[OSGeo-Standards] Version parameter missing in WMS 1.3 GetMap request

Dirk Stenger stenger at lat-lon.de
Thu Oct 7 02:59:54 PDT 2021

Hi all,

We have following problem and are interested in the opinion of other implementers of the WMS 1.3 specification.

For example, a GetMap request is sent to a deegree service:
* https://inspire.brandenburg.de/services/ef_sem_wms?BBOX=228152.00000000%2C5690412.00000000%2C493382.00000000%2C5939023.00000000&CRS=EPSG%3A25833&FORMAT=image%2Fpng&HEIGHT=500&LAYERS=EF.EnvironmentalMonitoringProgrammes&REQUEST=GetMap&SERVICE=WMS&STYLES=EF.EnvironmentalMonitoringProgrammes.Default.Point&WIDTH=500

A map is returned instead of an exception.
Reading the specification (OGC® 06-042) this is a bug in the software implementation as version is a mandatory parameter.

However, it is not 100% clear what exception type shall be thrown as the service does not know what WMS version is requested (WMS 1.3 has its own exception schema).

In addition, we should be aware that some clients may omit the version parameter in a GetMap request.
So, a fix of this behavior might break the compatibility with some clients.
As far as we see, GeoServer also ignores a missing version.

How do you handle such cases?
How do you determine what exception shall be thrown if, for example, the version parameter is missing?
Is the compatibility to the specification or to actual implementations of clients more important?

We are looking forward to your thoughts about this issue and appreciate any help.

Kind regards,
Dirk Stenger

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