Volcanic Ash Advisory "NO VA EXP" issue

[mgoberfield]

From TAC-to-XML Guidance document:

'NO VA EXP' When no volcanic ash is expected it shall be indicated with a nil "ashCloudExtent" and a nil reason of "http://codes.wmo.int/common/nil/nothingOfOperationalSignificance"

results in a validation error.

Aaron writes:

I looked into this and it appears to be a limitation built in to how AIXM defines their AirspaceVolumePropertyType, it is starting to look like they don't use the standard nilReason construct.

[braeckel]

As mentioned above this appears to be a limitation of the AIXM AirspaceVolumePropertyType, which restricts the nilReason contents. The ready solution would be to create our own PropertyType for the rest of the AIXM types, including AirspaceVolumePropertyType.

[blchoy]

These are the differences:

As mentioned by Aaron our current solution is to short-circuit the reference to the AIXM Property Type to one defined in common.xsd which includes gml:AssociationAttributeGroup that has the default gml:NilReason definitions.

[mgoberfield]

Should we contact Eddy to consider adding to their nilReason attributes in AIXM? For now, I understand the need for workarounds but for the long-term, patches and 'short-circuits' of many AIXM types are probably not desirable.

[blchoy]

I remember Aaron had already brought this to the attention of the AIXM folks some time ago. This is a matter of design philosophy, but we are not too sure why they choose to deviate from the default GML nilReason serialization. In fact, from the ISO 19136 standard:

gml:NilReasonEnumeration has never been used alone but always in union with anyURI.

[braeckel]

I submitted an issue to the AIXM CCB to add support for PropertyTypes for more AIXM types (in IWXXM 2 we only used one of their PropertyTypes because that is all that was available) but they are not aware of this particular issue yet with nilReason. I should augment the existing AIXM issue with this new information.

[jkorosi]

I think the va-advisory-A2-1.xml example should be corrected. As Mark mentioned there is rule in TAC-to-XML-Guidance.txt

'NO VA EXP' When no volcanic ash is expected it shall be indicated with a "ashCloudExtent" with a nilReason of "http://codes.wmo.int/common/nil/nothingOfOperationalSignificance" but the last forecast +18 HR is translated as

<iwxxm:analysis>
    <iwxxm:VolcanicAshConditions gml:id="uuid.e453c86f-6912-47f0-9649-19d656b1bd1f">
        <iwxxm:phenomenonTime>
            <gml:TimeInstant gml:id="uuid.9b7632de-7591-4c3a-a876-99304e3d9d51">
                <gml:timePosition>2008-09-23T19:00:00Z</gml:timePosition>
            </gml:TimeInstant>
        </iwxxm:phenomenonTime>
        <iwxxm:ashCloud nilReason="http://codes.wmo.int/common/nil/nothingOfOperationalSignificance"/>
    </iwxxm:VolcanicAshConditions>
</iwxxm:analysis>.

I believe it should be

<iwxxm:analysis>
    <iwxxm:VolcanicAshConditions gml:id="uuid.e453c86f-6912-47f0-9649-19d656b1bd1f">
        <iwxxm:phenomenonTime>
            <gml:TimeInstant gml:id="uuid.9b7632de-7591-4c3a-a876-99304e3d9d51">
                <gml:timePosition>2008-09-23T19:00:00Z</gml:timePosition>
            </gml:TimeInstant>
        </iwxxm:phenomenonTime>
        <iwxxm:ashCloud>
            <iwxxm:VolcanicAshCloud gml:id="uuid.bcc01180-95c0-4ac1-8f13-53bbbfa430b7">
                <iwxxm:ashCloudExtent nilReason="http://codes.wmo.int/common/nil/nothingOfOperationalSignificance">
            </iwxxm:VolcanicAshCloud>
        </iwxxm:ashCloud>
    </iwxxm:VolcanicAshConditions>
</iwxxm:analysis>

[blchoy]

Thanks Jan for pointing out. In IWXXM 3.0.0RC2, iwxxm:ashCloud should be absent under VA NOT EXP condition:

    <!-- 23/1900Z NO VA EXP -->
    <iwxxm:forecast>
        <iwxxm:VolcanicAshForecastConditions gml:id="uuid.e453c86f-6912-47f0-9649-19d656b1bd1f" status="NO_VOLCANIC_ASH_EXPECTED">
            <iwxxm:phenomenonTime>
                <gml:TimeInstant gml:id="uuid.9b7632de-7591-4c3a-a876-99304e3d9d51">
                    <gml:timePosition>2008-09-23T19:00:00Z</gml:timePosition>
                </gml:TimeInstant>
            </iwxxm:phenomenonTime>
        </iwxxm:VolcanicAshForecastConditions>
    </iwxxm:forecast>

I have also marked your finding in the 'Know Issue' section of the Wiki of this repository.