Talk:VSLUNT

jens 09:22, 13 October 2010 (UTC) all looks fine so far. I'm a bit in doubt about net and gross tonnage. GT and NT are defined with no units. One declares "The vessel has a NT of 5000". No extra unit is needed, therefore I guess they are wrong here. Having them defined at VSLCAR is sufficient.
DavidAcland 11:22, 20 October 2010 (UTC)
I am can see the benefits of your quarantined additions. Theoretically as numbers, a unit is not required, but this only works if you use the UKHO approach, which is a fudge and only works grammatically. However if we do not use a unit for Gross and Net tonnages, we lose rigour. We would also have to change the multiplicity of VSLUNT to 0..1. I guess the encoding software and ECDISs would then have to enforce or only offer appropriate unit options for each type of characteristic. In the case of Gross and Net tonnages it would also have to prevent the VSLUNT being completed.
However this approach will not work in practice because the Suez and Panama Canals and all their customers talk about "Gross tons" and "Net tons".
On the other hand if we take your proposals, we keep VSLUNT as mandatory, maintaining rigour, and I think that that is important. We also do what the industry does. I have added a sentence to VSLCAR in both cases to say that they are not strictly speaking weight units. So I am prepared to lift the quarantine and see how it looks. I conclude that Suez and Panama net tonnages are so fundamental to ship classification that they will need their own fields and therefore their own units.

jens 04:57, 22 October 2010 (UTC)
I totally understand your objections. I only feel a little pain in my mind when trying to give units where definitely no units exist. The German interpretation is similar to the UK version; no unit! In my opinion we can add a further value to VSLUNT saying "none". That would make it clear to the software and encoding people and goes beyond the currently used value "unknown" for uncertain information in ENC.
Additionally "none" makes the multiplicity bijective. The future display may provide:

   
"Length over all = 100.00 metre 
   
 Net Tonnage = 12000
   
 Height= 30,5 foot"

"none" should be interpreted as "display nothing".
We should hear if Raphael provides advice from the software point of view.

DavidAcland 14:02, 5 November 2010 (UTC)
Agree to try "None".

raphael 16:50, 5 November 2010 (UTC): There is indeed a unit ("gross tons", which is a unit of volume), but it is not explicitly written in publications because natural languages often diverge from strict logic.

"None" works from the software point of view, explicitly saying "none" is as good as specifying a unit. I think we should add "none" and also retain gross tons and net tons as allowed values for situations where the style is to write out the unit but not the quantity (natural language again...).