Many applications in analytical domains often have the need to connect the dots i.e., query about the structure of data. In bioinformatics for example, it is typical to want to query about interactions between proteins. The aim of such queries is to extract relationships between entities i.e. paths from a data graph. Often, such queries will specify certain constraints that qualifying results must satisfy e.g. paths involving a set of mandatory nodes. Unfortunately, most present day Semantic Web query languages including the current draft of the anticipated recommendation SPARQL, lack the ability to express queries about arbitrary path structures in data.
Implemented using Java and Berkley DB and the memory store Brahms. Also mentions PSPARQL (part of Exmo), which in February reached version complete status.