ADVANCING CE USING STEP *

Transcription

1 ADVANCING CE USING STEP * Tad A. Davis George Trapp Concurrent Engineering Research Center Drawer 2000 West Virginia University Morgantown, WV ABSTRACT A synergistic relationship exists between Concurrent Engineering (CE) frameworks and the PDES initiative of promulgating STEP. This paper emphasizes and punctuates the importance of the STEP-CE linkage and defines further cooperative bindings. One focus of the presentation is the use of STEP application protocols to create the shared information models necessary for Concurrent Engineering(CE). After a discussion of the natural fusion of CE and PDES/STEP application protocols, the need for the extension of STEP resource models and application protocols to include information sharing capabilities for process and organization data is presented. * This work has been sponsored by the Defence Advanced Research Agency (DAPRA) under Contract No. MDA for the DARPA Initiative in Concurrent Engineering(DICE).

2 Introduction In this paper we examine the interconnections of Concurrent Engineering and the STEP standard being developed in the United States by the PDES activity. We begin by reviewing various definitions and characterizations of Concurrent Engineering and a CE environment. We highlight the fact that a Shared Information Model is a central component of a CE framework. We then present various definitions and characterizations of product data as given by the PDES/STEP community. We see that there is a commonality in the definitions of CE and product data. We amplify these similarities by showing that one may view a STEP Application Protocol as a natural merging of the CE and STEP principles. Using examples drawn from the CERC CE testbed, we exhibit a working model for the CE - STEP marriage. Finally, we note that Concurrent Engineering is a "fast follower" of PDES/STEP in terms of product data and physical file format, and suggest that PDES/STEP will be a "fast follower" of the Concurrent Engineering requirements in the areas of process data, organization data and on-line data exchange. CONCURRENT ENGINEERING We begin by stating two definitions of Concurrent Engineering:

3 "Concurrent Engineering is a systematic approach to integrated product development, that emphasizes response to customer expectations and embodies team values of cooperation, trust, and sharing in such a manner that decision making proceeds with large intervals of parallel working by all life-cycle perspectives, synchronized by comparatively brief exchanges to produce consensus." 1 "Concurrent Engineering is a systematic approach to the integrated, concurrent design of products and their related processes, including manufacture and support. This approach is intended to cause the developers, from the outset, to consider all elements of the product life cycle from conception through disposal, including quality, cost, schedule, and user requirements." 2 The ideas behind Concurrent Engineering appear is other forms; some alternate name for CE are: Simultaneous Engineering Integrated Product Development Design the Product and Process at the same time Synchronous Product-Process Development Transition to Production A Concurrent Engineering Environment advances the enabling of: Total Quality Management, Satisfied Customers and Requirement Management; A Concurrent Engineering Environment advances the facilitation of: Early Problem Detection, Decision Making and Responsiveness. Although CE principles seem somewhat obvious and follow common sense, there are barriers to the establishment of a CE environment. Some of the barriers are: complex products, processes and systems; traditional and hierarchical organizations; and discipline incompatibility.

4 In Figure 1, we depict a cooperating human team. In Figure 2, we represent the interactions that take place in a concurrent engineering environment. Combining the notions of a team working in a CE environment we obtain the virtual team concept which is depicted in Figure 3. A short definition of CE in the enabling of a virtual tiger team. There are clearly two aspects involved in a virtual tiger team: First, the human or cultural element as represented by team behavior and second the technology element represented by a common information model and colocating decision making. unified product concept support materials design manufacturing FIGURE 1: The Human Team

5 R&D intent, requirements consequences, constraints changes Design Manufacturing Product Support progressive refinement FIGURE 2: Concurrency design design fusion support Unified Product Model materials analysis marketing management manufacture FIGURE 3: The CE Virtual Team Defining the scope, requirements and specifications for a CE environment is a complicated process. Some of the stumbling blocks are summarized in the following:

6 "... there are no models to identify how different engineering disciplines use analytical tools and associated results during the design of a complex system by a multidisciplinary team. In other words, intentional engineering of the engineering process itself has proven elusive. Requirements analysis is of primary importance in establishing any system's design characteristics.... CE may be spoken of as multidimensional, it integrates multiple engineering disciplines across three major dimensions: organization, life cycle and technology. " 3 Here organization is an enterprise or business environment; life cycle means concept to retirement from service; and technology is the engineering process or automation. Bruce Palmer lists the following features/issues for a current engineering/manufacturing environment: Data Sharing is essential and expanding Many electronic data producers and manipulators databases, , word processing, CAD, CAM, etc. Computational and Interpretive data must be and shared exist: organized Many platforms and systems exist: IBM, DEC, SUN, Apollo, HP, SG, etc. mainframes, workstations, PCs, etc. Companies are geographically dispersed At the core of any CE implementation is a common model because one of the fundamental aspects of concurrent engineering is the ability of all tasks/teams to access an information model which is commonly understood and shared. In order to do this, a set of information sharing

7 models, tools, services and utilities must be able to represent a virtual repository. One must be able to access and manipulate data which resides in diverse external formats and systems, and present it in a view which is specified by the user or application The components necessary for an integrated environment are a standard data modeling language, translators which allow data to bridge internal storage languages, and information sharing services which catalog, register, inspect, extract, modify, and browse information. PDES/STEP The common information models needed in a CE environment will include many components and aspects. Bill Burkett emphasizes this point for a CIM environment as follows: "One of the central and most important components of the implementation of CIM is the enterprise-wide database which will feed information to the production operations" 5 One of the most promising on-going efforts is the development of the STEP information models and STEP application protocols. At present STEP is being developed primarily for product data, in the future we expect STEP to encompass process and organization models - we will revisit this topic below. Here, we give various characterizations of product data with the goal of showing that PDES/STEP and CE are inexorably connected. Product Data are data that describe the functional and physical characteristics of each unit of a product throughout its life from its requirements at inception to its configuration at time of retirement. PDES, Inc. states "STEP, the proposed international standard, will provide a complete, unambiguous, computer interpretable definition of the physical and functional

8 characteristics of each unit of a product throughout its life cycle". 6 Bill Burkett states: " The intended scope of PDES, basically, is all the information required to produce a product, from preliminary design through product support, the complete product life-cycle." We note the similar wording in the product data definitions as compared with the definition of concurrent engineering - the common ground is: all of the required product data for all of the life cycle perspectives. Clearly, CE and PDES are interconnected. STEP APPLICATION PROTOCOLS One natural outcome resulting from the blending of Product Data Models and a Concurrent Engineering approach is the utilization of the PDES/STEP Application Protocols. "An Application Protocol is a standard that defines the context and scope for the use of product data and specifies the interpretation of the standardized integrated resources in that context to satisfy an industrial need." 7 A naive understanding of STEP would only be concerned with data entities, and a naive understanding of Concurrent Engineering would only be concerned with life cycle perspectives. An AP is natural development because in a shared information model of a CE environment one must deal both with the information and the use of the information. In Figure 5, we give a simplified matrix representing data entities and life cycle perspectives. An X in a box indicates that the corresponding row (perspective) "sees" or "needs" that column's data entity. In other words, that data entity

9 is required for that perspective. A naive understanding of PDES/STEP would only be concerned with the top list of data entities. Similarly, the naive understanding of a shared information model in a Concurrent Engineering environment would only be concerned with the left hand list of life cycle perspectives. In Figure 6, we present a simplistic way to view an Application Protocol, the symbol in the table specifies the data entities and perspectives involved in the AP. PRODUCT/PROCESS DATA ENTITIES D1 D2 D3 D4... Dn P E Accounting X X X R Design X X S Config. Control X X P Analysis X E Fabricating X X X C Logistics X X T... I v E Figure 5: Simplistic Data vs Perspective Matrix PRODUCT/PROCESS DATA ENTITIES D1 D2 D3 D4... Dn... P E Accounting

10 R Design S Config. Control P Analysis E Fabricating C Logistics T... I v E FIGURE 6: Representation of an AP For a very lucid discussion of Application Protocols, we refer to the reader to the article "Application Protocols - STEP Access" in reference 9. CERC CE TESTBED The Concurrent Engineering Research Center (CERC) at West Virginia University approach to an integrated environment has been to support the PDES/STEP effort by adopting the EXPRESS language as the means of modeling its master conceptual model. Further, the master conceptual model has been aligned with the PDES/STEP standard by incorporating various STEP models. The DARPA Initiative in Concurrent Engineering (DICE) project has also developed translators which convert the EXPRESS syntax into two implementation working forms. The working forms are a framestyle knowledge representation environment and an object oriented engineering database system, allowing application developers to chose the environment most suitable to their task. By design, this introduces the common "real world" problem of multiple representations, CERC developed generic translators between the two

11 representations, as well as translators among CAD systems, a spreadsheet, and a project planner. However, a much more encompassing approach is necessary to fulfill the requirements of a commercial engineering enterprise. In order to accommodate new representations and, more importantly, existing systems, information sharing services are needed to facilitate access to information which is distributed throughout the organization. CERC is addressing this issue by developing a suite of shared information services which will transparently extract data from various systems and present a unified view to the user. These services will initially accommodate the aforementioned framestyle knowledge representation environment, an object oriented engineering database system, a legacy database management system(such as Oracle) and a file management system. An essential component of the DICE/CERC CE environment is a shared information model. Figure 4 suggests the current CERC testbed configuration. MASTER EXPRESS SCHEMA ROSE SCHEMA EXPRESS SCHEMA LASER SCHEMA ROSE INSTANCE STEP PHYSICAL FILE LASER INSTANCE C++ Obj. C CLOS C

12 Figure 4: CE TESTBED Configuration LASER is... ROSE is..., see reference 8 for more information about ROSE as connected to STEP/EXPRESS. WHAT'S NEXT? Today CE and PDES can be viewed as being in a "leap frog" mode, that is in some ways STEP is in front of CE and in others CE is in front of STEP. For example, STEP developers have product data and physical file transfer adequately defined and CE environments are adopting the STEP technology. On the other hand CE technology developers are encouraging the PDES initiative to address process and organizational modeling STEP issues. To punctuate the importance of the STEP-CE linkage and to encourage further cooperation, CERC is continuing an information sharing initiative. The initiative will provide experience in identifying, assessing and integrating the technologies available for modeling, archiving and sharing of product, process and organization data. One activity is the development of the requirements for a CE process and organization model. This prototype process and organization modeling activity should be beneficial to the STEP community in terms of specifying some general process modeling requirements. At present some simple process models are being defined in terms of EXPRESS Schema. REFERENCES 1. Cleetus, J. and R. Wood, Internal CERC report, July, 1991.

13 2. Winner R., J. Pennell, H. Bertrand, and M. Slusarczuk, " The Role of Concurrent Engineering in Weapon System Acquisition", Institute for Defence Analysis, IDA Report R- 338, December Haridim, Y. and M. Watts "Information Architecture Considerations for Concurrent Engineering", CALS/ISG/CE Frameworks Committee Report, Draft, November Palmer, B., " The Infinite Possibility of Data" CERC report, August Burkett, W. C. " What is PDES and Why is Everyone Saying these Things about It?" May Kiggans, R., "PDES, Inc. - Presentation ", Product Data Exchange for the 1990's - Seminar Proceedings, New Orleans, February Palmer, M, M. Gilbert and J. Anderson, " Guidelines for the Development and Approval of STEP Application Protocols", May, Harwick, M et. al., " Managing Change Using STEP/EXPRESS", Third Annual National Symposium on Concurrent Engineering, Washington DC, June 1991, pp Warthen, B., Product Data International, Vol 1., No. 2, Warthen Communications, November ABOUT THE AUTHORS Mr. Tad Davis received his B. A. from Frostburg State University and will receive his M. S. from West Virginia University. He is a senior software engineer for Bell Atlantic

14 Software Systems. He is currently working as a data modeling consultant for the Concurrent Engineering Research Center ( CERC ) Testbed. He has worked on a LASER based system called the Knowledge Server, EXPRESS software tools and schema translators. He has authored two CERC reports pertaining to EXPRESS and LASER software utilities and the CERC testbed common information model. Dr. George Trapp is a Professor of Computer Science and a Researcher at the Concurrent Engineering Research Center at West Virginia University. He received his degrees from Carnegie-Mellon University. Dr. Trapp has authored and co-authored over 50 professional publications. He has refereed numerous manuscripts, and is an Associate Editor for J. Circuits Systems and Signal Processing. He is a member of the following professional and honor societies: Phi Kappa Phi, Tau Beta Pi, Sigma Xi, AMS, SAE and SIAM. He is an active participant in the IGES PDES Organization.