In the implementation of ISO 19103 Date in the gco namespace baseTypes 1.2.0 Date is implemented as an union:
<xs:simpleType name="Date_Type"> <xs:union memberTypes="xs:date xs:gYearMonth xs:gYear"/> </xs:simpleType>
This allows a mistake in interpretation and encoding with values like 19990101, which is (a) intended as a date in ISO basic format, but (b) permitted by the above implementation as a year-only date, i.e., the year 19,990,101. This means an invalid date like 19999999 (basic format) is not detected by schema validation because it is a valid year-only date though it was intended as a yyyymmdd date.
I suggest making Date_Type a complex type, a choice of XML elements named according to the XML schema built-in date types. Here is a related example from S-100. (It is for truncated date, which is slightly different in using more XML Schema built-in types, but it should convey the idea.)
The result would be like this:
Application schema: <xs:element name="dateStart" type="S100_TruncatedDate" ...
Dataset: <dateStart><gMonthDay>--06-01</gMonthDay></dateStart>
(I am posting this as an XML issue because I think it is just an implementation change and shouldn't need a change to the ISO 19103 standard, but feel free to move it to StandardsTracker if appropriate.)
In the implementation of ISO 19103 Date in the gco namespace baseTypes 1.2.0 Date is implemented as an union:
<xs:simpleType name="Date_Type"> <xs:union memberTypes="xs:date xs:gYearMonth xs:gYear"/> </xs:simpleType>This allows a mistake in interpretation and encoding with values like 19990101, which is (a) intended as a date in ISO basic format, but (b) permitted by the above implementation as a year-only date, i.e., the year 19,990,101. This means an invalid date like 19999999 (basic format) is not detected by schema validation because it is a valid year-only date though it was intended as a yyyymmdd date.
I suggest making Date_Type a complex type, a choice of XML elements named according to the XML schema built-in date types. Here is a related example from S-100. (It is for truncated date, which is slightly different in using more XML Schema built-in types, but it should convey the idea.)
The result would be like this:
Application schema:
<xs:element name="dateStart" type="S100_TruncatedDate" ...Dataset:
<dateStart><gMonthDay>--06-01</gMonthDay></dateStart>(I am posting this as an XML issue because I think it is just an implementation change and shouldn't need a change to the ISO 19103 standard, but feel free to move it to StandardsTracker if appropriate.)