5,939 research outputs found
Implementation of Web Query Languages Reconsidered
No full textVisions of the next generation Web such as the "Semantic Web" or the "Web 2.0" have triggered the emergence of a multitude of data formats. These formats have different characteristics as far as the shape of data is concerned (for example tree- vs. graph-shaped). They are accompanied by a puzzlingly large number of query languages each limited to one data format. Thus, a key feature of the Web, namely to make it possible to access anything published by anyone, is compromised.
This thesis is devoted to versatile query languages capable of accessing data in a variety of Web formats. The issue is addressed from three angles: language design, common, yet uniform semantics, and common, yet uniform evaluation. % Thus it is divided in three parts:
First, we consider the query language Xcerpt as an example of the advocated class of versatile Web query languages. Using this concrete exemplar allows us to clarify and discuss the vision of versatility in detail.
Second, a number of query languages, XPath, XQuery, SPARQL, and Xcerpt, are translated into a common intermediary language, CIQLog. This language has a purely logical semantics, which makes it easily amenable to optimizations. As a side effect, this provides the, to the best of our knowledge, first logical semantics for XQuery and SPARQL. It is a very useful tool for understanding the commonalities and differences of the considered languages.
Third, the intermediate logical language is translated into a query algebra, CIQCAG. The core feature of CIQCAG is that it scales from tree- to graph-shaped data and queries without efficiency losses when tree-data and -queries are considered: it is shown that, in these cases, optimal complexities are achieved. CIQCAG is also shown to evaluate each of the aforementioned query languages with a complexity at least as good as the best known evaluation methods so far. For example, navigational XPath is evaluated with space complexity O(q d) and time complexity O(q n) where q is the query size, n the data size, and d the depth of the (tree-shaped) data.
CIQCAG is further shown to provide linear time and space evaluation of tree-shaped queries for a larger class of graph-shaped data than any method previously proposed. This larger class of graph-shaped data, called continuous-image graphs, short CIGs, is introduced for the first time in this thesis. A (directed) graph is a CIG if its nodes can be totally ordered in such a manner that, for this order, the children of any node form a continuous interval.
CIQCAG achieves these properties by employing a novel data structure, called sequence map, that allows an efficient evaluation of tree-shaped queries, or of tree-shaped cores of graph-shaped queries on any graph-shaped data. While being ideally suited to trees and CIGs, the data structure gracefully degrades to unrestricted graphs. It yields a remarkably efficient evaluation on graph-shaped data that only a few edges prevent from being trees or CIGs
Do dolphins benefit from nonlinear mathematics when processing their sonar returns?
No full textAn interview with author Tim Leighton about the paper
Opportunities for linking young surveyors across professional surveying member organisations and FIG
No full textAMaχoS—Abstract Machine for Xcerpt
No full textWeb query languages promise convenient and efficient access
to Web data such as XML, RDF, or Topic Maps. Xcerpt is one such Web
query language with strong emphasis on novel high-level constructs for
effective and convenient query authoring, particularly tailored to versatile
access to data in different Web formats such as XML or RDF.
However, so far it lacks an efficient implementation to supplement the
convenient language features. AMaχoS is an abstract machine implementation
for Xcerpt that aims at efficiency and ease of deployment. It
strictly separates compilation and execution of queries: Queries are compiled
once to abstract machine code that consists in (1) a code segment
with instructions for evaluating each rule and (2) a hint segment that
provides the abstract machine with optimization hints derived by the
query compilation. This article summarizes the motivation and principles
behind AMaχoS and discusses how its current architecture realizes
these principles
Ten Theses on Logic Languages for the Semantic Web
No full textThis articles discusses the logic, or logic-based, languages
required for a full deployment of the SemanticWeb. It presents ten theses
addressing
1. the kinds of logic languages needed,
2. data and data processing,
3. semantics, and
4. engineering and rendering issues.
The views reported about in this article have been presented at the W3C
Workshop on Rule Languages for Interoperability (27-28 April 2005,Washington,
D.C., USA, http://www.w3.org/2004/12/rules-ws/)
Tim Di Muzio on 'Sabotage'
No full textIn a series of essays published in 2013 and 2014 on capitaspower.com, political economist Tim Di Muzio explored the concept of ‘sabotage’ as it applies to capitalist power. I recently rediscovered these essays and was so impressed by them that I have reposted them here as a single piece.
About the author: Tim Di Muzio is a researcher at the University of Wollongong. He is the author of numerous books, including Debt as power, Carbon capitalism, and The 1% and the Rest of us
1996-1997 Tim Gautreaux
No full textTim Gautreaux is the author of three novels and two earlier short story collections. His work has appeared in The New Yorker, The Best American Short Stories, The Atlantic, Harper’s, and GQ. After teaching for thirty years at Southeastern Louisiana University, he now lives, with his wife, in Chattanooga, Tennessee. (Photo credit: Randy Bergeron)https://egrove.olemiss.edu/grisham_res/1023/thumbnail.jp
Data Model and Query Constructs for Versatile Web Query Languages
No full textAs the Semantic Web is gaining momentum, the need for
truly versatile query languages becomes increasingly apparent. A Web
query language is called versatile if it can access in the same query program
data in different formats (e.g. XML and RDF). Most query languages
are not versatile: they have not been specifically designed to cope
with both worlds, providing a uniform language and common constructs
to query and transform data in various formats. Moreover, most of them
do not provide a flexible data model that is powerful enough to naturally
convey both Semantic Web data formats (especially RDF and
Topic Maps) and XML. This article highlights challenges related to the
data model and language constructs for querying both standard Web
and Semantic Web data with an emphasis on facilitating sophisticated
reasoning. It is shown that Xcerpt’s data model and querying constructs
are particularly well-suited for the Semantic Web, but that some adjustments
of the Xcerpt syntax allow for even more effective and natural
querying of RDF and Topic Maps
First person - Tim Petzold
No full textFirst Person is a series of interviews with the first authors of a selection of papers published in Biology Open, helping researchers promote themselves alongside their papers. Tim Petzold is first author on ‘ Connexin 41.8 governs timely haematopoietic stem and progenitor cell specification’, published in BiO. Tim conducted the research described in this article while a PhD student in Julien Bertrand's lab at the Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Switzerland. He is now a postdoc in the lab of Holger Gerhardt at the Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, investigating developmental biology – previously his focus was on how blood stem cells develop and now it has shifted to how the vascular system develops
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