Convert very simple DTD-file to XSD

[Eric Lilja]

Hello, this is an xml-file with a nested DTD. It validates, test-1-
with-dtd.xml:

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE persons [
<!ELEMENT persons (person*)>

<!ELEMENT person EMPTY>
<!ATTLIST person name CDATA #REQUIRED>
]>
<persons>
<person name="Eric Lilja" />
</persons>


Now I want to use an XML Schema (located in a separate file) instead
of a nested DTD. I've created the following schema (test-1.xsd):
<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="myns"
xmlns="myns"
elementFormDefault="unqualified">
<xs:element name="persons">
<xs:complexType>
<xs:sequence>
<xs:element name="person">
<xs:complexType>
<xs:attribute name="name" type="xs:string"
use="required"/>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>

I want this schema to accomplish what my DTD above accomplishes. The
schema itself validates, but this xml file that tries to use does not.
test-1-with-xsd.xml:
<?xml version="1.0" encoding="utf-8"?>
<persons xmlns="myns" xmlns:xsi="http://www.w3.org/2001/XMLSchema-
instance" xsi:schemaLocation="myns test-1.xsd">
<person name="Eric Lilja"/>
</persons>

The validator says:
Location: 4:4
Description: cvc-complex-type.2.4.a: Invalid content was found
starting with element 'person'. One of '{person}' is expected.

I'm very new with xml (second day, hehe) and this is my very first
schema. What is the problem? I guess it's a problem with the XML
schema even though it validates becuase the test-1-with-xsd.xml that
uses it looks OK to me (and it should look like the one using the
DTD).

- Eric

 

[usenet]

Hello, this is an xml-file with a nested DTD. It validates, test-1-
with-dtd.xml:

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE persons [
<!ELEMENT persons (person*)>

<!ELEMENT person EMPTY>
<!ATTLIST person name CDATA #REQUIRED>
]>
<persons>
<person name="Eric Lilja" />
</persons>

Now I want to use an XML Schema (located in a separate file) instead
of a nested DTD. I've created the following schema (test-1.xsd):
<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="myns"
xmlns="myns"
elementFormDefault="unqualified">
<xs:element name="persons">
<xs:complexType>
<xs:sequence>
<xs:element name="person">
<xs:complexType>
<xs:attribute name="name" type="xs:string"
use="required"/>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>

I want this schema to accomplish what my DTD above accomplishes. The
schema itself validates, but this xml file that tries to use does not.
test-1-with-xsd.xml:
<?xml version="1.0" encoding="utf-8"?>
<persons xmlns="myns" xmlns:xsi="http://www.w3.org/2001/XMLSchema-
instance" xsi:schemaLocation="myns test-1.xsd">
<person name="Eric Lilja"/>
</persons>

The validator says:
Location: 4:4
Description: cvc-complex-type.2.4.a: Invalid content was found
starting with element 'person'. One of '{person}' is expected.

To clear up a simple things first, to match your DTD, the line:

<xs:element name="person">

should be:

<xs:element name="person" minOccurs="0" maxOccurs="unbound">

The main problem you have though is a bit more involved. In your XML
instance you've defined the default namespace to be 'myns'. In your
schema you've specified that local elements are unqualified. When the
tag of the person element is read, the default namespace takes
precedence over the 'no' namespace. So the name returned in
effectively:

{ namespace="myns"; localName="person"; }.

However, because the local elements are marked as unqualified, the
processor is expecting:

{ namespace=""; localName="person"; }.

As you can see, they don't match, hence the problem.

To fix this, you can either set elementFormDefault="qualified", which
is probably the right thing to do in a schema.

Or you can say that DTDs are not namespace aware, and if you want to
replicate your DTD exactly you should not associate your schema with a
namespace either. In this case you would remove the
targetNamespace="myns" and xmlns="myns" attributes from teh schema.

HTH,

Pete.
--
=============================================
Pete Cordell
Tech-Know-Ware Ltd
for XML to C++ data binding visit
http://www.tech-know-ware.com/lmx
(or http://www.xml2cpp.com)
=============================================

 

[Eric Lilja]

Hi Pete and thanks for your reply! My answers are below...

Hello, this is an xml-file with a nested DTD. It validates, test-1-
with-dtd.xml:

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE persons [
<!ELEMENT persons (person*)>

<!ELEMENT person EMPTY>
<!ATTLIST person name CDATA #REQUIRED>
]>
<persons>
<person name="Eric Lilja" />
</persons>

Now I want to use an XML Schema (located in a separate file) instead
of a nested DTD. I've created the following schema (test-1.xsd):
<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="myns"
xmlns="myns"
elementFormDefault="unqualified">
<xs:element name="persons">
<xs:complexType>
<xs:sequence>
<xs:element name="person">
<xs:complexType>
<xs:attribute name="name" type="xs:string"
use="required"/>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>

I want this schema to accomplish what my DTD above accomplishes. The
schema itself validates, but this xml file that tries to use does not.
test-1-with-xsd.xml:
<?xml version="1.0" encoding="utf-8"?>
<persons xmlns="myns" xmlns:xsi="http://www.w3.org/2001/XMLSchema-
instance" xsi:schemaLocation="myns test-1.xsd">
<person name="Eric Lilja"/>
</persons>

The validator says:
Location: 4:4
Description: cvc-complex-type.2.4.a: Invalid content was found
starting with element 'person'. One of '{person}' is expected.

To clear up a simple things first, to match your DTD, the line:

<xs:element name="person">

should be:

<xs:element name="person" minOccurs="0" maxOccurs="unbound">

Ah, thanks for spotting that one! Changed to <xs:element name="person"
minOccurs="0" maxOccurs="unbounded">

The main problem you have though is a bit more involved. In your XML
instance you've defined the default namespace to be 'myns'. In your
schema you've specified that local elements are unqualified. When the
tag of the person element is read, the default namespace takes
precedence over the 'no' namespace. So the name returned in
effectively:

{ namespace="myns"; localName="person"; }.

However, because the local elements are marked as unqualified, the
processor is expecting:

{ namespace=""; localName="person"; }.

As you can see, they don't match, hence the problem.

To fix this, you can either set elementFormDefault="qualified", which
is probably the right thing to do in a schema.

Or you can say that DTDs are not namespace aware, and if you want to
replicate your DTD exactly you should not associate your schema with a
namespace either. In this case you would remove the
targetNamespace="myns" and xmlns="myns" attributes from teh schema.

HTH,

Pete.

Oh, yes, that helps alot, Pete! Thanks so much! I've made a version
that doesn't incorporate namespaces and it passes validation. It looks
like this:
persons.xsd:
<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="persons">
<xs:complexType>
<xs:sequence>
<xs:element name="person" minOccurs="0"
maxOccurs="unbounded">
<xs:complexType>
<xs:attribute name="name" type="xs:string"
use="required"/>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>

persons.xml:
<?xml version="1.0" encoding="utf-8"?>
<persons xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="persons.xsd">
<person name="Eric Lilja"/>
</persons>

Now I'm going to try to make a namespace version and when that works I
will try to tackle some more complicated DTDs (but still simple).
Thanks again, you've been a tremendous help!

- Eric

 

[Eric Lilja]

See namespace version below

Hi Pete and thanks for your reply! My answers are below...

Hello, this is an xml-file with a nested DTD. It validates, test-1-
with-dtd.xml:
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE persons [
<!ELEMENT persons (person*)>
<!ELEMENT person EMPTY>
<!ATTLIST person name CDATA #REQUIRED>
]>
<persons>
<person name="Eric Lilja" />
</persons>
Now I want to use an XML Schema (located in a separate file) instead
of a nested DTD. I've created the following schema (test-1.xsd):
<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="myns"
xmlns="myns"
elementFormDefault="unqualified">
<xs:element name="persons">
<xs:complexType>
<xs:sequence>
<xs:element name="person">
<xs:complexType>
<xs:attribute name="name" type="xs:string"
use="required"/>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
I want this schema to accomplish what my DTD above accomplishes. The
schema itself validates, but this xml file that tries to use does not.
test-1-with-xsd.xml:
<?xml version="1.0" encoding="utf-8"?>
<persons xmlns="myns" xmlns:xsi="http://www.w3.org/2001/XMLSchema-
instance" xsi:schemaLocation="myns test-1.xsd">
<person name="Eric Lilja"/>
</persons>
The validator says:
Location: 4:4
Description: cvc-complex-type.2.4.a: Invalid content was found
starting with element 'person'. One of '{person}' is expected.

To clear up a simple things first, to match your DTD, the line:

<xs:element name="person">

should be:

<xs:element name="person" minOccurs="0" maxOccurs="unbound">

Ah, thanks for spotting that one! Changed to <xs:element name="person"
minOccurs="0" maxOccurs="unbounded">

The main problem you have though is a bit more involved. In your XML
instance you've defined the default namespace to be 'myns'. In your
schema you've specified that local elements are unqualified. When the
tag of the person element is read, the default namespace takes
precedence over the 'no' namespace. So the name returned in
effectively:

{ namespace="myns"; localName="person"; }.

However, because the local elements are marked as unqualified, the
processor is expecting:

{ namespace=""; localName="person"; }.

As you can see, they don't match, hence the problem.

To fix this, you can either set elementFormDefault="qualified", which
is probably the right thing to do in a schema.

Or you can say that DTDs are not namespace aware, and if you want to
replicate your DTD exactly you should not associate your schema with a
namespace either. In this case you would remove the
targetNamespace="myns" and xmlns="myns" attributes from teh schema.

Pete.

Oh, yes, that helps alot, Pete! Thanks so much! I've made a version
that doesn't incorporate namespaces and it passes validation. It looks
like this:
persons.xsd:
<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="persons">
<xs:complexType>
<xs:sequence>
<xs:element name="person" minOccurs="0"
maxOccurs="unbounded">
<xs:complexType>
<xs:attribute name="name" type="xs:string"
use="required"/>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>

persons.xml:
<?xml version="1.0" encoding="utf-8"?>
<persons xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="persons.xsd">
<person name="Eric Lilja"/>
</persons>

Now I'm going to try to make a namespace version and when that works I
will try to tackle some more complicated DTDs (but still simple).
Thanks again, you've been a tremendous help!

Here's my namespace version, does it look ok? It passes validation.
persons.xsd:
<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="myns" xmlns="myns" elementFormDefault="qualified">
<xs:element name="persons">
<xs:complexType>
<xs:sequence>
<xs:element name="person" minOccurs="0"
maxOccurs="unbounded">
<xs:complexType>
<xs:attribute name="name" type="xs:string"
use="required"/>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>

persons.xml:
<?xml version="1.0" encoding="utf-8"?>
<persons xmlns="myns" xmlns:xsi="http://www.w3.org/2001/XMLSchema-
instance" xsi:schemaLocation="myns persons.xsd">
<person name="Eric Lilja"/>
</persons>

All input appreciated!

- Eric