More info in case of aggregated data

[coret]

Some of the dataset descriptions describe data aggregated from one or more other data sources.
To make the aggregation clear to users (readers of datasetdescriptions) there are currently 3 properties which could be used:

• schema:description (required)
• schema:isBasedOn (recommended)
• schema:creator (recommended)

In practice these properties are lacking or don't contain insufficient (machine-readable) information.
Sometimes it's not clear from the dataset description that the dataset only contains a selection of data of another source (like, wo2 related).

The quality of dataset descriptions of aggregated sources needs improvement. Some may be fixed by tightening the requirements. Additionally communication with publishers (and their suppliers) is warranted.

In the development of the KG the aggregation aspect might be added (when publisher and creator are different, this usually means the publisher is an aggregator).