Searching and browsing Linked Data with SWSE: The Semantic Web Search Engine

In this paper, we discuss the architecture and implementation of the Semantic Web Search Engine (SWSE). Following traditional search engine architecture, SWSE consists of crawling, data enhancing, indexing and a user interface for search, browsing and retrieval of information; unlike traditional search engines, SWSE operates over RDF Web data – loosely also known as Linked Data – which implies unique challenges for the system design, architecture, algorithms, implementation and user interface. In particular, many challenges exist in adopting Semantic Web technologies for Web data: the unique challenges of the Web – in terms of scale, unreliability, inconsistency and noise – are largely overlooked by the current Semantic Web standards. Herein, we describe the current SWSE system, initially detailing the architecture and later elaborating upon the function, design, implementation and performance of each individual component. In so doing, we also give an insight into how current Semantic Web standards can be tailored, in a best-effort manner, for use on Web data. Throughout, we offer evaluation and complementary argumentation to support our design choices, and also offer discussion on future directions and open research questions. Later, we also provide candid discussion relating to the difficulties currently faced in bringing such a search engine into the mainstream, and lessons learnt from roughly six years working on the Semantic Web Search Engine project.     

Ease of interaction plus ease of integration: Combining Web2.0 and the Semantic Web in a reviewing site

Web2.0 has enabled contributions to the Web on an unprecedented scale, through simple interfaces that provide engaging interactions. This wealth of data has spawned countless mashups that integrate heterogenous information, but using techniques that will not scale beyond a handful of sources. In contrast, the Semantic Web provides the key to large-scale data integration, yet still lacks approachable interfaces allowing contributions from non-specialists. In this paper we present Revyu, a reviewing and rating site in the Web2.0 mould that is built on Semantic Web infrastructure and both publishes and consumes linked RDF data. This combination of approaches affords ease of interaction for regular users and ease of integration with external data sources.     

SETL: A programmable semantic extract-transform-load framework for semantic data warehouses

In order to create better decisions for business analytics, organizations increasingly use external structured, semi-structured, and unstructured data in addition to the (mostly structured) internal data. Current Extract-Transform-Load (ETL) tools are not suitable for this “open world scenario” because they do not consider semantic issues in the integration processing. Current ETL tools neither support processing semantic data nor create a semantic Data Warehouse (DW), a repository of semantically integrated data. This paper describes our programmable Semantic ETL (SETL) framework. SETL builds on Semantic Web (SW) standards and tools and supports developers by offering a number of powerful modules, classes, and methods for (dimensional and semantic) DW constructs and tasks. Thus it supports semantic data sources in addition to traditional data sources, semantic integration, and creating or publishing a semantic (multidimensional) DW in terms of a knowledge base. A comprehensive experimental evaluation comparing SETL to a solution made with traditional tools (requiring much more hand-coding) on a concrete use case, shows that SETL provides better programmer productivity, knowledge base quality, and performance.     

Bridging the semantic Web and Web 2.0 with Representational State Transfer (REST)

Semantic Web technologies must integrate with Web 2.0 services for both to leverage each others strengths. We argue that the REST-based design methodologies [R.T. Fielding, R.N. Taylor, Principled design of the modern web architecture, ACM Trans. Internet Technol. (TOIT) 2 (2) (2002) 115–150] of the web present the ideal mechanism through which to align the publication of semantic data with the existing web architecture. We present the design and implementation of two solutions that combine REST-based design and RDF [D. Beckett (Ed.), RDF/XML Syntax Specification (Revised), W3C Recommendation, February 10, 2004] data access: one solution for integrating existing web services and one server-side solution for creating RDF REST services. Both of these solutions enable SPARQL [E. Prud’hommeaux, A. Seaborne (Eds.), SPARQL Query Language for RDF, W3C Working Draft, March 26, 2007] to be a unifying data access layer for aligning the Semantic Web and Web 2.0.     

SESLDS: An Extension Scheme for Linked Data Sources Based on Semantically Enhanced Annotation and Reasoning

In the era of Big Data, users prefer to get knowledge rather than pages from Web. Linked Data, a rather new form of knowledge representation and publishing described by RDF, can provide a more precise and comprehensible semantic structure to satisfy the aforementioned requirement. Besides, as the standard query language for RDF data, SPARQL has become the foundation protocol of Linked Data querying. The core idea of RDF Schema (RDFS) is to extend upon RDF vocabulary and allow attachment of semantics to user defined classes and properties. However, RDFS cannot fully utilize the potential of RDF since it cannot express the implicit semantics between linked entities in Linked Data sources. To fill this gap, in this paper, we design a new semantic annotating and reasoning approach that can extend more implicit semantics from different properties. We firstly establish a well‐defined semantically enhanced annotation strategy for Linked Data sources. In particular, we present some new semantic properties for predicates in RDF triples and design a Semantic Matrix for Predicates (SM_P). We then propose a novel general Semantically Extended Scheme for Linked Data Sources (SES_LDS) to realize the semantic extension over the target Linked Data source through semantically enhanced reasoning. Lastly, based on the experimental analyses, we verify that our proposal has advantages over the initial Linked Data source and can return more valid results.     

RDF数据的并行处理及性能评价

语义Web作为数据之网不断汇集并组织Web信息,相关应用因此面临着对语义Web所含大规模RDF数据高效访问的挑战.利用并行处理技术提高性能是一种解决之道,其核心是RDF数据的放置策略和并行查询处理.已有工作尚未系统研究RDF数据放置策略的分类与特点,及其对查询处理性能的影响.分析了RDF数据上各类数据放置幕略及其对查询处理性能影响,通过LUBM测试基准结果分析评价了典型的RDF并行处理策略(数据放置策略及相应并行查询处理)的实际性能,为提出更有效的并行处理策略奠定了基础.     

Adding value to Linked Open Data using a multidimensional model approach based on the RDF Data Cube vocabulary

Most organisations using Open Data currently focus on data processing and analysis. However, although Open Data may be available online, these data are generally of poor quality, thus discouraging others from contributing to and reusing them. This paper describes an approach to publish statistical data from public repositories by using Semantic Web standards published by the W3C, such as RDF and SPARQL, in order to facilitate the analysis of multidimensional models. We have defined a framework based on the entire lifecycle of data publication including a novel step of Linked Open Data assessment and the use of external repositories as knowledge base for data enrichment. As a result, users are able to interact with the data generated according to the RDF Data Cube vocabulary, which makes it possible for general users to avoid the complexity of SPARQL when analysing data. The use case was applied to the Barcelona Open Data platform and revealed the benefits of the application of our approach, such as helping in the decision-making process.     

RDF数据浏览的研究综述

随着语义网的快速发展,目前Web上语义网数据已经达到相当的规模,成为重要的信息和知识来源.因此,RDF数据浏览的研究开始得到广泛关注.通过对比传统Web信息浏览和RDF数据浏览两个问题,指出RDF数据浏览的5个重要问题:确定浏览子图的模式、数据的收集、大规模数据的处理、数据的组织方式以及数据的呈现方式.基于这些挑战,我们调研了多个系统和不同的解决方案.最后,总结了目前的研究现况,讨论存在的挑战,并提出未来的研究方向.     

ActiveRDF: Embedding Semantic Web data into object-oriented languages

Semantic Web applications share a large portion of development effort with database-driven Web applications. Existing approaches for development of these database-driven applications cannot be directly applied to Semantic Web data due to differences in the underlying data model. We develop a mapping approach that embeds Semantic Web data into object-oriented languages and thereby enables reuse of existing Web application frameworks.We analyse the relation between the Semantic Web and the Web, and survey the typical data access patterns in Semantic Web applications. We discuss the mismatch between object-oriented programming languages and Semantic Web data, for example in the semantics of class membership, inheritance relations, and object conformance to schemas.We present ActiveRDF, an object-oriented API for managing RDF data that offers full manipulation and querying of RDF data, does not rely on a schema and fully conforms to RDF(S) semantics. ActiveRDF can be used with different RDF data stores: adapters have been implemented to generic SPARQL endpoints, Sesame, Jena, Redland and YARS and new adapters can be added easily. We demonstrate the usage of ActiveRDF and its integration with the popular Ruby on Rails framework which enables rapid development of Semantic Web applications.     

语义网站点的发现与排序

随着语义网中RDF数据的大量涌现,语义搜索引擎为用户搜索RDF数据带来了便利.但是,如何自动地发现包含语义网信息资源的站点,并高效地在语义网站点中收集语义网信息资源,一直是语义搜索引擎所面临的问题.首先介绍了语义网站点的链接模型.该模型刻画了语义网站点、语义网信息资源、RDF模型和语义网实体之间的关系.基于该模型讨论了语义网实体的归属问题,并进一步定义了语义网站点的发现规则;另外,从站点链接模型出发,定义了语义网站点依赖图,并给出了对语义网站点进行排序的算法.将相关算法在一个真实的语义搜索引擎中进行了初步测试.实验结果表明,所提出的方法可以有效地发现语义网站点并对站点进行排序.     

Laying the foundations for a World Wide Argument Web

This paper lays theoretical and software foundations for a World Wide Argument Web (WWAW): a large-scale Web of inter-connected arguments posted by individuals to express their opinions in a structured manner. First, we extend the recently proposed Argument Interchange Format (AIF) to express arguments with a structure based on Walton's theory of argumentation schemes. Then, we describe an implementation of this ontology using the RDF Schema Semantic Web-based ontology language, and demonstrate how our ontology enables the representation of networks of arguments on the Semantic Web. Finally, we present a pilot Semantic Web-based system, ArgDF, through which users can create arguments using different argumentation schemes and can query arguments using a Semantic Web query language. Manipulation of existing arguments is also handled in ArgDF: users can attack or support parts of existing arguments, or use existing parts of an argument in the creation of new arguments. ArgDF also enables users to create new argumentation schemes. As such, ArgDF is an open platform not only for representing arguments, but also for building interlinked and dynamic argument networks on the Semantic Web. This initial public-domain tool is intended to seed a variety of future applications for authoring, linking, navigating, searching, and evaluating arguments on the Web.     

语义Web上本体与智能信息Agent的集成研究

该文介绍了语义Web新技术,它可以为处理Web信息的智能应用程序提供帮助。文中描述了语义Web的层次结构及其支持语义Web的基础技术如RDF(资源描述框架)和本体(Ontology)等,文章表明,Agent技术与本体的集成会扩展程序能力,更有效地为用户执行任务而较少需要人的干预,也会对Web服务的使用产生重大影响。文中介绍了本体与智能信息Agent结合的应用实例,为用户搜索Web上的服务提供帮助。     

An integration site for Semantic Web metadata

The Semantic Web has motivated many communities to provide data in a machine-readable format. However, the available data has not been utilized to far to the extent possible. The data, which has been created by a large number of people, is dispersed across the Web. Creating the data without central coordination results in RDF of varying quality and makes it obligatory to cleanse the collected data before integration. The SECO system presented in this paper harvests RDF files from the Web and consolidates the different data sets into a coherent representation aligned along an internal schema. SECO provides interfaces for humans to browse and for software agents to query the data repository. In this paper, we describe the characteristics of RDF data available online, the architecture and implementation of the SECO application, and discuss some of the experienced gained while collecting and integrating RDF on the Web.     

基于本体的语义Web研究

语义Web与本体的关系极为特殊,本体在语义Web本身的体系结构中扮演着极为重要的角色,同时,位于语义Web体系结构的其它层的XML、RDF(S)等与本体也有着千丝万缕的联系。为阐述两者的关系,探讨基于本体的语义Web的特点及应用,介绍了本体和语义Web的产生和发展,在此基础上对基于本体的语义Web进行研究,重点分析了本体在描述语义方面弥补了XML、RDF(S)等的不足,并结合Web服务检索的实例介绍了本体在Web服务上的应用。