PathLog: a Query Language for Schemaless Databases of Partially Labeled Objects

In the paper we deal with the problem of modeling and querying information in schemaless databases of partially labeled objects (PLO-DB). Partially labeled objects are used for modeling data within repositories integrating both structured and semistructured data. The proposed PLO (Partially Labeled Objects) data model originates from the OEM data model and extends it by allowing partial labeling of objects. For PLO-DB we propose a rule-oriented query language PathLog, which data manipulation paradigm is based on set-theoretical operations and on rules (in Datalog style) involving Skolem functions and referential variables. The main contribution of the paper is the development of a formalized and consistent model of schemaless databases of partially labeled objects and its query language PathLog.