is not a valid "NCName" value. ":" is not allowed.
"footer" is not a valid ENTITY, because it is defined as a parsed external entity.
"quot" is not a valid ENTITY, because it is defined as a parsed internal entity.
"amp" is not a valid ENTITY, because it is a built-in parsed internal entity.
If you run JDK 1.7 tool XsdSchemaValidator.java on this test,
you will see 5 groups of errors for the last 5 invalid elements.
c:\Progra~1\Java\jdk1.7.0_07\bin\java.exe XsdSchemaValidator
entity_datatype_test.xsd entity_datatype_test.xml
Error:
Line number: 22
Column number: 34
Message: UndeclaredEntity: Entity 'bg-image' is not declared.
Error:
Line number: 22
Column number: 34
Message: cvc-type.3.1.3: The value ' bg-image ' of element
'ENTITY' is not valid.
Error:
Line number: 23
Column number: 34
Message: cvc-datatype-valid.1.2.1: 'std:out' is not a valid value
for 'NCName'.
Error:
Line number: 23
Column number: 34
Message: cvc-type.3.1.3: The value ' std:out ' of element
'ENTITY' is not valid.
Error:
Line number: 24
Column number: 34
Message: UndeclaredEntity: Entity 'footer' is not declared.
Error:
Line number: 24
Column number: 34
Message: cvc-type.3.1.3: The value ' footer ' of element
'ENTITY' is not valid.
Error:
Line number: 25
Column number: 34
Message: UndeclaredEntity: Entity 'quot' is not declared.
Error:
Line number: 25
Column number: 34
Message: cvc-type.3.1.3: The value ' quot ' of element
'ENTITY' is not valid.
Error:
Line number: 26
Column number: 34
Message: UndeclaredEntity: Entity 'amp' is not declared.
Error:
Line number: 26
Column number: 34
Message: cvc-type.3.1.3: The value ' amp ' of element
'ENTITY' is not valid.
Failed with errors: 10
Note that you may have difficulties to validate this XML document with the XSD schema
with other XML tools, because it has the embedded DTD statements.