step-based multiview integrated product modelling for concurrent engineering

Int J Adv Manuf Technol (2002) 20:896–906Ownership and Copyright 2002 Springer-Verlag London Limited

STEP-Based Multiview Integrated Product Modelling forConcurrent Engineering

K.-S. Chin1, Y. Zhao2 and C. K. Mok1

1Department of Manufacturing Engineering and Engineering Management, City University of Hong Kong; 2Institute of ManufacturingSystems, Beijing University of Aeronautics and Astronautics

The demand for high-quality and low-cost products with ashort development time for the dynamic global market hasforced researchers and industries to focus on various effectiveproduct development strategies. Product modelling has beenrecognised as one of the key factors in determining the successof various product development strategies and for industrialcompetitiveness now and in the future. This paper proposesa methodology that represents multiview integrated productmodelling based on the outcome of a research project on ISO10303 STEP. The methodology consists of the architecture andinformation requirements for an integrated product model anda mapping mechanism for the multiview operations of themodel, which support product development in a concurrentengineering environment. This methodology will facilitatefurther research in developing sophisticated product modellingfor concurrent product development.

Keywords: Concurrent engineering; Integrated product devel-opment; Multiview; Product model

1. Introduction

Manufacturing competitiveness supports sustained growth andearnings through building customer loyalty by creating high-value products for the very dynamic global market [1]. Thedemand for higher quality and lower cost products with shorterdevelopment time has forced industries to focus on the variousnew product development strategies. It is well known thatcomputer-integrated manufacturing (CIM) is an advancedmanufacturing system using information technology, whichinvolves the interconnection of different technical and manage-ment functions within a company [2]. Concurrent engineering(CE) has been proposed and defined by many researchers asa means to minimise product development time [3–10]. CE isa systematic approach to the integrated, concurrent design of

Correspondence and offprint requests to: Dr K. S. Chin, Departmentof Manufacturing Engineering, City University of Hong Kong, TatChee Avenue, Hong Kong, China, E-mail [email protected]

products and their related processes, including manufacture andsupport. This approach is intended to cause the developers,from the outset, to consider all the elements of the productlife-cycle from conception through disposal, including quality,cost, schedule, and user requirements [5]. Other strategies, suchas lean production, [11,12], agile manufacturing [13,14], virtualmanufacturing [15–17], holonic manufacturing [18,19], continu-ous acquisition and life-cycle support (CALS – formerly knownas computer-aided acquisition and logistics support) [20] andknowledge-based intelligent system approach [21], all contrib-ute in different ways to product development (from conceptualdesign to production and distribution) to enhance the indus-trial competitiveness.

The integrated product design and development process, asrepresented by all of the above strategies, is the foundation ofthe final product realisation, which involves numerous manage-ment and information technologies. The truth is that technologyonly enables these strategies, it does not create them [22]. Thechanges in market conditions are driving the usage of the newemerging technologies, which in turn is driven by the changingprocesses it has to support. Product modelling is considered tobe one of the key technologies that enables the realisation ofthese strategies during product development activities. Figure 1shows the scope of complete product modelling, in whichenterprise objective, enterprise development strategies,enterprise manufacturing resources and product realisation pro-cess are four major factors relating to how to develop, tomaintain and subsequently to use product models within an

Fig. 1. The realm of product modelling.

STEP-Based Multiview Integrated Product Modelling 897

industry. The enterprise manufacturing resources include humanresources, which are the most important, and the effective toolsand the IT infrastructure. The objective of an enterprise is toprovide the right product at the right time with acceptablequality and cost, and at the right place, by adopting differentdevelopment strategies. These four aspects are interlinked bythe information flow of product modelling. It is understandable,then, that Krause [23] should state that “the issues of infor-mation processing for product modelling are very complex inengineering practice”. The product realisation process modelsthe product life cycle from ideas through to final details.There are, in parallel, many subproduct models with differentinformation contents and structures. Hence, product modellingtechnology is critical [24–26].

The importance of product modelling has been generallyrecognised, and wider research and the application of productmodelling technology has been achieved in recent years. It isbe logical to assume that definite and commonly agreed uponproduct modelling approaches already exist; however, this isnot the case. In a similar vein, there are still major debateson the best approach to this problem, and many unresolvedfundamental issues must be addressed in order to fully realisethe benefits of product modelling [23]. This is due to theinherent complexity of modelling, whereby it is difficult tocover all aspects of interest concerning the product design anddevelopment life cycle. This paper will propose a STEP-basedproduct modelling methodology, and present ways in whichthis methodology has been implemented in an integratedCAD/CAM system. STEP is an international standard ISO10303 [27–30] for the computer interpretable representationand exchange of product data. Using STEP to form the basisfor modelling has many advantages. These will be discussedin Section 3.1.

2. Product Modelling

2.1 Definition of Product Modelling

In 1950, Murphy [31] gave a classic definition of the term“model”: “A model is a device which is so related to aphysical system that observations of the model may be usedto predict accurately the performance of the physical systemin the desired respect”. This definition applies mainly todescribing the behaviour of physical systems. With the increas-ing importance of computer-aided technologies, Ross [32] intro-duced the concept of modelling by mathematical meansincluding data, structure, interface, and algorithms, within thecontext of CAD/CAM in 1960, with more relevant behaviours.A model is thus defined as an abstract specification for domainfunctions that perform operations. Modelling simulates thevarious options in order to make informed decisions early inthe process. It becomes the dominant design tool in all aspectsof current design. Product, in this paper, refers to a unit of afunction with exact materials, a fixed form and designatedcolour and other features, which is made in an enterprise tosatisfy the requirements of a customer.

With the combination of the above definitions of model,modelling and product, the term product model can be

described as the sum of all useful information concerning aproduct within the life cycle of its development. Therefore,product modelling includes the important processes used todesign and develop the product on the basis of product specifi-cations. It is now the key technology in computer-aided productdesign and development. Product model data is the result ofproduct modelling action. In different modelling phases, itprovides different interrelated model data.

2.2 Representation of Product Models

From the technological point of view, there has been noexplicit description of product models, until the introductionof geometric models for various CAD applications. Since then,the fast development of product models and product modellingtechnology has followed, and reacted to the improvements inCAD systems. In the early days, CAD was primarily used tohelp the designer to create two-dimensional product drawings.With the development of computer hardware and supportingsoftware technologies, two-and-a-half, and then three-dimen-sional CAD systems have appeared. Now CAD systems notonly facilitate drawing tasks, but in a very real sense theyaid design.

The demand for rapid integrated product development (IPD)in recent years has led to the sharing of product informationduring design and manufacture through such applications asCAD, CAPP, and CNC, which, in the past were isolatedsystems. Therefore, an important step towards IPD is to employthe concepts of product model and modelling technology.

2.2.1 Types of Information Representation

In the basic derivation, all the information within the productdevelopment cycle can be reduced to a modelling processinvolving different kinds of product models that are interrelatedin nature. According to Biren [1], three types of representationalschemes are often employed during this modelling process:

1. Physical model.2. Conceptual model.3. Analytical model.

As presented in Fig. 2, physical, conceptual, and analyticalmodels are used to represent objects (the product), from differ-

Fig. 2. Models representing various types of information.

898 K.-S. Chin et al.

ent points of view, and to introduce various views of theinformation. For instance, a physical model is useful for con-ventional physical representation. A conceptual model is morerelevant when dealing with the information in the conceptualdesign phase during product realisation, while an analyticalmodel is more useful for supporting conventional CAD/CAMapplications by using parametric or solid modelling. In thispaper, the term product models, which is used as a mechanismfor representing the valid combinations of product informationmore efficiently, belongs to the category of analytical model.Central to the success of product modelling is the conjunctionof computer-aided techniques with the designer’s knowledge.

2.2.2 Classification of Product Modelling

Krause [23] summarised the development of product modellingand the proposed categories of product models, as presentedin Fig. 3. There are five types of product models:

1. Structure-oriented product models.2. Geometry-oriented product models.3. Feature-oriented product models.4. Knowledge-based product models.5. Integrated product models.

The structure-oriented product model is the first actual appli-cation of a computer-supported product modelling technique tothe representation of the structure of products. As the productstructure is the core of development activities, such things asspecific product data and formats can be stored within thisstructure-oriented model. Although this kind of model has

Fig. 3. Descriptive summary of product models.

many limitations for product representation, such as the lackof representation of product shape, it is important in that itprovides a basis for further enhancement by other modellingtechniques.

As an extension of the structure-oriented model, thegeometry-oriented model was developed with such functionsas the representation of the product shape including wire frame,surface, solid and hybrid models. The geometry-oriented modelhas been widely used to support CAD/CAM, and CNC pro-gramming applications. It satisfies the requirements of thecomputer-based representation of the shape of a specific pro-duct, but it is unable to describe non-geometric product infor-mation. The concept of feature, usually a form feature, wasthen first put forward for the purpose of representing thegeneral shape patterns of the surface and form of a productas coherent geometric items [33]. With the subsequent wideuse of feature techniques in CAD applications, a feature hasbecome a general information mode for representing a part ofa product [34]. In the process of product modelling, featurescan be classified as design features, machining features,assembly features and also abstract features. Each feature hasits special domain of implementation.

A knowledge-based model is an advanced model adoptingAI (artificial intelligence) techniques. This model supports theinformation reasoning, by referring to former designs, humanexpertise and past experience about a class of products storedin the internal model during the product modelling process. Atpresent, a few implementation methods can be used in theknowledge-based model, such as rule-based reasoning, con-straints-based reasoning, and object-oriented techniques. Theintroduction of knowledge in the product modelling domaindenotes great progress, as the degree of automated reasoningis still an important research topic.

The integrated product model, or global product model, isthe functional combination of all the product models discussedabove, including structure-, geometry-, feature-, and knowledge-based models. The integrated model is used to support allproduct development activities from the product requirementanalysis, conceptual design, detail design, process planning,CNC programming, machining, and assembly to quality assess-ment. It can be structured into interrelated multiview logicalmodels, such as design models and a machining model. Oneof the systematic methods used to integrate product modellingis the ISO 10303 STEP. This will be discussed in Section 3.1.

In recent years some new modelling techniques, such asparametric feature modelling, variable dimension modelling,virtual modelling and behavior modelling have been developedto enhance the abilities of three-dimensional geometric designin software tools. Although much progress has been achievedin the research domain of product modelling, there are stillmany uncertainties and debates, such as what is the bestmethodology to use for a particular problem domain, and whatis the appropriate procedure for the implementation of productmodelling. These will also be covered in this paper.

2.3 Product Modelling and Concurrency

Concurrent engineering (CE) emphasises the synergy of multid-isciplinary teams incorporating different aspects of the product


life cycle into the final product, [35]. The realisation of synergyis mainly about communication and collaboration in the productdevelopment processes among various functional teams. As afoundation for communication and collaboration, it is importantto have a clear and user-friendly product model. The develop-ment of integrated product modelling can support such acommunication and collaboration system from early productspecification through detailed design to manufacturing [36].Product modelling for supporting multiple disciplines is also acentral topic in implementing CE [24,26,37,38].

Concurrency is the major force of CE [1,9]. The concurrencycomes from product decomposition and seamless integration,both of which are considered as fundamental approaches tohandling complexity in product design, by identifying activitiesthat can be performed simultaneously. Hence, the essenceof adopting CE is the implementation of integrated productdevelopment, which, in turn, is achieved by the implementationof integrated product modelling. Figure 4 shows the relationshipbetween product models and the concurrent product designactivities in which model 1 to model n are the different aspectsof the integrated product model.

3. Proposed STEP-Based IntegratedProduct Modelling

The integration of CAD/CAM applications based on the shar-able common product information model, including the func-tions of product data and workflow management, is consideredto be one of the key links in the implementation of CE [38,39].However, the integration is not fully implemented because ofthe lack of a unified, single and complete representation ofthe product and process information model. Consequently, thetransfer of product design information from one system tothe other often causes incompatible or incomplete data [40].Therefore, it is necessary to build an integrated product modelfor supporting the various activities during the product develop-ment cycle, i.e. realising product information sharing, andexchanging information within the computer-integrated environ-ment in the enterprise.

Fig. 4. Product models and concurrency.

3.1 STEP – a Product Model Exchange Standard

ISO 10303, under the general title of industrial automationsystems and integration-product data representation andexchange, is an international standard for the computer-inter-pretable representation and exchange of product data (STEP).The STEP standard provides a mechanism that is capable ofdescribing product data throughout the life cycle of a product,and is independent of any particular system (ISO 10303-1,1994 [27]). STEP was formally accepted as an internationalstandard in 1994. It was the first standard concerning completeproduct model exchange, and is also a platform and method-ology for the implementation of object-oriented software devel-opment. It enables consistent implementations across multipleapplications and systems, and is suitable not only for neutralfile exchange and application programming interfaces, but alsoas a basis for implementing and sharing product databases.The STEP standard covers a large scope and deals with highlyabstract product modelling information. Therefore, in order tospeed up standardisation, STEP is organised as a series ofparts, and each is extended and published separately. All ofthe parts belong to one of the following series:

1. Description methods2. lIntegrated resources3. Application protocols4. Abstract test suites5. Implementation methods6. Conformance testing

STEP product modelling is based on integrated resources.Integrated resources, which consist of generic resources andapplication resources, define a generic information model forproduct data. As an element of STEP, an application protocolincludes the definitions of scope, context, and informationrequirements of an application. It provides the capability ofinterpreting the integrated resources to meet the product infor-mation requirements of specific applications. The applicationactivity model (AAM), application reference model (ARM),and application-interpreted model (AIM) are the three importantresulting models documented in an informative annex to theapplication protocol. A mapping from the information require-ments to the AIM is also provided within an applicationprotocol. An example of an application protocol for the automo-tive mechanical design processes is AP214 (ISO 10303-214,1997 [28]); another for the configuration control is AP203 (ISO10303-203, 1995 [29]). In order to support the development ofintegrated product models, STEP put forward a formal infor-mation modelling language named EXPRESS, which itself isa part of STEP standard (Part 11) (ISO 10303-11, 1994 [30]).The product data in integrated resources and application proto-cols are described by EXPRESS to ensure consistency andavoid ambiguity. The graphical representation of EXPRESSis EXPRESS-G, which is provided to aid in understandingthe definitions.

Compared with the previous data exchange standards such asIGES and SET, STEP provides a product modelling approach inwhich all the aspects concerning product development lifecycle, including geometry and organisational data, are taken


into account. At present, STEP is still a developing standard.Many companies around the world have promised to supportthis new industrial standard of STEP-based commercialCAD/CAM and CAE applications; and software toolkits arebeing developed for systems integration and information shar-ing. In the following sections, an integrated product modellingmethodology is presented. It is proposed on the basis ofSTEP standards, and EXPRESS is used as the informationdescription language.

3.2 Architecture of Integrated Product Model

In the authors’ opinion, the successful implementation of pro-duct modelling depends upon the effective architecture of anintegrated product model. According to the compositions ofthe knowledge from the product design and development, theproposed integrated product model (IPM) consists of the fol-lowing components: a geometric model, a feature model, aproduct definition model (including the domain product model),and an integrated core model. The architecture and relationshipof these models are described below; see Fig. 5.

1. The geometric model is the basic description and definitionof the product geometric shape using the combination ofCSG and B-rep solid representation. From the initial conceptshape description in conceptual design to further elaborationof product detail design, geometric information about onespecific product can be dealt with in a geometric model.As the result of geometric modelling, the data structured ina STEP AP214 schema are provided for the followingfeature model. STEP AP214 is used as the framework ofthe geometric shape description.

2. The feature model is an extension of the geometric model.The features with different definitions and attributes specifythe geometric characteristics and engineering semantics ofthe objects. The information generated from the geometricmodel can then be prepared to support the design andmanufacturing of the product. The feature model is thebasis for creating mechanical parts and composing the pro-duct definition model and domain product models. Thefeature related entities as a type of shape-aspect like machin-ing feature, replicate feature, and transition feature areprovided by STEP AP214. In addition, the shape aspect has

Fig. 5. The architecture of integrated product model.

self-defined features like a design feature and anassembly feature. The feature model can be used to supportthe whole product design process with the advantages ofeasier information transformation and integration.

3. The product definition model, including domain productmodels, is the parametric feature-based product model. It isgenerated during the process of defining the engineeringdescription and structure of the product in order to meet therequirements of product design and process. The identifier,descriptive text, product definition formation, and productdefinition context are the main components of the productdefinition model. The product definition model considersthe product and process as a whole, while the domainproduct model refers to the specific domain of theimplementation aspects, such as the machining process, NCfabrication and the assembly process. A mapping mechanismbetween the product definition model and its related domainproduct models is set up to support the data exchange, suchas the link between the product definition data and theassembly domain data.

4. The integrated core model is a description of architecturefor the implementation of the information management fromthe product definition model and domain product modelsvia the feature model to the geometric model. It alsomanages the knowledge required to define and implementall the product design and development activities.

3.3 Information Requirement for Integrated ProductModel

Product definition data and configuration control data pertainingto the design phase of product development are within thescope of AP214 of ISO 10303. AP214 has a wide applicationnot only for the automotive industry, but also in the aviationmanufacturing industry and other heavy industries. As men-tioned above, the integrated product model (IPM) should coverall of the activities throughout the product development cycle,and each activity has corresponding application in the concur-rent engineering environment. Then, the information requiredfor the integrated product modelling process could be specifiedas a set of application objects, application assertions and unitsof functionality (UoF), referring to STEP AP214.

UoFs, grouped together, provide the solution to identifieddata flows derived from the application activity model (ARM)for developing the IPM. For example, there are seven UoFs(including a user extending UoF) that are selected and refinedfrom STEP AP214, to specialise the information requirementsfor establishing the product structure in the IPM. The graphicalrepresentation of this ARM is given in Fig. 6.

The major components of this ARM are described below:

UoF1 (Product Management Data): specifies the represen-tation of product management information, and the connectionbetween product management data and product descriptiondata. It describes the information about an Item (either Part orTool), an Item-version of this Item, and information resultingfrom the release and approval process. The application objectsof this UoF are Item, Part, Tool, Item version, General-

description, and Design-discipline-item-definition.


Fig. 6. Information requirements for integrated product model (referringto STEP AP214).

UoF2 (Element Structure): includes the information fordescribing structures of data elements. The data elements canbe FEA elements, geometric elements, or annotation elements.Included-element is used at high level for application objects.UoF3 (Item Definition Structure): clarifies the representationof the relationship between parts and tools, and between differ-ent parts and different tools to build up various kinds ofstructures. The application object is Item definition rel-ationship.UoF4 (Work Management): specifies the representation ofwork order, project, and contract-related information. Therelationship between versions is also included. Description re-lationship, Work order, Change description, Item version-

relation, and Work request are the application objects.UoF5 (Classification): specifies information for the classi-fication of parts and tools due to various categories. Theapplication object used in this high level is Item classification.UoF6 (Process Plan): expounds information necessary tohandle process plans and versions of process plans with versiontracking. A process plan is divided or separated into one ormore process operations. This UoF uses the application objectsof process description, and process state.UoF7 (User refinement and extension): provides the possi-bility for representing an application oriented extension schema

of product structure with the subtype of the Item. The user ext-ension is selected as the application object.

In this approach, the refinement and extension to the standard-ised UoFs from AP214 can be fulfilled by using the EXPRESSlanguage. As these components of extension are application-specific and are not shared with other applications, a mech-anism is needed to omit any enhancement, refinement andextension. In addition, enhancement must be a proper extensioncomplying with the AP214 according to the related integratedresources. The result would be an EXPRESS schema thatconsists of the necessary integrated resource. Other expressionswithin the IPM are also refined and extended in a user-definedschema according to the STEP standard.

3.4 Multiview Representation

The integrated product model (IPM) is designed to meet therequirements of information for the rapid integrated productdevelopment within the concurrent engineering environment. Itis used to support the activities associated with the processesof product development including the design, manufacture,utilisation, maintenance, and disposal phases. On the basis ofsuch things as the submodels of the design, process plan andmachining, the product-related information generated through-out the product development cycle can be stored in the IPM.It thus facilitates the physical integration, information inte-gration, and functional integration in the enterprise.

3.4.1 The Multiview Concept

The sharable information, which is stored in the IPM, can bedescribed as the alternatives in different application domains.For example, an abstract representation of features in the IPMcan be reflected in the Design feature, Process feature andMachining feature in the product design domain, the processplanning domain and the manufacturing domain respectively.All of these different descriptions of features are interactiveand interrelated. Therefore, the abstract information about theproduct is represented by the IPM, while the detailed infor-mation is located in the domain submodels.

An effective abstract description mechanism is employed torepresent the information shared in the IPM, and the infor-mation used in specific application domains can also beobtained from the IPM by relevant mapping algorithms. Sincethe proposed IPM can be viewed as different aspects ofthe application domains, it is called a multiview model. Theimplementation of multiview function is through the manage-ment of both global and local mapping agents. The globalagent generates top-level (integrated) specifications based onthe requirements via the concurrent engineering team builder;then the domain-related information and associated constraintsare delivered to various local (domain submodel) agents. Dueto space constraints, details of such mapping agents will notbe elaborated further in this paper.

3.4.2 The Mechanism of Multiview Modeling

The multiview IPM, denoted by MI, consists of a series ofsubmodels. These submodels, which are represented by the


Fig. 7. The mechanism of multiview product model.

symbols MS1, MS

2,. . .,MSn, are used as the unit of functionality

(UoF) in the product design and development process, such asthe form feature model, the dimension tolerance model, andthe surface condition model. Then

MI = MS1 � MS

2 � . . . � MSn

Suppose MDi is a domain model, which is viewed from the

IPM to this domain (i), then

MDi = �

mi

i=1Tij MS

j , mi � n, MSj � MI

where Tij is the mapping operator that is transforming theintegrated product model data into domain product model data.The collection of all these mapping operators is representedby the symbol T, which constitutes the mapping algorithm:

T = {Ti}, Ti = {Tij}, i = 1, 2, . . ., m, j = 1, 2, . . ., n

The graphical representation of the mechanism of multiviewintegrated product modelling is given in Fig. 7. A softwaretool named AP214-ref toolkit has been developed according tothe UoFs of AP214 to support the information mapping fromthe integrated product model to the domain product model[25]. The development of such a software tool has demonstratedthe realisation of system integration.

3.4.3 The Mapping Schema

The defined entities of views are derived from the entities inthe schema of the IPM. The submodels of individual viewscould be represented by EXPRESS language; therefore, themappings are also developed according to the EXPRESSdescription. A mapping schema defines a relationship betweena group of entity types in the integrated model and its views.Figure 8 presents the mapping specifications. E is the collection

Fig. 8. The mapping specification.

of integrated EXPRESS entities; VE is also the collection ofview entities. The mapping schema (compiler and management)is an information model, which is represented by theEXPRESS-X language.

The EXPRESS-X language is evolved from EXPRESS-V(ISO TC184/SC4/WG5 N251), where V denotes View. TheEXPRESS-X defines mappings among information modelsdefined in EXPRESS. The algorithm for deriving the entitytypes in a view from the entities in an original EXPRESSmodel is specified by various types of mapping declarationsin the EXPRESS-X language, referring to the model [ISOTC184/SC4/WG11/N002].

There are four types of mapping methods proposed withreference to Fig. 8. The first one is that N entities, from severalUoFs in the integrated product model schema, are mapped intoone entity only in the view submodel domain. The secondmapping is between one UoF and the N entities in the viewsubmodels. The third and fourth are N-to-N entities, ie theone-to-one entities between the integrated product model andview submodels.

On the basis of the EXPRESS-X language, a group ofmapping operators is proposed, as described in Table 1, toenhance the mapping functions between the integrated modeland domain models. These operators are classified into threedifferent operations; namely, the operation for schema, theoperation for entity and the operation for type.

3.4.4 The Abstract Class of Integrated Product Model

The representation of the abstract object of the product isdescribed in Fig. 9, where Product is an abstract SUPERTYPEwhich consists of the characteristics of domain product infor-mation such as design view, process view and machin-ing view. Each of the view models is the SUBTYPE of theproduct in which the view model data can be respectivelyconfigured by the requirements. The entities of structure andmanagement, which deal with the functions of managing thestructure model and implementing the operation for the modeland related model data, are the two important attributes ofthe product.

A product consists of components and parts. A part has theattribute of a parametric feature and a feature relation. Thegeometric description can be defined by two dimensions,namely, form feature and location feature. As these two dimen-sions can be described by parameters, the geometric model iscalled a parametric feature model. The parametric features canbe developed according to the form feature and UoFs drawnfrom the product requirements. The description of parametricfeatures is proposed in Fig. 10.

The relationship of features in the integrated product modelconsists of location relation, through which the locationbetween features is elaborated, and hierarchy relation, throughwhich the dependent relation among features in the productdevelopment cycle is described. The structure of feature relationis presented in Fig. 11.

3.5 The Management of Model Data

As mentioned in Section 3.4.1, the goal of integrated productmodelling is to support the information integration between


Table 1. Self-defined mapping operators

Name of the Operators Description

Operation for the SCHEMA

Combine—Schema (schema1, schema2) The combination of two schemasDelete—Entity (schema1, entity) Deleting an entity from the schema1Add—Entity (Schema1, entity1) Adding the entity1 to the schema1Rename—Schema (name1, name2) Changing the name of schema from name1 to name2

Operation for the Entity

Rename—Entity (name1, name2) Changing the name of entity from name1 to name2Add—Attribute (entity1, attr1, …attrn) Adding the new attribute 1~n to entity1Delete—Attribute (entity1, attr1, …attrn) Deleting the attribute 1~n from entity1Modify—Attribute—Type (attribute1, type1) Modifying the attribute1 to the new tpye1Map—New—Entity (entity1,entity2) Mapping the entity1 to a new entity2Add—Supertype (entity1, entity2) Adding entity2 as the supertype of entity1Adding—Subtype (entity1, entity2) Adding entity2 as the subtype of entity1Delet—Supertype (entity1, entity2) Deleting entity2 (supertype) from entity1Delet—Subtype (entity1, entity2) Deleting entity2 (subtype) from entity1

Operation for the Type

Derive—New—Type (type1, type2) Deriving new type2 from the existent type1Rename—Type (name1, name2) Changing the name of type from name1 to name2

Fig. 9. The proposed abstract product class.

Fig. 10. The description of parametric feature.

the related CAD/CAM applications throughout the productdevelopment cycle. The process of integration has been demon-strated by the development of an AP214 ref toolkit, where:

1. Product definition model data (PDMD) is kept as the con-figured core data, and

Fig. 11. The description of feature relation.

2. Domain product model data (DPMD) is defined by, andlinked with, product definition model data.

In practice, the defined linkage is a process of using DFxexpert systems to create relationships between product defi-nition model data and domain product model data, which isalso the process management for the integration within thescope of the defined design and the domain of downstreamengineering applications (Fig. 12).

4. A Prototype of Proposed IntegratedProduct Model

The proposed STEP-based integrated product modelling meth-odology has been implemented to develop a CAD/CAM inte-gration system called LONICERA in a Chinese enterprise. Theimplementation architecture of the LONICERA system is sim-ply described in Fig. 13. As discussed in Section 3.3, themodelling process of LONICERA consists of two parts. Oneis the product definition model and the other is domain productmodel. Both of these models are set up on the basis of theelements Feature and Geometry, which are described in STEP


Fig. 13. The architecture for developing LONICERA based on STEP.

Fig. 12. The integrated management of model data.

AP214 AIM but these two models are designed to performdifferent functions within the different stages of the productdevelopment process. The domain model is designed to followthe definition model. With the support of integrated productmodelling methodology, the product definition model is locatedwithin the first stage of the product development process tosupport product requirement analysis, development preparationand product conceptual design. The information, which iscollected from the market or customers in the requirementanalysis phase, will be transferred into a standard informationformat with the help of the product definition model. Then, asthe input to the conceptual design toolkit, the information isconsidered as the original data to perform the conceptual designfor a new product. Through the conceptual design, the proto-type of the new product is described in the product definitionmodel data with initial three-dimensional visualisation. Thisimplementation process is totally controlled by the workflowmanagement toolkit. The work of refinement and reorganisationof this information is implemented by interaction. In the secondmodelling process, the domain product model aims to providesufficient domain information to meet the requirements of thefollowing product manufacturing process. The activities suchas machining process planing, NC fabrication, and assembly,etc. are all supported by this domain model. It is the coremodel for manufacturing. This process is managed by thedesign for X toolkits, such as DFA, DFM. After this domaindevelopment stage, a new product with new features requiredby the **** that will be delivered quickly to the customer.

More details of this prototype and implementation method willbe presented in other paper. As these models are all developedbased on STEP AP214 the model data can be exchangedand modified easily between different commercial CAD/CAMsystems, which have the interfaces for STEP files. The LON-ICERA system is fully supported by the proposed integratedproduct model methodology, as illustrated in Fig. 14.Figure 14(a) gives the example of a function of feature mode-ling for the part called Aeroengine, and the wire frame modelrepresentation is demonstrated in Fig. 14(b). Figures 14(c) and14(d) express the mapping relationships in the proposed meth-odology.

5. Further Work

The methodology and related figures described above representpart of the authors’ research work in implementing the pro-posed integrated product model. Accordingly, several compo-nents of the methodology are still under study. For instance,the authors are carrying out research concerning the agent-based mapping management of product information, as themechanism of sending and receiving messages is veryimportant. Another research focus concerns the extension ofSTEP to meet various requirements for product development,but this should not conflict with the conformance of theselected application protocol, such as AP214. In addition, howto move towards a complete digital representation of all pro-duct- and process-related information to support product model-ling activities from the conceptual design, via product machin-ing, to disposal, is another major research and application areabeing pursued.

6. Conclusions

On the basis of the lessons learned from this research work,the following points are highlighted:


Fig. 14. Aeroengine: (a) Feature modelling (Advanced Rendering). (b) Wire frame model representation. (c) Modifying the dimension feature.(d) Adding a new feature hole.

1. The important role of integrated product modelling withinthe overall product development process that determinesengineering productivity and industrial competitiveness.

2. The fact that the description of product models is a highlyabstract modelling process. There are no well-establishedtheoretical foundations and no existing implementation stra-tegies at present.

3. ISO 10303 STEP is a product modelling approach that takesinto account all the aspects of a product development pro-ject, so that it is suitable for supporting the establishmentof the integrated product model.

4. The integrated product model is defined using multiviewcharacteristics, which is the distinct mapping of the domainproduct model.

5. A prototype integrated product model based on STEP AP214has been developed, which is the combination of the geo-metric model, the feature model, the product definitionmodel (including domain product model) and the integratedcore model.

6. The competitive benefit of adopting the integrated productmodelling process is that all the information required forthe product development can be integrated. This, in turn,enhances the effectiveness and efficiency of the productdevelopment process.

7. The STEP EXPRESS language has proven applicable fordescribing the integrated product model, while the mappinghas been successfully developed by EXPRESS-X language.


Acknowledgement

The authors would like to express their sincere appreciation toProfessor J. T. Deng for his support in the implementation ofthe described methodology.

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