[eml-dev] [Bug 3541] New: - clarify documentation on polygons and grings, indicate relationship to FGDC

[bugzilla-daemon at ecoinformatics.org]

http://bugzilla.ecoinformatics.org/show_bug.cgi?id=3541

           Summary: clarify documentation on polygons and grings, indicate
                    relationship to FGDC
           Product: EML
           Version: 2.0.1
          Platform: Other
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: eml - general bugs
        AssignedTo: jones at nceas.ucsb.edu
        ReportedBy: mob at icess.ucsb.edu
         QAContact: eml-dev at ecoinformatics.org


The documentation in this section is sparse. The NEON project is currently
evaluating EML, and has pointed out a discrepancy between FGDC and EML which
should be either explained or the 2 specifications should agree.

FGDC: types that are equivalent to  "datasetGPolygonOuterGRing" and
"datasetGPolygonExclusionGRing" require a minimum of 4 points for polygons
EML: a) datasetGPolygonOuterGRing: requires 3 minimum, and b)
datasetGPolygonExclusionGRing requires 1.
Reasoning: a) FGDC documentation states that a polygon needs to have 4 points,
and the first and last should be identical. However, XMLSchema does not have a
way to enforce this. So EML requires only 3, and the 4th is implied.
b) allowing the exclusionRing to have only one point means that a single point
can be excluded, presumably, a single station.

EML's documentation for datasetGPolygonOuterGRing should make this clear. It
also could recommend that xsl stylesheets that transform EML to FGDC should
repeat the first lat/lon pair as the last when creating a list of points.

the alternative to both datasetGPolygonOuterGRing and
datasetGPolygonExclusionGRing is gRingType, which is a string of ordered pairs.
Presumably, this was supposed to be a field that could be directly translated
to FGDC. If so, the documentation should state this, and recommended that a
minimum of 4 pairs be included. However, if this field remains an unrestricted
string, this is not enforceable with xmlschema.