[Exist-open] fn:id() returns empty sequence

[Daniel S. <dan...@ao...>]

Hi,
I'm somewhat out of luck, getting fn:id() to work with a set of METS records. Here's what I've done so fare:

1) make sure the entry in $EXIST_HOME/webapp/WEB-INF/catalog.xml is present
2) and check location of (local) mets-xsd in $EXIST_HOME/webapp/WEB-INF/
3) successfully set validation mode to "yes" in conf.xml (invalid documents are rejected)

I thought, querying an instance like 

<mets xsi:schemaLocation="http://www.loc.gov/METS/ http://www.loc.gov/standards/mets/mets.xsd" xmlns="...">
  ...
    <dmdSec ID="projectDMD">
    ...
    </dmdSec>
  ...
</mets>

with the expression

doc("instance.xml")/id("projectDMD")

should return the dmdSec element (as @ID is defined in the schema to be of type xs:ID). 
Yet, it results in the empty sequence.

The admin interface shows that the relevant grammars are cached, I thought everything should be set ...
I also tried to error-log fn:id() by adding

    <category name="org.exist.xquery.functions.fn.FunId">
        <priority value="error" /> 
        <appender-ref ref="console"/>
        <appender-ref ref="exist.core"/>
    </category>

to log4j.xml, to no avail either: the logs are just silent about the function.

So... I'm sure I'm missing something really obvious - maybe anyone sees what that might be? :)

Thanks,
Daniel