Laws and Algebras – A Comparison Gerhard Navratil TU Vienna Institute for Geoinformation

Contents Introduction Structure of a legal system Structure of algebraic models Similarities Differences Conclusions Questions REV!GIS-Meeting Austria, 2001

Introduction Why is integration of data so difficult? Different classification Different resolution .... Different view of reality Different ontology REV!GIS-Meeting Austria, 2001

The five tiers (Frank) 0 The physical reality 1 Observable reality 2 Object world 3 Social reality 4 Cognitive agents REV!GIS-Meeting Austria, 2001

Influence of laws Laws define: Meaning of objects (When do we call a piece of land a parcel?) Procedures on objects (What must be done to subdivide a parcel?) Effects on the social reality (A boundary line in a cadastral map means ...) REV!GIS-Meeting Austria, 2001

Structure of a legal system System of rules that regulate the coexistence of the humans. The rules are enforced by the government The rules define behaviour (commandments and prohibitions) – legal norms (laws) REV!GIS-Meeting Austria, 2001

Inconsistencies Apparent inconsistencies: Derogation Real inconsistencies: Only solved by invalidating of one rule REV!GIS-Meeting Austria, 2001

Laws and computers Storing the law text in a database „Stepping on a parcel“ – 217 times in 208 laws/contracts/decisions Improvements? Phrases, synonyms, dictionary, ... REV!GIS-Meeting Austria, 2001

Expert systems Logic-based system (Lachmayer) Representation language (McCarthy) Logic + Rules + Time + Actions Agent-based system (Stamper) Functional approach (Morscher, van Kralingen, Visser) REV!GIS-Meeting Austria, 2001

Algebraic models Consist of three elements: Sets Links Axioms Algebra Stack (Stack of a, a) Links: Push, New, Pop, Top Axioms: Top (Push a s) = a ... REV!GIS-Meeting Austria, 2001

Construction of an algebraic model Definition of small pieces Combination of these pieces REV!GIS-Meeting Austria, 2001

Similarities Description of models Subdivision into small pieces Abstraction Use of axioms REV!GIS-Meeting Austria, 2001

Differences Laws use imprecise definitions (lawyers avoid explicit values) Laws contain organisational aspects Time (law is valid from) Links to other laws Enforced by somebody Real inconsistencies REV!GIS-Meeting Austria, 2001

Conclusions Many similarities Differences come from Method of modelling Differences come from Reality vs. mathematics Transition (law -> algebra) is possible REV!GIS-Meeting Austria, 2001

Questions Can we use algebras to help the user deal with legal aspects of data? Can we compare legal situations in different countries? (European Union) REV!GIS-Meeting Austria, 2001