Showing papers by "Srikanta Bedathur published in 2016"

ESPRESSO: Explaining Relationships between Entity Sets

Abstract: Analyzing and explaining relationships between entities in a knowledge graph is a fundamental problem with many applications. Prior work has been limited to extracting the most informative subgraph connecting two entities of interest. This paper extends and generalizes the state of the art by considering the relationships between two sets of entities given at query time. Our method, coined ESPRESSO, explains the connection between these sets in terms of a small number of relatedness cores: dense sub-graphs that have strong relations with both query sets. The intuition for this model is that the cores correspond to key events in which entities from both sets play a major role. For example, to explain the relationships between US politicians and European politicians, our method identifies events like the PRISM scandal and the Syrian Civil War as relatedness cores. Computing cores of bounded size is NP-hard. This paper presents efficient approximation algorithms. Our experiments with real-life knowledge graphs demonstrate the practical viability of our approach and, through user studies, the superior output quality compared to state-of-the-art baselines.

Quark-X: An Efficient Top-K Processing Framework for RDF Quad Stores

Abstract: There is a growing trend towards enriching the RDF content from its classical Subject-Predicate-Object triple form to an annotated representation which can model richer relationships such as including fact provenance, fact confidence, higher-order relationships and so on. One of the recommended ways to achieve this is to use reification and represent it as N-Quads "or simply quads" where an additional identifier is associated with the entire RDF statement which can then be used to add further annotations. A typical use of such annotations is to have quantifiable confidence values to be attached to facts. In such settings, it is important to support efficient top-k queries, typically over user-defined ranking functions containing sentence level confidence values in addition to other quantifiable values in the database. In this paper, we present Quark-X, an RDF-store and SPARQL processing system for reified RDF data represented in the form of quads. This paper presents the overall architecture of our system -- illustrating the modifications which need to be made to a native quad store for it to process top-k queries. In Quark-X, we propose indexing and query processing techniques for making top-k querying efficient. In addition, we present the results of a comprehensive empirical evaluation of our system over Yago2S and DBpedia datasets. Our performance study shows that the proposed method achieves one to two order of magnitude speed-up over baseline solutions.

Instant Espresso: Interactive Analysis of Relationships in Knowledge Graphs

Abstract: We demonstrate InstantEspresso, a system to explain the relationship between two sets of entities in knowledge graphs. Instant-Espresso answers questions of the form. Which European politicians are related to politicians in the United States, and how? or How can one summarize the relationship between China and countries from the Middle East? Each question is specified by two sets of query entities. These sets (e.g. European politicians or United States politicians) can be determined by an initial graph query over a knowledge graph capturing relationships between real-world entities. Instant-Espresso analyzes the (indirect) relationships that connect entities from both sets and provides a user-friendly explanation of the answer in the form of concise subgraphs. These so-called relatedness cores correspond to important event complexes involving entities from the two sets. Our system provides a user interface for the specification of entity sets and displays a visually appealing visualization of the extracted subgraph to the user. The demonstrated system can be used to provide background information on the current state-of-affairs between real-world entities such as politicians, organizations, and the like, e.g. to a journalist preparing an article involving the entities of interest. InstantEspresso is available for an online demonstration at the URL http://espresso.mpi-inf.mpg.de/.