Michael Hausenblas

Exploiting Linked Data to Build Web Applications

Semantic Web technologies have been around for a while. However, such technologies have had little impact on the development of real-world Web applications to date. With linked data, this situation has changed dramatically in the past few months. This article shows how linked data sets can be exploited to build rich Web applications with little effort.

Linked Open Government Data [Guest editors' introduction]

Government data covers authoritative and valuable information about our society. Public access to government data, however, remains challenging largely due to the heterogeneity and complexity of the public information ecosystem which results in high costs for locating, decoding, inter-linking and reusing existing government data. Recently, linked data–based solutions have been adopted by the leading practitioners (such as Data.gov in the US and Data.gov.uk in the UK) to offer an open and incremental ecosystem that interconnects providers, consumers, and contributors of open government data. This article first reports a community consensus on the architecture of the linked open government data ecosystem, then reviews the key technologies reported by works included in this special issue, and finally concludes with three grand challenges towards opening, linking, and reusing government data.

Combining social and government open data for participatory decision-making

In the last years, several research endeavors were launched aiming at involving popular social media platforms in electronic participation. These early endeavors seem to present some essential limitations related mainly to scalability and uptake. In order to avoid these limitations, we introduce a two-phased approach for supporting participatory decision-making based on the integration and analysis of social and government open data. The proposed approach is based on the literature related to the analysis of massive amounts of social data for future events prediction. In this paper we also present a Web data driven architecture for the implementation of the proposed approach. The architecture is based on the use of linked data paradigm as a layer that will enable integration of data from different sources. We anticipate that the proposed approach will (i) allow decision makers to understand and predict public opinion and reaction about specific decisions; and (ii) enable citizens to inadvertently contribute in decision-making.

Understanding Linked Open Data as a Web-Scale Database

While Linked Open Data (LOD) has gained much attention in the recent years, requirements and the challenges concerning its usage from a database perspective are lacking. We argue that such a perspective is crucial for increasing acceptance of LOD. In this paper, we compare the characteristics and constraints of relational databases with LOD, trying to understand the latter as a Web-scale database. We propose LOD-specific requirements beyond the established database rules and highlight research challenges, aiming to combine future efforts of the database research community and the Linked Data research community in this area.

Live linked open sensor database

There are millions of sensors being deployed all over the world. Data generated by these sensors is provided in different formats and interfaces and is rarely associated with semantics that describe its meaning. The heterogeneity and lack of semantic descriptions pose a big barrier for accessing sensor data and combining it with other data sources. The Live Linked Open Sensor Database project is the first project to provide a live database of semantically enriched sensor data, where each sensor reading is extended by adding proper metadata and by linking it to resources in the Linked Open Data Cloud. Currently, the database provides information of approximately 200,000 sensors and we are currently working on expanding it to incorporate even more data sources.

Enabling multimedia metadata interoperability by defining formal semantics of MPEG-7 profiles

MPEG-7 can be used to create complex and comprehensive metadata descriptions of multimedia content. Since MPEG-7 is defined in terms of an XML schema, the semantics of its elements have no formal grounding. In addition, certain features can be described in multiple ways. MPEG-7 profiles are subsets of the standard that apply to specific application areas, which can be used to reduce this syntactic variability, but they still lack formal semantics. In this paper, we propose an approach for expressing semantics explicitly by formalizing the semantic constraints of a profile using ontologies and rules, thus enabling interoperability and automatic use for MPEG-7 based applications. We demonstrate the feasibility of the approach by implementing a validation service for a subset of the semantic constraints of the Detailed Audiovisual Profile (DAVP).

Distributed affordance: an open-world assumption for hypermedia

Hypermedia links and controls drive the Web by transforming information into affordances through which users can choose actions. However, publishers of information cannot predict all actions their users might want to perform and therefore, hypermedia can only serve as the engine of application state to the extent the users intentions align with those envisioned by the publisher. In this paper, we introduce distributed affordance, a concept and architecture that extends application state to the entire Web. It combines information inside the representation with knowledge of action providers to generate affordance from the users perspective. Unlike similar approaches such as Web Intents, distributed affordance scales both in the number of actions and the number of action providers, because it is resource-oriented instead of action-oriented. A proof-of-concept shows that distributed affordance is a feasible strategy on todays Web.

RESTful SPARQL? You name it!: aligning SPARQL with REST and resource orientation

SPARQL is the standard query language for RDF, but currently is a read-only language defined in a way similar to SQL: Queries can be formulated, are submitted to a single processing facility, which then returns a result set. In this paper, we examine the shortcomings of this approach with regard to Web architecture, and propose a path towards a language that is more in line with basic principles of Web architecture. While this work has been done in the context of a proposed update extension for SPARQL, our focus is on how to apply the principles of Representational State Transfer (REST) to SPARQL. Our claim is that a RESTful redesign of SPARQL allows the Semantic Web to evolve in a more decentralized and openly accessible way than the current RPC-style design of SPARQL.

Integrating developer-related information across open source repositories

Software developers use various software repositories in order to interact with each other or to solve software related problems. They are required to adopt an identity for each of the software repositories they wanted to use. Quite often developers are also found on different code forges developing open source projects. It is worth mentioning that the information relevant to the developers are distributed on the Web among different data sources each requires an ID and an authentication mechanism. In this paper, we propose to interlink the identities of a developer across different data sources on the Web. Further, we show the benefit of integrating developer-related information from different data sources using some real-world scenarios.

Official Statistics and the Practice of Data Fidelity

Official statistics are the “crown jewels” of a nation’s public data. They are the empirical evidence needed for policy making and economic research. Statistics offices are also among the most data-savvy organisations in government and often have a strong history of publishing data in electronic form. There is hardly any analytical task involving government data that doesn’t require some statistical data, such as population figures or economic indicators. At the same time, the handling of statistical data as Linked Data requires particular attention in order to maintain its integrity and fidelity. This chapter gives an introduction to the field of official statistics, discusses the modelling of statistical data in RDF including its integration with other kinds of government data, tools for data conversion and publishing of statistics as Linked Data, and methods for using statistical data in queries, reports, and visualisations.