Master Thesis Kick-Off: Extraction of Legal Term Definitions from German Statutory Texts and Court Decisions Fabian Thomas, 08.07.2019

Key Facts Title: Extraction of Legal Term Definitions from German Statutory Texts and Court Decisions Author: Fabian Thomas Advisor: M.Sc. Ingo Glaser Supervisor: Prof. Dr. Florian Matthes Start: July 1st, 2019 End: December 30th, 2019 190708 Thomas MA Kick-Off Presentation © sebis

Outline Legal theory background Motivation Approach Research Questions How can legal definitions be identified from statutory texts and court decisions using rule-based approaches? How can the definitional relevance of legal statements in statutory texts and court decisions be determined? Timetable 190708 Thomas MA Kick-Off Presentation © sebis

Legal theory background Subsumption Description of Facts Implies? Legal consequence Imply Directs search for Legal norms Consist of Legal norms Consist of Interpretation Legal norms Legal norms Characteristics Legal terms 190708 Thomas MA Kick-Off Presentation © sebis

Legal theory background Definite and indefinite legal terms Definite Defined by legal definitions in statutory texts Indefinite Not explicitly defined Leave (purposely) much more room for interpretation May be defined by laws of nature or common sense Often depend on further specification by court decisions Continuous spectrum between definite and indefinite terms Terms most often lack a clear legal definition Still specified to some extent inside the statutory texts Other sources of information for term interpretation 190708 Thomas MA Kick-Off Presentation © sebis

Legal theory background Definition specifications Both definite and indefinite legal terms are often further specified in other norms or court decisions Examples: Legal definition (§ 2 LandesbauO NRW): … (2) Gebäude sind selbständig benutzbare, überdeckte bauliche Anlagen, die von Menschen betreten werden können und geeignet oder bestimmt sind, dem Schutz von Menschen, Tieren oder Sachen zu dienen. … Specification from a court decision (BFH, March 25th 1977): ... (1) Bewertungsrechtlich ist ein Bauwerk als Gebäude anzusehen, wenn es […] fest mit dem Grund und Boden verbunden ist. (2) Das ist der Fall, wenn […] Fundamente vorhanden sind, das Bauwerk auf diese gegründet und dadurch mit dem Boden verankert ist. …. 190708 Thomas MA Kick-Off Presentation © sebis

Legal theory background Sources of information for legal term interpretation Meaning in common language Purpose of the law History of the law‘s origins Legal definitions Auxiliary norms which elaborate on the legal definition General use of the term in this and other legal contexts Interpretation of the term in court decisions Focus of this work 190708 Thomas MA Kick-Off Presentation © sebis

Motivation User perspective To apply legal norms a lawyer or judge has to … Identify all contained legal terms Find legal definitions for every term Find all norms which elaborate on these legal definitions or are otherwise relevant for understanding Get an overview of the use of every term inside the law and other laws Find definitions and specifications in court decisions 190708 Thomas MA Kick-Off Presentation © sebis

Motivation Problems with legal term research Legal definitions are realised in various ways Elaborating information lacks a consistent structure Legal definitions and other relevant norms may be scattered across the law text Scope of a legal definition may span across different laws and is hard to overview Information contained in only one norm or court decision may be deciding for a legal case 190708 Thomas MA Kick-Off Presentation © sebis

Approach Solution steps Extract legal definitions from statutory texts and court decisions Determine the definition scope (statutory texts and related court decisions) Find all legal statements containing the term to provide a full overview and assign them to the respective definition scope Rank legal statements by their definitional relevance Extracted definitions and ranked term instances can be used to Automatically annotate the legal texts with relevant information Summarize and structure legal definitions in a consistent way Improve search results 190708 Thomas MA Kick-Off Presentation © sebis

Term instance retrieval Approach System conception Text Text Indexing Indexed DB Statutory texts Court decisions Data Analysis Annotation Analysis Training data Rules Rules Definition extraction (RQ1) Term instance retrieval Definite l.t. Ranking model Legal definitions Indefinite l.t. Term instances + context Ranked term instances User Term instance ranking (RQ2) 190708 Thomas MA Kick-Off Presentation © sebis

Research Questions RQ1: How can definitions be identified using rule-based approaches? Structure of legal definitions Most legal definitions follow a limited set of rules, e.g.: Approach Regular expressions and grammatical rules Building upon previous work of rule-based definition extraction Exceptions to the defined rules will be covered in RQ2 Bracket terms Die Ehegatten sollen einen gemeinsamen Familiennamen (Ehenamen) bestimmen. Copula structures Sachen im Sinne des Gesetzes sind nur körperliche Gegenstände. Definitional lists Im Sinne dieses Gesetzes sind 1.    Pflanzenschutz: … […] 3.    Pflanzen: … 190708 Thomas MA Kick-Off Presentation © sebis

Research Questions RQ1: How can definitions be identified using rule-based approaches? Determining definition scope Legal definitions can be valid inside A single law Multiple laws A whole legal domain Legal definitions can be explicitly “borrowed” from another law by referencing the definition Solution approaches: Identifying signal key words (e.g. “im Sinne dieses Gesetzes”) Analysing norm reference structure 190708 Thomas MA Kick-Off Presentation © sebis

Research Questions RQ1: How can definitions be identified using rule-based approaches? Sub-Questions RQ1.1: What different types of legal definitions exist? RQ1.2: What types of legal definitions are suitable for rule-based extraction? RQ1.3: How effective are rule-based approaches for definition extraction applied to the German federal statutory and court decision corpus? RQ1.4: What are suitable methods for determining the scope of legal definitions? 190708 Thomas MA Kick-Off Presentation © sebis

Research Questions RQ2: How can the definitional relevance of legal statements be determined? What is definitional relevance? Term instances can be especially relevant if the containing legal statement … falls out of the rule-based definition extraction, but has definitional characteristics explictly extends or limits an existing definition is dependent of another norm for its validity has a generalization level which allows for application in many legal cases 190708 Thomas MA Kick-Off Presentation © sebis

Research Questions RQ2: How can the definitional relevance of legal statements be determined? Existing work Court decisions Extensive formalization and categorization schemes for definitions and elaborating statements Definition of a large set of linguistic features which indicate definitions Classification (Naive Bayes, kNN, NBTree etc.) and ranking using a regression model Statutory texts Classification schemes for functional types of legal norms Semantic classification of legal norm sentences (duty, prohibition, definition etc.) using linguistic feature extraction and ML models 190708 Thomas MA Kick-Off Presentation © sebis

Research Questions RQ2: How can the definitional relevance of legal statements be determined? Sub-Questions RQ2.2: How can elaborating legal statements in statutory texts and court decisions be categorized? RQ2.3: What are suitable methods for determining definitional relevance of a legal statement? RQ2.4: How can existing ranking methods for legal statements in court decisions be improved? RQ2.5: How effective are the proposed ranking approaches applied to the German federal statutory corpus? 190708 Thomas MA Kick-Off Presentation © sebis

Design & Implementation Timeline Jun Jul Aug Sep Oct Nov Dec Literature Research Design & Implementation Evaluation Writing Review Start Date Kickoff Submission 190708 Thomas MA Kick-Off Presentation © sebis

Fabian Thomas 17132 matthes@in.tum.de

References Glaser, I., Scepankova, E., & Matthes, F. (2018). Classifying semantic types of legal sentences: Portability of machine learning models. Frontiers in Artificial Intelligence and Applications, 313, 61–70. https://doi.org/10.3233/978-1-61499-935-5-61 Waltl, B., Muhr, J., Glaser, I., Bonczek, G., Scepankova, E., & Matthes, F. (2017). Classifying legal norms with active machine learning. Frontiers in Artificial Intelligence and Applications, 302, 11–20. https://doi.org/10.3233/978-1-61499-838-9-11 Waltl, B., Bonczek, G., Scepankova, E., & Matthes, F. (2019). Semantic types of legal norms in German laws: classification and analysis using local linear explanations. Artificial Intelligence and Law, 27(1), 43–71. https://doi.org/10.1007/s10506-018-9228-y Waltl, B., Matthes, F., Waltl, T., & Grass, T. (2016). LEXIA: a data science environment for Semantic analysis of German legal texts. Walter, S. (2010). Definitionsextraktion aus Urteilstexten. 190708 Thomas MA Kick-Off Presentation © sebis