$ xmllint --version
/home/tobi/bulk/run/libxml/2.6.2/bin/xmllint: using libxml version 20602
   compiled with: DTDValid FTP HTTP HTML C14N Catalog XPath XPointer
XInclude Iconv Unicode Regexps Automata Schemas

Hi

When I validate invalid documents against an RNG then often I don't know
what I should fix; below are some examples.

Here's the test data:

$ cat list.rng
<?xml version="1.0"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0">
  <start>
    <ref name="list-element"/>
  </start>
  <define name="list-element">
    <element name="list">
      <attribute name="version">
        <value type="string">0.1</value>
      </attribute>
      <zeroOrMore>
        <ref name="item-element"/>
      </zeroOrMore>
    </element>
  </define>
  <define name="item-element">
    <element name="item">
      <text/>
    </element>
  </define>
</grammar>

$ cat list.xml
<?xml version="1.0"?>
<list version="0.1">
  <item/>
</list>

$ xmllint --noout --relaxng list.rng list.xml
list.xml validates

1. Missing Attribute

When I remove the required attribute

$ cat list.xml
<?xml version="1.0"?>
<list>
  <item/>
</list>

I get

$ xmllint --noout --relaxng list.rng list.xml
list.xml:2: element list: Relax-NG validity error : Element list failed to
validate attributes
list.xml fails to validate

Perhaps it would be possible to report something like
"list.xml:2: element list: Relax-NG validity error : Required attribute
'version' missing."

2. Invalid Attribute Value

When I add the required attribute but supply an invalid value, I get the
same error message; in this case it might be possiible be be more specific
as well, eg:
"[...] Attribute 'version' must have value '0.1'."

3. Invalid Text

When there is invalid text:

$ cat list.xml
<?xml version="1.0"?>
<list version="0.1">
  <item/>
  invalid text in line 4
</list>

I get
"list.xml:2: element list: Relax-NG validity error : Did not expect text in
element list content"

When the document has many lines then it's not easy to find the place where
to make the correction. Perhaps it would be possible to report the line in
which the invalid text is located (/starts), in this case this would mean
reporting line 4 instead of line 2.

Tobi