Schema-Backed Visual Queries over Europeana and other Linked Data Resources
Demo authors	Karlis Cerans, Julija Ovcinnikova, Uldis Bojars, Mikus Grasmanis, Lelde Lace, Aiga Romane Institute of Mathematics and Computer Science, University of Latvia
	Visual Queries: Explore Europeana and other data sets
	Data schema used for query auto-completion both in visual constructs and textual expressions
Query environment	Open http://185.23.162.165/. Register as a new user (email checking not done), then create a new project; to start working with Europeana, choose 'Initialize by Europeana example project'. Alternatively, the same project contents can be uploaded after the empty project creation from this link (see the table below for other available example projects). See the ViziQuer main page for query support resources. Check out the code for local tool setup (Docker-based running options available, as well).
Schema extraction	Schema extractor builds the data schema, comprising classes, properties, their relations, as well as cardinalities, triple count statistics and the lists of principal source/target classes for a property. Check the paper for details. Check out the schema extractor from GitHub (an executable .jar file is available in the build folder). Note. The executable starts a service that can be accessed by default at localhost:8080/swagger-ui.html. Use (version 2) for detailed schema extraction.
SHACL data shapes	Generation of SHACL data shapes describing the actual data format is currently available from within the visual tool. The SHACL file involves auto-generated node shapes for all classes as well as their respective property shapes for both incoming and outgoing links. The cardinalities are computed and the other end of the link are characterized, where possible. The extended SHACL mode includes instance and triple count statistics to characterize the profile of a property shape at a class.
Results	Links to the projects, schemas and extraction process details Europeana British National Bibliography Endpoint access SPARQL endpoint Named graph: "http://data.europeana.eu/" SPARQL endpoint Example visual tool project (pre-configured with the endpoint data and the schema; involves some query examples; can be loaded into the visual environment) Europeana example project BNB example project Data schema (visual tool internal .json format, obtained via extraction; can be examined as text/json or loaded into the visual tool) Europeana data schema BNB data schema Data shapes in SHACL (saved from the visual tool) Basic SHACL for Europeana Extended SHACL for Europeana Basic SHACL for BNB Extended SHACL for BNB Schema extraction log (shows the steps performed during the schema extraction) Europeana schema extraction log BNB schema extraction log
Notes	Images of visual queries over the Europeana endpoint (.pdf).
The paper	Karlis Cerans, Julija Ovcinnikova, Uldis Bojars, Mikus Grasmanis, Lelde Lace, Aiga Romane Schema-Backed Visual Queries over Europeana and other Linked Data Resources . Demonstration at ESWC 2021.
Contacts	E-mail karlis.cerans@lumii.lv regarding the paper. E-mail viziquer@lumii.lv for support (incl. server problem/downtime reports), local installation options and other ViziQuer-related matters