**3.4 Completing the BIM model**

In this study, the working unit settings were set first. Then, the floor information of the sample housing project was named. The project information was entered under five headings; different types of building elements were modeled. Thus, the BIM model of the sample housing project was completed with all these procedures. The

**Figure 5.** *The representation of the BIM model of the sample housing project.*

*The Data Representations of a Building Project: BIM Model, and IFC or IFCXML Data Standard DOI: http://dx.doi.org/10.5772/intechopen.104580*

BIM model consisted of 9 floors, 8 flats, and 2 elevators. Except for the 7. Floor, which was shaped as a terrace, each floor was designed as one flat. Apart from the vertical circulation, mechanical ventilation, and installation spaces, each floor's flat plans were formed differently from the others. Finally, the representation of the sample housing project's BIM model was shown as a three-dimensional view in **Figure 5**.

As seen in **Figure 5**, the sample housing project's project documents were automatically prepared with ArchiCAD software. The project documents of the project were printed with the default publisher settings in ArchiCAD. These are:


### **3.5 Exporting the IFCXML data file**

The IFCXML data file was exported with the completion of the BIM model of the sample housing project. The Save As Type option was selected as IFCXML, and the Export option was selected as Entire Project by clicking the Save As sub-menu under the File menu in ArchiCAD. After selection, the IFCXML data file of the sample housing project was exported. The first page of the IFCXML data file consisting of approximately 5.700.000 strings is shown in **Figure 6**.

In IFCXML, the data starts with the "Ifc" prefix, just like in the IFC data representation. According to the CamelCase naming convention, the first letters are

#### **Figure 6.**

*The representation of the IFCXML data file of the sample housing project.*

capitalized, and English words are without underlines. The word must be shown in a string (< … .>). Each class has an ID number in a string. ID number is given mainly for each class, and it is specified in the string with ref = " … .". ID numbers are required to provide, clarify and verify relationships between classes. The logical relationship between IfcProject and IfcBuildingStorey of the sample housing project is shown in the IFCXML language in **Figure 7**.

A superclass matches one or more subclasses with <IfcRelAggregates> in IFCXML. The superclass is specified with <RelatingObject> and its number is always one. Therefore, it is not represented by the ex: pos = "…" number. Subclasses or classes are

*The Data Representations of a Building Project: BIM Model, and IFC or IFCXML Data Standard DOI: http://dx.doi.org/10.5772/intechopen.104580*

#### **Figure 7.**

*The representation of the IFC class, the IFC class sorting, and ID number in IFCXML.*

sorted with <RelatedObjects>. If there is more than one subclass, they are sorted by sequence number in the string like ex: pos = "0", ex: pos = "1", ex: pos = "2", etc. <RelatingObject> and <RelatedObjects> are always linked to <IfcOwnerHistory>. An <IfcRelAggregates> is used to sort and present all these relationships. An example of sorting subclasses in strings in IFC is shown in **Figure 7**.

An example of a hierarchical scheme of the IFC is shown in **Figure 7**. The abbreviations of the IFC data are given according to the IFC standard in **Figure 4**. The first equivalent of the sample housing project is IfcProject in IFC data. The logical

relationships between IfcProject - IfcSite, IfcSite - IfcBuilding, and IfcBuilding - IfcBuildingStorey are provided IfcRelAggregates. IfcRelAggregates is where the data is sorted between the two IFC types. Since this data belongs to the building project, IfcRelAggregates is always linked to the IfcOwnerHistory representing the project owner. IfcRelAggregates makes the previous IFC type's logical relationship with RelatingObject and the next IFC type with RelatedObjects.

IfcProject contains necessary information about the building project. The IfcProject number must be one because the BIM model always represents a building project number. On the contrary, it is not possible to mention IFC for situations other than this. IfcSite contains information about the site, area, or plot on which the building project will be built. The building project can be built on more than one site. Therefore, the number of IFC types can be more than one except IfcProject. IfcBuilding involves the information of the building or buildings included in the building project. On the other hand, IfcBuildingStorey gives each floor information by sorting the number of floors in the building project. Finally, the information of building elements named IfcBuildingElement is listed.

The list of building elements included in the building project is put in order in two ways:

