# Integration of BIM and GIS for the Digitization of the Built Environment
## 3 Methodology
### Open-Source Methodology  
In the field of information technology, the term \"OS\" refers to a specific type of software that is released under certain licenses that allow access to the source code for potential developers. During the 1980s, as the computer industry underwent a period of rapid expansion, there was a shift from a free approach to restrictions imposed by proprietary software, with all its implications. The advent of the OS concept in 1998 represented an attempt to reverse the prevailing trend by promoting the free circulation of program information. Access to the source code enables programmers and advanced users to modify software according to their specific requirements. This feature serves to distinguish OS programs from freeware programs, which, although freely usable, remain the property of their creators and cannot be modified by others. The OS approach should therefore be considered not only as an alternative to avoid the purchase of proprietary software, but also as a choice aimed at fostering the free circulation of information and the exchange of ideas, thereby promoting inclusive and participative growth. In this context, the Italian Ministry for Innovation and Technology issued a directive in December 2003 inviting public administrations to consider the use of OSS as a new way of development and diffusion. This was done with the aim of promoting interoperability between public administration IT systems and preventing dependence on a single supplier and/or proprietary technology [58]. In the building production sector, it is of paramount importance that the various stakeholders collaborate and share information, utilizing cloud platforms, in order to ensure the success of projects throughout the construction lifecycle. Consequently, the use of common standards and protocols is of paramount importance. These tools provide a common basis for communication and data exchange, thereby enhancing interoperabilitybetween the various systems and applications employed in the construction sector. The collective endeavors of the principal actors in the sector have resulted in the development of software platforms and tools such as the IFC [59] and the Construction Operations Building Information Exchange (COBie) [60]. The IFC represents an open standard file format utilized for the exchange of BIM information between disparate software applications. It provides a standard digital description of the built environment, including buildings and building infrastructure. Such platforms permit the exchange of parametric three-dimensional models, design data and information on the geometry and properties of building components in an interoperable manner. The IFC (which was originally created as an open and interoperable interchange file format) is able to fulfil various needs, but it should be noted that it represents a specific data structure. The IFC schema may be conceptualized as a \"storage system\" for organizing and transporting digital data, which must be usable by several operators over a fairly long period of time. It follows that the IFC format is accessible to any user, regardless of the software employed and its version. In addition to the aforementioned preservation requirements, the storage of the IFC file must also ensure that it is easily accessible for consultation. This necessitates the structured storage of the model data and the identification of the models themselves, according to their intended use and function. In summary, it is possible to state the following points:  
* IFC models contain geometric and non-geometric entities;
* IFC models contain the geometry of the building and the data associated with its elements;
* Exporting the data of a project carried out using the BIM methodology by means of an IFC file transfers the data from one application to another;
* The IFC format is open, free, and contains a large amount of information.