Legislation as a complex network: Modelling and analysis of European Union legal sources Marios KONIARIS a,1 , Ioannis ANAGNOSTOPOULOS b and Yannis VASSILIOU a a KDBSL Lab, School of ECE, Nat. Tech. Univ. of Athens, Greece b Dep of CS & Biomedical Inf., Univ. of Thessaly, Greece Abstract. Legislators, designers of legal information systems, as well as citizens face often problems due to the interdependence of the laws and the growing number of references needed to interpret them. Quantifying this complexity is not an easy task. In this paper, we introduce the ”Legislation Network” as a novel approach to address related problems. We have collected an extensive data set of a more than 60-year old legislation corpus, as published in the Official Journal of the European Union, and we further analysed it as a complex network, thus gaining insight into its topological structure. Results are quite promising, showing that our approach can lead towards an enhanced explanation in respect to the structure and evolution of legislation properties. Keywords. Legal Digital Libraries, Network Analysis, Complex networks, Legislation, Knowledge extraction Introduction Legislation is a large collection of different normative documents, which keeps grow- ing and changing with time. As legislation increases in size and complexity, finding a relevant norm may be a challenging task even for experts. Furthermore, the process of drawing up a consistent and coherent legislation frame- work becomes a more and more challenging task. Drafting of new and amending exist- ing legislation are very complicated processes. As a result authorities at European, na- tional and local level, often consider proposed regulations for months or years before they finally become effective. Thus, it is critical to firstly quantify the legal complexity and then work towards the provision of a model that will assist us to reveal the emergent dependencies among the legislation corpus. Typically, legal documents refer to authoritative documents and sources (e.g. most commonly regulations, treaties, court decisions, and statutes). Computer scientists and legal experts have used citation analysis methods, in order to construct case law cita- tion networks, as well as to further model and quantify the complexity of the legislation corpus [5,13,11,17]. 1 This is an author’s copy version. The final publication is available at http://ebooks.iospress.nl/ volumearticle/38450