[NeXus-tech] NXDL definition of "link"

[Pete R. Jemian]

While developing documentation for NXDL, I see that the definition of a 
link (in nxdl.xsd) is not what I was expecting.
It's wrong.  I want to fix it.

See http://trac.nexusformat.org/definitions/ticket/129

Presently, the NXDL schema defines a link (in <xs:group 
name="groupGroup">) as a child element of a <group/>. This means an NXDL 
specification could have a <link/> element at the same level as a 
<field/> element. That's not how we use links in NeXus. Instead, links 
are used within the target attribute of a <field/>, such as

   <polar_angle target="/NXentry/NXinstrument/NXdetector/polar_angle">

My proposition is to change nxdl.xsd:

    1. remove the existing definition of "link" from
       <xs:group name="groupGroup">
    2. remove the definition of <xs:complexType name="linkType">
    3. add an optional attribute target to
       <xs:complexType name="fieldType"> defined similarly to
       the existing linkType definition.


Pending remarks to the contrary, I should like to commit this change on 
October 21.

Pete

-- 
----------------------------------------------------------
  Pete R. Jemian, Ph.D.                <jemian at anl.gov>
  Beam line Controls and Data Acquisition, Group Leader
  Advanced Photon Source,   Argonne National Laboratory
  Argonne, IL  60439                   630 - 252 - 3189
-----------------------------------------------------------
     Education is the one thing for which people
        are willing to pay yet not receive.
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