[GRASS-dev] Re: terminology issues in grass7

[Moritz Lennert]

On 16/06/09 18:50, Michael Barton wrote:
> Many users writing to the lists seem baffled by GRASS layers. They are 
> complicated to explain whatever we name them. My opinion--completely 
> unsupported by any systematic data and only by anecdotal experience--is 
> that these would be more understandable to more users if we used a term 
> that emphasized the database nature of this feature rather than a term 
> that suggests that it is most similar to multiple geospatial data layers 
> combined into one file--the vector equivalent of a geotiff.

But this is _not_ - primarily - a database feature. It is a way of 
organising objects within the same file - thus allowing topological 
relationships - but with different meanings. The fact that you can then 
link these different meanings to different attribute table is just an 
additional - very useful - feature. But you can use the layer feature 
without connecting any of the layers to tables. In the examples Radim 
gives (for example in [1]), he always talks about attribute tables, but 
I never see them as central to the concept, but it is the possibility of 
attributing different "natures" to the same objects.

I think that when we think about layers as "purely" database-related, 
then we miss the main point, and it is actually debatable whether this 
database-related usage is best dealt with through a layers paradigm (see 
the thread starting with [2] and then moving to the -dev list with [3]

Yes, layers are complicated. I normally tell my students just to ignore 
them as when they come to a stage where they might actually need them, 
they should already be advanced enough in GRASS to be able to dig into 
the documentation/lists to learn more about them.

I also believe that many users will never need layers. They are useful 
for very specific needs, which are not database related. See [4] for an 
example.

Moritz



[1]http://lists.osgeo.org/pipermail/grass-dev/2006-March/021650.html
[2]http://lists.osgeo.org/pipermail/grass-user/2006-September/036284.html
[3]http://grass.itc.it/pipermail/grass5/2006-September/025907.html
[4]http://lists.osgeo.org/pipermail/grass-dev/2003-November/013091.html