Common validation errors

Owned by Jo Cook
Last updated: 13 Aug, 2020Version comment
4 min read

This page is designed as a brief reference for constructing a minimal valid metadata record for data.gov.uk. It is not an exhaustive reference and should be used in conjunction with the published guidance on Gemini.

The GeoNetwork validation wizard is divided into sections relating to a particular validation schema or ruleset. For UK Gemini 2.3 the sections are as follows:

  • Schema validation: xml syntax errors, root namespace errors, and some missing or invalid values in mandatory sections
  • UK GEMINI Standard Draft Version 2.3: Mandatory rules for Gemini 2.3
  • ISO / TS 19139 Table A.1 Constraints: Additional mandatory rules that data.gov.uk uses for validation
  • UK GEMINI Standard Draft Version 2.3 (supplemental): Additional non-mandatory rules for Gemini 2.3

Validation errors may occur in more than one section. Fixing the mandatory Gemini rules first is generally the most efficient approach.

The official Gemini guidance contains information on common errors encountered for each element. Navigate to the element that you are interested in, and expand the section Metadata errors observed... for more information.


The sections below should cover most errors. Please contact your Astun Consultant if you encounter any other errors and are unable to correct them.

Schema Validation Common Errors

The value " of element <element> is not valid/" is not a valid value of union type <type>: Both errors refer to the same problem- a mandatory value is blank or invalid, such as a blank date field, or a character in an integer field. If possible GeoNetwork will highlight the offending element in the main metadata editor. If this is not visible, mouse over the error to find the xpath location of the error. 

Schematron validation UK GEMINI Standard Draft Version 2.3:

This one is self-explanatory- the abstract must be at least 100 characters long!

Element-NotNillable: The given mandatory element is blank. The error explains the elements where this error may occur.

Legal constraints: The Gemini standard requires a section on Limitations on public access or Access Constraints, and Conditions for access and use or Use Constraints. Use the buttons to add the appropriate elements.

Keywords or INSPIRE themes are mandatory: A keyword from the GEMET - INSPIRE themes, version 1.0 is mandatory. In default edit mode, navigate to Descriptive Keywords, Add new keywords and choose or select them in a thesaurus. Choose GEMET - INSPIRE themes, version 1.0 from the dropdown list and click the search bar to get the list of terms. 


INSPIRE - Lineage is mandatory: Gemini describes this as "information that led to the creation of the resource". If this is empty it can be completed in the default view, in Data Quality Info/Lineage to complete. If it is missing then it can be added in advanced view, at the bottom of the Data quality tab.

Schematron validation UK GEMINI Standard Draft Version 2.3 (supplemental):

Resource Locator ~ additional information: External links are more useful if the name is filled in. This can be done in the Additional resources wizard.

Coordinate Reference System (warning): According to the INSPIRE guidance, only specific coordinate reference systems are valid, and EPSG:27700 is not one of them. The Gemini guidance on this element is unclear, so our recommendation is to include a default coordinate system (such as EPSG:4258) as the first, and then include any additional ones that you require, and to ignore this warning.