12,256 research outputs found
Computing Majority with Triple Queries
Consider a bin containing balls colored with two colors. In a -query,
balls are selected by a questioner and the oracle's reply is related
(depending on the computation model being considered) to the distribution of
colors of the balls in this -tuple; however, the oracle never reveals the
colors of the individual balls. Following a number of queries the questioner is
said to determine the majority color if it can output a ball of the majority
color if it exists, and can prove that there is no majority if it does not
exist. We investigate two computation models (depending on the type of replies
being allowed). We give algorithms to compute the minimum number of 3-queries
which are needed so that the questioner can determine the majority color and
provide tight and almost tight upper and lower bounds on the number of queries
needed in each case.Comment: 22 pages, 1 figure, conference version to appear in proceedings of
the 17th Annual International Computing and Combinatorics Conference (COCOON
2011
Using SPARQL – the practitioners’ viewpoint
A number of studies have analyzed SPARQL log data to draw conclusions about how SPARQL is being used. To complement this work, a survey of SPARQL users has been undertaken. Whilst confirming some of the conclusions of the previous studies, the current work is able to provide additional insight into how users create SPARQL queries, the difficulties they encounter, and the features they would like to see included in the language. Based on this insight, a number of recommendations are presented to the community. These relate to predicting and avoiding computationally expensive queries; extensions to the language; and extending the search paradigm
How Many and What Types of SPARQL Queries can be Answered through Zero-Knowledge Link Traversal?
The current de-facto way to query the Web of Data is through the SPARQL
protocol, where a client sends queries to a server through a SPARQL endpoint.
Contrary to an HTTP server, providing and maintaining a robust and reliable
endpoint requires a significant effort that not all publishers are willing or
able to make. An alternative query evaluation method is through link traversal,
where a query is answered by dereferencing online web resources (URIs) at real
time. While several approaches for such a lookup-based query evaluation method
have been proposed, there exists no analysis of the types (patterns) of queries
that can be directly answered on the live Web, without accessing local or
remote endpoints and without a-priori knowledge of available data sources. In
this paper, we first provide a method for checking if a SPARQL query (to be
evaluated on a SPARQL endpoint) can be answered through zero-knowledge link
traversal (without accessing the endpoint), and analyse a large corpus of real
SPARQL query logs for finding the frequency and distribution of answerable and
non-answerable query patterns. Subsequently, we provide an algorithm for
transforming answerable queries to SPARQL-LD queries that bypass the endpoints.
We report experimental results about the efficiency of the transformed queries
and discuss the benefits and the limitations of this query evaluation method.Comment: Preprint of paper accepted for publication in the 34th ACM/SIGAPP
Symposium On Applied Computing (SAC 2019
Finding a non-minority ball with majority answers
Suppose we are given a set of balls each colored
either red or blue in some way unknown to us. To find out some information
about the colors, we can query any triple of balls
. As an answer to such a query we obtain (the
index of) a {\em majority ball}, that is, a ball whose color is the same as the
color of another ball from the triple. Our goal is to find a {\em non-minority
ball}, that is, a ball whose color occurs at least times among the
balls. We show that the minimum number of queries needed to solve this
problem is in the adaptive case and in the
non-adaptive case. We also consider some related problems
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