adjust xpath for gmd:MD_Metadata/gmd:contact instead of using general…

[wangf1122]

gmd:contact exists not only under gmd:metadata but it can appears MD_MaintenanceInformation as well.

Here is the schema definition. https://github.com/metadata101/iso19139.ca.HNAP/blob/6066bd8a1504feebf2291d5945a6428d6c002c27/src/main/plugin/iso19139.ca.HNAP/schema/gmd/maintenance.xsd#L27

Therefore the current schematron validates for any //gmd:contact xpath is causing unnecessary validation errors.

[ianwallen]

Please explain why MD_MaintenanceInformation that would have a gmd:contact would not be required to follow the same validation?

[wangf1122]

I will close this PR as I found the validation is needed for