An object-oriented, formal approach to the design of cadastral systems

Modeling GIS or applications of GIS with object-oriented tools is difficult for the practitioners. In this case study the deed registration system is studied using formal, object-oriented tools. The formal modeling approach also shows the differences and the similarities in the deed registration system used in the USA and the property registration system in Europe. A formal modeling approach will demonstrate the functional similarities, caused by the similar social demands, and the differences owing to different historic developments. It is found that the models are comparable and the rules are fundamentally similar. The checks for a valid transfer of ownership are quite similar, but the time of checking is different. A Continental title registration system checks documents when they are received, whereas the US registers first without checking and only later the validity is checked by a prospective buyer's lawyer. Several results can be generalized to other administrative GIS applications: The question of identity plays a primary role and several types of identities may be hierarchically nested. Administrative rules are less strict than database logic on what constitutes an entity or an identifier (the unique name assumption is maintained only within a context). Administrative time for a registry is a simple ordered scale. These results are of practical importance for the design of GIS software which includes a land ownership layer and should be applicable in countries with different property registration systems. It shows the designers of property registration software what can be built into a general, widely usable system and when adaptation to local rules is necessary. The study was motivated by efforts to design a property registration system for a reform country in Eastern Europe. In this situation, one has to understand how social demands and legal rules relate to the technical solution. To start with a formal model is the best way to achieve this.