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LOD Surfer at BH17
What is LOD Surfer
LOD Surfer is a search system to obtain data from LOD based on class-class relationships. Typical usage is:
- A user first inputs a certain class or a set of instances of a certain class.
- LOD Surfer suggests classes that are reachable from the class input by the user.
- The user selects output class.
- Then, a set of instances in the output class related the input set of classes.
LOD Surfer searches instances in the output class by finding paths of properties from the input class to the output class.
What we did
Day 1 (Sep 11)
Clarifying problems in a search on class-class relationships
How to process the property "subClassOf"
- Details: To avoid high order descriptions such as "a class is an instance of another class", subClassOf is sometimes used instead of type (e.g. chemical compounds, diseases). For such datasets, our method can not find any data because our method searches "instances".
- Discussion: For selected class by a user, subclasses of the class should be considered together with instances. For example, if class A has subclass B, C and an instance a, LOD surfer should find paths of triples not only from a, but also subclasses B and C (as they were instances of A). To enable such search, we should improve SPARQL Builder metadata.
- Note: Maybe we need a kind of transformation from dag (structure using subClassOf) to star (tree with depth 1).
How to describe a path between classes
- If we change the specification of a path between classes, how to describe paths and how to construct SPARQL queries from paths should be considered.
How to deal with resources not being typed by any class.
- For resources not being typed by any class, our method can not find them, not only for output but also for intermediate results (= intermediate nodes of paths).
Day 2 (Sep 12)
Specification of LOD Surfer metadata
Design of Web API
Day 3 (Sep 13)
hack hack hack & midterm wrapup
Day 4 (Sep 14)
Hacking crawler and web API
- a bug found in search of class-class relationships and fixed (we hope!)
- Web API
- a query is decomposed to triple patterns with type or subClassOf
- because of time limitation, we search subClassOf only one step. (But we will expand the search to all subclasses in the future.)