# A Unified Database Solution to Process BIM and GIS Data
## 1 Introduction  
Intensive scientific research on the integration of databases created within GIS (Geographic Information System) and BIM (Building Information Modeling) systems has only been conducted over the last 10 years. This is a relatively short period, considering that GIS systems date back to the 1960s and BIM systems to the beginning of the 1980s. However, in the case of BIM, the terms \"building information model\" and \"building information modeling\" (including the BIM acronym) were started to be widely used in the 1990s [1]. In 2002, Autodesk Inc. published a document titled \"Building Information Modeling\" [2], which popularized the idea of BIM.  
For many years, the objective of spatial databases created using GIS technology was to provide information about the space outside of buildings. Significant development of such technologyat the beginning of the 21 st century, new tools of quick data acquisition (e.g., laser scanning), and growing user needs resulted in the modeling of the space inside buildings as well. Elaborated standards, such as the Building Interior Space Data Model (BISDM) and, later, CityGML, facilitated and encouraged such procedures. BIM technology, targeted at other users and slightly different applications, was developing simultaneously. Technology developers, users, and scientists started to notice, however, that works turned out to be repetitive and that combining two different technologies was not simple. Many applications require continuous (in a spatial sense) access to information inside and outside of buildings (e.g., navigation applications). The significance of this need is evident, among others, in the agreement between the key companies of both branches (i.e., ESRI and Autodesk announcement on 15 November 2017 [3]) and establishing a workgroup on the ISO 19166 standard of BIM-GIS conceptual mapping (B2 GM) [4].  
From many years of practice in BIM and GIS, the authors conclude that there is a need to display and analyze data from BIM resources in GIS systems without the need to import such data repeatedly after each update of the BIM dataset. The authors' motivation was to find a solution that makes it easier to handle BIM and GIS data in a uniform environment. Developing a common data model and one format is difficult and will take some time, so this solution is dedicated to software developers, mainly for an interim period until a common standard for BIM-GIS has been developed and accepted. However, even then, there will still be a need to use previously created data resources in their original form. The existing tools and proposals presented in the literature did not solve our problem. Looking for alternative solutions, the authors developed a concept and then conducted a study that showed the possibility to implement it. This article shows the results of research in the area of connecting the world of BIM and GIS. It presents the authors' concept of using a single database for BIM and GIS systems while preserving the IFC (Industry Foundation Classes) and CityGML source data models typical for them. The research joins some other works in this field, complementing them and adding a new perspective. To prove the concept, practical tests were performed that confirmed the correctness of the assumptions and the viability of the procedure. This research was, among others, a base for a doctoral thesis [5], a project commissioned by the industry, and it was used for the development of an information system on real estate for one of the big universities.