XML Gives Error in Processing External Entity References

Problem

You are trying to include data from another xml document into another.

You use

child XML document

<?xml version="1.0"?>
<!DOCTYPE spec [
<!ENTITY inherit SYSTEM "generic.xml">
]>

<configuration>

&inherit;
</configuration>

generic.xml

<?xml version="1.0"?>
<configuration>
...
</configuration>

Parsing gives the following error:

error in processing external entity reference at line

You must include the version tag in the <?xml?> begin line in all documents such that:

child XML document

<?xml version="1.0" encoding="ISO-8859-1"?>
...

and

generic.xml

<?xml version="1.0"  encoding="ISO-8859-1"?>