[LandXML] Un-enumeration for LandXML 1.1

  • From: "Anselm Haanen" <ahaanen@xxxxxxxxxxxx>
  • To: <landxml@xxxxxxxxxxxxx>
  • Date: Mon, 12 Sep 2005 17:18:22 +1200

Looking at some of the changes that Queensland are proposing, and with the 
benefit of hindsight, I want to propose that we remove some the enumeration of 
selected elements from the LandXML schema.  Individual jurisdictional (national 
/ state) requirements to limit fields to certain values could be dealt with 
through their unique mapping document (such as LINZ's "Cadastral Survey Data 
Exchange Format - LandXML").  These documents should include specific 
definition of the limited lists of values for that LandXML element.
 
Having now had some experience with various schemas, my view is that XML schema 
enumerations are appropriate where the values are:
  - stable and don't change or extend very often
  - common to the broad subject community (in this case international).
 
If these criteria don't apply, the schema community would be revisiting the 
enumerations regularly, and schema users would have to change their 
applications to comply with new values, when in fact they may have no interest 
in them.
 
Good examples of elements suitable for enumeration would be gender (limited to 
male, female, ??), day (Monday, Tuesday, etc), or perhaps status (pending, 
approved, historical).  
 
However an element that would be unsuited to enumeration would be Mark Type, 
where every jurisdiction will use different marks (eg.  disk, nail, peg, pin, 
spike, etc. etc.).  
 
As far as I can tell, removing enumerations in the next version of the schema 
would have minor impact.  Importing software would need to ensure that it 
allows for unknown values in the fields.  Existing applications tailored for 
particular jurisdictions could simply carry on with the existing values.  
"Mapping" documents detailing jurisdictional enumeration requirements would 
need to be updated.
 
I propose that at least the following LandXML enumerations are un-enumerated:
 
EquipmentType
MonumentCondition
MonumentPurpose (an enumerated List)
MonumentState
MonumentType
ParcelClass
ObservationType

 
I would welcome feedback on this proposal before making any modifications to 
the proposed 1.1 schema itself.
 
Anselm Haanen
 
 
===============================
Anselm Haanen
Senior Development Advisor
Land Information NZ - Customer Services
PO Box 5501
Wellington
Ph  (64) 4 460 0376 (direct)
Mb  027 249 5901
Fx  (64) 4 498 3837
www.linz.govt.nz
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