How to use the Tabular Online Validator:

The top left field (purple) should contain your schema. It might already be filled out, if not add it there. In the white field to the left enter the SPARQL query. The items returned by the query will be validated to check if they conform to the schema. Then press the validate button to have the items you are querying for validated against the schema entered. After some time the table of validation results appears below. Each row in the table is a potential error in the data. However the error being recorded might not be the actual error but indicate an error in a different location, if an error makes little sense look at different rows for the same item. For example it might suggest a property has a missing value, and the existing value for the same property is of a type not allowed according to the schema, in two rows beneath each other. In that case changing the existing value to be valid will likely also remove the error indicating the value is missing. If the results seem to make no sense at all, consider that schemas are, like the data, created by Wikidata contributors who are only human, and there may be an error in the schema. Consider bringing this up in the talk page for the schema, or in any other place where schema users come together. The most common problem types are:

• Missing property: Too few triples with the specified property exist.
• Complex Error: Often a triple has a value that isn't allowed for that property. Look in Further Error Info for information about what isn't allowed.
• Too many values: There are more triples using a specific property than allowed by the shape.