[NeXus-tech] NXDL definition of "link"

[Peterson, Peter F.]

Thank you for noticing (and fixing) this. You are right about links being an attribute of fields rather than fields themselves. Freddie will have to speak up on if (and how) this affects validation.

A practical issue that you can probably ignore is that we can have links to groups themselves. I don't know if we need to deal with this at all.

P^2

On Oct 14, 2010, at 3:48 PM, Pete R. Jemian wrote:

> 
> 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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