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Citation graphs representing a body of scientific literature convey measures of scholarly activity and productivity. In this work we present a study of the structure of the citation graph of the computer science literature. Using a web robot we built several topic-specific citation graphs and their union graph from the digital library ResearchIndex. After(More)
[1] We conducted two experiments, one long term with a 2°C increase (Experiment 1) and one short term with a 4.4°C increase (Experiment 2), to investigate main and interactive effects of warming, clipping, and doubled precipitation on soil CO 2 efflux and its temperature sensitivity in a U.S. tallgrass prairie. On average, warming increased soil CO 2 efflux(More)
A recent special issue of AI Magazine (AAAI 2005) was dedicated to the topic of semantic integration — the problem of sharing data across disparate sources. At the core of the solution lies the discovery the " semantics " of different data sources. Ideally, the semantics of data are captured by a formal ontology of the domain together with a semantic(More)
Bodies of information available through the Internet, such as digital libraries and distributed file-sharing systems, often form a self-organizing networked information space, i.e. a collection of interconnected information entities generated incrementally over time by a large number of agents. The collection of electronically available research papers in(More)
There are many problems requiring a semantic account of a database schema. At its best, such an account consists of mapping formulas between the schema and a formal conceptual model or ontology (CM) of the domain. This paper describes the underlying principles, algorithms, and a prototype of a tool which infers such semantic mappings when given simple(More)
We present a novel graph ranking model to extract a diverse set of answers for complex questions via random walks over a negative-edge graph. We assign a negative sign to edge weights in an answer graph to model the redundancy relation among the answer nodes. Negative edges can be thought of as the propagation of negative endorsements or disapprovals which(More)
In many applications it is important to find a meaningful relationship between the schemas of a source and target database. This relationship is expressed in terms of declarative logical expressions called schema mappings. The more successful previous solutions have relied on inputs such as simple element correspondences between schemas in addition to local(More)
Many problems in Information and Data Management require a semantic account of a database schema. At its best, such an account consists of formulas expressing the relationship (" mapping ") between the schema and a formal conceptual model or ontology (CM) of the domain. In this paper we describe the underlying principles, algorithms, and a prototype tool(More)