Quantity.xsd on twiki

[Ed Shaya]

I posted XML Quantity materials to the DM QuantityWP twiki.  Brian 
Thomas sent me a set of XML Schemas and example XML files for the 
Quantity DM.  I went through them and made some, mostly cosmetic, 
improvements.  The only improvement I made worth mentioning is that I 
made coreQuantityType a restriction from standardQuantityType and  I 
made basicQuantityType a restriction from coreQuantityType.    It was 
not possible (without a complicate namespace system) to go the other way 
with extensions because extensions only permit addition of  a  Sequence 
at the end of the base.  However, restrictions allow  any  change that 
is  not in direct conflict with  the  base  type.  So restrictions are 
very flexible by permitting any subclass to be defined.  The result is, 
if we have software that properly understands the standardQauntity then 
it is guaranteed to understand coreQuantity and baseQuantity or any 
other subclass of quantity that we create via restrictions.  I expect 
that there will be plenty of these because core and baseQuantity are 
just the subclasses based on the dimension of values (d=0,1, and N) but 
there are many other ways to subclass it.

It is clear here that  UML and XMLSchema do not and should not 
necessarily mirror each other closely.  XML Schema inheritance is 
designed for documents to inherit properties of other documents without 
breaking existing software.  UML is for building that software in the 
first place.  So, it may very well be that the UML classes build up from 
base to core to standard.  On the other hand, the UML could follow the 
XML and also use restrictions. 


I called it v01 to indicate that it is right at the very beginning of  
development, but in fact when I uploaded it to the twiki I saw that Ray 
had uploaded a VOQuantity-v0.1.  So perhaps I should call this
0.11 or 0.2.  On the other hand they are so radically different these 
are perhaps different sequences.


Schemas (the top level schema is Quantity.xsd):  _
http://www.ivoa.net/twiki/bin/view/IVOA/IVOADMQuantityWP__/__Quantity01_xsd.tar 
<http://www.ivoa.net/internal/IVOA/IVOADMQuantityWP/Quantity01_xsd.tar>
_
Document & Diagrams:  
_http://www.ivoa.net/twiki/bin/view/IVOA/IVOADMQuantityWP__/__Quantity01_htmldocs.tar 
<http://www.ivoa.net/internal/IVOA/IVOADMQuantityWP/Quantity01_xsd.tar>
_
Tests: 
_http://www.ivoa.net/twiki/bin/view/IVOA/IVOADMQuantityWP__/__Quantity01_xml.tar 
<http://www.ivoa.net/internal/IVOA/IVOADMQuantityWP/Quantity01_xsd.tar>_

test15.xml  has a problem because the wcsMapping has not yet been defined.