You can access and query the Census data not only by using the database, but by working directly with semantically-encoded Census data that is regularly exported and published. About every three months, the Census data is exported and deposited in the form of RDF / XML files on the edoc server of the Humboldt Universität. Since this dataset has been created with the goal of providing Census data as Linked Open Data and FAIR data, the files are provided for re-use in any way, provided attribution is given to The Census of Antique Works of Art and Architecture Known in the Renaissance, Humboldt-Universität zu Berlin, according to the terms of the CC BY 4.0 DE license.
The RDF / XML files contain a re-representation of the entirety of the original dataset, with the exception of log data, image files attached to image records, and PDF files of academic texts attached to bibliographic records.
The semantically-encoded data uses the CIDOC CRM ontology to represent the informational content of the original structure, but has been transformed from a relational database format into RDF / XML using the X3ML mapping language and X3ML Engine.
The particular application of the CIDOC CRM to express the Census data has been fully documented and can be found in the links below.