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An increasing amount of public procurement data is nowadays being ported to linked data format, in view of its exploitation by government, commercial as well as non-profit subjects. One of the crucial tasks in public procurement is matchmaking demand with supply. We conceived this task as that of finding a supplier with previous successful history of contracts similar to a current call for tenders. In this paper we show how to implement a portable matchmaking service that relies solely on the capability of SPARQL 1.1. In order to show its effectiveness, the proposed service has been tested and evaluated on the RDFized versions of 2 procurement databases: the European Union's Tenders Electronic Daily and the Czech public procurement register. We evaluate several factors influencing matchmaking accuracy, including score aggregation and weighting, query expansion, contribution of additional features obtained from linked data, data quality and volume.

Abstract. Public procurement is an area that could largely benefit from linked open data technology. The respective use case of the LOD2 project covered several aspects of applying linked data on public contracts: ontological modeling of relevant concepts (Public Contracts Ontology), data extraction from existing semi-structured and structured sources, support for matchmaking the demand and supply on the procurement market, and aggregate analytics. The last two, end-user oriented, functionalities are framed by a specifically designed (prototype) web application. Public Procurement DomainAmong the various types of information produced by governmental institutions as open data, as obliged by the law, are descriptions of public contracts, both at the level of requests for tenders (RFT, also 'calls for bids' or the like)-open invitations of suppliers to respond to a defined need (usually involving precise parameters of the required product/s or service/s)-and at the level of awarded contract (revealing the identity of the contractor and the final price). The whole process is typically denoted as public/government procurement. The domain of public procurement forms a fundamental part of modern economies, as it typically accounts for tens of percents of gross domestic product.1 Consequently, due to the volume of spending flows in public procurement it is a domain where innovation can have significant impact. Open disclosure of public procurement data also improves the transparency of spending in the public sector. 2An interesting aspect of public contracts from the point of view of the semantic web is the fact that they unify two different spheres: that of public needs and that of commercial offers. They thus represent an ideal meeting place for data models, methodologies and information sources that have been (often) independently designed within the two sectors. Furthermore, the complex life cycle of 1 For example, as of 2010 it makes up for 17.3 % of the EU's GDP [8]. 2 See, e.g., http://stopsecretcontracts.org/.