A common perception is that there are two competing visions for the future evolution of the Web: the Semantic Web and Web 2.0. A closer look, though, reveals that the core technologies and concerns of these two approaches are complementary and that each field can and must draw from the other’s strengths. We believe that future web applications will retain the Web 2.0 focus on community and usability, while drawing on Semantic Web infrastructure to facilitate mashup-like information sharing. However, there are several open issues that must be addressed before such applications can become commonplace. In this paper, we outline a semantic weblogs scenario that illustrates the potential for combining Web 2.0 and Semantic Web technologies, while highlighting the unresolved issues that impede its realization. Nevertheless, we believe that the scenario can be realized in the short-term. We point to recent progress made in resolving each of the issues as well as future research directions for each of the communities.

Abstract. Blogging, as a subset of the web as a whole, can benefit greatly from the addition of semantic metadata. The result — which we will call Semantic Blogging — provides improved capabilities with respect to search, connectivity and browsing compared to current blogging technology. Moreover, Semantic Blogging will allow new ways of convenient data exchange between the actors within the blogosphere — blog authors and blog users alike. This paper identifies structural and content-related metadata as the kinds of semantic metadata which are relevant in the domain of blogging. We present in detail the nature of these two kinds of metadata, and discuss ways of creating such metadata in a convenient and non-obstrusive way for the user, how to publish such metadata on the web, and how to best make use of such metadata from the point of view of a blog consumer. 1

Abstract. Semantic Social Software – the combination of social software and Semantic Web technology – has recently been gaining significant attention in the Semantic Web community. This article first discusses the two different perspectives the research community takes on “Semantic Social Software”, namely the “Semantically Enabled Social Software ” – meaning social software enhanced by semantics, and the “Socially Enabled Semantic Web ” – meaning exploiting social software properties for creating Semantic Web data. It then introduces three example applications of Semantic Social Software (Semantic Wikis, Semantic Weblogs, and ePortfolios) and derives challenges for the Semantic Web community to address in order to overcome open issues of both, Semantic Social Software and the Semantic Web.

The blogosphere refers to the distributed network of user opinions published on the WWW. Whereas centralized review sites such Amazon.com previously allowed users to post opinions on goods such as books and CDs, blogging software allows users to publish opinions on any topic without constraints on predefined schema. However, centralized review sites such as Amazon.com have one significant advantage: reviews pertaining to a single topic are collected together in one place, allowing readers to peruse a diverse range of opinions quickly. In this paper we examine how such a topiccentric view of the Blogosphere can be created. We characterise the problems in aligning similar concepts created by a set of distributed, autonomous users and describe current initiatives to solve the problem. Finally, we introduce the Tagsocratic project, a novel initiative to solve the concept alignment problem using techniques derived from research in language acquisition among distributed, autonomous agents. 1.

Abstract. A typical computer user’s desktop contains large amount of formal data, such as addresses, events or bibliopraphies. Especially within a corporate or organizational environment, it is often important to exchange this data between employees. However, state-of-the-art communication technologies such as email or bulletin boards don’t allow to easily integrate desktop data in the communication process, with the effect that the data remains locked within a user’s computer. In this paper, we propose that the recent phenomenon of blogging, combined with a tool to easily generate Semantic Web (SW) data from existing formal desktop data, can result in a form of semantic blogging which would help to overcome the aforementioned problem. We discuss a number of preconditions which must be met in order to allow semantic blogging and encourage users to author a semantic blog, and we present a prototype of the semiBlog editor, which was created with the purpose of user-friendly semantic blogging in mind. We argue that such a semantic blog editor should integrate tightly with a user’s desktop environment, as this would make integration of existing data into the blog as easy as possible. 1

Abstract. We study the continuous evaluation of conjunctive triple pattern queries over RDF data stored in distributed hash tables. In a continuous query scenario network nodes subscribe with long-standing queries and receive answers whenever RDF triples satisfying their queries are published. We present two novel query processing algorithms for this scenario and analyze their properties formally. Our performance goal is to have algorithms that scale to large amounts of RDF data, distribute the storage and query processing load evenly and incur as little network traffic as possible. We discuss the various performance tradeoffs that occur through a detailed experimental evaluation of the proposed algorithms. 1

The Web is experiencing an exponential growth in the use of weblogs or blogs, websites containing dated journal-style entries. Blog entries are generally organised using informally defined labels known as tags. Increasingly, tags are being proposed as a ‘grassroots ’ alternative to Semantic Web standards. We demonstrate that tags by themselves are weak at partitioning blog data. We then show how tags may contribute useful, discriminating information. Using content-based clustering, we observe that frequently occurring tags in each cluster are usually good meta-labels for the cluster concept. We then introduce the Tr score, a score based on the proportion of high-frequency tags in a cluster, and demonstrate that it is strongly correlated with cluster strength. We demonstrate how the Tr score enables the detection and removal of weak clusters. As such, the Tr score can be used as an independent means of verifying topic integrity in a cluster-based recommender system. 1

Sharing of bibliographic information is very important in a research community. SocioBiblog is a semantic blogging system that provides a decentralized environment to share bibliographic information. It uses the SWRC ontology for adding metadata about publications in blogs and aggregates publications from the social network neighborhood and coauthors of the researcher. RSS aggregation has been extended to handle embedded publication metadata in BuRST feeds. The FOAF network of the researchers is crawled to gather FOAF profiles for discovering aggregation feeds. Interoperability with other systems has been maintained by adopting standard formats. The aggregated collections may be searched and filtered flexibly by defining metadata criteria. The aggregated and filtered results can be redistributed as new feeds which can further be used by other systems. Thus, a decentralized ecosystem can be formed where each unit can publish, aggregate and redistribute information.

Information sharing can be effective with structured data. The Semantic Web is mainly aimed at structuring information by creating widely accepted ontologies. However, users have different preferences and evolving requirements. It is not practical to attempt perfect schema definitions with strict constraints. Creating structured formats should be a collaborative and evolutionary process. Social software motivates wide participation by providing easy interface. We propose a system called StYLiD for sharing a wide variety of structured information. Users freely define their own structured concepts. The system consolidates different versions defined by different users. The attributes of the different concept versions are aligned semi-automatically into a single unified view. Popular concepts gradually emerge from the concept cloud and stabilize. Concept definitions are flexible. An attribute value can take a literal or a resource URI and the suggestive range does not constrain the contributors. StYLiD generates unique dereferenceable URIs so that data items can form a linked data web. Structured data is embedded in machine readable form using RDFa. Search and browsing features are provided to utilize the structured data and consolidated concepts.

A common perception is that there are two competing visions for the future evolution of the Web: the Semantic Web and Web 2.0. A closer look, though, reveals that the core technologies and concerns of these two approaches are complementary and that each field can and must draw from the other’s strengths. We believe that future web applications will retain the Web 2.0 focus on community and usability, while drawing on Semantic Web infrastructure to facilitate mashup-like information sharing. However, there are several open issues that must be addressed before such applications can become commonplace. In this paper, we outline a semantic weblogs scenario that illustrates the potential for combining Web 2.0 and Semantic Web technologies, while highlighting the unresolved issues that impede its realization. Nevertheless, we believe that the scenario can be realized in the short-term. We point to recent progress made in resolving each of the issues as well as future research directions for each of the communities.