VTT-TEC-ADA-01 Page 1 SECOM Co., Ltd. / VTT Building and Transport Yoshinobu Adachi E-Mail: yoshinobu.adachi@vtt.fi VTT-TEC-ADA-01 Outline of IFC Model Server Development Project 2001/07/25 1. INTRODUCTION...1 2. OBJECTIVE...1 3. GOAL...2 4. COMPONENTS IN IFC MODEL SERVER...2 4.1. EXPRESS TO XML SCHEMA CONVERTER (EXC)...2 4.2. IFC MODEL DATA ACCESS LAYER COMPONENT (DALC)...3 4.3. WEB SERVICE LAYER (WSL)...4 5. CONCLUSION...4 6. SCHEDULE...5 1. Introduction This document describes a proposal for development of IFC Model Server which stores IFC object model within the database system and runs on the internet. I believe that the necessity of IFC compatible model server has been increased by the worldwide IFC implementation experiences in recent years. Without this kind of model server functionality, sharing of IFC data by IFC compatible applications would be limited to file base exchanges. If a model server functionality is provided on the internet, IFC compatible applications can communicate with each other via the internet and utilize function implemented in the model server such as partial model import / export. The model server will import and export IFC model by BLIS-XML and STEP file format. In the future development, it will also provide a wide variety of Web Service functions, i.e. scheduling doors windows, external library data merger into IFC model with property set system, VRML converter, and so on. On top of that, using SOAP for the communication between model server and client software, the model server functionality can be used by many kinds of client software such as web browsers and java applets. To realize this model server, several basic technologies need to be cleared up. Storing IFC model data in a database system. (SQL Server, Oracle, etc) Automatic schema conversion from IFC EXPRESS to database schema XML based SOAP communication between model server and client software By storing IFC model data in a database, the model server secures the utilization of a large size building model. At present, most of database management systems include XML data storing functions, thus the development of IFC model server will utilize those XML related tools and functions in order to cooperate with BLIS-XML technology. 2. Objective The objective of this project is to develop an IFC Model Server prototype. The prototype will be positioned as a basis of the future IFC Model Server products for IFC compliant software applications, and therefore the
VTT-TEC-ADA-01 Page 2 prototype must have extensibility, scalability and be built on standard technologies. In this development stage, IFC Release 2.0 is focused on, because the first wave of BLIS project products will come up in 2001. Tools and components that will be developed by this development project will be compatible with further IFC releases like IFC 2x. 3. Goal The goal of this development project is to realize following points: Storing IFC model data in a database system. (SQL Server, Oracle, etc) Automatic schema conversion from IFC EXPRESS schema to database schema by using XML technology XML based SOAP communication between model server and client software 4. Components in IFC Model Server In this project, following components will be realized: EXPRESS to XML schema Converter (EXC) IFC Object Model Data Access Layer Component (DALC) Web Service Layer (WSL) 4.1. EXPRESS to XML Schema Converter (exc) This component realizes conversion from EXPRESS to XML Schema format. This conversion consists of tow stages. At the first stage, EXPRESS schema information is converted to an intermediate XML format, i.e. Part28 XML format, OIM 1 (Open Information Model) format, or ifcxml format. In the second stage, the intermediate XML format is converted a specific schema defining language such as SQL DDL by XSLT, scripting and applet by using DOM parser. There is a need to research about the necessity to develop the first stage, because the functionality that converts EXPRESS to Part28 XML format will be able to use some existing tools or library. EXPRESS parser Module: The CSTB open source project will be utilized in this part. Other possibility is the public software from NIST. EXPRESS schema intermediate XML schema Module: After parsing EXPRESS schema, the schema information is stored in XML DOM tree in the memory of the converter. This DOM tree will be based on Part28 XML format, OIM format or ifcxml format. Intermediate XML to destination Schema Module: The intermediate XML format is very neutral information and contains almost the same information as EXPRESS schema. This module converts intermediate XML data into the destination schema defining language, i.e. SQL DDL(Data Definition Language) or other XML Schema format. 1 OIM: Open Information Model is a framework that was developed by MDC(Meta Data Coalition) for defining meta data.
VTT-TEC-ADA-01 Page 3 EXPRESS EXC EXPRESS To XML Schema Converter XML Schema Part28 OIM ifcxml XSL Module XSL Module XSL Module SQL DDL for SQL Server SQL DDL for Oracle other XML Schema SQL Server Oracle XML Datastore Fig. 1: Outline of EXPRESS to XML Schema Converter 4.2. IFC Model Data Access Layer Component (DALC) DALC accesses a database for importing and exporting IFC model data. It provides functions that resemble SDAI model server function, and includes following APIs : BLIS-XML importing and exporting IfcXML support will be a challenge Primitive IFC object access functions IFC object search (by entity type, GUID) DALC is based on the database schema which is made by EXC tool. ADO component is used for accessing to
VTT-TEC-ADA-01 Page 4 the database in DALC. In this project, Microsoft SQL Server 2000 will be a target database system, because it has XML compatible functions. ADO can access to other database such as Oracle by changing the database provider component. To handle the STEP files, IFCsvr ActiveX Component will be used in DALC. When a client application uses STEP files, IFCsvr component accesses the STEP files and invokes DALC primitive IFC object access functions to import and export the IFC model data with database. 4.3. Web Service Layer (WSL) WSL provides the IFC model data upload and download services. There are two ways to upload and download the IFC model data in this proposal. 1. With user interface on the web pages: Users operate upload and download procedures on the web pages manually. This is a quite traditional way to use web pages. ASP scripts will run the DALC directly. Http protocol is used for downloading/uploading IFC files. 2. By using SOAP protocol: Client applications can access to the Web Service Component on the IFC Model Server site via SOAP protocol. A request is sent out to the Web service by client applications in order to download and upload the IFC Model Data. The IFC Model data written by BLIS-XML will be encapsulated by SOAP. WSL also provides IFC Model handling user interfaces to client applications. This means that a kind of partial model select and merge functions, quantity take off function, property set edit function and so on, will be attached into the Web Service in the future. In this proposal, preliminary limited model select and merge function, defined by the building storey, will be implemented. In the first stage of this proposal, ASP (Active Server Page) on IIS (Internet Information Server) will be used. To support XML and SOAP protocol, Windows 2000 Server, SOAP SDK and BizTalk Server (if needed) will be necessary. 5. Conclusion Application via SOAP CAD Internet IFC Model Data (XML or STEP) Model As BLIS- XML Request by SOAP SOAP Listner IFC EXPRESS Schema EXPRESS XML Schema Converter Database Schema (SQL) Non CAD Web Browser Internet Web Server Scriptlet IFCsvr ActiveX Component IFC Object Model Access Module ADO Database.Net client Catalog Data (XML by PSML) IFC Model Server Web Service Layer Data Access Layer Door Window Manufacturer Fig. 2: Outline of IFC Model Server Components In this development project, following software modules will be implemented: EXPRESS to XML Schema Converter (exc)
VTT-TEC-ADA-01 Page 5 Data Access Layer Component (DALC) Web Service Layer (WSL) This development project aims to solve following key points: How to define the database schema What should be the intermediate XML schema Design for APIs of Data Access Layer Component How to use the SOAP function for Web Services 6. Schedule 1/7 1/8 1/9 1/10 1/11 1/12 1/1 1/2 1/3 1/4 1/5 6/2001 6/2002 Preparation 1/6 30/6 1/8 1/9 1/10 1/7 31/10 2/7 31/7 Research for XML Schema candiates 1/8 31/8 EXPRESS to XML Converter Progrm Design 1/9 31/10 1/11 1/12 1/10 31/12 EXRRESS to XML Database Schema Converter EXPRESS to XML Converter Implementation Data Access Layer Component 1/2 1/3 1/1 31/3 Fig. 3: Schedule of IFC Model Server Project Web Service Layer 1/5 1/4 31/5 Test and evaluation Note: The schedule is tentative and might be changed.