integrating building information models with ...

INTEGRATING BUILDING INFORMATION MODELS WITH GEOGRAPHIC INFORMATION SYSTEMS: TECHNOLOGY REVIEW Umit Isikdag1, Prof. Ghassan Aouad1, Dr. Jason Underwood1, Dr. Nigel M Trodd2 1. School of Construction and Property Management University of Salford, Salford, M7 9NU E-mail: [email protected] 2. School of Science and Environment, Coventry University Abstract: The nature of the construction industry is very much fragmented and the concept of interoperability and integrated model based engineering is now becoming an industrial need, to address the difficulties of information exchange at all stages and between all parties involved in the construction life cycle. The International Alliance for Interpretability’s Industry Foundation Classes(IFC) (common building information model standard) is now maturing in supporting the various phases of the construction life cycle. In addition, the industry is beginning to use geographical information systems (GIS) in various stages of the construction life cycle. This paper presents the research that aims to contribute to the efforts of bridging the gap between integrated building information model based systems and GIS by investigating the approaches and methods of integration. This paper explains the first phase of the research, which is focused on a technology review to establish the state of art technology of both these technologies. The general concepts of building information modelling, types of IFC based systems architectures, the data management approaches in geographical information systems is investigated along with the potential and proposal for the integration of building information models with GIS is presented in this paper. Keywords: Construction Integration, GIS, IAI, IFC, Building Information Modelling 1. INTRODUCTION The construction industry is composed of many disciplines. Each of these disciplines has evolved independently, with its own unique terminology, technology, and way of expressing and communicating information. This fragmented nature of the industry has caused many problems relating to information exchange. The industry used paper based drawings and neutral file formats or file types of several systems (which became de facto standards) to overcome the problem of information exchange. In the mid 1980’s a new initiative was set up by International Standards Organisation, to standardize the efforts of exchanging information throughout the product life cycle. This initiative has developed a standard (ISO10303), called -Industrial Automation Systems Product Data Representation and Exchange-also known as Standard for the Exchange of Product Model Data(STEP). In the early 1990’s the construction industry started to develop STEP compliant platform neutral and interoperable information models for the exchange of construction information. Having developed some successful and unsuccessful information models, a group of software vendors founded the International Alliance for Interoperability to develop a commonly agreed STEP compliant model for the industry. The agreed model is called the Industry Foundation Classes and is now maturing. Model based information exchange is gaining importance to overcome increasing problems of information exchange.

Geographical Information Systems(which link the geographical information with descriptive information), are used in urban planning and management also in various stages of construction life cycle .GISs contain rich information about the entities in its intelligent maps, however the building layers of a geographical information system are not information rich. The construction/building related data is not sufficient enough for a detailed GIS analysis and also for effective GIS support for construction activities.3D visualisation capability of GISs is also limited for buildings. The overall research aims to investigate the ways and methods of integration between building information models and geographical information systems. The objectives of the research include, understanding the business drivers for integration, and the problems and strengths of integration, and to investigate the methods & possibilities for integration and implementation of a purposed integration solution. The technology review stage was one of the beginning stages of the research. This paper presents the initial technology review of this research and also discusses the need for a possible implementation. 2. INFORMATION MODELLING AND THE CONSTRUCTION INDUSTRY 2.1 What is an information model An information model can be described as a formal description of types of ideas, facts and processes which together form a model of a portion interest of the real world. Schenk and Wilson (1994) explain that information modelling is an outgrowth of data modelling. Data modelling is concerned with specifying the appearance and structure within a computer system of the data which represents particular types of information. Information modelling has a goal of describing information so that the representative data could be computer processed. Information modelling has connections with both data modelling and some aspects of the design of the object oriented systems. Table 2.1 shows the different uses of both terminologies. Table 2.1 Different usage of terminologies in Information and Data Modelling Information Modelling Data Modelling (Conceptual Level) (Logical Level) Generic Entity Entity / Class Particular Instance Occurrence / Object 2.2 The importance of information modelling in the construction industry The concept of information modelling is becoming an important issue for the construction industry to overcome several barriers of information exchange. In the construction industry there are number of different organizations, acting within their own distinct set of rules involved in construction projects. These different organizations use different type of software in various phases of the construction life cycle. This fragmented nature of the industry causes diversity of software in use, which prevents effective information exchange between all parties. An example to this barrier is problems faced during extraction of data from a CAD system for input into an analysis application (such as structural or thermal) and loading the output data back to the CAD system. A second barrier arises with the development of a new information system which uses different data to represent the same information as the previous system (providing some new functions and types of information).The information created by the new system can not be read and processed by the other system.

Deriving bills of material automatically from construction drawings is not very effective without the use of information models. Information models also facilitate the effective management of construction information through the project lifecycle in 4(3D+time), 5(4D+cost) or N dimensions. The ongoing nD modelling research project appears as an effort to examine these different dimensions. 2.3 Previous work in construction information modelling Information models in construction industry are usually defined in ISO-10303 (STEP) compliant modelling language EXPRESS. Eastman (1999) explains that the structure of STEP is composed of five classes of tools. These tools are description methods, integrated resources, application protocols, implementation methods and conformance tests. The description methods are the information modelling languages (EXPRESS, NIAM, EXPRESS-G and IDEF1x) that define other tools. Integrated resources are re-usable subcomponents that are used in the definition of application protocols. Application protocols are information models defined in particular area.(e.g. Automotive, Ship Building, Electricity or AEC). Implementation methods define the physical file structures of the information models and also define the access interfaces to the physical files. A conformance test assesses the implementation and confirms that the STEP languages and tools have been properly used and interpreted. Schenk (1998) explains that the EXPRESS language rapidly became the language of choice for the formal specification of many data exchange standards, in the electronics, aircraft, mechanical, automotive engineering as well as in the construction industry. 2.3.1 A brief history of construction information modelling Eastman (1999) indicates that, in the early days of CAD systems, the exchange of construction related data in the industry has been conducted through the exchange of drawings in neutral file formats. The neutral data formats had become a need as different CAD vendors appeared. Most common neutral file formats include Autodesk’s DXF (which has become today’s de facto data exchange format for 2D) and IGES. In the early 1990’s the data exchange structures evolved from neutral file formats to ISO10303 compliant information models, i.e. developed using EXPRESS modelling language. In 1990 a number of researchers proposed a new model, the ‘integration reference model architecture’(IRMA).This was followed by the ATLAS project, which focused on the development, implementation, demonstration and dissemination of semantical project information models, taking the IRMA results as its starting point. The model architecture developed under ATLAS, supported project information sharing, storing and exchange on four different layers. After the completion of the ATLAS project, the STEP AEC group initiated its own Application Protocol (AP) planning project, which, resulted in the plan to develop a layered model architecture for construction industry. The core model hierarchy researched in ATLAS formed the basis of the plan. Below an AEC core model, five sectors developed a ‘sector core’ model surrounded by ‘discipline’ models. Each discipline model contained a ‘discipline core’ model. This model is called the Building Construction Core Model (BCCM). As the proposed ISO10303 Part 106 standard in the STEP initiative, BCCM was an international effort to define a ‘lowest common denominator’ information model for the building industry. In addition to its main objective for enabling information exchange across different AEC disciplines, BCCM is intended to facilitate the creation of consistent Application Reference Models (ARMs) and provide the basis for the interoperability of APs in the industry.

Development projects for discipline models for HVAC, steel structures, and architecture followed shortly thereafter. 2.3.2 AEC related information models The original aim of ISO10303 initiative was to define middle level “application domains” that address data exchange needs. Eastman (1999) defines these middle level “application domains” as building aspect models. Building aspect models include CIMSTEEL, COMBINE and STEP Part 225. The CIMsteel project was a major initiative with the goal of improving efficiency and effectiveness of the European constructional steelwork industry. The focus of CIMsteel was the application of Computer Integrated Manufacturing techniques to steel fabrication. The project ended in 1998.The resulting data standards are known as CIS (CIMsteel Integration Standards).The CIS version 2(CIS/2) was released in 1999. The main changes in version 2 included covering more conditions encountered in structural steel design and fabrication, and attaining closer consistency with the ISO-STEP exchange models and practices, including adoption of several ISO-STEP Integrated Resource libraries. COMBINE was another major development project funded by EU. It had two phases Phase 1 which ran between 1990-1992 and Phase 2 which ran from 1993-1995.The project was not focused on developing new IT capabilities, but rather on demonstrating the potential of existing capabilities. The goal was to combine a number of state of art energy and HVAC consultant’s tools in an integrated environment, to demonstrate efficiency improvements in the design process and related energy efficiency improvements of the planned buildings that these new systems will enable. Zamanian and Pittman (1999) mentioned some information models and projects developed between 1990-1999, for the AEC domain .The important ones were RATAS,EDM and SME. The RATAS building product model was developed as part of a large effort by the Technical Research Centre of Finland (VTT) to establish a standard CAD environment for the Finnish national construction industry. The organization of entities in this model is based on a network decomposition scheme and is modelled via an abstraction hierarchy with five levels: 1 building, 2 system, 3 sub-system, 4 part, and 5 detail. Class hierarchies with single and multiple inheritance mechanisms are supported for the objects of the RATAS model. The RATAS model used the view concept to limit the data, (i.e., objects, relations, and attributes, considered for a specific discipline or a design stage.) Examples of views include drawings and specification documents produced for various design or analysis applications. The Engineering Data Model (EDM) can be considered as the most formal data model for the representation of engineering information. The primary objectives of this work were representation of function as well as the form and physical properties of the product and provide support for multiple levels of abstraction and for the various phases of the product lifecycle In contrast to many other AEC information models that are first defined statically and then populated, semantic modelling extension (SME) is referred as a ‘virtual product model’ since it arises dynamically as a result of the user’s actions while designing a building. This approach in turn provides flexibility to generate information models for emerging and nonroutine conceptual designs, which can in turn be used as the basis for more rigid models used in later phases of the project. SME is intended to capture functional and behavioural information about the building components in addition to the traditional geometry centred,

physical information, thus providing richer content for information sharing by various AEC disciplines across different phases of a project.

2.3.3 Other studies on construction information modelling Other studies include Stuurstraat and Tolman (1999) who carried out a research project to develop a system that allows its users, designers and engineers to quickly instantiate a product model that describes a building in global terms. The schema that describes the global building model contains entities such as: mass element, type_of_facade, type of installation, type_of_structure, etc. The system utilizes Express-G (a graphical ISO-STEP information modelling language) and Pmshell, (a R&D tool that supports the generation of various database formats like SQL and SDAI), and is able to transform an Express model into C++. As an additional aspect of the research, a number of simple rule-based experts systems are being developed. Arnold et al (1999) built an intermediate model framework IBES(Internet Broker for Engineering Services).It defines data types and provides rule-based inference to define an intermediate model that translates engineering content between a CAD/CAE model and a software application for component analysis. The intermediate model furnishes a common vocabulary to describe information from distinct knowledge sources, a product model, and a software application. There are also several ongoing and completed research projects focused on creating integrated construction environments by using information models. The major ones include BLIS (focused on effective implementation of information models), DIVERCITY (research on creating a toolkit for construction briefing design and management), ISTforCE (focused on creating a concurrent engineering service platform and a logistics system), GALLICON(research on enabling integrated information exchange water and housing industry projects), WISPER (focused on creating a distributed computer integrated environment to management of information, at the component level, through a single database ) and the ongoing nD Modelling Project. 2.4 International Alliance for Interoperability and Industry Foundation Classes In 1994, 12 US based companies joined together to examine the potential for interoperability in the AEC area. The first effort of this community was based on ARX development system for AutoCAD Release 13.The organisations realised after the first effort that there was economic benefit to be gained from this interoperability of software. The participants then decided to develop a vendor neutral standard for software interoperability and in October 1995, and they established the International Alliance for Interoperability (IAI).The first version of the IAI’s vendor neutral standard (called IFCs) is released in 1997. The Industry Foundation Classes(IFCs) are a collection of entities(classes), that form an information model. The IFC are defined using ISO10303 EXPRESS conceptual modeling language. The objects defined by IFC allow AEC/FM professionals to share a project model, and each profession to define its own view of the objects contained in that model. This leads to improved efficiency through the project lifecycle, i.e. cost estimating, building services design, construction, and facility management. IFC enables interoperability among AEC/FM software applications. Software developers can use IFCs to create applications that use universal AEC/FM objects based on the IFC specification. Applications that support IFC allow members of a project team to share project data in an electronic format. This ensures that the data is consistent and coordinated.

Furthermore, this shared data can continue to evolve after design, through construction, and occupation of the building. Information generated by the project design team will be available in intelligent, electronic format to the building construction team through their IFC compliant software and to building facilities managers through their IFC compliant software ,(IAI,2003) 3. GEOGRAPHIC INFORMATION SYSTEMS AND THE CONSTRUCTION INDUSTRY 3.1 Fundamental concepts of geographic information systems There are many definitions for geographical information systems, Environmental Systems Research Institute white paper, (2002) defines GIS as computer software that links geographic information (where things are) with descriptive information (what things are). Unlike a flat paper map, a GIS can present many layers of different geographic information. Each layer in a geographic information system represents a particular theme or feature of the map. (i.e. Roads are placed in one layer and parcels in another). These layers can be laid on top of one another, creating a stack of information about the same geographic area. Each layer can be turned on and off, to control the amount of information about an area. GISs are used for many AEC related disciplines such as Pipeline, Surveying, Landscape Architecture, Water and Wastewater Management 3.2 Representation of data in geographic information systems. In geographic information systems the geographic data is represented with several different data models. In this section several different representations of geographic data and data models used in GIS will be explained. 3.2.1 Raster Data Model Raster data is usually stored as an array of grid values, with metadata about the array held in a file header. Typical metadata include the geographic coordinate of the upper-left corner of the grid, the cell size, and the number of row and column elements. The array itself is usually stored as a compressed file or as a record in a database management system. Two basic raster encoding algorithms are run-length encoding, which involves encoding row cells that have the same value, with a pair of values indicating the number of cells with the same value, and the actual value, and block encoding, which is like a two-dimensional version of run-length encoding in which the array is defined as a series of square blocks of the largest size possible. Data encoded using the raster data model are particularly useful as a backdrop map display because they look like conventional maps and can communicate a lot of information quickly. They are also widely used for analytical applications such as disease dispersion modelling, surface water flow analysis, and store location modelling. 3.2.2 Vector Data Representation In the vector data representation each object in the real world is first classified into a geometric type: point, line, or polygon. Geographic entities encoded using the vector data models are often called features. Features of the same geometric type (point,line,etc) are called feature classes and stored in several forms: a) Feature geometries in a binary file and attributes in a DBMS table b) Feature geometries in a binary file and attributes and topology in a DBMS table

c) Feature geometries ,topology and attributes in a DBMS table with a special field for geometric shape. GISs commonly deal with two types of features: simple and topologic. Simple feature datasets are useful in GIS applications because they are easy to create and store. The structure of simple feature line and polygon datasets is sometimes called spaghetti because ,lines and polygons can overlap and there are no relationships between any of the objects Topologic features are essentially simple features structured using topologic rules. Longley et al, (2001) indicates that topological structuring of line layers forces all line ends that are within a userdefined distance to be snapped together so that they are given exactly the same coordinate value. A node is placed wherever the ends of lines meet. In a topologically structured polygon layer, each polygon is defined as a collection of lines, that in turn are made up of an ordered list of coordinates (vertices). The list of lines that make up a polygon is stored with the geometry data. Storing common boundaries between adjacent polygons avoids the potential problems of gaps (slivers) or overlaps between adjacent polygons. There are several data models representing the data in the vector form. 3.2.2.1 Vector Topologic Feature Data Model (Geo-Relational Model) The term geo-relational derives from the way the topologic feature model is implemented. In this model, the geometry is stored in regular computer (binary) files and associated attribute information is held in relational database management system tables. The GIS software maintains the intimate linkage between the geometry, topology, and attribute information. 3.2.2.2 Network Data Model The network data model is a special type of vector topologic feature data model. Networks are modelled as points (for example, street intersections, fuses, switches, water valves, and the confluence of stream reaches: usually referred to as nodes in topologic models), and lines (for example: streets, transmission lines, pipes, and stream reaches). Network topologic relationships define how lines connect with each other at nodes. It is also useful to define rules about how flows can move through a network. There are two types of networks: radial and looped. In radial or tree networks flow always has an upstream and downstream direction. Stream and storm drainage systems are examples of radial networks. In looped networks self-intersections are common occurrences. Water distribution networks are looped by design to ensure that service interruptions affect the fewest customers. 3.2.2.4 Triangulated Irregular Network (TIN) Data Model Triangulated irregular networks (TINs) are used to create and represent 3D surfaces in geographic information systems. The TIN structure represents a surface as contiguous nonoverlapping triangular elements. A TIN is created from a set of mass points, that is, points with x, y, and z coordinate values. Longley et al., (2001) explains TIN surfaces are frequently created by performing what is called, a Delaunay triangulation of the points to create a series of triangular areas (also called faces), that touch their neighbours at each edge. As with other topologic data structures, information about a TIN may be conveniently stored in a file or database table.

3.2.3 Object Data Model The central focus of an object data model is the collection of geographic objects and the relationships between the objects. Each geographic object is an integrated package of geometry, properties, and methods. In the object data model, geometry is treated like any other attribute of the object and not as its primary characteristic. Geographic objects of the same type are grouped together as object classes, with individual objects in the class referred to as instances. In modern GIS software systems each object class is stored in the form of a database table, with each row an object and each property a column. The methods that apply are attached to the object instances when they are created in memory for use in the application. 3.3 The use of geographic information systems in the construction industry The need for the use of GIS in the AEC industry is increasing, as GIS is used for planning, maintaining and protecting cities which requires an infrastructure of information. Sun and Hasell, (2002) have developed a GIS based tool to improve the management of the architectural design, engineering and construction project process. In the study, CAD entities are modelled as specific building components rather than generic shapes .The philosophy behind a GIS-based spatial information system development was to construct a model in terms of a GIS system that matched a building project process as closely as possible. An application protocol was developed building upon existing GIS software to test the GIS-based integration strategy proposed. A prototype system was built on a GIS system to test the effectiveness of the proposed research approach. Cote, (2002) explains an application which is developed with the aim to bridge the gaps between GIS, enterprise data management systems and CAD. ESRI has developed a CAD Client for its Spatial Data Engine (SDE). SDE is a GIS component for several enterprise database management systems. The CAD Client is the interface that permits access of GIS data through CAD programs, and the storage of CAD objects in the GIS database. This combination provides a facility for managing virtually unlimited amounts of detail representing most any aspect of the built environment for entire cities, along with different future or past scenarios, all in an architecture that would permit distributed access for reading and writing. The use of GIS in the AEC industry is not limited to the building construction Hu and Yoshide, (2002) have used GIS in disaster management, to asses the damage that an earthquake can cause. Yan and Switala, (2002) have explained the use of GIS in an urban demolition project in Philadelphia. GIS is also used in pipeline management, Brush, (2002) explained how PODS (Pipeline Open Data Standard) can be used together with ESRI Geodatabases. Murphy, (2003) explains the use of integrated CAD-GIS system in management of water facilities. Morgan and Jave, (2002) have also presented the integration a of CAD, GIS and GPS. Song et al (2003) demonstrated the use of web based GIS, in facilitating public participation activates in urban planning and regeneration. GIS’s spatial databases, can assist in various modelling applications through the development of automated tools for constructing and maintaining hydraulic network models of water distribution systems. Schaetzen and Boulos, (2002) have explained how to build up a water distribution management system using a GIS based component technology .

4. THE NEED AND POTENTIAL FOR INTEGRATION GIS applications are becoming common in diverse areas related to building projects such as facilities location and planning, site selection and preparation, land management, road planning, management and design, environmental monitoring and analysis, residential and commercial site surveying, public works surveys and engineering, municipal and utility surveys, infrastructure evaluation, soils modelling. Sun and Hasell, (2002) explain that GIS technology has potential for building a construction information management application that can provide pragmatic solutions to the problems of integrity and consistency of the information. The authors state that for most building projects, CAD applications are used and so are database applications. Since CAD is designed for facility design, it provides a good package of graphic capability but lacks data management functions. Also since the information in the database does not include graphic representations, it is hard to browse objects. To resolve the practical limitation of both CAD and database systems, many research projects on integrated information system have developed integrated CAD- database programs that link CAD graphic elements to database records. These types of applications indeed integrate the graphics with the data to some degree, but they are built with a special utility to link graphic and non-graphic data. GIS applications provide similar graphical interfaces just as CAD, but in addition extend the capability of associating non-graphic data with graphics, and incorporating the database applications too. Cote, (2002) indicates that in most cities the information infrastructure does not yet adequately represent the fullness of important three-dimensional aspects of the city, such as:  How many square-feet of commercial/office/housing might be affected by an emergency in a given area?  What windows have views of a particular spot?  How will a design proposal affect views and shadows in an urban scene? The author also assumes that the next step in planning for implementation of urban models in GIS , will be extending GIS data models to three dimensions and being interoperable with CAD. 5. CRITICAL ANALYSIS OF THE TECHNOLOGY 5.1 Model based information exchange architectures Three different levels of architectures exist to exchange IFC information models. The first level is, sharing the information between software applications using physical files. Physical file exchange is also the most common way of sharing models. At the second level, working form level-, information can be retrieved from the model by using application programming interfaces(APIs).This is a two tier architecture, first tier (APIs acting as servers) and clients on the second tier. At the third, database level, the information is held in the object , relational or express database. At this level the architecture can be with two or three tiers. Two tier architecture is used when the information model is mapped to a relational database (tier-1 being the database server) and entity instances are retrieved by using SQL in client application(tier-2).Three tier architecture is used when information models are mapped to object databases or held in the express database. The first tier being the database server, second tier the object or express database API and third tier is the client application.

5.1.1. Level 1(Physical File Level): Data sharing between applications using building information models as physical files Physical file exchange is done by creating a physical file of information that may be shared across a network. The file is exchanged by email or on a physical medium such a floppy disk. The EXPRESS language specification view of the IFC Object Model determines the structure of the file and the syntax of the file is determined by ISO 10303 Part 21. The architecture diagram of this level can bee seen in figure 5.1

IFC file (STEP-P21)

XCAD

YCAD

Fig 5.1 Level-1 Architecture Diagram 5.1.2 Level 2( Working Form Level): Accessing the IFCs through APIs Working form level has a 2-tier architecture, first tier is formed by an API .There are two options in the first tier. First option is that the API can be an IFC API which can read and import data from an IFC physical file .This process is usually a one way process (import from IFC), most of the IFC API’s do not have the capability to create an IFC physical file from raw data IFC files can also be read by using SDAI(Standard Data Access Interface) based APIs -which are standard data exchange APIs- developed to query all ISO10303 compliant information models.

IFC File (STEP-P21)

XCAD

IFC API

SDAI API

Client A

Client B

Fig. 5.2 Level-2Architecture Diagram

The second tier will be a client application using the API .There can also be more tiers if the system will be built with a distributed architecture The commercial IFC API’s include BSPRo Server, IFC Active Toolbox, IFCsrv ActiveX Component, and SDAI APIs include StepCase and JSDAI. The architecture diagram of this level can be seen in figure 5.2

5.1.3 Level 3 (Database Level): Accessing the IFC from the database Integrated product databases can store data that covers many aspects of the engineering life cycle. The advantage of storing the IFC data in the database is that, multiple applications can access the product data, and make use of the database features such as query processing. The IFC files can be stored in the database in two ways: 1. Object or relational database 2. EXPRESS database 5.1.3.1 Storing the IFC data in an object or relational database Data modelling with STEP EXPRESS (or in other words information modelling)can be defined as a method of data modelling at conceptual level. To store the IFC physical file data in an object or relational database, the database structure needs to be built by mapping the metadata, i.e. the schema, to the desired logical and physical data model and the IFC data needs to be mapped to the desired database. The mapping process is as follows: Step 1: Define the data structures from EXPRESS schemas: Map Express Data Model Metadata (IFC Schema) to an Object Data Model to construct classes Map Express Data Model Metadata (IFC Schema) to a Relational Data Model to construct entities

Step 2: Provide Standard Data Access Interface(SDAI ) access to the database. Import/Export .STEP-P21 data (IFC Physical File) to an object database using SDAI/OTHER API Import/Export .STEP-P21 data (IFC Physical File) to a relational database using SDAI/OTHER API

As seen in the table 5.1 classes/entities are formed by mapping the IFC schema, and objects/occurrences are formed by mapping the IFC physical file. Table 5.1 Mapping from conceptual models to logical models LOGICAL LEVEL

CONCEPTUAL LEVEL EXPRESS DATA MODEL

METADATA(.EXP) IFC SCHEMA DATA(.P21) IFC PHYSICAL FILE

FORMS

OBJECT DATA MODEL

RELATIONAL DATA MODEL

CLASS

ENTITY

ASSOCIATION

RELATIONSHIP

ATTRIBUTE

PROPERTY

OBJECT

OCCURENCE

The data can be retrieved from object or relational databases by using client applications. The architecture can be two or three tiers (database being as the first and the client being as the last tier) 5.1.3.2 Storing the ISO10303 compliant data in ISO10303 compliant databases IFC physical files can also be stored in the ISO10303 compliant databases, which can be named as EXPRESS databases. The core of the EXPRESS database is a meta-meta model (EXPRESS language defined in the form of an EXPRESS schema). The desired database structure is defined by using metadata (the IFC schema).By using the meta-meta model the Express Database Management System (EDMS) interprets the IFC schema and constructs appropriate entities for IFC. After that the physical file is imported to the database, the express database management system creates entity instances by using the created entities. The data then can be queried by using the database API or an SDAI based API(which forms

the second tier). The third tier is the client application that retrieves the information from the database by interacting with the database API. There can also be more tiers if the system will be built as a distributed system. The architecture can be seen in figure 5.3.

IFC SCHEMA

XCAD

IFC File (STEP-P21)

Client A

SDAI API

EXPRESS DBMS

Database API

Client B

Fig. 5.3 Level-3 Architecture Diagram 5.2 Information exchange architecture in geographic information systems The architecture of a geographical information system is flexible. Various software components can be added or removed according to the user requirements. A sample for commonly used client/server architecture is shown in figure 5.4.

Client Applications

GIS Software

GIS APIs

Client Applications

Web Browsers

Data Conversion Tools Web Services

GIS Web Server

GIS GATEWAY

Raster and Vector Data Files

Spatially Enabled DBMS

Data Layer

Fig. 5.4 A sample GIS architecture Raster or vector data files and a spatially enabled database forms the data layer. The spatially enabled database is mostly a relational database management system with a

capability of handling spatial data. GIS gateway enables the communication between the data layer and web server, application programming interfaces and geographical information systems software. Web and distributed services layer enables wire protocol (SOAP, DCOM and CORBA) components to interact with the spatially enabled database. The GIS related data can be acquired by any desired client application using application programming interfaces. 6. SUMMARY AND CONCLUSION According to the literature research that has been conducted, the use of geographic information systems is becoming important for the construction industry, and model based construction lifecycle management is becoming a need. Current research shows that there is a strong potential for the integration of building information models with the geographic information systems. The integration between geographic information systems and building information models will ; provide a decision support for construction site selection & analysis, enable fast &effective disaster damage analysis(based on GIS) ,enable nD management support for geo-related construction operations/activities, provide a decision support for urban demolition projects and for many projects in the area of urban management. The next stage of the research will be to further understand the business need through an industrial survey. Further stages of the research will be focusing on the implementation of integration. Different ways and possibilities of data exchange and sharing between both geographic information systems and construction information models will be investigated. IFC will be used as the building information model, as this is becoming a common denominator for most of the model based integration efforts in the construction domain. A prototype data exchange/sharing system will be built on upon the purposed solution and will be tested by case studies. It is proposed to develop a prototype to demonstrate the potential for GIS and Building Information Model integration.

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