[clue] XML review of draft-ietf-clue-protocol

["Martin Thomson" <[e-mail]>]

(I sent the original of this email in October 2018, then forgot about it.  Apparently it never made it through.  Here's hoping that it works this time.  Trying with a different, maybe better privileged, account.)
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I was asked to provide expert review of the registrations for the XML
schema in this document and noticed a few problems.  I also have a few
suggestions.

1. Don't use schemaLocation in this document, especially in the
schema, but also in examples.

2. Please try to be more consistent with prefixes throughout.  The
namespace defined in the draft is sometimes given no prefix, sometimes
the overly generic "ns2".  I appreciate that these are generated
examples, but more thought needs to be given to that.  In particular,
the schema assigns two different prefixes to the same namespace.

3. This definition is useless:

    <xs:attribute name="protocol" type="xs:string" fixed="CLUE"
        use="required" />

All that a definition like this does is force people to waste bytes.
The namespace is sufficient to identify the protocol.  Use of fixed
and required attributes is best left to restrictions of complex types.

4. You can add the attribute extension point to the base message
definition.  Element extensions unfortunately have to be attached to
specific message types for ordering reasons, but attributes are
unordered.

5. Consider vertical whitespace in your code.  It helps readability
considerably.