| Article of the 
	  Month - July 2022 | 
		3D Description of Condominium Rights in Turkey: 
		Improving the Integrated Model of LADM and IFC 
		
			
			Dogus GULER and Tahsin YOMRALIOGLU, Turkey 
		
			
				|  |  | 
			
				| Dogus Guler | Tahsin Yomralioglu | 
		
		
			
			 
		
			
			This article in .pdf-format (27 pages)
		This article improves the previous conceptual model 
		that links the classes of LADM and entities of the IFC schema such that 
		it covers a detailed delineation of condominium rights. The models that 
		cover packages of LADM and the related code lists are presented. This 
		study contributes to the 3D LASs transition in Turkey by providing a 
		significant basis for IFC-based modeling of condominium rights. The 
		paper will be presented in the FIG Congress 2022 in Warsaw Poland
		In 2021 Dogus Guler received the FIG Foundation Ph.D. 
		scholarship incl a travel grant to the FIG Congress to present this 
		successfully peer reviewed paper. 
		SUMMARY
		Efficient management of land is vital for sustainable development. 
		The growing densification in the built environment however makes 
		difficult the job of land administration. In addition, the built 
		environment now contains a large number of buildings and facilities that 
		are complex and multilayered. In this sense, Land Administration Systems 
		(LASs) are of great importance to cope with emergent problems that 
		should be paid attention to for economic, social, and environmental 
		aspects. It is for this reason that three-dimensional (3D) LASs that 
		enable to unambiguously delineate the cadastral Rights, Restrictions, 
		and Responsibilities (RRRs) with their physical counterparts are a hot 
		topic. On the other hand, digitalization has gained a lot of attention 
		all around the world for improving and facilitating the processes 
		regarding both public services and different sectors such as 
		Architecture, Engineering, and Construction (AEC) industry. Considering 
		the AEC industry is one of the primal sectors that implement the 
		alterations in the built environment, there exists a close relationship 
		between this industry and the land administration sector that deals with 
		efficient management of the built environment. Today’s AEC industry is 
		performing a huge effort for the adaptation of Building Information 
		Modeling (BIM) that allows to create highly detailed models of buildings 
		and their immediate surroundings with semantically and spatially rich 
		information. Whereas the Land Administration Domain Model (LADM) 
		provides a conceptual model for land administration practices, Industry 
		Foundation Classes (IFC) enables the interoperability in terms of 
		construction/building modeling through its comprehensive schema that 
		contains a great number of entities. It is thus important to benefit 
		from the (as-built)building models for registration and depiction of 
		condominium rights in Turkey. This paper, therefore, improves the 
		previous conceptual model that links the classes of LADM and entities of 
		the IFC schema such that it covers a detailed delineation of condominium 
		rights. The models that cover packages of LADM and the related code 
		lists are presented. This study contributes to the 3D LASs transition in 
		Turkey by providing a significant basis for IFC-based modeling of 
		condominium rights. 
		1. INTRODUCTION
		Information regarding the land is highly important for countries 
		since it contributes to development in terms of various aspects such as 
		economic, cultural, legal, and social. Land registry and cadastre is the 
		paramount issue that provides and preserves this kind of information 
		completely (Yomralioglu and McLaughlin, 2017). Land administration aims 
		to benefit from the information with respect to land and water, and 
		Rights, Restrictions, and Responsibilities (RRRs) that are subject to 
		it. The importance of land administration also appears in the 
		sustainable development goals and targets, for example, goal 11, which 
		is to make cities and human settlements inclusive, safe, resilient, and 
		sustainable (United Nations, 2015). Land Administration Systems (LASs) 
		that enable the management of the ownership information with their 
		spatial components together are implemented such that they focus on 
		two-dimensional (2D) data (Kalogianni et al., 2020). However, ownerships 
		regarding underground and aboveground of land should be considered and 
		integrated into LASs. In addition, the built environment is now more 
		complex and denser than ever before globally. The challenges for the 
		registration of RRRs on buildings and facilities on the land are 
		therefore notably increasing (van Oosterom, 2018; Williamson et al., 
		2010). Evolving the LASs in a way that they have the capabilities to 
		manage, store, analyze, visualize, and disseminate ownership rights in 
		three-dimensional (3D) is considered an important solution to cope with 
		these challenges (van Oosterom et al., 2020). It is important to mention 
		that the term 3D land administration is taking the place of the 3D 
		cadastre notion because it encompasses the cadastral and land registry 
		activities as a whole (Kalogianni et al., 2020). The need for the 
		conceptual basis that facilitates the 3D land administration is 
		fulfilled with the publication of the Land Administration Domain Model 
		(LADM) Edition I as an International Organization for Standardization 
		(ISO) standard 19152 (ISO, 2012). Countries concentrate to develop their 
		models that are modified by taking as a reference the LADM (Kalogianni 
		et al., 2021). Creating a country profile of the LADM is of significance 
		since the legal basis and implementation approach with respect to land 
		administration differs within countries and jurisdictions. Condominium 
		ownership that can be formed in the units of the building that are 
		suitable to exploit independently is a special type of ownership. In the 
		context of 3D land administration, there is a need for the registration 
		and representation of condominium rights in great detail. Noteworthy to 
		mention that there are various types that can be subject to 3D land 
		administration such as tunnels, utilities, and mining; however, this 
		paper zooms in on buildings/condominiums. Spatial data standards that 
		enable to the model of physical objects in the built environment in 3D 
		are of importance to delineate the condominium rights in buildings or 
		facilities. CityGML, as an Open Geospatial Consortium (OGC) standard, 
		provides Geography Markup Language (GML)-based model for creating 3D 
		models in different themes such as building, land use, and 
		transportation (OGC, 2021). It is thus practiced by a large number of 
		scholars to model legal rights with physical counterparts within 
		buildings (see (Guler and Yomralioglu, 2021a)). In this regard, Sun et 
		al. (2019) presented an example to use the CityGML 3.0 for 3D cadastre 
		purposes. Geoinformation that constitutes the vital basis for Geographic 
		Information Systems (GIS) is exploited considerably in the land 
		administration domain and its related fields such as spatial planning 
		(Indrajit et al., 2020), urban management (Lemmen et al., 2015), and 
		real estate valuation (Kara et al., 2021, 2020; Mete et al., 2022). The 
		Architecture, Engineering, and Construction (AEC) industry intersects 
		with the land administration sector because it should be conformed to 
		decisions on how land should be used before designing and constructing a 
		completely new building or transforming an existing building. In the AEC 
		industry, Building Information Modeling (BIM) that provides to create 3D 
		models of buildings and immediate surroundings detailedly through 
		object-based modeling techniques that allow storing spatial information 
		and semantic information is replacing of traditional Computer-Aided 
		Design (CAD) (Teicholz et al., 2018). Statistics show that the use of 
		BIM has become widespread in many countries (BIMgenius, 2020; McGraw 
		Hill Construction, 2014; NBS, 2020). BIM models (BIMs) are also 
		significant for digital transformation that should be paid attention to 
		by administrations for facilitating and improving public services such 
		as building/construction permitting (Guler and Yomralioglu, 2021b; 
		Noardo et al., 2020b). Considering the as-built BIMs of buildings will 
		be existing, there is a highly promising opportunity to use these BIMs 
		for implementing 3D LASs (Broekhuizen, 2021; Meulmeester, 2019; Oldfield 
		et al., 2018, 2017, 2016; Rajabifard et al., 2019; Ramlakhan et al., 
		2021). Researchers from different countries hence focus on the modeling 
		of RRRs in the buildings and immediate surroundings using BIMs (see 
		(Guler and Yomralioglu, 2021a)). This paper aims to improve the initial 
		conceptual model (Guler and Yomralioglu, 2021a) in a way that integrates 
		LADM and Industry Foundation Classes (IFC) for thoroughly representing 
		the condominium rights in Turkey by considering legal spaces and 
		detailed building elements as well. The purpose of the model is to 
		enable the IFC models that contain and provide physical objects with the 
		required semantics for 3D representation of condominium rights. The 
		integrated model can be utilized by land registry and cadastre agencies 
		for registering and disseminating cadastral information and also by 
		architects/designers as a guideline in creating building models in a way 
		that includes legal spaces. The paper continues with the background 
		section providing information on the standards. The subsequent section 
		informs readers about the current situation in Turkey. Section 4 
		presents the integrated model in this study. The last section discusses 
		the advantages of the model in terms of 3D land administration and 
		concludes the paper.
		 
		2. BACKGROUND
		2.1 Standards
		2.1.1 Land Administration Domain Model (LADM) ISO 19152:2012 
		LADM is an ISO standard that provides a conceptual model for land 
		administration practices. The main aim of the standard is to ease the 
		transition to an efficient land administration system by benefiting from 
		the standardized model that encompasses a wide range of components 
		involving land administration. The conceptual schema of the LADM 
		includes three main packages namely Party, Administrative, Spatial Unit, 
		and one sub package of Spatial Unit as Surveying and Representation. 
		Whereas the Party package allows to model different types of parties 
		that involve land administration practices, the Administrative package 
		provides classes that can be used to detailedly represent specific 
		occasions and elements with respect to RRRs. The Spatial Unit package of 
		the schema describes how to model features that should be delineated 
		spatially. The land parcel, buildings, and infrastructure facilities are 
		examples of features that can be modeled within this package. The goal 
		of the Surveying and Representation package is to provide an efficient 
		spatial modeling concept for features in the Spatial Unit package. 
		LA_BoundaryFaceString, LA_BoundaryFace, and LA_Point are the classes 
		that are created to represent LA_SpatialUnit instances. The geometries 
		of these classes are GM_MultiCurve, GM_MultiSurface, and GM_Point 
		respectively. It is significant to note that LADM benefits from ISO 
		19107 standard that provides a spatial schema for geographic 
		information, in order to obtain geometry specifications in the 
		conceptual model. There is an ongoing activity on preparing the next 
		version of LADM. The updated version of LADM will contain new parts, 
		including Valuation Information (Part 4) and Spatial Plan Information 
		(Part 5) (ISO/TC 211, 2021), so as to cover all main components of land 
		administration. It is also aimed to improve the modeling of 3D spatial 
		units. There is additionally an ambition to provide fundamental steps 
		for the transition to the implementation (Part 6) from conceptualization 
		in the context of the revision of LADM (Kalogianni et al., 2021). 
		2.1.1 Industry Foundation Classes (IFC) ISO 16739-1:2018 
		IFC is the primary, open standard for BIM data (buildingSMART, 2022). 
		This standard is developed by buildingSMART to provide interoperability 
		regarding data exchange between different stakeholders and software in 
		construction or facility management. IFC provides a comprehensive schema 
		that enables to digitally represent the whole lifecycle of buildings and 
		facilities. IFC contains four main data schemas namely core, shared 
		element, domain-specific, and resource definition. These data schemas 
		include a great number of defined types, enumeration types, select 
		types, entities, functions, rules, property sets, quantity sets, and 
		individual properties (buildingSMART, 2022). IfcRoot is the root entity 
		in the IFC schema. IfcProject is the main entity that enables to store 
		of information about the project such as location and coordinate 
		reference system. IfcActor, as a subtype of the IfcObject entity, 
		enables to record information with regards to actors involved in a 
		project lifecycle. The actors can be a person or an organization. 
		IfcSpatialElement and IfcElement are two of the subtypes of the 
		IfcProduct entity. IfcElement has several subtypes such as 
		IfcGeographicElement, IfcDistributionElement, IfcCivilElement, and 
		IfcBuildingElement. These entities provide modeling specifications for 
		the different elements that might be in building or facility projects. 
		For example, IfcGeographicElement can be used to model different kinds 
		of features related to landscape. IfcBuildingElement is the primal 
		entity that is used to store a wide range of elements regarding 
		buildings. Doors, beams, columns, stairs, walls, windows are examples of 
		these elements. IfcSpatialElement has three subtypes as 
		IfcExternalSpatialStructureElement, IfcSpatialStructureElement, and 
		IfcSpatialZone. IfcExternalSpatialElement, as a subtype of 
		IfcExternalSpatialStructureElement, enables to model of the external 
		regions of the building site logically or physically. 
		IfcSpatialStructureElement has four subtypes namely IfcSite, 
		IfcBuilding, IfcBuildingStorey, and IfcSpace in order to define the 
		possible spatial elements for different structure levels of buildings. 
		There exists the aggregation relationship between these subtypes through 
		the IfcRelAggregates entity. The current version of IFC is IFC4 ADD2 TC1 
		however there is an ongoing activity for developing the IFC (4.3). 
		3. CURRENT SITUATION IN TURKEY
		3.1 Legislative Background
		There are several laws and legislative documents regarding land 
		administration and cadastral registration in Turkey. Turkish Civil Code 
		No.4721 (Official Gazette, 2001) is the main law that describes real 
		estate ownership. It is stated in Article 704 of this law that the 
		subjects of real estate ownership are land, independent and permanent 
		rights that are recorded on the separate pages of the land register, and 
		condominiums that are recorded to the condominium register. This article 
		manifests the condominium rights officially. The Civil Code also 
		contains a number of articles that describe a wide range of rights such 
		as superficies, usufruct, and right of way. In addition to the Civil 
		Code, Cadastre Law No.3402, Land Registry Law No.2644, and Zoning Law 
		No.3194 are the important legal references for cadastral registration. 
		Condominium Law No.634 (Official Gazette, 1965) is the main legislative 
		document that defines the RRRs with respect to condominiums. Article 1 
		of the Condominium Law states that independent ownership rights can be 
		established by the owner or joint owners on the different units such as 
		storey, apartment, office, store, cellar, and storage of a constructed 
		building that are suitable to be used independently and separately. 
		Clause 1 of Article 2 of the same law provides the definitions of the 
		main real estate, main building, condominium, annex, condominium right, 
		and condominium owner. According to the law, a condominium owner can 
		have the right to use on condominium itself and spaces that are in the 
		outside of the condominium as well. Annexes can be coal cellar, water 
		tank, garage, electric meter box, or toilet. The Condominium law also 
		states that condominium owners have jointly right to use on shared 
		facilities and spaces that are in the outside of the condominiums in 
		real estate and serve for protection and exploitation. Main walls, 
		beams, columns, curtain walls, floors, ceilings, patios, stairs, 
		elevators, and corridors are examples of shared facilities and spaces. 
		Noteworthy to mention that 2D representations might be insufficient to 
		realistically delineate the condominium rights in multilayered 
		buildings. Building permitting is another important issue for 
		condominium rights because it is mandated in the Condominium Law that 
		the condominium plans that are approved in the occupancy permit 
		procedure should be used for the registration of condominium rights 
		after the construction of the building (Guler and Yomralioglu, 2021c).
		
		3.2 Recent Advancements
		3.2.1 Academic Works
		First efforts with respect to 3D cadastre in Turkey started with 
		academic studies. There are a couple of graduate theses regarding the 
		establishment of a database for 3D cadastre (for example, (Döner, 
		2010)). Afterward, a CityGML ADE that covers the modeling and storing of 
		the condominiums is proposed with the aim of taxation (Cagdas, 2013). 
		Döner & Şirin (2020) examine the 3D cadastre approaches in Turkey in 
		terms of legal, technical, and organizational aspects. With the 
		publication of the LADM as an ISO standard, a country profile for the 
		management of 3D RRR is developed by researchers (Alkan et al., 2021). 
		In addition, an ADE for 3D cadastre purposes in Turkey is created by 
		benefiting from the integration of LADM and CityGML (Gürsoy Sürmeneli et 
		al., 2022). Scholars use CityGML 2.0 in their studies. An implementation 
		that focuses on the real estate valuation in the context of the 
		developed LADM Valuation Information Model (VIM) is also shown (Kara et 
		al., 2021). The VIM contains modeling of condominiums and their 
		attributes so as to use for valuation purposes. Guler & Yomralioglu 
		(2021b) underline that it can be exploited interrelation between digital 
		building permitting and registration of condominium rights through 
		exchanging 3D digital models such as BIMs. Celik Simsek and Uzun (2021) 
		propose to use of BIMs to model condominium rights and to find the 
		values of condominium units for calculating the land share. Recently, an 
		initial conceptual model that benefits from IFC and LADM standards to 
		delineate the condominium rights in Turkey is developed (Guler and 
		Yomralioglu, 2021a). The abovementioned studies mainly focused on the 
		use of LADM and CityGML standards for representing the vertical 
		ownership rights in Turkey even though the international research agenda 
		concentrates on the opportunity that results from benefiting the BIM/IFC 
		models recently. There is thus a strong need for a model mapping in 
		Turkey that enables obtaining the semantics regarding condominium rights 
		with their physical components by using the BIM models in the context of 
		realizing the 3D LAS. The approaches that were proposed to model the 
		property rights by means of standards such as CityGML and LADM can be 
		exploited to develop a complete model connecting LADM and IFC. 
		3.2.2 Governmental Projects and Strategies
		The 11th Development Plan, which is the current plan, contains the 
		completion of the multidimensional cadastre. It covers the publication 
		of the digital, up-to-date, and trustworthy cadastral data in order to 
		create the basis for investments that are made by public and private 
		sector organizations. The plan also underlines that ownership data will 
		be transferred to the electronic environment. “2020-2023 National Smart 
		Cities Strategy and Action Plan” is of significance because it 
		highlights that BIMs will be used in building permitting procedures. 
		This means that there will be an important opportunity to use of BIMs in 
		cadastral registration. 
		Before the 3D modeling of cadastral rights, it is aimed to create a 
		national Spatial Data Infrastructure (SDI) for Turkey. Interoperable 
		spatial data production by a wide range of public organizations is 
		highly essential for establishing and maintaining SDI. For this reason, 
		the Turkey National Geographic Information System (TNGIS) project is 
		carried out by the General Directorate of Geographic Information Systems 
		(GDoGIS). Within the project, the conceptual models and their 
		application schemas for various themes such as building, cadastre, and 
		land use are developed based on the Infrastructure for Spatial 
		Information in the European Community (INSPIRE) data specifications and 
		shared. These conceptual models and application schemas are updated in 
		specific periods. While the previous versions of the Building Theme 
		contain only 2D-based building models, the new version of this theme 
		will cover the 3D building models that are modeled as a CityGML ADE 
		based on the latest version of the CityGML standard (MoEUCC, 2021). With 
		the increasing international attention for 3D cadastre, the project 
		titled “3D Urban Models and Cadastre” is started to carry out by the 
		General Directorate of Land Registry and Cadastre (GDoLRC). Whereas one 
		aim of the project is to create 3D digital models of cities, the other 
		aim is to produce 3D building models that store and represent the 
		cadastral rights. Within the project, 2D floor plans are digitized and 
		labeled in CAD software. Afterward, these CAD files are converted to 
		CityGML 2.0 files by populating cadastral rights in the buildings.
		4. MODEL DEVELOPMENT
		In this study, a conceptual model that is developed previously is 
		improved such that it provides to model condominium rights in buildings 
		more completely. Two ISO standards namely LADM and IFC that are widely 
		accepted are used for developing the model. Figure 1 presents the Party 
		and Administrative packages of the developed model. As can be seen from 
		Figure 1, all features in the Party and Administrative packages of LADM 
		are utilized in the model. TR_Party has twelve attributes that are 
		needed in cadastral registration. It has four attribute defined by code 
		list as TR_NationalityType, TR_PartyType, TR_IDType, and 
		TR_PartyRoleType. The different parties involved in the registration of 
		condominium rights can be delineated using TR_Party. There are 
		generalization and aggregation relationships between TR_Party and TR_ 
		GroupParty classes. TR_ GroupParty can be used to model the parties that 
		represent a number of parties as a whole. TR_RRR has three subclasses 
		namely TR_Responsibility, TR_ Right, and TR_Restriction. RRRs that can 
		be subject to a condominium can be depicted using these classes. 
		TR_Mortgage that might be applied to a specific condominium has an 
		association relationship with TR_Right and a generalization relationship 
		with TR_Restriction. TR_AdministrativeSource class has four attributes 
		namely journalNumber, registrationDate, volume, and pageNumber that 
		store the necessary information for cadastral registration. It is 
		important to note that some of this information comes from the 
		non-digital registration of cadastral rights. TR_Right has an attribute 
		namely TR_RightType that provides different types such as superficies, 
		usufruct, and timeshare. TR_BAUnit, which represents the registration 
		object in the Turkish land administration system, has an attribute type 
		as TR_BAUnitType that enables to select parcel, building, or 
		condominium. Figure 2 demonstrates the code lists that are prepared for 
		attributes of Party and Administrative packages. It is possible to add 
		new property sets to IFC entities in a BIM authoring tool. Table S.1 
		itemizes the property set names, property names, property types, and 
		data types that can be used to store the attributes of the classes in 
		the Party and Administrative packages of the developed model. It is 
		important to note that the IFC file would not be complete without these 
		properties. There are several entities in the IFC schema to use in the 
		representation of the classes in the developed model. IfcActor entity 
		that expresses the persons or organizations involved in a project can be 
		used to model TR_Party. More than one IfcActor instance can be modeled 
		as IfcGroup through the IfcRelAssignsToGroup entity. In this way, 
		TR_GroupParty class can be depicted by using IfcGroup. 
		IfcDocumentInformation that is aimed to store metadata information for 
		an external document can be utilized to represent the 
		TR_AdministrativeSource class. IfcZone is an entity that enables to the 
		group of multiple spaces. It can be used to model different legal spaces 
		that belong to a condominium. Furthermore, source information of 
		cadastral registration can be linked to the registration object via the 
		IfcRelAssociatesDocument entity. 
		
			
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		Figure 1. Party and Administrative packages of the 
		developed model. 
		The different building elements can be subject to a condominium as an 
		instance of TR_BAUnit class. In this case, different building element 
		instances can be grouped using the IfcBuildingSystem entity. To model 
		the TR_RRR, TR_Responsibility, TR_Restriction, TR_Right, and TR_Mortgage 
		classes, the relationship between IfcActor, IfcDocumentInformation, 
		IfcZone, and IfcBuildingSystem can be benefited. By doing so, the 
		information about which actor is responsible for what kind of RRR can be 
		stored in the database. Whereas IfcActor can be enhanced with the 
		attributes of TR_Party, IfcGroup is suitable for being added attributes 
		of TR_GroupParty. The property set pertaining to TR_AdministrativeSource 
		can be included in IfcDocumentInformation. 
		
		Figure 2. Code lists for the Party and Administrative 
		package of the developed model. 
		Figure 3 shows the Spatial package and Surveying and Representation 
		sub package of the developed model. Figure 4 demonstrates the code lists 
		that are prepared for the Spatial package and Surveying and 
		Representation sub package of the developed model. TR_SpatialUnit is an 
		abstract class that has three subclasses namely TR_Parcel, TR_Building, 
		and TR_BuildingElement. TR_Parcel class has seven attributes that 
		provide necessary information regarding the land parcels for the 
		cadastral database. Two of them are defined by code list namely 
		TR_ParcelType and TR_LandUseType. TR_Building that has an association 
		with TR_Parcel represents the buildings that can be constructed in a 
		parcel. It has a great number of attributes that might be beneficial for 
		different applications such as urban regeneration. TR_CondominiumUnit is 
		one of the crucial classes that is utilized to condominium rights. It 
		has an aggregation relationship with TR_MainUnit, TR_Annex, and 
		TR_SharedFacility. There is a composition relationship between 
		TR_CondominiumUnit and TR_Building classes since one condominium unit 
		should be existing at least to be composed of condominium rights within 
		a building. TR_MainUnit has a good number of attributes that provides 
		information with regards to the apartment unit. As mentioned before, a 
		condominium can have different accessory parts such as a water tank, 
		coal cellar, and storage according to the Condominium Law. This is why 
		TR_Annex class has an attribute namely relatedUnitNumber in order to 
		assign the external legal spaces to the related condominium. It has also 
		the TR_AnnexType attribute type to enable the defining the particular 
		accessory types. TR_SharedFacility class has an attribute type namely 
		TR_SharedFacilityType that represents the different facilities and 
		spaces that are exploited in common, for example, elevator, corridor, 
		and swimming pool. TR_BoundaryFace has an association with 
		TR_CondominiumUnit for delineating the faces of condominium units. 
		TR_BoundaryFaceString is utilized to represent the boundaries of land 
		parcels. TR_Point has associations with TR_BoundaryFace and 
		TR_BoundaryFaceString as well. TR_BuildingElement class is used to 
		express the building elements such as walls, doors, and columns that can 
		be subject to condominium rights. There is a composition relationship 
		between TR_BuildingElement and TR_Building classes. Whereas 
		relatedUnitName and relatedUnitNumber provide information about which 
		condominium unit has the right to use on which specific building 
		element, buildingElementType is exploited to store the element type. In 
		the IFC schema, IfcBuildingElement has many subtypes to depict the 
		different building elements. 
		
			
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		Figure 3. Spatial package and Surveying and 
		Representation sub package of the developed model. 
		 
		
		Figure 4. Code lists for Spatial package and 
		Surveying and Representation sub package of the developed model. 
		 
		Figure 3 illustrates the selected entities that can be used to model 
		condominium rights pertaining to building elements. The reason for 
		showing the association between TR_CondominiumUnit and IFC entities 
		regarding these elements is that condominium units can have different 
		building elements. It is important to note that each element in a 
		building are modeled only one time as a TR_BuildingElement instance. In 
		other words, aforementioned attributes such as relatedUnitName and 
		relatedUnitNumber are exploited for RRR regarding a building element. As 
		mentioned before IfcSpatialStructureElement has four subtypes. One of 
		these subtypes is IfcSite can be used to represent land parcels. It can 
		be noted that IfcSite is defined as an area of land in the IFC schema. 
		Another subtype is the IfcBuilding entity that can be used to delineate 
		TR_Building class in the model. IfcSpace is another subtype that is 
		provided to model areal or volumetric spaces that are defined logically 
		or physically. It is feasible to model legal spaces regarding 
		condominium units. In this way, TR_MainUnit, TR_Annex, and 
		TR_SharedFacility classes can be also represented via IfcSpace. To 
		delineate all spaces that the condominium has the right to use, the 
		IfcZone entity that represents the group of spaces can be utilized. The 
		space boundaries can be represented using IfcRelSpaceBoundary that 
		allows expressing boundaries of spaces virtually or physically through 
		IfcConnectionSurfaceGeometry. In this way, it can be depicted what 
		condominium is responsible which faces of the wall. Whereas 
		IfcCartesianPoint, as a subtype of IfcPoint, is feasible for describing 
		TR_Point. IfcPolyLine can be used to model the TR_BoundaryFaceString 
		class. The property sets regarding TR_MainUnit, TR_Annex, and 
		TR_SharedFacility can be added to the IfcSpace entity. Whereas the 
		property set of TR_Parcel is suitable for being added to IfcSite, 
		IfcBuilding can be enhanced with the property sets of TR_Building. The 
		property set of TR_BuildingElement can be added to subtypes of 
		IfcBuildingElement that are included in the developed model. Table S.2 
		lists the property set names, property names, property types, and data 
		types that can be used to store the attributes of the classes in the 
		Spatial package and Surveying and Representation sub package of the 
		developed model. While IfcPropertySingleValue can be used for the 
		attributes that have a single value such as integer and string, 
		IfcPropertyEnumeratedValue is suitable for attribute types that can be 
		selected from a defined list. 
		5. DISCUSSION AND CONCLUSION
		This paper presents the improved version of the conceptual model for 
		delineating the condominium rights in Turkey. The model exploits LADM as 
		a basis for modeling the semantically and spatially necessary classes in 
		the representation of condominium rights in a realistic manner. To 
		benefit from the opportunity that results from being designed the 
		buildings using BIM, existing classes are linked to suitable entities in 
		the IFC schema to depict the condominium rights. These entities enable 
		to unambiguously model the buildings and their immediate surroundings as 
		well as the logical spaces that the condominium owner has the right to 
		use. It is important to note that the use of specific entities and 
		relationships between them might differ based on the legislative 
		regulations of the countries or administrations regarding registration 
		and definition of condominium rights. It is however shown in this paper 
		that the reuse of as-built BIMs can be highly beneficial in the 
		registration and visualization of condominium rights with their physical 
		counterparts in Turkey, as similarly demonstrated in the literature on 
		various study regions (Atazadeh et al., 2017). Statistics, governmental 
		visions, and literature together show a growing trend for digitalization 
		in the AEC industry through the efficient and widespread use of BIM. 
		This study therefore specifically focuses on the use of IFC models in 
		the depiction of condominium rights in the context of 3D land 
		administration evolvement.
		Another reason for concentrating on the use of BIMs is due to 
		challenges regarding the integration of GIS and BIM domains. Recent 
		studies point out that although there exists a vast amount of progress 
		for integration between GIS and BIM-based models through being revised 
		standards in terms of modeling approaches, the flowless transformation 
		is not at the expected level in terms of georeferencing, accuracy, and 
		consistency (Noardo et al., 2020a). Accordingly, it should be paid 
		attention to prospective conversions between GIS and BIM-based models 
		within information flow regarding the registration of condominium 
		rights. The representation of the IFC models that current or prospective 
		condominium owners can detailedly view and explore their cadastral 
		rights as 3D is a crucial part of 3D LASs because in this way the 
		probable misinterpretations that might cause problems within land 
		administration practices can be hindered. 
		As it is known, land valuation and land development are significant 
		elements of the land administration paradigm, and hence LADM Edition II 
		will cover these elements by adding two new parts namely VIM and Spatial 
		Plan Information. It is thus important to first highlight that there is 
		a huge potential to estimate values of condominium units by means of IFC 
		models that provide a large amount of information regarding attributes 
		that affect the value. A few studies (e.g., (Mete et al., 2022)) focus 
		on the likely use of IFC models for valuation and/or taxation but this 
		can be enhanced in future studies. Secondly, it is vital to investigate 
		the usability of IFC models for spatial planning purposes since the 
		urban planning checks that restrictions are specified in approved zoning 
		plans are one of the first processes within building permitting (Noardo 
		et al., 2022). In this sense, the conceptual model that can benefit from 
		the IFC schema, and related property sets can be extended by taking 
		valuation and spatial planning paradigms into account. By doing so, the 
		conceptual model that encompasses all components of 3D land 
		administration can be achieved.
		ACKNOWLEDGEMENTS
		The first author is supported by the FIG Foundation PhD Scholarship. 
		This work is supported by the Scientific Research Projects Department of 
		Istanbul Technical University (Project Number: MDK-2019-42092). 
		SUPPLEMENTARY MATERIAL
		Supplementary material can be found at:
		
		https://doi.org/10.6084/m9.figshare.19354103. 
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BIOGRAPHICAL NOTES
		Dogus Guler is a research & teaching assistant at 
		the Department of Geomatics Engineering of Istanbul Technical University 
		(ITU), Turkey. He obtained BSc and MSc degrees in 2015 and 2016, 
		respectively, and is pursuing his PhD at the same department. He 
		published several papers on 3D land administration and GIS-aided urban 
		planning. He worked on different projects that are supported by The 
		Scientific and Technological Research Council of Turkey (TUBITAK). He 
		was a visiting researcher for a year at the University of Colorado 
		Boulder, USA starting from August 2019 through International Research 
		Scholarships for Research Assistants (YUDAB) by the Turkey Council of 
		Higher Education (YOK). He is also awarded the FIG Foundation PhD 
		Scholarship in 2021. 
		Prof. Tahsin Yomralioglu graduated from the 
		Department of Surveying Engineering of Karadeniz Technical University 
		(KTU), Trabzon, Turkey, in 1985. He worked on Land Information Systems 
		at the University of New Brunswick (UNB) in Fredericton, Canada. In 
		1993, he obtained his PhD from the University of Newcastle upon Tyne, 
		England. First, he was appointed as a full-time professor at KTU in 2001 
		and then at Istanbul Technical University (ITU) in 2009. He has been 
		served as a member on various commissions and also worked as a project 
		manager and consultant in several public and private institutions. As a 
		supervisor, he supervised over 30 MScE and PhD theses. He established 
		the ITU-GeoIT graduate programme and the first national GIS R&D 
		innovation center of Turkey. He has published many scientific research 
		publications in the field of GIS, SDI, cadastre, land management, etc. 
		
		CONTACTS
		Dogus Guler  
 Department of Geomatics Engineering, Istanbul Technical 
		University 
 Maslak Campus, Civil Engineering Faculty, 34469 
 Istanbul 
		TURKEY 
 Website: 
		https://akademi.itu.edu.tr/en/gulerdo/
		
		Tahsin Yomralioglu 
 Department of Geomatics Engineering, Istanbul 
		Technical University 
 Maslak Campus, Civil Engineering Faculty, 34469 
		Istanbul 
 TURKEY 
 Website: 
		https://tahsinhoca.net/