[GRASS-dev] terminology issues in grass7

[Dylan Beaudette]

On Monday 11 August 2008, Maciej Sieczka wrote:
> Paul Kelly pisze:
> > On Sun, 10 Aug 2008, Moritz Lennert wrote:
> >> Well, to be absolutely precise, you don't need linked attribute tables
> >> to have multiple layers, so I'm not sure that reducing the layer
> >> concept to table links is really 100% correct.
> >
> > I think though, that connecting multiple layers to different tables is
> > the main application for layers? Are they much use for anything else? In
> > which case, calling them tables makes things clearer. Perhaps even table
> > would be enough - each vector map can be connected to multiple tables,
> > each vector map can have multiple tables, each vector map can have
> > multiple table links... is there a big difference in meaning between
> > those different sentences? I feel removing the word "link" improves the
> > clarity of the meaning without adding any additional ambiguity.
>
> I don't agree with Paul. In GRASS vector terminology the term "table"
> already has a very well defined meaning and it must not be used for
> anything else.
>
> (A "table" is an object in the database that stores the given "layer"'s
> attributes, and the "table" and "layer"'s geometrical features are
> linked using "key column" in which the "categories" are stored inside
> the "table".)
>
> Regarding Moritz's remark I indeed missed the fact that the vector map
> having 0 or more "layers" does not directly imply it has the same number
> of data "tables". Given that, "table link" to replace "layer" as I
> suggested is bad. If we are to change the term, we should do it right.
> How do you like "category set" then, "catset" in short? Together with
> with replacing term vector "map" with vector "layer" it would yield:
>
> Each vector "feature" (line, point etc.) can have 0 or more "categories"
> in a vector "layer". Each "category" belongs to only 1 "category set".
> Each "category set" of a vector "layer" can be connected or not with a
> single database "table". The "key column" in that "table" stores the
> "categories" of "features" present in the given "category set".
>
> Any good?
>
> Talking about layers (in their current meaning) - there is no convenient
> tool to report the number of layers in a vector map. There is only
> v.category opt=report. Could v.info be extended in this regard? Oh, and
> the regular v.info already reports number of "dblinks" (which I guess
> might be renamed to "table links", but I won't insist), while v.info -t
> doesn't. Could this be addressed too please?
>
> > With regard to calling maps something different though, I think that
> > would be very confusing and not a good idea (especially if they were
> > renamed to layers). Map has IMHO a much clearer meaning than layer.
> > There is the issue of ambiguity with a printed map I suppose, but use of
> > the word in that context is kind of non-technical I feel. The use of the
> > word map has a clearly defined historical meaning in GRASS (and
> > influences other words too, e.g. a mapset = a collection of maps -
> > should this be renamed a layerset?) and I feel that it should stay.
>
> Paul has points here. Yet I *guess* I'd prefer to trade legacy for
> clarity anyway. Calling GRASS "maps" "layers" would improve clarity
> IMHO, especially for newcommers. Word "map" has been in use for
> centuries and the word immediately brings a nice picture with north
> arrow, legend and stuff to my mind. "Layer" is *the* GIS word for a set
> of features that can be represented graphically as a map, as well as a
> table or a set of statistic properties etc.
>
> Maciek

+1 on Maciek's suggestions. This has been a point of controversy and confusion 
for some time now, and we could potentially have a nice clean start from the 
7.0 branch.

Cheers,

Dylan

-- 
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341