[GRASS-dev] terminology issues in grass7

GRASS GIS GRASS GIS developer
1

On Jun 11, 2009, at 11:59 AM, grass-dev-request@lists.osgeo.org wrote:

Date: Thu, 11 Jun 2009 20:36:18 +0200
From: Maciej Sieczka <msieczka@sieczka.org>
Subject: Re: [OSGeo-Discuss] Re: [GRASS-dev] terminology issues in
  grass7
To: Micha Silver <micha@arava.co.il>
Cc: OSGeo Discussions <discuss@lists.osgeo.org>, grass-dev list
  <grass-dev@lists.osgeo.org>, Helena Mitasova <hmitaso@unity.ncsu.edu>
Message-ID: <4A314EA2.8000306@sieczka.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Micha Silver pisze:

Martin Landa wrote:

map -> layer (Map Layer)

Yes, that sounds right to me. A map in other GIS context is the final
product of many overlapping "layers". I'd like to see that change
propogated to both raster and vector.

I'm all for this. A "map" is a graphic representation of geographic
features (contained in GIS vector and raster data layer(s)) + additional
information like scale, north arrow and decorations. Say ps.map output.
Using the term "map" in GRASS for what is commonly reffered to as
"layer" is against the common sense IMHO.

layer -> catset (Category Set)

This change does not remove the confusion. The concept of "layer" is
explained both on the vectorintro wiki page [1], and in the manuals as
database links. If that's what it is, that's what it should be called.
So layer might become "data link" or "attribute link"

A "layer" is not a link between a db and GRASS vector map - you can have
a vector map with multiple layers, neither of which, or only some, being
connected with a db table. "layer" is indeed merely a set of categories.
If we change "cat" to "key", maybe "keyset" would be OK?

And what will the term "cat" be changed to?? I still like Michael
Barton's suggestion [2] of cat being renamed "key" (or "id")

"id" is already used in lower-level vector feature identification (see
e.g. v.edit help). "key" sounds fine IMHO.

I probably shouldn't add more, but I will anyway.

I like calling vector and raster files maps. It is really easy for users to understand what these files are. Maps can be added to display layers (i.e., like layers in a CAD or drawing package) for display and visualization.

The features that are currently called vector "layers" really serve a database function. Given that, my preference is that they be called something in database jargon that is also very easily recognizable. AFAIK, the term "layer" is not a term commonly used for DBMS files and functions. The closest common term for what our "layer" does is a key field. Whether or not the key field is use to connect the vector to an attribute table, that is what it is good for ultimately. So that is why I favor some version of "key" for this feature.

FWIW, I always thought that "theme" was a poor choice in terminology for a display layer in ESRI. This is an example of something that makes some sense from an abstract perspective, but makes for a more difficult user experience in actual practice.

Michael

2

Hi,

2009/6/12 Michael Barton <michael.barton@asu.edu>:

[...]

I probably shouldn't add more, but I will anyway.

I like calling vector and raster files maps. It is really easy for users to
understand what these files are. Maps can be added to display layers (i.e.,
like layers in a CAD or drawing package) for display and visualization.

that can be also confusing, data can be stored e.g. in the database as
PostGIS tables - vector and also raster data (see wktraster) instead
of files. I would hesitate to use "files" in this connection. Also
"files maps" seems to be strange to me - I still see "map" as
something related to the cartography. I would call it "data layers".

The features that are currently called vector "layers" really serve a
database function. Given that, my preference is that they be called
something in database jargon that is also very easily recognizable. AFAIK,
the term "layer" is not a term commonly used for DBMS files and functions.
The closest common term for what our "layer" does is a key field. Whether or
not the key field is use to connect the vector to an attribute table, that
is what it is good for ultimately. So that is why I favor some version of
"key" for this feature.

It's not always related to the database function, but you are right in
the most cases it is. I still see "something-set" as good choice,
because it's grouping cats/keys/ids to the set. E.g. if we use
'keyset', then we should call 'cat' as 'key'. Note that we already use
'feature id' for different meaning - every feature has unique fid.

Martin

--
Martin Landa <landa.martin gmail.com> * http://gama.fsv.cvut.cz/~landa

3

Hi Martin,

See below.

On Jun 12, 2009, at 11:27 AM, Martin Landa wrote:

Hi,

2009/6/12 Michael Barton <michael.barton@asu.edu>:

[...]

I probably shouldn't add more, but I will anyway.

I like calling vector and raster files maps. It is really easy for users to
understand what these files are. Maps can be added to display layers (i.e.,
like layers in a CAD or drawing package) for display and visualization.

that can be also confusing, data can be stored e.g. in the database as
PostGIS tables - vector and also raster data (see wktraster) instead
of files. I would hesitate to use "files" in this connection. Also
"files maps" seems to be strange to me - I still see "map" as
something related to the cartography. I would call it "data layers".

From this perspective, data layers seems sensible and I even talk about geospatial data when I teach GIS. I also understand the cartographic perspective that maps are the final, often paper, result of combining multiple geospatial data layers. Nonetheless, most users will find it less confusing if we just continue to call them maps--with the idea that we've moved maps from paper to digital media. Note that this was the original usage in one of the world's oldest GIS systems still in use (i.e., GRASS). And looking at the 1980's video that someone rediscovered, the parallels between paper maps and digital maps were made so that potential users could better understand a GIS. From a personal perspective, I really don't mind data layers at all. I just think that map is easer for most users to understand even if it seems somewhat inaccurate from a more technical perspective.

The features that are currently called vector "layers" really serve a
database function. Given that, my preference is that they be called
something in database jargon that is also very easily recognizable. AFAIK,
the term "layer" is not a term commonly used for DBMS files and functions.
The closest common term for what our "layer" does is a key field. Whether or
not the key field is use to connect the vector to an attribute table, that
is what it is good for ultimately. So that is why I favor some version of
"key" for this feature.

It's not always related to the database function, but you are right in
the most cases it is. I still see "something-set" as good choice,
because it's grouping cats/keys/ids to the set. E.g. if we use
'keyset', then we should call 'cat' as 'key'. Note that we already use
'feature id' for different meaning - every feature has unique fid.

Keyset is fine with me too. We are talking about a single column of values, or database field. So simply "key" is OK too-as in the vector has 2 keys, one of which is linked with attribute table A.

I agree with you that feature ID is incorrect. Each vector has a unique feature ID, but this is not what links it with an attribute table. The ID relates to the vector object. Cat values can be identical to the ID values, but this is not at all necessary.

Michael

Martin

--
Martin Landa <landa.martin gmail.com> * http://gama.fsv.cvut.cz/~landa

______________________________
C. Michael Barton, Professor of Anthropology
Director of Graduate Studies, School of Human Evolution & Social Change
Director, Center for Social Dynamics & Complexity
Arizona State University
Tempe, AZ 85287-2402
USA

voice: 480-965-6262; fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton

4

Hi,

2009/6/12 Michael Barton <Michael.Barton@asu.edu>:

[...]

From this perspective, data layers seems sensible and I even talk about
geospatial data when I teach GIS. I also understand the cartographic
perspective that maps are the final, often paper, result of combining
multiple geospatial data layers. Nonetheless, most users will find it less
confusing if we just continue to call them maps--with the idea that we've

Which users? The users who I know are confused by "map" in the context
that is used in GRASS. I remember when I started to use GRASS as my
first GIS - I didn't understood why I should call raster file as
"map". Probably my feeling is too much cartographic one - map is some
kind of composition with given layout, decorations, text labels, etc.
When I display raster file/dataset/layer or whatever in GRASS, e.g.
'elevation' from spearfish location, it's not a map in my eyes. I
think that 'map' in this context is not right and whatever would be
better. Sorry probably to much radical this evening;-)

moved maps from paper to digital media. Note that this was the original
usage in one of the world's oldest GIS systems still in use (i.e., GRASS).
And looking at the 1980's video that someone rediscovered, the parallels
between paper maps and digital maps were made so that potential users could
better understand a GIS. From a personal perspective, I really don't mind
data layers at all. I just think that map is easer for most users to
understand even if it seems somewhat inaccurate from a more technical
perspective.

OK, anyway I still think that we should find more accurate term then
the current one. GRASS7 is good occasion (it takes time, and many
users will be confused for the short period).

Martin

--
Martin Landa <landa.martin gmail.com> * http://gama.fsv.cvut.cz/~landa

5

On Jun 12, 2009, at 12:37 PM, Martin Landa wrote:

Hi,

2009/6/12 Michael Barton <Michael.Barton@asu.edu>:

[...]

From this perspective, data layers seems sensible and I even talk about
geospatial data when I teach GIS. I also understand the cartographic
perspective that maps are the final, often paper, result of combining
multiple geospatial data layers. Nonetheless, most users will find it less
confusing if we just continue to call them maps--with the idea that we've

Which users? The users who I know are confused by "map" in the context
that is used in GRASS. I remember when I started to use GRASS as my
first GIS - I didn't understood why I should call raster file as
"map". Probably my feeling is too much cartographic one - map is some
kind of composition with given layout, decorations, text labels, etc.
When I display raster file/dataset/layer or whatever in GRASS, e.g.
'elevation' from spearfish location, it's not a map in my eyes. I
think that 'map' in this context is not right and whatever would be
better. Sorry probably to much radical this evening;-)

Well, in part this may be a US perspective, but it is also an intro versus advanced user perspective. Intro GIS texts here (e.g., Clark or Heywood, Cornelius, & Carver) tend to talk about maps. More advanced texts (and perhaps more European texts) seem to talk more about data layers and spatial data (e.g., Burrough & McDonnell). In fact, what we are using are spatial database files (or tables if in something like PostGIS) and so data or spatial data are more accurate technical terms. But these data are formatted/constructed so that they directly translate into something that is visually very akin to a paper map.

I'm usually teaching beginning GIS users, so I've always found GRASS's "maps" easy to to get across (and say in English and Spanish: mapas vs. datos espaciales). However, I really don't have a problem with switching to spatial data or something like that if we want to be more technically correct.

moved maps from paper to digital media. Note that this was the original
usage in one of the world's oldest GIS systems still in use (i.e., GRASS).
And looking at the 1980's video that someone rediscovered, the parallels
between paper maps and digital maps were made so that potential users could
better understand a GIS. From a personal perspective, I really don't mind
data layers at all. I just think that map is easer for most users to
understand even if it seems somewhat inaccurate from a more technical
perspective.

OK, anyway I still think that we should find more accurate term then
the current one. GRASS7 is good occasion (it takes time, and many
users will be confused for the short period).

I agree

Michael

Martin

______________________________
C. Michael Barton, Professor of Anthropology
Director of Graduate Studies, School of Human Evolution & Social Change
Director, Center for Social Dynamics & Complexity
Arizona State University
Tempe, AZ 85287-2402
USA

voice: 480-965-6262; fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton

6

I've not responded on-list for a while now, but this thread touches on
something that has bothered me for a while.

I'm an advanced user, but I'm still using 6.3. Have subsequent releases
changed the use of "layer" in 6.0 through 6.3? I recall that in those
cases, a "layer" in the vector apps referred to a database table, and
not to anything with a graphical representation. If that has been
already fixed, then perhaps the term "layer" can be used for something
else, but it shouldn't be used at all unless the former uses have been
removed.

I prefer terminology in which the word "map" refers to a graphical
representation of geospacial data. The map may be simple or complex,
printed or on-screen. If I can look at it and see spacial relations
then it is a map. That graphical representation can be composed of one
or more than one set of geospacial data. A single raster data set may
comprise a map, or a map may (and often does) include representations of
many sets of geospacial data, plus decoration and annotation.

In conversations with my peers I usually try to avoid using the term
"layer" for any kind of GIS entity. The term provides a handy mental
image, but it is also a term widely used for other purposes. I often
use GRASS to support ground water models that have layers of their own.
The "layer" terminology becomes confusing. I believe there are other
applications where the term presents potential confusion.

For most of my uses, I refer to the data components of a map as "data
sets." If you need to distinguish between the spacial data and the
tabular data associated with it then the modifications are simply
"spacial data sets" and "tabular data sets."

Roger

On Fri, 2009-06-12 at 13:08 -0700, Michael Barton wrote:

On Jun 12, 2009, at 12:37 PM, Martin Landa wrote:

> Hi,
>
> 2009/6/12 Michael Barton <Michael.Barton@asu.edu>:
>
> [...]
>
>> From this perspective, data layers seems sensible and I even talk
>> about
>> geospatial data when I teach GIS. I also understand the cartographic
>> perspective that maps are the final, often paper, result of combining
>> multiple geospatial data layers. Nonetheless, most users will find
>> it less
>> confusing if we just continue to call them maps--with the idea that
>> we've
>
> Which users? The users who I know are confused by "map" in the context
> that is used in GRASS. I remember when I started to use GRASS as my
> first GIS - I didn't understood why I should call raster file as
> "map". Probably my feeling is too much cartographic one - map is some
> kind of composition with given layout, decorations, text labels, etc.
> When I display raster file/dataset/layer or whatever in GRASS, e.g.
> 'elevation' from spearfish location, it's not a map in my eyes. I
> think that 'map' in this context is not right and whatever would be
> better. Sorry probably to much radical this evening;-)

Well, in part this may be a US perspective, but it is also an intro
versus advanced user perspective. Intro GIS texts here (e.g., Clark or
Heywood, Cornelius, & Carver) tend to talk about maps. More advanced
texts (and perhaps more European texts) seem to talk more about data
layers and spatial data (e.g., Burrough & McDonnell). In fact, what we
are using are spatial database files (or tables if in something like
PostGIS) and so data or spatial data are more accurate technical
terms. But these data are formatted/constructed so that they directly
translate into something that is visually very akin to a paper map.

I'm usually teaching beginning GIS users, so I've always found GRASS's
"maps" easy to to get across (and say in English and Spanish: mapas
vs. datos espaciales). However, I really don't have a problem with
switching to spatial data or something like that if we want to be more
technically correct.

>
>> moved maps from paper to digital media. Note that this was the
>> original
>> usage in one of the world's oldest GIS systems still in use (i.e.,
>> GRASS).
>> And looking at the 1980's video that someone rediscovered, the
>> parallels
>> between paper maps and digital maps were made so that potential
>> users could
>> better understand a GIS. From a personal perspective, I really
>> don't mind
>> data layers at all. I just think that map is easer for most users to
>> understand even if it seems somewhat inaccurate from a more technical
>> perspective.
>
> OK, anyway I still think that we should find more accurate term then
> the current one. GRASS7 is good occasion (it takes time, and many
> users will be confused for the short period).

I agree

Michael

>
> Martin

______________________________
C. Michael Barton, Professor of Anthropology
Director of Graduate Studies, School of Human Evolution & Social Change
Director, Center for Social Dynamics & Complexity
Arizona State University
Tempe, AZ 85287-2402
USA

voice: 480-965-6262; fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton

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