Requirements Levels

Variables requirements levels from IFC/CItyGML3.0- based LoIN :
3D variables can be obtained from BIM, CIM or other data external sources. For each data source, integration workflows should be developed to retrieve the precise information. For each scale of the analysis (building or city or both), the degree of granularity should consider the smallest part/element of the model that holds significant information for simulating the property value (Biljecki et al, 2015). For example, indoor sunlight requires attributes at the level of IFC (ifcspace) and the value is stored in a CityGML class (Room).

Figure 3: Variables specifications based LoIN - variables examples: Indoor (e.g., Property cost), Interactive (e.g., Indoor daylight, Sunlight exposure) and Outdoor (e.g., View quality) (italic: spatial elements; bold: non-spatial elements)( El Yamani et al. 2021).
In the following, we propose two information specification levels for property valuation, named LoIN-1 and LoIN-2, for property valuation, which are described below.

• LoIN-1 :
The specifications at this stage focus on the fundamental and generic entities and attributes that are necessary in any initial step for property valuation simulation and modeling. One such example is the Property Unit, which has boundaries that are required for defining other variables. The Property Unit can be defined as a boundary of space, volume, or building elements, and it can be obtained from either the IFC building elements or the IfcSpace (see this link for tables details).

• LoIN-2 :
At the second level of the approach, detailed information is obtained for each variable by analyzing the input/output specifications of entities, attributes/Pset_properties, or relationships. The IFC/CityGML schema is used to select relevant classes or subclasses to retrieve the required varia-bles.
The Pset_properties, which are attributes generated during the building modeling process according to IFC schema specifications, are used to provide more comprehensive information for each varia-ble. For instance, indoor daylight is modeled as a Pset_properties, which is created during the BIM modeling stage and is not exported as IFC parameters by default. This approach allows for a more granular and accurate simulation of 3D property valuation variables.(see this link for tables de-tails ).