Concepts inMaximizing Conjunctive Views in Deletion Propagation
Deletion (genetics)
In genetics, a deletion (also called gene deletion, deficiency, or deletion mutation) is a mutation in which a part of a chromosome or a sequence of DNA is missing. Deletion is the loss of genetic material. Any number of nucleotides can be deleted, from a single base to an entire piece of chromosome. Deletions can be caused by errors in chromosomal crossover during meiosis. This causes several serious genetic diseases. Deletion also causes frameshift.
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APX
In complexity theory the class APX (an abbreviation of "approximable") is the set of NP optimization problems that allow polynomial-time approximation algorithms with approximation ratio bounded by a constant (or constant-factor approximation algorithms for short). In simple terms, problems in this class have efficient algorithms that can find an answer within some fixed percentage of the optimal answer.
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Submodular set function
In mathematics, submodular functions are set functions which usually appear in approximation algorithms, functions modeling user preferences in game theory. These functions have a natural diminishing returns property which makes them suitable for many applications.
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Conjunctive query
In database theory, a conjunctive query is a restricted form of first-order queries. A large part of queries issued on relational databases can be written as conjunctive queries, and large parts of other first-order queries can be written as conjunctive queries. Conjunctive queries also have a number of desirable theoretical properties that larger classes of queries (e.g. , the relational algebra queries) do not share.
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Hardness of approximation
In computer science, hardness of approximation is a field that studies the algorithmic complexity of finding near-optimal solutions to optimization problems. It complements the study of approximation algorithms by proving, for certain problems, a limit on the factors with which their solution can be efficiently approximated.
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Approximation algorithm
In computer science and operations research, approximation algorithms are algorithms used to find approximate solutions to optimization problems. Approximation algorithms are often associated with NP-hard problems; since it is unlikely that there can ever be efficient polynomial time exact algorithms solving NP-hard problems, one settles for polynomial time sub-optimal solutions.
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Matroid
In combinatorics, a branch of mathematics, a matroid or independence structure is a structure that captures and generalizes the notion of linear independence in vector spaces. There are many equivalent ways to define a matroid, a phenomenon sometimes called cryptomorphism. Significant definitions of matroid include those in terms of independent sets, bases, circuits, closed sets or flats, closure operators, and rank functions.
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Hypergraph
An example hypergraph, with and . ]] In mathematics, a hypergraph is a generalization of a graph, where an edge can connect any number of vertices. Formally, a hypergraph is a pair where is a set of elements, called nodes or vertices, and is a set of non-empty subsets of called hyperedges or links. Therefore, is a element of, where is the power set of . While graph edges are pairs of nodes, hyperedges are arbitrary sets of nodes, and can therefore contain an arbitrary number of nodes.
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