[Geoserver-users] Evaluation of GeoServer and OWS Specifications

GeoServer GeoServer User
1

Dear All

I am currently studying for a Master's degree in GIS with UNIGIS. I am
currently doing my dissertation which evaluates the main FOSS GIS web
service products (GeoServer, MapServer, Deegree Web Services & MapGuide Open
Source). I propose to compare and contrast the four products using the OWS
specifications.

I have taken the main part of my dissertation and created a document which:
1. summarises the OWS specifications (chapters 1 to 4).
2. summarises the organisational structure and functionality of the four
products (chapter 5).
3. creates a matrix based on the OWS specifications against which each
product is compared (chapter 6).

I have trimmed down the document for GeoServer by removing the sections
pertaining to the other 3 products. I attach the document to this e-mail.

I would be very interested for any comments/corrections people may have. I
have highlighted any area I am not sure of in yellow. I am mainly looking
for input as follows (in order of importance):

1. Chapter 6, the OWS matrix. There is alot of functionality which I am not
sure if GeoServer supports (such as GetStyles, PutStyles). I have tried to
gather as much information from the website as possible. However time
limitations has meant that I have not been able to investigate each product
as much as I would have liked.
2. Chapter 5, organisational structure. I have gathered as much information
from the website as I could find but I still have some queries.
3. Chapters 1 to 4, OWS specifications. I feel I have got most of the
information correct here but would welcome anybody who has the time to go
through this text.

I will acknowledge anybody who provides input in the acknowledgements
section of my dissertation. If the input is straightforward functionality
(e.g. GeoServer supports WFS GetCapabilities) then I would use the
information and I would not make an explicit reference. However, if I wanted
to make an explicit reference (for example if I am referring to a more
subjective comment with regard to the relative pros and cons of the 4
products) then I would contact the person again to ask his/her permission.

Once everything is complete, I would like to post the final document with
information on all four products on the mailing list.

Thank you all very much in advance for any time you are able to give.

Kind Regards

John Roberts
Manchester, UK

FOSS_GeoServer.doc (347 KB)

2

Dear All,

I am looking for a platform implementing the WMS,WCS,WFS interfaces.
The latest stable version Geoserver(1.4) only supports WMS and WFS correct?
Althought there is the 1.5 version which supports also WCS but how stable is it ?
I mean can I use it only for prototyping? When do you think the next stable version will be available?

An some final question: Is it possible through the WFS interface to make advanced spatial queries (inner/outer joins etc just as will do it from the postgis directly)

Thx in advance
George

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3

Yes GeoServer 1.5 supports WCS and 1.4 does not.
GeoServer 1.5.0 should become stable this month. The current version is definitely usable for testing and relatively standard usage. But for production you should wait until 1.5.0 official stable release.

As for using filters to join, I don't think you can but I could be wrong. From what I can tell each filter has to be against a single feature type. Some of the other developers who have worked on Filter extensively should chime in soon and help you out.

Brent Owens
(The Open Planning Project)

gpio Oxxce wrote:

Dear All,

I am looking for a platform implementing the WMS,WCS,WFS interfaces.
The latest stable version Geoserver(1.4) only supports WMS and WFS correct?
Althought there is the 1.5 version which supports also WCS but how stable is it ?
I mean can I use it only for prototyping? When do you think the next stable version will be available?

An some final question: Is it possible through the WFS interface to make advanced spatial queries (inner/outer joins etc just as will do it from the postgis directly)

Thx in advance
George

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4

gpio Oxxce ha scritto:

Dear All,

An some final question: Is it possible through the WFS interface to make advanced spatial queries (inner/outer joins etc just as will do it from the postgis directly)

In a word, no, you can't, filters to hit a single feature type, which
at the moment (and for months to come) is mapped to a single table.
There is a workaround which works if your joins are known beforehand:
create views in postgis that do perform the joins, and register
them as feature types.
Then you can expose these views as feature types, and query them the
usual way. This usually works fine if your join is the kind that
returns one record for each record of your "main" table, not really
nice if you are returning n records for each one (since you would
end up with multiple features having the same geometry and main
attributes...)

Hope this helps
Cheers
Andrea

5

Hi All,

If I can not issue advanced queries through WFS, and the only workaround is to create views then I must know in advance the queries that the user will like to issue. Correct?

Also I am not sure if I understand the last comment :

This usually works fine if your join is the kind that
returns one record for each record of your “main” table, not really
nice if you are returning n records for each one (since you would
end up with multiple features having the same geometry and main
attributes…)

This mean that if the tables have MxN relationship this solution is not working ?

Thx
George

Andrea Aime aaime@anonymised.com Ýãñáøå:

gpio Oxxce ha scritto:

Dear All,

An some final question: Is it possible through the WFS interface to make
advanced spatial queries (inner/outer joins etc just as will do it from
the postgis directly)

In a word, no, you can’t, filters to hit a single feature type, which
at the moment (and for months to come) is mapped to a single table.
There is a workaround which works if your joins are known beforehand:
create views in postgis that do perform the joins, and register
them as feature types.
Then you can expose these views as feature types, and query them the
usual way. This usually works fine if your join is the kind that
returns one record for each record of your “main” table, not really
nice if you are returning n records for each one (since you would
end up with multiple features having the same geometry and main
attributes…)

Hope this helps
Cheers
Andrea

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6

gpio Oxxce ha scritto:

Hi All,

If I can not issue advanced queries through WFS, and the only workaround is to create views then I must know in advance the queries that the user will like to issue. Correct?

Yes

Also I am not sure if I understand the last comment :
-----
This usually works fine if your join is the kind that
returns one record for each record of your "main" table, not really
nice if you are returning n records for each one (since you would
end up with multiple features having the same geometry and main
attributes...)
----
This mean that if the tables have MxN relationship this solution is not working ?

Well, I don't think it'll work nicely for you. Consider the classical
weather station situation, for the sake of simplicity, let's assume each station has a single sensor, recording temperature each x minutes.
One table defines the station and another, linked, the time series:
STATION(ID, NAME, POINT, ...)
TIMESERIES(STATION_ID, TIME, VALUE)

If you join the two, what you get is a view where each record
contains the location (POINT) and a VALUE. So, if you have 100.000
values for a certain station, you'll get 100.000 points, repeated, too.
I don't think that's what you want to output, in general.

The view output works fine if you have a main table and ancillary tables
that are simply look up tables, for classifications and such, in general.

It's a pity we can't handle this properly, unfortunately that would
require quite some overhaul of our data access codebase, so it would
probably require some funded development, and some good design as well,
since datastore are in Geotools, a library that's not used only by Geoserver.

Hope this helps
Cheers
Andrea

7

Ok, I finally had some time to really go through this.

The first feedback is about WMS Post. It's actually not an official spec, it's just a recommendation paper. Which is probably why you're having a tough time figuring out what parts of WMS have Post. My advice would be to just drop it from your survey, since it's not an official OWS spec. See http://lists.eogeo.org/pipermail/wms-dev/2005-April/000749.html for a bit more info and http://portal.opengeospatial.org/files/?artifact_id=1118 for the actual paper.

There also was a question in yellow about REMOTE_OWS_TYPE and REMOTE_OWS_URL being required with SLD. To my knowledge they are not, unless you are using SLD against a layer that doesn't exist on the server, is only on a remote server. The SLD spec is a bit ambiguous, they're actually splitting it out in to two specs, one to deal with the symbology, one to deal with remote services.

GetGmlObject is generally agreed upon to be a pretty worthless operation that was stuck in to the spec sort of as an after thought to make a few organizations happy. And none of those organizations were actually software developers. To my knowledge there are no implementations of it, and no one is planning to implement it, since it just doesn't make a ton of sense. We refused to touch it as part of WFS 1.1 reference implementation. I'm not sure how much of that you want to include, but it may make sense to mention a bit of explanation as to why none of the open source servers are implementing it.

GetStyles is not supported in GeoServer at all, and PutStyles is supported but not spec compliant. They are likely to be implemented in the not too distant future though.

You missed PDF as an output format for GeoServer WMS.

We don't support any GetGMLObject - I'd remove it from your matrix.

best regards,

Chris

John Roberts wrote:

Dear All

I am currently studying for a Master's degree in GIS with UNIGIS. I am
currently doing my dissertation which evaluates the main FOSS GIS web
service products (GeoServer, MapServer, Deegree Web Services & MapGuide Open
Source). I propose to compare and contrast the four products using the OWS
specifications.

I have taken the main part of my dissertation and created a document which:
1. summarises the OWS specifications (chapters 1 to 4).
2. summarises the organisational structure and functionality of the four
products (chapter 5).
3. creates a matrix based on the OWS specifications against which each
product is compared (chapter 6).

I have trimmed down the document for GeoServer by removing the sections
pertaining to the other 3 products. I attach the document to this e-mail.

I would be very interested for any comments/corrections people may have. I
have highlighted any area I am not sure of in yellow. I am mainly looking
for input as follows (in order of importance):

1. Chapter 6, the OWS matrix. There is alot of functionality which I am not
sure if GeoServer supports (such as GetStyles, PutStyles). I have tried to
gather as much information from the website as possible. However time
limitations has meant that I have not been able to investigate each product
as much as I would have liked.
2. Chapter 5, organisational structure. I have gathered as much information
from the website as I could find but I still have some queries.
3. Chapters 1 to 4, OWS specifications. I feel I have got most of the
information correct here but would welcome anybody who has the time to go
through this text.

I will acknowledge anybody who provides input in the acknowledgements
section of my dissertation. If the input is straightforward functionality
(e.g. GeoServer supports WFS GetCapabilities) then I would use the
information and I would not make an explicit reference. However, if I wanted
to make an explicit reference (for example if I am referring to a more
subjective comment with regard to the relative pros and cons of the 4
products) then I would contact the person again to ask his/her permission.

Once everything is complete, I would like to post the final document with
information on all four products on the mailing list.

Thank you all very much in advance for any time you are able to give.

Kind Regards

John Roberts
Manchester, UK

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The Open Planning Project
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