[NeXus-tech] FW: Dimensions in NXDL

[Akeroyd, FA (Freddie)]

For info

-----Original Message-----
From: Akeroyd, FA (Freddie) 
Sent: 20 January 2009 09:02
To: 'jemian at anl.gov'
Subject: RE: [NeXus-tech] Dimensions in NXDL

Pete,

I chose dim1, dim2 etc. as they can be matched by xs:selector in xs:key
/ xs:keyref
Unfortunately xs:selector only supports a subset of xpath expressions,
in particular it does not support predicates and so I do not believe you
would be able to match <dim level="1">

We do not have to do dimensions checking via schema - we could leave
that to nxvalidate itself and just write enough information into the
schama to allow it to know what to do

Regards,

Freddie  


> -----Original Message-----
> From: Pete Jemian [mailto:prjemian at gmail.com]
> Sent: 19 January 2009 19:33
> To: Akeroyd, FA (Freddie)
> Subject: Re: [NeXus-tech] Dimensions in NXDL
> 
> I've got some comments but no time to respond yet.
> Basic thought is dim1, dim2, dim3 is not the easy way to do this (and
> handle it later or explain it in documentation).
> Alternative (needs more thought for sure) is <dim level="1"/> or
> something.  Needs work and no time for that now.
> 
> Pete
> 
> 
> 
> Akeroyd, FA (Freddie) wrote:
> > There is a trac ticket for this
> > (http://trac.nexusformat.org/definitions/ticket/32) which we could
> use
> > for discussion, but it would mean everybody interested would need to
> > either join the nexus-definitions-tickets mailing list or add
> themselves
> > top the CC: of the above ticket
> >
> > While we think about that, I'll mail a couple of initial ideas to
> > nexus-tech
> >
> > What we want to be able to do is specify the dimensions of a
quantity
> > and be able to reference it back to other quantities to, say,
specify
> > that two arrays must be the same length. We may also want to be able
> to
> > restrict the size or specify exactly the size of a dimension.
> >
> > Say in NXDL we had
> >
> > <field name="data">
> > <dimensions size="3"><dim3>5</dim3> </dimensions> </field>
> >
> > This could specify a 3 dimensional array with the final dimension
> value
> > restricted to 5
> >
> >
> > <field name="data2">
> > <dimensions ref="data" / >
> > </field>
> >
> > This means data2 should have exactly the same dimensions as data1.
> How
> > far do we go in allowing references to fields in other groups?
> >
> >
> > <field name="data2">
> > <dimensions size="3"><dim1 ref="data" dim="dim2" /></dimensions>
> > </field>
> >
> > This means that data2 should have dim1 the same size as dim2 in data
> >
> >
> > <field name="data2">
> > <dimensions size="3"><dim1 ref="data" dim="dim2"
> incr="1"/></dimensions>
> > </field>
> >
> > As above, but   dim1 = dim2 + 1 (so allowing for histograms etc.)
> >
> > These could then be converted into appropriate XML schema key/keyref
> > combinations.
> >
> > Freddie
> >
> >
> 
> --
> ----------------------------------------------------------
>   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.
> -----------------------------------------------------------
> 

-- 
Scanned by iCritical.