[Platforms] Nulls

[Roy Lowry]

Hi Marilynn,

Whilst I'm all for getting rid of our other shoe-horning codes (e.g. 'helicopter') and repetitions by country I think that using the codes in the way you suggest commits three cardinal sins.

First, it is embedding semantics into the code, in this case mapping platform type in just the same way as we've mapped countries using the first two digits.

Secondly, it sets up what I call a 'semantically loaded null', which is a null that carries additional information.  Nulls should be pure and conform to the OGC standard definitions (Unknown, Inapplicable etc.).

Thirdly, it is polluting the entity.  Our entity definition is an instance of hull/name/governance.  It is a single, physical object that given a time machine you could go and touch.  What you are proposing is setting up codes for 'platform classes'.  Hjalte eloquently paraphrased the problem in the discussion on inclusion of ISO3166-2 in country codes by saying ''it's mixing apples and oranges".  I know we already have codes for platform classes (helicopter) and even spatial coverages (Route: Folkestone - Boulogne).  However, we should be working towards finding ways to eliminate these, not create more.

Cheers, Roy.

>>> Marilynn Sørensen <marilynn at ices.dk> 3/5/2009 1:19 pm >>>
Dear All,

I agree that we should not have "unknown" per country. However, I would like to take this a little farther to also address other platform classes currently coded individually for a country, for example, helicoptors (06HP, 32HP), divers (33DV), fixed platforms or stations (09FS, 18FX, 267F) etc.. 

How about a more direct link to the platform classes (BODC/SeaDatanet L06 list) using some identifier plus the existing code in L06? This would allow mapping the existing country-based unknowns to one "unknown" code, but also for mapping other "unspecified" platform classes that are currently linked individually to country. 

For example, here AA is the identifier and the last 2 digits are the L06 codes:

AA00	UNSPECIFIED PLATFORM                              
AA13	UNSPECIFIED BEACH/INTERTIDAL ZONE STRUCTURE	  
AA14	UNSPECIFIED LAND/ONSHORE STRUCTURE                
AA16	UNSPECIFIED OFFSHORE STRUCTURE                    
AA17	UNSPECIFIED COASTAL STRUCTURE                     
AA30	UNSPECIFIED SHIP	                          
AA31	UNSPECIFIED RESEARCH VESSEL	                  
AA32	UNSPECIFIED VESSEL OF OPPORTUNITY	          
AA33	UNSPECIFIED SELF-PROPELLED SMALL BOAT	          
AA35	UNSPECIFIED VESSEL OF OPPORTUNITY ON FIXED ROUTE  
AA36	UNSPECIFIED FISHING VESSEL	                  
AA39	UNSPECIFIED NAVAL VESSEL	                  
AA3A	UNSPECIFIED MAN-POWERED SMALL BOAT	          
AA41	UNSPECIFIED MOORED SURFACE BUOY	                  
AA42	UNSPECIFIED DRIFTING SURFACE FLOAT                
AA46	UNSPECIFIED DRIFTING SUBSURFACE PROFILING FLOAT	  
AA61	UNSPECIFIED RESEARCH AEROPLANE	                  
AA67	UNSPECIFIED HELICOPTER	                          
AA71	UNSPECIFIED HUMAN	                          
AA72	UNSPECIFIED DIVER	                          

A default mapping of "xx99" would then go to AA00, helicopters to AA67 etc.

Cheers,
Marilynn


-----Original Message-----
From: platforms-bounces at biwebs1.nerc-liv.ac.uk [mailto:platforms-bounces at biwebs1.nerc-liv.ac.uk] On Behalf Of Roy Lowry
Sent: 05 March 2009 12:56
To: platforms at biwebs1.nerc-liv.ac.uk 
Subject: [Platforms] Nulls

Dear All,

Another issue waiting in the wings is the ship code for 'unknown' - we've actually got 68 different ones: one per country.  Embedding semantics in 'null metadata' is bad practice, but we do have one code (ZZ99) that means 'unknown' and nothing else.

SeaDataNet needs an 'unknown' ship code, so I've proposed 'ZZ99'.  If nobody has any objections I suggest we deprecate the other 67 mapped to 'ZZ99' in the same way as the 'multiple hull' issue has been handeled within RECO.

Cheers, Roy.


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