Assets catalog available in DCAT format

[MBadea17]

Make assets metada available also following the DCAT standard, in addition to DDO schema.

Why is it needed:
This is indeed a legal requirement if the data asset is about geolocated information as per the EU INSPIRE Directive. This has emerged as a strong requirement in the context of the CEADS EU project, which is deploying the Common European Agriculture Data Space.

For geographic information, the easiest way to comply with the directive is to follow the GeoDCAT extension of DCAT.

We have already addressed this issue for our Pontus-X based data space AgrospAI. We have developed a wrapper API that just gets the DDO from Aquarius given a DID and converts its metadata into DCAT.

Using Aquarius, you can retrieve the metadata for any asset, for instance, for the assets with geo metadata:
https://aquarius.pontus-x.eu/api/aquarius/assets/ddo/did:op:4d6f4ca585ad87372950da178689e2baf8b8e2668968765ca305bfb718af9cf3
https://aquarius.pontus-x.eu/api/aquarius/assets/ddo/did:op:4e1e2ec4c4b9790a933ed8b1d31252e03e2a3c6860a9c64072f03b74972ff187

And with our wrapper, the mapping of the corresponding asset metadata to DCAT-AP:
https://dcat.agrospai.udl.cat/api/aquarius/assets/ddo/did:op:4d6f4ca585ad87372950da178689e2baf8b8e2668968765ca305bfb718af9cf3
https://dcat.agrospai.udl.cat//api/aquarius/assets/ddo/did:op:4e1e2ec4c4b9790a933ed8b1d31252e03e2a3c6860a9c64072f03b74972ff187

In both cases, the original DDO from Aquarius already features GeoDCAT-AP in its AdditionalInformation field, which is moved to the Dataset as defined in the GeoDCAT specification.

We have also been able to validate the output against the GeoDCAT-AP 3.0 SHACL shapes without any errors or warnings raised. We have used the online service at https://www.itb.ec.europa.eu/shacl/any/upload, which is also available through an API, for instance, to validate the first one:

curl -X 'POST' 'https://www.itb.ec.europa.eu/shacl/any/api/validate' -H 'accept: application/ld+json' -H 'Content-Type: application/json' -d '{ "contentToValidate": "https://dcat.agrospai.udl.cat/api/aquarius/assets/ddo/did:op:4d6f4ca585ad87372950da178689e2baf8b8e2668968765ca305bfb718af9cf3", "contentSyntax": "application/ld+json", "embeddingMethod": "URL", "reportSyntax": "text/turtle", "externalRules": [ { "ruleSet": "https://semiceu.github.io/GeoDCAT-AP/releases/3.0.0/shacl/geodcat-ap-SHACL.ttl", "embeddingMethod": "URL", "ruleSyntax": "text/turtle" } ] }'