WMS server time tests and issues

Tue Nov 9 10:26:01 EST 2004

Kralidis,Tom [Burlington] wrote:

>>-----Original Message-----
>>From: UMN MapServer Developers List
>>[mailto:MAPSERVER-DEV at LISTS.UMN.EDU] On Behalf Of
>>Kralidis,Tom [Burlington]
>>Sent: Tuesday, 09 November, 2004 07:37
>>To: MAPSERVER-DEV at LISTS.UMN.EDU
>>Subject: Re: [UMN_MAPSERVER-DEV] WMS server time tests and issues
>>
>>
>>
>>>-----Original Message-----
>>>From: UMN MapServer Developers List
>>>[mailto:MAPSERVER-DEV at LISTS.UMN.EDU] On Behalf Of Havard Tveite
>>>Sent: Tuesday, 09 November, 2004 05:48
>>>To: MAPSERVER-DEV at LISTS.UMN.EDU
>>>Subject: Re: [UMN_MAPSERVER-DEV] WMS server time tests and issues
>>>
>>>
>>>Yewondwossen Assefa wrote:
>>>
>>>>Kralidis,Tom [Burlington] wrote:
>>>>
>>>>
>>>>>Hi,
>>>>>
>>>>>I've been testing this out on latest CVS.  Observations:
>>>>>
>>>>>- OS: FC2
>>>>>Linux devgeo.cciw.ca 2.6.5-1.358smp #1 SMP Sat May 8 09:25:36 EDT
>>>>>2004 i686 i686 i386 GNU/Linux
>>>>>- httpd: Apache 2.0.49
>>>>>
>>>>>I constructed a dummy .shp/.shx/.dbf with 4 columns 3
>>>
>>>records with a
>>>
>>>>>timefield.
>>>>>
>>>>>Here's a dump of what the shapefile is:
>>>>>
>>>>>stid | lat          | lon        | obsdate
>>>>>----------------------------------------------
>>>>>tom  | 45.412766    | -71.920082 | 2004-10-12
>>>>>bob  | 45.399400    | -75.704200 | 2003-09-30
>>>>>joe  | 55.399400    | -95.704200 | 2002-03-17
>>>>>
>>>>>
>>>>>...and here's the time defines in LAYER/METADATA in mapfile:
>>>>>
>>>>>   "wms_timeextent" "2002-03-17/2004-10-12"
>>>>>   "wms_timedefault" "2003-09-30"
>>>>>   "wms_timeitem" "obsdate"
>>>>>
>>>>>
>>>>>...and here's my tests:
>>>>>
>>>>>Single value:
>>>>>
>>>>>
>>>
>>http://devgeo.cciw.ca/cgi-bin/mapserv/ecows?version=1.1.1&service=WMS
>>
>>>>>&re
>>>>>
>>>
>>>quest=GetMap&layers=obs&format=image/gif&srs=EPSG:4326&transpa
>>>rent=TRUE&
>>>
>>>exceptions=application%2Fvnd.ogc.se_inimage&bbox=-140.243500,2
>>
>>8.606653,-
>>
>>>51.243500,81.998653&width=500&height=300&time=2004-10-12-T00:0
>>>0:00&style
>>>
>>>>>s=default
>>>>>
>>>>>Result: no problem, as expected
>>>>>
>>>>>Multple value:
>>>>>
>>>>>
>>>
>>http://devgeo.cciw.ca/cgi-bin/mapserv/ecows?version=1.1.1&service=WMS
>>
>>>>>&re
>>>>>
>>>
>>>quest=GetMap&layers=obs&format=image/gif&srs=EPSG:4326&transpa
>>>rent=TRUE&
>>>
>>>exceptions=application%2Fvnd.ogc.se_inimage&bbox=-140.243500,2
>>
>>8.606653,-
>>
>>>51.243500,81.998653&width=500&height=300&time=2004-10-12-T00:0
>>>0:00,2003-
>>>
>>>>>09-30-T00:00:00&styles=default
>>>>>
>>>>>Result: no problem, as expected
>>>>>
>>>>>Single range:
>>>>>
>>>>>
>>>
>>http://devgeo.cciw.ca/cgi-bin/mapserv/ecows?version=1.1.1&service=WMS
>>
>>>>>&re
>>>>>
>>>
>>>quest=GetMap&layers=obs&format=image/gif&srs=EPSG:4326&transpa
>>>rent=TRUE&
>>>
>>>exceptions=application%2Fvnd.ogc.se_inimage&bbox=-140.243500,2
>>
>>8.606653,-
>>
>>>51.243500,81.998653&width=500&height=300&time=2002-03-17-T00:0
>>>0:00/2004-
>>>
>>>>>10-12-T00:00:00&styles=default
>>>>>
>>>>>
>>>>>Result: when the start time or end time is out of range of the
>>>>>default. For example, if you change the start year to
>>>
>>>2001, only one
>>>
>>>>>point shows
>>>>>up:
>>>>>
>>>>>
>>>
>>http://devgeo.cciw.ca/cgi-bin/mapserv/ecows?version=1.1.1&service=WMS
>>
>>>>>&re
>>>>>
>>>
>>>quest=GetMap&layers=obs&format=image/gif&srs=EPSG:4326&transpa
>>>rent=TRUE&
>>>
>>>exceptions=application%2Fvnd.ogc.se_inimage&bbox=-140.243500,2
>>
>>8.606653,-
>>
>>>51.243500,81.998653&width=500&height=300&time=2001-03-17-T00:0
>>>0:00/2004-
>>>
>>>>>10-12-T00:00:00&styles=default
>>>>>
>>>>>...so it looks like the default is returned when the range
>>>
>>>given is
>>>
>>>>>outside the range defined in "wms_timeextent".
>>>>>
>>>>>Is this the expected behaviour?  As a WMS client, I would
>>>
>>>expect that
>>>
>>>>>temporal queries would return everything inside two given
>>>
>>>dates, just
>>>
>>>>>like a spatial query does.
>>>>>
>>>>>..Tom
>>>>>
>>>>>
>>>>
>>>>I think that the specs indicates that if the given values are
>>>>"incorrect" the server would return values for the default
>>>
>>>declared :
>>>
>>>>Section C5.1 (Annexe C wms 1.1.1 ):
>>>>" ...An OGC Web Service may declare a default for any dimension. A
>>>>'default' is optional but recommended. If a request does
>>>
>>>not include a
>>>
>>>>value along this dimension, and a default has been
>>>
>>>declared, then the
>>>
>>>>server shall send the default value..."
>>>
>>>I read the specifications as follows:
>>>If a request does not specify a value for a dimension, and
>>>there is a default declared, the declared should be used. The
>>>spec also says that if a default is not declared, such a
>>>request *shall* result in an exception being thrown.
>>>
>>>I thought that Tom *had* specified a value (range) for the
>>>dimension, and hence this rule should not apply. If the
>>>interval specified is out of the wms_timeextent range, I
>>>would guess an exception should be returned, but I could not
>>>find it documented in the WMS 1.1.1 spec.
>>>
>>>If an interval *is* specified on the dimension, and the the
>>>interval overlaps the range of "valid" times
>>>(wms_timeextent), I would, as Tom, expect all the data within
>>>the overlapping range to be returned. (C.3 - the value of
>>>"multipleValues" is also relevant.)
>>>
>>
>>This makes sense.
>>
>>Keep in mind Dimensions and Extents in WMS cover much more
>>than just time.  So let's take another example:
>>
>>If I have a Dimension defined "elevation", and an extent of
>>1000 - 3000 (in units metres), and if I query with an extent
>>of 500-2000, then I should have data returned, no?
>>
>>At any rate, I've queried wms-dev, and will come back to this
>>list with an answer to this.
>>
>>..Tom
>
>
> Here's Jeff DLB's response to my request:
>
> == BEGIN ==
>
> At 07:39 11/09/2004, Kralidis,Tom [Burlington] wrote:
>
>>If a WMS has a time extent of:
>>2001-10-30/2004-10-30
>>..of, let's say, daily observations, and my time request is:
>>2000-10-30/2002-10-30 ...is this extent out of range?
>
>
> If the available dates are declared as 2001-10-30/2004-10-30/P1D and the
>
> request is for 2000-10-30/2002-10-30/P1D, then I recommend the
> following:
>
> (a) IF attribute 'nearestValue' is missing or has the value 0, then
> issue
> an InvalidDimensionValue exception.
>
> (b) ELSE return content for 2001-10-30/2002-10-30/P1D and include the
> HTTP
> response header "Warning: 99 Nearest value used:
> TIME=2001-10-30/2002-10-30/P1D".
>
> See WMS 1.1.1 Annexes C.3 & C.5.2 or WMS 1.3/ISO DIS 19128 Annexes C.2 &
> C.4.3. (Note error in WMS 1.1.1, p.59 where the plural "nearestValues"
> is used in
> the text.)
>
> -Jeff DLB, Editor
>
> == END
>
> ..Tom
>
>
I have enetered a bug on this (Bug 1045). We currently are in situation
a) . Not sure though if the nearestValue will be supported before the
4.4 release.

Later,

--
----------------------------------------------------------------
Assefa Yewondwossen
Software Analyst

Email: assefa at dmsolutions.ca
http://www.dmsolutions.ca/

Phone: (613) 565-5056 (ext 14)
Fax:   (613) 565-0925
----------------------------------------------------------------