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Data Formats | Could simple XML reunite all canSAS factions?

R. Ghosh, with most helpful comments from C. Moreton-Smith,ISIS

What is XML?

XML is a protocol for containing and managing information; it extends to include actively filtering and formatting documents within a network context of filter programs and linked files.

At first glance the structure of an XML document resembles an HTML file, with similar possibilities for including links both to local and remote files. One main difference is that the HTML tags (typically the anchor <a>) is replaced by sets of element names which can have either local or network wide significance if suitably defined.

As an exercise two examples follow containing ILL data packed as XML files, and part of a sasCIF file from Steve King at ISIS, again repacked as an XML file. This is to demonstrate how we might reconcile two ASCII file formats where the primary interest is the table of intensities, which are identified similarly.

Example of ILL data in XML form

<?xml version = "1.0" encoding = "UTF-8"?>
<SANSdatafile>
<head_sasill><![CDATA[
teflon              instrument tests                 40 lines+(Q, I(Q), errI(Q))
ILL  SANS D11  
     22100         0        19         1        38        34
         1         0        32         0         3         1
rnil  15-Jan-2001 16:42:32
    0.0000 ! Theta-0 Detector offset angle 
   32.0000 ! X0 cms Beam centre            
   31.5000 ! Y0 cms Beam centre            
    2.0000 ! Delta-R cms regrouping step   
   10.0000 ! SD m Sample-detector distance 
   12.0000 ! Angstroms incident wavelength 
    8.0000 ! m collimation distance        
    1.0000 ! concentration                 
       66. ! ISUM central window sum       
   100000. ! flux monitor counts           
       :
       : 
   0.0000 ! K sample temperature          
    0.0000 ! sample transmission           
    0.0000 ! mm sample thickness           
   34.9000 ! counting time secs            
    0.0000 ! reserved                      
    0.0000 ! reserved                      
    0.0000 ! reserved                      
    0.0000 ! reserved                      
    0.0000 ! reserved                      
    0.0000 ! reserved                      
    0.0000 ! reserved                      
    0.0000 ! reserved                      
       19         0         0         0         0         0         0         6
  0.100000E+01   0.100000E+04   0.000000E+00   0.100000E+01   0.120000E+01
  0.000000E+00   0.000000E+00   0.000000E+00   0.000000E+00   0.000000E+00
]]></head_ill>
<iqdata columns="3" col1_title="Angstroms-1" col2_title="Intensity" col3_title="Error">
  2.617993E-04   3.700000E+01   4.301163E+00
  1.062462E-03   6.412500E+01   1.634587E+00
  2.107973E-03   1.410135E+03   5.207492E+00
  3.167636E-03   1.752197E+03   4.801586E+00
  4.189463E-03   7.581771E+02   2.810281E+00
                   :
                   :
  1.255376E-02   1.486688E+01   2.197023E-01
  1.360724E-02   1.204012E+01   1.927716E-01
  1.466810E-02   1.026648E+01   1.679423E-01
  1.572930E-02   8.808511E+00   1.530585E-01
  1.672592E-02   7.862857E+00   1.498843E-01
  1.775654E-02   7.079167E+00   1.717455E-01
  1.857273E-02   6.913043E+00   2.741200E-01
<\iqdata>
</SANSdatafile>

Example of sasCIF in XML form

<?xml version = "1.0" encoding = "UTF-8"?>
<SANSdatafile>
        <head_sascif><![CDATA[ 
_sas_intensity.title                    "SAMPLE: 83396     EMPTY CAN: 83393" 
 
# Next Item : Error in the name or in the value
#entry.id                       "default_LOQ_sasCIF_tpl"                        
                                                                                
_audit.creation_date                    2000-09-22                              
_audit.creation_method                  "part typed, part updated by COLETTE"   
_audit.update_record                                                            
; 2000-09-27     Many revisions by SMK                                          
  2000-11-09     Revised to work with COLETTE o/p routine                       
  2000-11-18     Revised by SMK following changes to sasCIF dictionary by MM    
  2000-11-22     Corrected by MM                                                
  2000-11-23     Revised by SMK                                                 
;                                                                               
 
loop_ _publ.contact_author_name                                                       
      _publ.contact_author_email                                                      
      _publ.contact_author_phone                                                      
      _publ.contact_author_fax                                                        
                                        'King, S M    '                         
                                        'smk@isise.rl.ac.uk                   ' 
                                        '+44(0)1235-446437'                     
                                        '+44(0)1235-445720'                     
 
                                        'Bucknall, D G'                         
                                        'david.bucknall@materials.oxford.ac.uk' 
                                        '+44(0)1865-273763'                     
                                        '+44(0)1865 273789'                     
                                        'Beckham, H W '                         
                                        'haskell.beckham@tfe.gatech.edu       ' 
                                        '+1(404)894-4198  '                     
                                        '+1(404)894-9766  '                     
 
_publ.contact_author_address                                                    
;                                       ISIS Facility                           
                                        Rutherford Appleton Laboratory          
                                        Chilton                                 
                                        Oxfordshire                             
                                        OX11 0QX                                
                                        United Kingdom                          
;                                                                               
_diffrn_source.source                   "ISIS UK"                               
_diffrn_source.type                     "spallation source"                     
_diffrn_source.details                  "200 uA 800 MeV 50Hz proton synchrotron"
_diffrn_source.power                    160.0                                   
_diffrn_source.target
     :
     :
loop_ _sas_intensity.detc_id                                                          
      _sas_intensity.detc_resp_raw                                                    
                                        "MainDet"     DIRECT913_001.FUDGE       
                                         "HighDet"  DIRECTHAB.983               
 
 
# q-axis units : 4*Pi sin [ theta ] / Lambda [Angstrom-1]
loop_ _sas_intensity.momentum_transfer                                          
      _sas_intensity.intensity                                                  
]]></head_sascif>
<iqdata columns="3" col1_title="Angstroms-1" col2_title="Intensity" col3_title="Error">
     0.00900    1.456441E+01    4.897460E-01
     0.01100    7.079165E+00    1.688033E-01
     0.01300    3.699121E+00    8.279238E-02
     0.01500    2.112296E+00    5.290537E-02
     0.01700    1.338770E+00    3.596483E-02
     0.01900    1.018834E+00    2.735320E-02
     0.02100    8.131560E-01    2.213864E-02
     0.02300    6.901327E-01    1.878839E-02
     0.02500    5.894193E-01    1.642621E-02
     0.02700    5.418695E-01    1.480873E-02
</iqdata>
</SANSdatafile>

The aim is to get to <iqdata> in the simplest fashion, since this contains the real results and which must be easily read using existing languages or packages.

The CDATA descriptor terminated by ]] indicates that special characters occurring within should be ignored.

Other aspects of XML include the possibility of including binary (could these be NeXus ? ) sections, and, of course the filters might be links to data browser programs.

If these files are cut and pasted into files a.xml, b.xml, then Internet Explorer 5 can open them and recognise the XML structures.

References:
http://www.xml.com
http://msdn.microsoft.com/xml