Efficient federated query processing is of significant importance to tame the large amount of data available on the Web of Data. Previous works have focused on generating optimized query execution plans for fast result retrieval. However, devising source selection approaches beyond triple pattern-wise source selection has not received much attention. This work presents HiBISCuS, a novel hypergraph-based source selection approach to federated SPARQL querying. Our approach can be directly combined with existing SPARQL query federation engines to achieve the same recall while querying fewer data sources. We extend three well-known SPARQL query federation engines with HiBISCus and compare our extensions with the original approaches on FedBench. Our evaluation shows that HiBISCuS can efficiently reduce the total number of sources selected without losing recall. Moreover, our approach significantly reduces the execution time of the selected engines on most of the benchmark queries.
FedX - Optimization Techniques for Federated Query Processing on Linked Dataaschwarte
The final slides of our talk about FedX at the 10th International Semantic Web Conference in Bonn. For details about FedX see http://www.fluidops.com/fedx/
A single interface for accessing life sciences (LS) data is a natural consequence to master the data deluge in this domain. The data in the LS requires integration and current integrative solutions increasingly rely on the federation of queries for distributed resources. We introduce a federated query processing system name ``BioFed", customised for LS-LOD. BioFed federates SPARQL queries over more than 130 public SPARQL endpoints.
FedX - Optimization Techniques for Federated Query Processing on Linked Dataaschwarte
The final slides of our talk about FedX at the 10th International Semantic Web Conference in Bonn. For details about FedX see http://www.fluidops.com/fedx/
A single interface for accessing life sciences (LS) data is a natural consequence to master the data deluge in this domain. The data in the LS requires integration and current integrative solutions increasingly rely on the federation of queries for distributed resources. We introduce a federated query processing system name ``BioFed", customised for LS-LOD. BioFed federates SPARQL queries over more than 130 public SPARQL endpoints.
RDF is a general method to decompose knowledge into small pieces, with some rules about the semantics or meaning of those pieces. The point is to have a method so simple that it can express any fact, and yet so structured that computer applications can do useful things with knowledge expressed in RDF.
This presentation was given at the International Workshop on Interacting with Linked Data (ILD 2012) co-located with the 9th Extended Semantic Web Conference 2012, Heraklion, and is related the publication of the same title.
Much research has been done to combine the fields of Data-bases and Natural Language Processing. While many works focus on the problem of deriving a structured query for a given natural language question, the problem of query verbalization -- translating a structured query into natural language -- is less explored. In this work we describe our approach to verbalizing SPARQL queries in order to create natural language expressions that are readable and understandable by the human day-to-day user. These expressions are helpful when having search engines that generate SPARQL queries for user-provided natural language questions or keywords. Displaying verbalizations of generated queries to a user enables the user to check whether the right question has been understood. While our approach enables verbalization of only a subset of SPARQL 1.1, this subset applies to 90% of the 209 queries in our training set. These observations are based on a corpus of SPARQL queries consisting of datasets from the QALD-1 challenge and the ILD2012 challenge.
The publication is available at http://www.aifb.kit.edu/images/b/b7/VerbalizingSparqlQueries.pdf
Lightening talk for Semantic Web in Libraries (SWIB13) conference at 2013-11-27 about another method of expressing RDF data. See http://gbv.github.io/aREF/ for a preliminary specification.
"SPARQL Cheat Sheet" is a short collection of slides intended to act as a guide to SPARQL developers. It includes the syntax and structure of SPARQL queries, common SPARQL prefixes and functions, and help with RDF datasets.
The "SPARQL Cheat Sheet" is intended to accompany the SPARQL By Example slides available at http://www.cambridgesemantics.com/2008/09/sparql-by-example/ .
Invited talk at USEWOD2014 (http://people.cs.kuleuven.be/~bettina.berendt/USEWOD2014/)
A tremendous amount of machine-interpretable information is available in the Linked Open Data Cloud. Unfortunately, much of this data remains underused as machine clients struggle to use the Web. I believe this can be solved by giving machines interfaces similar to those we offer humans, instead of separate interfaces such as SPARQL endpoints. In this talk, I'll discuss the Linked Data Fragments vision on machine access to the Web of Data, and indicate how this impacts usage analysis of the LOD Cloud. We all can learn a lot from how humans access the Web, and those strategies can be applied to querying and analysis. In particular, we have to focus first on solving those use cases that humans can do easily, and only then consider tackling others.
MULDER: Querying the Linked Data Web by Bridging RDF Molecule TemplatesKemele M. Endris
The increasing number of RDF data sources that allow for
querying Linked Data via Web services form the basis for federated SPARQL query processing. Federated SPARQL query engines provide a unified view of a federation of RDF data sources, and rely on source descriptions for selecting the data sources over which unified queries will be executed. Albeit efficient, existing federated SPARQL query engines usually ignore the meaning of data accessible from a data source,
and describe sources only in terms of the vocabularies utilized in the data source. Lack of source description may conduce to the erroneous selection of data sources for a query, thus affecting the performance of query processing over the federation. We tackle the problem of federated SPARQL query processing and devise MULDER, a query engine for federations of RDF data sources. MULDER describes data sources in terms of RDF molecule templates, i.e., abstract descriptions of entities
belonging to the same RDF class. Moreover, MULDER utilizes RDF molecule templates for source selection, and query decomposition and optimization. We empirically study the performance of MULDER on existing benchmarks, and compare MULDER performance with state-of-the-art federated SPARQL query engines. Experimental results suggest that RDF molecule templates empower MULDER federated query processing, and allow for the selection of RDF data sources that not only reduce execution time, but also increase answer completeness.
RDF is a general method to decompose knowledge into small pieces, with some rules about the semantics or meaning of those pieces. The point is to have a method so simple that it can express any fact, and yet so structured that computer applications can do useful things with knowledge expressed in RDF.
This presentation was given at the International Workshop on Interacting with Linked Data (ILD 2012) co-located with the 9th Extended Semantic Web Conference 2012, Heraklion, and is related the publication of the same title.
Much research has been done to combine the fields of Data-bases and Natural Language Processing. While many works focus on the problem of deriving a structured query for a given natural language question, the problem of query verbalization -- translating a structured query into natural language -- is less explored. In this work we describe our approach to verbalizing SPARQL queries in order to create natural language expressions that are readable and understandable by the human day-to-day user. These expressions are helpful when having search engines that generate SPARQL queries for user-provided natural language questions or keywords. Displaying verbalizations of generated queries to a user enables the user to check whether the right question has been understood. While our approach enables verbalization of only a subset of SPARQL 1.1, this subset applies to 90% of the 209 queries in our training set. These observations are based on a corpus of SPARQL queries consisting of datasets from the QALD-1 challenge and the ILD2012 challenge.
The publication is available at http://www.aifb.kit.edu/images/b/b7/VerbalizingSparqlQueries.pdf
Lightening talk for Semantic Web in Libraries (SWIB13) conference at 2013-11-27 about another method of expressing RDF data. See http://gbv.github.io/aREF/ for a preliminary specification.
"SPARQL Cheat Sheet" is a short collection of slides intended to act as a guide to SPARQL developers. It includes the syntax and structure of SPARQL queries, common SPARQL prefixes and functions, and help with RDF datasets.
The "SPARQL Cheat Sheet" is intended to accompany the SPARQL By Example slides available at http://www.cambridgesemantics.com/2008/09/sparql-by-example/ .
Invited talk at USEWOD2014 (http://people.cs.kuleuven.be/~bettina.berendt/USEWOD2014/)
A tremendous amount of machine-interpretable information is available in the Linked Open Data Cloud. Unfortunately, much of this data remains underused as machine clients struggle to use the Web. I believe this can be solved by giving machines interfaces similar to those we offer humans, instead of separate interfaces such as SPARQL endpoints. In this talk, I'll discuss the Linked Data Fragments vision on machine access to the Web of Data, and indicate how this impacts usage analysis of the LOD Cloud. We all can learn a lot from how humans access the Web, and those strategies can be applied to querying and analysis. In particular, we have to focus first on solving those use cases that humans can do easily, and only then consider tackling others.
MULDER: Querying the Linked Data Web by Bridging RDF Molecule TemplatesKemele M. Endris
The increasing number of RDF data sources that allow for
querying Linked Data via Web services form the basis for federated SPARQL query processing. Federated SPARQL query engines provide a unified view of a federation of RDF data sources, and rely on source descriptions for selecting the data sources over which unified queries will be executed. Albeit efficient, existing federated SPARQL query engines usually ignore the meaning of data accessible from a data source,
and describe sources only in terms of the vocabularies utilized in the data source. Lack of source description may conduce to the erroneous selection of data sources for a query, thus affecting the performance of query processing over the federation. We tackle the problem of federated SPARQL query processing and devise MULDER, a query engine for federations of RDF data sources. MULDER describes data sources in terms of RDF molecule templates, i.e., abstract descriptions of entities
belonging to the same RDF class. Moreover, MULDER utilizes RDF molecule templates for source selection, and query decomposition and optimization. We empirically study the performance of MULDER on existing benchmarks, and compare MULDER performance with state-of-the-art federated SPARQL query engines. Experimental results suggest that RDF molecule templates empower MULDER federated query processing, and allow for the selection of RDF data sources that not only reduce execution time, but also increase answer completeness.
Re-using Media on the Web: Media fragment re-mixing and playoutMediaMixerCommunity
A number of novel application ideas will be introduced based on the media fragment creation, specification and rights management technologies. Semantic search and retrieval allows us to organize sets of fragments by topical or conceptual relevance. These fragment sets can then be played out in a non-linear fashion to create a new media re-mix. We look at a server-client implementation supporting Media Fragments, before allowing the participants to take the sets of media they have selected and create their own re-mix.
Information access over linked data requires to determine
subgraph(s), in linked data's underlying graph, that correspond to the required information need. Usually, an information access framework is able to retrieve richer information by checking of a large number of possible subgraphs. However, on the ecking of a large number of possible subgraphs increases information access complexity. This makes information access frameworks less eective. A large number of contemporary linked data information access frameworks reduce the complexity by introducing dierent heuristics but they suer on retrieving richer information. Or, some frameworks do not care about the complexity. However, a practically usable framework should retrieve richer information with lower complexity. In linked data information access, we hypothesize that pre-processed data statistics of linked data can be used to eciently check a large number of possible subgraphs. This will help to retrieve comparatively richer information with lower data access complexity. Preliminary evaluation of our proposed hypothesis shows promising performance.
Linked lists represent a countable number of ordered values, and are among the most important abstract data types in computer science. With the advent of RDF as a highly expressive knowledge representation language for the Web, various implementations for RDF lists have been proposed. Yet, there is no benchmark so far dedicated to evaluate the performance of triple stores and SPARQL query engines on dealing with ordered linked data. Moreover, essential tasks for evaluating RDF lists, like generating datasets containing RDF lists of various sizes, or generating the same RDF list using different modelling choices, are cumbersome and unprincipled. In this paper, we propose List.MID, a systematic benchmark for evaluating systems serving RDF lists. List.MID consists of a dataset generator, which creates RDF list data in various models and of different sizes; and a set of SPARQL queries. The RDF list data is coherently generated from a large, community-curated base collection of Web MIDI files, rich in lists of musical events of arbitrary length. We describe the List.MID benchmark, and discuss its impact and adoption, reusability, design, and availability.
Lecture at the advanced course on Data Science of the SIKS research school, May 20, 2016, Vught, The Netherlands.
Contents
-Why do we create Linked Open Data? Example questions from the Humanities and Social Sciences
-Introduction into Linked Open Data
-Lessons learned about the creation of Linked Open Data (link discovery, knowledge representation, evaluation).
-Accessing Linked Open Data
SPARQL Query Verbalization for Explaining Semantic Search Engine QueriesBasil Ell
This presentation was given at the 11th Extended Semantic Web Conference (ESWC '14), Anissaras/Heronissou, Crete, Greece, and is related the publication of the same title.
In this paper we introduce Spartiqulation, a system that translates SPARQL queries into English text. Our aim is to allow casual end users of semantic applications with limited to no expertise in the SPARQL query language to interact with these applications in a more intuitive way. The verbalization approach exploits domain-independent template-based natural language generation techniques, as well as linguistic cues in labels and URIs.
This slides I've used on talk about Semantic Web use-case. Not all know what exactly Semantic Web is about. So I've created set of slides showing this in a simple and correct way. Use-case slides are removed on this public available slides. Animated version here goo.gl/qKoF6k . Contact me for sources!
Two graph data models : RDF and Property Graphsandyseaborne
Talk given at ApacheConEU Big Data 2015.
This talk describes the two common graph data approaches, RDF and Property Graphs. It concludes with observations about the different emphasis of each and where each is focused.
Presentation done* at the 13th International Semantic Web Conference (ISWC) in which we approach a compressed format to represent RDF Data Streams. See the original article at: http://dataweb.infor.uva.es/wp-content/uploads/2014/07/iswc14.pdf
* Presented by Alejandro Llaves (http://www.slideshare.net/allaves)
Selectivity Estimation for SPARQL Triple Patterns with Shape ExpressionsAbdullah Abbas
We optimize the evaluation of conjunctive SPARQL queries, on big RDF graphs, by taking advantage of ShEx schema constraints. Our optimization is based on computing ranks for query triple patterns, which indicates their order of execution. We first define a set of well-formed ShEx schemas, that possess interesting characteristics for SPARQL query optimization. We then define our optimization method by exploiting information extracted from a ShEx schema. The experimentations performed shows the advantages of applying our optimization on the top of an existing state-of-the-art query evaluation system.
This presentation looks in detail at SPARQL (SPARQL Protocol and RDF Query Language) and introduces approaches for querying and updating semantic data. It covers the SPARQL algebra, the SPARQL protocol, and provides examples for reasoning over Linked Data. We use examples from the music domain, which can be directly tried out and ran over the MusicBrainz dataset. This includes gaining some familiarity with the RDFS and OWL languages, which allow developers to formulate generic and conceptual knowledge that can be exploited by automatic reasoning services in order to enhance the power of querying.
How Representative Is a SPARQL Benchmark? An Analysis of RDF Triplestore Benc...Muhammad Saleem
Triplestores are data management systems for storing and querying RDF data. Over recent years, various benchmarks have been proposed to assess the performance of triplestores across different performance measures. However, choosing the most suitable benchmark for evaluating triplestores in practical settings is not a trivial task. This is because triplestores experience varying workloads when deployed in real applications. We address the problem of determining an appropriate benchmark for a given real-life workload by providing a fine-grained comparative analysis of existing triplestore benchmarks. In particular, we analyze the data and queries provided with the existing triplestore benchmarks in addition to several real-world datasets. Furthermore, we measure the correlation between the query execution time and various SPARQL query features and rank those features based on their significance levels. Our experiments reveal several interesting insights about the design of such benchmarks. With this fine-grained evaluation, we aim to support the design and implementation of more diverse benchmarks. Application developers can use our result to analyze their data and queries and choose a data management system.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
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HiBISCuS: Hypergraph-Based Source Selection for SPARQL Endpoint Federation
1. HiBISCuS: Hypergraph-Based Source
Selection for SPARQL Endpoint
Federation
Muhammad Saleem, Axel-Cyrille Ngonga Ngomo
{lastname}@informatik.uni-leipzig.de
Agile Knowledge Engineering and Semantic Web (AKSW), University of Leipzig, Germany
11th Extended Semantic Web Conferece (ESWC), Crete, Greece, 25th-29th of May 2014
12. Problem Statement
• An overestimation of triple pattern-wise
source selection can be expensive
– Resources are wasted
– Query runtime is increased
– Extra traffic is generated
• How do we perform join-aware triple pattern
wise source selection in time efficient way?
13. HiBISCuS: Key Concept
• Makes use of the URI’s authorities
http://dbpedia.org/ontology/party
Scheme Authority Path
For URI details: http://tools.ietf.org/html/rfc3986
28. Experimental Setup
• Benchmark
– FedBench
– Real-world datasets collection
– Real queries showing typical request
– Used all of the 25 queries
• HiBISCuS Extensions
– FedX 2.0
– DARQ
– SPLENDID
• We also included ANAPSID (version of 12/2013)
without HiBISCus extension
29. Experimental Setup
• Metrics
– Index generation time
– Index size
– Total triple pattern-wise sources selected
– Total number of SPARQL ASK requests used
– Source selection time
– Query execution time
30. Index Generation Time and Compression Ratio
FedX SPLENDIDLHD DARQ ANAPSID ADERIS Qtree HiBISCus
Index
Generation
Time (min) NA 75 75 102 6 6 - 36
Compression
Ratio NA 99.998 99.998 99.997 99.999 99.999 96.000 99.997
Compression Ratio = 1 - index size/ total datadump size
37. Conclusion and Future Work
• An overestimation of triple pattern-wise source
selection can be expensive
• Join-aware triple pattern-wise source selection is
more efficient than simple triple pattern-wise source
selection
• Performance improvements
– FedX : 24.61 %
– SPLENDID: 82.72 %
– DARQ: 92.22 %
– SPLENDID+HiBISCus is 98% faster than ANAPSID
• BigRDFBench is on the roadmap
38. Thanks!
homepage and source code:
https://code.google.com/p/hibiscusfederation/
{saleem,ngonga}@informatik.uni-leipzig.de
AKSW, University of Leipzig, Germany
39. Source Selection
• Triple pattern-wise source selection
– Ensures 100% recall
– Can over-estimate capable sources
– Can be expensive, e.g., total number of SPARQL ASK
requests used
– Performed by FedX, SPLENDID, LHD, DARQ, ADERIS etc.
• Join-aware triple-pattern wise source selection
– Ensures 100% recall
– May selects optimal/close to optimal capable sources
– Can be expensive, e.g., total number of SPARQL ASK
requests used
– Can significantly reduce the query execution time
– Performed by ANAPSID