Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Left Bit Right: For SPARQL Join Queries with OPTIONAL Patterns
  (Left-outer-joins)   SPARQL basic graph pattern (BGP) (a.k.a. SQL inner-join) query optimization
is a well researched area. However, optimization of OPTIONAL pattern queries
(a.k.a. SQL left-outer-joins) poses additional challenges, due to the
restrictions on the \textit{reordering} of left-outer-joins. The occurrence of
such queries tends to be as high as 50% of the total queries (e.g., DBPedia
query logs).
  In this paper, we present \textit{Left Bit Right} (LBR), a technique for
\textit{well-designed} nested BGP and OPTIONAL pattern queries. Through LBR, we
propose a novel method to represent such queries using a graph of
\textit{supernodes}, which is used to aggressively prune the RDF triples, with
the help of compressed indexes. We also propose novel optimization strategies
-- first of a kind, to the best of our knowledge -- that combine together the
characteristics of \textit{acyclicity} of queries, \textit{minimality}, and
\textit{nullification}, \textit{best-match} operators. In this paper, we focus
on OPTIONAL patterns without UNIONs or FILTERs, but we also show how UNIONs and
FILTERs can be handled with our technique using a \textit{query rewrite}. Our
evaluation on RDF graphs of up to and over one billion triples, on a commodity
laptop with 8 GB memory, shows that LBR can process \textit{well-designed}
low-selectivity complex queries up to 11 times faster compared to the
state-of-the-art RDF column-stores as Virtuoso and MonetDB, and for highly
selective queries, LBR is at par with them.

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The categories of this paper are: math
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The categories of this paper are: cmp-lg
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The categories of this paper are: nlin
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The categories of this paper are: cond-mat
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The categories of this paper are: math-ph
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The categories of this paper are: econ
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-lat
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The categories of this paper are: comp-gas
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The categories of this paper are: stat
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The categories of this paper are: quant-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: gr-qc
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The categories of this paper are: acc-phys