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The Web has been rapidly "deepened" by the prevalence of databases online. With the potentially unlimited information hidden behind their query interfaces, this "deep Web" of searchable databses is clearly an important frontier for data access. This paper surveys this relatively unexplored frontier, measuring characteristics pertinent to both exploring and(More)
This paper introduces RankSQL, a system that provides a systematic and principled framework to support efficient evaluations of ranking (<i>top-k</i>) queries in relational database systems (RDBMS), by extending relational algebra and query optimization. Previously, <i>top-k</i> query processing is studied in the middleware scenario or in RDBMS in a(More)
This paper presents a principled framework for efficient processing of ad-hoc <i>top-k</i> (ranking) aggregate queries, which provide the <i>k</i> groups with the highest aggregates as results. Essential support of such queries is lacking in current systems, which process the queries in a na&#239;ve materialize-group-sort scheme that can be prohibitively(More)
We present a novel query language for large-scale analysis of XML data on a map-reduce environment, called MRQL, that is expressive enough to capture most common data analysis tasks and at the same time is amenable to optimization. Our evaluation plans are constructed using a small number of higher-order physical operators that are directly implementable on(More)
This paper presents a source selection system based on attribute co-occurrence framework for ranking and selecting Deep Web sources that provide information relevant to users requirement. Given the huge number of heterogeneous Deep Web data sources, the end users may not know the sources that can satisfy their information needs. Selecting and ranking(More)
We introduce EntityEngine, a system for answering entity-relationship queries over text. Such queries combine SQL-like structures with IR-style keyword constraints and therefore, can be expressive and flexible in querying about entities and their relationships. EntityEngine consists of various offline and online components, including a position-based(More)
MapReduce has become a common programming model for processing very large amounts of data, which is needed in a spectrum of modern computing applications. Today several MapReduce implementations and execution systems exist and many MapReduce programs are being developed and deployed in practice. However, developing MapReduce programs is not always an easy(More)
— The scalar-level predicates in SQL become increasingly inadequate to support a new class of operations that require set-level comparison semantics, i.e., comparing a group of tuples with multiple values. Complex SQL queries composed by scalar-level operations are often formed to obtain even very simple set-level semantics. Such queries are not only(More)