WMS 1.3.0 should allow boolean values in WMS-Capabilities

[remyguillaume]

Hi there,

Since WMS 1.3.0, some attributes of WMS Layer accept boolean values (true, false) and not only integer values (0,1). See https://portal.ogc.org/files/?artifact_id=14416, page 30.

Today, OWSLib is only allowing integer values, for example for the queryable attribute: https://github.com/geopython/OWSLib/blob/master/owslib/map/wms130.py#L449

I think boolean values should also be accepted for WMS 1.3.0 here.
What do you think?
Thanks,
Guillaume.

[geographika]

@remyguillaume sounds good to me, and would support a PR implementing the above.

Relevant parts from the spec:

Boolean values shall be represented in a manner consistent with the specification for Boolean in XML Schema
Datatypes ([8], section 3.2.2). The values “0” and “false” are equivalent. The values “1” and “true” are equivalent.
Absence of an optional value is equivalent to logical false. This International Standard shall explicitly indicate
where a Boolean value is mandatory.

And list of XML tags accepting booleans:

<attribute name="queryable" type="boolean" default="0"/>
<attribute name="opaque" type="boolean" default="0"/>
<attribute name="noSubsets" type="boolean" default="0"/>
<attribute name="multipleValues" type="boolean" />
<attribute name="nearestValue" type="boolean" />
<attribute name="current" type="boolean" />

Strangely, TRANSPARENT accepts TRUE and FALSE but only as uppercase strings (although several servers accept non-case sensitive values. This discussion came up recently in MapServer: MapServer/MapServer#7280

From the spec:

7.3.3.9 TRANSPARENT
The optional TRANSPARENT parameter specifies whether the map background is to be made transparent or not.
TRANSPARENT can take on two values, "TRUE" or "FALSE". The default value is FALSE if this parameter is
absent from the request.

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[geographika]

@remyguillaume - any plans to add this feature in?
Also a link to a live service with Boolean values would be useful to add to this issue as an example.

[tomkralidis]

We could implement a function as we did in pygeoapi:

def str2bool(value: Union[bool, str]) -> bool:
    """
    helper function to return Python boolean
    type (source: https://stackoverflow.com/a/715468)

    :param value: value to be evaluated

    :returns: `bool` of whether the value is boolean-ish
    """

    value2 = False

    if isinstance(value, bool):
        value2 = value
    else:
        value2 = value.lower() in ('yes', 'true', 't', '1', 'on')

    return value2

The result would be True / False in the code.

Would this help? I would keep this contained to the WMS 1.3.0 codepath, with clear docs on the next release.