A User Interface for the QLever SPARQL+Text engine (project or theses)

Background info: Broccoli is our current system for convenient semantic search on text combined with a knowledge base. Here is a demo. The demo is described in [1]. Broccoli works with a special backend, which only supports a particular subset of queries (in a nutshell: treelike SPARQL queries with a text-search component). The backend is described in [4]. In the meantime, we have developed a full-featured SPARQL+Text engine, called QLever [1]. QLever supports full SPARQL queries with a text-search component. However, the current UI is very simplistic and hard to use: it's a essentially a text field, where one can enter a SPARQL query, and then one gets a table with the result tuples. Here is a link to a demo (searching the Freebase knowledge base in combination with the ClueWeb12 web corpus). An example query for copy&paste is given under [5].

Goal: design a front-end for QLever that makes it easy to ask SPARQL+Text queries, also without prior knowledge of the entity and predicate names of the underlying knowledge base (in the demos above: Freebase). The user interface should be simpler than that for Broccoli.

Subgoal 1: Broccoli has four boxes with suggestions, see the demo linked above. This confused users a lot. One of the main tasks will be to devise a simpler interface, but that is still powerful enough to formulate all queries.

Subgoal 2: One problem with the current Broccoli interface is that the user has to know what is a predicate and what is an object. However, this depends a lot on how the statements are represented in the knowledge base. Which is not something the user can or is supposed to know a priori. TODO: give an example. It would be better to provide completions for a predicate combined with an object at the same time.

[1] H. Bast and B. Buchhold. QLever: a Query Engine for Efficient SPARQL+Text Search. Paper currently under review. Code and setup instructions on GitHub

[2] H. Bast, F. Bäurle, B. Buchhold, E. Haußmann. Semantic Full-Text Search with Broccoli (Demo paper). SIGIR 2014: 1265-1266

[3] H. Bast, F. Bäurle, B. Buchhold, E. Haußmann. Broccoli: Semantic Full-Text Search at your Fingertips (System and Evaluation Paper). CoRR abs/1207.2615 (2012)

[4] H. Bast and B. Buchhold. An index for efficient semantic full-text search. CIKM 2013: 369-378

[5] Example SPARQL+Text query (astronauts who walked on the moon) for copy&paste to the text field of the QLever demo:

PREFIX fb: <http://rdf.freebase.com/ns/>
SELECT ?person ?name TEXT(?c) SCORE(?c) WHERE {
  ?person fb:people.person.profession ?profession .
  ?profession fb:type.object.name.en "Astronaut" .
  ?person fb:type.object.name.en ?name .
  ?person <in-context> ?c .
  ?c <in-context> walk* moon
}
LIMIT 100
ORDER BY DESC(SCORE(?c))