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Traditional databases store sets of relatively static records with no pre-defined notion of time, unless timestamp attributes are explicitly added. While this model adequately represents commercial catalogues or repositories of personal information, many current and emerging applications require support for on-line analysis of rapidly changing data streams.(More)
We study sliding window multi-join processing in continuous queries over data streams. Several algorithms are reported for performing continuous, incremental joins, under the assumption that all the sliding windows fit in main memory. The algorithms include multiway incremental nested loop joins (NLJs) and multi-way incremental hash joins. We also propose(More)
Conditional functional dependencies (CFDs) have recently been proposed as a useful integrity constraint to summarize data semantics and identify data inconsistencies. A CFD augments a functional dependency (FD) with a pattern tableau that defines the context (i.e., the subset of tuples) in which the underlying FD holds. While many aspects of CFDs have been(More)
Violations of functional dependencies (FDs) are common in practice, often arising in the context of data integration or Web data extraction. Resolving these violations is known to be challenging for a variety of reasons, one of them being the exponential number of possible “repairs”. Previous work has tackled this problem either by producing a single repair(More)
This paper discusses updating a data warehouse that collects near-real-time data streams from a variety of external sources. The objective is to keep all the tables and materialized views up-to-date as new data arrive over time. We define the notion of data staleness, formalize the problem of scheduling updates in a way that minimizes average data(More)
Internet traffic patterns are believed to obey the power law, implying that most of the bandwidth is consumed by a small set of heavy users. Hence, queries that return a list of frequently occurring items are important in the analysis of real-time Internet packet streams. While several results exist for computing frequent item queries using limited memory(More)
A defining characteristic of continuous queries over on-line data streams, possibly bounded by sliding windows, is the potentially infinite and time-evolving nature of their inputs and outputs. New items continually arrive on the input streams and new results are continually produced. Additionally, inputs expire by falling out of range of their sliding(More)
We describe DataDepot, a tool for generating warehouses from streaming data feeds, such as network-traffic traces, router alerts, financial tickers, transaction logs, and so on. DataDepot is a streaming data warehouse designed to automate the ingestion of streaming data from a wide variety of sources and to maintain complex materialized views over these(More)
We study sequential dependencies that express the semantics of data with ordered domains and help identify quality problems with such data. Given an interval g, we write X →g Y to denote that the difference between the Y -attribute values of any two consecutive records, when sorted on X , must be in g. For example, time →(0,∞) sequence number indicates that(More)
Conditional functional dependencies (CFDs) have recently been proposed as extensions of classical functional dependencies that apply to a certain subset of the relation, as specified by a <i>pattern tableau</i>. Calculating the support and confidence of a CFD (i.e., the size of the applicable subset and the extent to which it satisfies the CFD)gives(More)