Marker Labels are not validated against permitted values in the computed scope of the Label.

[palemieux]

ST 2067-3, 6.14.1.2, specifies that the scope attribute of the Label element shall determine the permissible values of the Label element.

This is not checked by Photon, which, for example, does not emit an error if a Label equal to Mark5 is used within the "http://www.smpte-ra.org/schemas/2067-3/2013#standardmarkers" default scope.

              <Marker xsi:type="MarkerType" scope="http://www.smpte-ra.org/schemas/2067-3/2013#standardmarkers">
                <Annotation>annotation 1</Annotation>
                <Label>Mark5</Label>
                <Offset>876</Offset>
              </Marker>

Photon should emit an error if it encounters a Label value that is not defined within the scope defined by the computed value of the scope attribute.

Photon should emit a warning if it encounters a scope that it does not recognize.