1. STEP for Multi-Disciplinary Model Management: “Intelligent PDM”
NASA’s Intelligent Synthesis Environment (ISE) initiative and its Collaborative Engineering Environment (CEE) will require sophisticated capabilities for the sharing and configuration management of engineering models. Engineers using these advanced environments will have state-of-the-art tools for Computer-Aided Design, Analysis, Simulation, Systems Engineering, Software Engineering, and other engineering disciplines. Each of these discipline’s tools focuses on a view that is in some ways unique and separate from other engineering disciplines, and yet the design of a particular item often requires a collaboration between two or more disciplines -- for example, a printed circuit assembly must be designed and analyzed from the mechanical as well as the electrical point of view in order to meet all system requirements.
The engineering models on which the tools of different disciplines operate are unique in important ways, but if tools from different disciplines are brought to bear on a single product, it is important for data integrity that all tools work to a common underlying structure. This common underlying structure is contained in the STEP standard (ISO 10303), “STandard for the Exchange of Product model data”.
This presentation will discuss how STEP can be used to provide a common structure to which all engineering discipline models refer, so that data integrity and configuration management are maintained.
Stephen C. Waterbury
NASA/Goddard Space Flight Center
Presentation for the
ESA/NASA Video/Teleconference
“STEP for Aerospace Applications”
July 16, 1999

2. The Product Master Model
The Product Master Model is a integrated global model of the totality of information contained in all engineering discipline view-models of the product:
Mechanical design (MCAD)
Electronic design (ECAD)
Analysis (CAE) -- all types
Systems (requirements, behavior, function, rules)
Simulation
Visualization
STEP Application Protocols provide the basis for a Product Master Model

3. Without PDM, CAx Models are “Islands” Models Are Isolated Within Disciplines
Mechanical (MCAD)
Analysis (CAE)
Electronic (ECAD)
Systems Engineering
Tools
Discipline-
Specific
Model
Databases
Item X MCAD
Item X CAE
Item X ECAD
Item X SE
CAD tools typically either save their data to files or to a vendor-specific database, which is also usually specific to a particular engineering discipline, such as mechanical design. There are some vendor-specific solutions to sharing data between two disciplines, such as mechanical design and finite-element analysis, for example, but these solutions are not open, extensible architectures.
In a collaborative engineering environment in which many engineering disciplines are involved, the most valuable resources are the engineers themselves. The engineers should therefore be provided with the “best-of-breed” tools with which they will be most comfortable, capable, and efficient. Although it is sometimes desirable to select a single tool vendor as an enterprise-wide solution in a single engineering discipline (e.g., mechanical CAD), no single vendor can provide a tool suite that contains the best solution for *every* engineering discipline,
Therefore, particularly in large enterprises like NASA, the engineering environment includes a wide variety of disciplines, tools, and vendors. The challenge of sharing and managing the data in this type of environment is precisely the motivation for the development of the STEP standard, which is designed to enable multi-tool and multi-discipline data exchange.
Item Y MCAD
Item Y CAE
Item Y ECAD
Item Y SE

4. Current Product Data Management (PDM): Models Can Be Associated But Not Integrated
Mechanical (MCAD)
Analysis (CAE)
Electronic (ECAD)
Systems Engineering
Tools
PDM
System
Item X MCAD
Item X CAE
Item X ECAD
Item X SE
Item X
Models
Product Data Management, or “PDM”, systems were developed in answer to the requirements of managing large and diverse sets of CAD files, data, and documents in a product development environment. Current state-of-the-art PDM systems provide sophisticated configuration management, versioning, association, product structure representation, viewing, and reporting capabilities. They offer a high-level product-oriented view (vs. a “file-oriented” view) of engineering models and data, grouping together all files and documents associated with a particular product version and configuration,
In this diagram, a PDM system is tracking the two products “Item X” and “Item Y”, and it has grouped the various model files associated with them so that they can be managed as sets. The PDM system can then be programmed to recognize the event of one of the files being updated (for example the Item X MCAD file), and can then execute an appropriate business rule, which might be to automatically create a new version of that file and to notify the users of the other discipline files for Item X that a new version of their files may be needed (e.g., an analysis on the new Item X version, a new layout of Item X’s circuit board, etc.). However, the PDM system will not be able to generate the new views of Item X required for the other discipline models, since PDM systems do not understand the internal semantics of the models. (Note: some of the more advanced commercial PDM systems are implementing the capability to extract assembly structure information from STEP files.)
Item Y MCAD
Item Y CAE
Item Y ECAD
Item Y SE
Item Y
Models

5. “Intelligent PDM” (IPDM): Master Models Integrate Discipline Models
Mechanical (MCAD)
Analysis (CAE)
Electronic (ECAD)
Systems Engineering
Tools
Models (Discipline Views)
AP 203
AP 209
AP 210
AP 233
STEP AP's
This diagram illustrates the concept of “Intelligent PDM”. The essential ingredients for Intelligent PDM are:
(1) a set of discipline-specific information models (the examples shown are the STEP Application Protocols 203 [MCAD], 209 [Finite-Element Analysis], 210 [ECAD], and 232 [Systems Engineering]);
(2) STEP translators for the discipline tools: since Intelligent PDM is based on STEP, each tool to participate in this environment must have a STEP import/export capability;
(3) a Product Master Model, which incorporates the STEP AP’s as subsets and represents each common object once. For example, the geometry of the product is a subset of the Product Master Model, and is “reflected” in the MCAD, ECAD, and Analysis models, in which it may have different projections (e.g., 2-D or “2.5”-D in an ECAD model) or transformations to lower fidelity. The Product Master Model could be thought of as a “union” or “superset” of all the discipline models of the product.
(4) mappings between the discipline-specific views of the product (the STEP AP’s) and the Product Master Model. These mappings are being developed using the EXPRESS-X mapping language, a new part of the STEP standard.
The diagram depicts the discipline tools feeding their models through the STEP AP’s and mappings into the Master Models for Spacecraft X and Instrument Y. The Intelligent PDM system can then generate, through the reverse mappings, the changed versions of the other discipline models.
NASA
Discipline
View Mappings
STEP
Testbed
Integrated
Master Models
Instrument Y
Master Model
Spacecraft X
Master Model

6. Plug-and-Play IPDM: CORBA PDM Enablers Object Interfaces
Mechanical (MCAD)
Analysis (CAE)
Electronic (ECAD)
Systems Engineering
CORBA-
Enabled Tool
IIOP
AP 203
AP 209
AP 210
AP 233
Instrument Y
Object
This diagram illustrates the concept of “Intelligent PDM”. The essential ingredients for Intelligent PDM are:
(1) a set of discipline-specific information models (the examples shown are the STEP Application Protocols 203 [MCAD], 209 [Finite-Element Analysis], 210 [ECAD], and 232 [Systems Engineering]);
(2) STEP translators for the discipline tools: since Intelligent PDM is based on STEP, each tool to participate in this environment must have a STEP import/export capability;
(3) a Product Master Model, which incorporates the STEP AP’s as subsets and represents each common object once. For example, the geometry of the product is a subset of the Product Master Model, and is “reflected” in the MCAD, ECAD, and Analysis models, in which it may have different projections (e.g., 2-D or “2.5”-D in an ECAD model) or transformations to lower fidelity. The Product Master Model could be thought of as a “union” or “superset” of all the discipline models of the product.
(4) mappings between the discipline-specific views of the product (the STEP AP’s) and the Product Master Model. These mappings are being developed using the EXPRESS-X mapping language, a new part of the STEP standard.
The diagram depicts the discipline tools feeding their models through the STEP AP’s and mappings into the Master Models for Spacecraft X and Instrument Y. The Intelligent PDM system can then generate, through the reverse mappings, the changed versions of the other discipline models.
Discipline
Model Mappings
Integrated
Master Models
Spacecraft X
Master Model
Instrument Y
Master Model
NASA
STEP
Testbed

7. Preliminary Components Interface Control Docs
The Product Master Model: Progressive Population of Model Over the Mission Life Cycle
Pre-Phase A
Requirements
Functional Model
Mission Parameters
Preliminary Components
Integrated Mission Proposal
Phase A/B
Prototyping and Analysis
Requirements
Functional Design
Behavioral Model
Mission Parameters
Physical Model
Phase C/D
Requirements
Functional Design
Behavioral Design
Physical Design/Arch.
Interface Control Docs
Mission Parameters
Detailed Design, Build, and Test
Another benefit of the Intelligent PDM approach is that it provides continuity of the product’s definition as it evolves through the various phases of its development life cycle.
Imagine the Product Master Model’s framework as a large set of “shelves” or labeled compartments for the various aspects of a comprehensive product model. In the early conceptual definition of the product (corresponding to Pre-Phase A studies for a NASA mission), only a few of the shelves or compartments are populated, and that data may not be complete in the early stages. Still, it is important to propagate that high-level data, containing requirements and mission parameters, to the later phases of development and to allocate it to the various aspects of system design that it defines and constrains. These allocation relationships are supported in the Product Master Model, and can be viewed by the systems engineer at any point by extracting the systems engineering view of the evolving Master Model.
In the early phases, the model may be populated just enough to enable low-fidelity simulations, for example. Another benefit of the Product Master Model is the capability to identify what additional data is needed in order to generate particular types of analysis or simulation models.
As the Product Master Model becomes fully populated, more detailed views and simulation models can be generated, until finally the design model can be used to generate detailed drawings and fabrication models.

8. Product Master Model-Enabled Capabilities
“Intelligent Product Data Management”
Features:
Integration of heterogeneous, multi-disciplinary models into a progressively and continuously defined Master Model
Algorithmic generation of discipline-specific view-models (where possible) on demand
Interdisciplinary tool “object services” (e.g., live linkage of design features between CAD and analysis models)
Integration & persistence of global product model knowledge
Integrated Model-based Systems Engineering
Master Model explicitly identifies and maintains discipline model interdependencies
Can provide immediate feedback on change impacts
Supports cross-disciplinary view of requirements, function allocation, and behavior

9. Initial IPDM Capabilities: NASA STEP Testbed FY99 Plans
Initial PDM Enablers (PDME) interfaces (CORBA/IIOP access)
Check-in/out via PDME (or via file upload thru Web browser) of STEP models/files
User-specified project/system/subsystem hierarchy
Standardization of a NASA Systems Engineering Information Model
Harmonization of Mission Design Parameters among NASA’s Integrated Design Centers
Mapping of harmonized parameters to STEP AP 233 (Systems Engineering)
Prototyping of MCAD/ECAD/CAE model integration and sharing
The NASA STEP Testbed is collaborating with Boeing, IBM, and Delco-Delphi in the PDES, Inc. Electromechanical Pilot*
* The PDES, Inc. Electromechanical Pilot Project is implementing MCAD/ECAD model exchange using STEP AP 203 and AP 210.
The FY99 Plan for the NASA STEP Testbed includes the following features. The first 2 are basic PDM functions, which will be implemented using the STEP model for PDM. The second 2 items represent the initial phase of development of the multi-disciplinary Product Master Model:
* File check-in/check-out (via Web interface) -- this will be the initial user interface for input to the system. The Object Management Group’s “PDM Enablers” interface will also be implemented (using CORBA and/or Java), and as more tool vendors implement that interface, a more transparent connection between CAx tools and the system will become available.
* Input and reporting of project system/subsystem hierarchy. This can include “Work-Breakdown”-style structuring and/or product assembly structuring.
* The standardization of a NASA Systems Engineering Information Model will be coordinated with NASA’s various Integrated Design Centers, which are often the first activities to populate the Product Master Model.
* As a contribution to the PDES, Inc. Electromechanical Pilot, the NASA STEP Testbed will develop the capability to “split” and “merge” MCAD (AP 203) models and ECAD (AP 210) models. This will be the first increment in the implementation of the Product Master Model, integrating the mechanical and electrical views of an electromechanical product.

10. For More Info: STEP/OMG URL’s!
STEP On-Line Information Service (SOLIS) --
Expresso for 95/NT (free download) --
Note: if interested in the server (Unix) version of Expresso, contact Steve Waterbury
STEP On A Page (a capsule summary and current status of STEP)
PDES, Inc.: a government-industry consortium implementing STEP --
USPRO (U.S. Product Data Association), distributor for STEP documents --
NASA STEP Central: the main NASA site for STEP information --
The NASA STEP Testbed: STEP/OMG infrastructure pilot project --
The OMG Manufacturing Domain Task Force (MfgDTF): PDM Enablers, etc. --

11. AP 203: Configuration Controlled 3D Designs of Mechanical Parts and Assemblies
Configuration Management
Authorization
Control(Version/Revision)
Effectivity
Release Status
Security Classification
Supplier
Geometric Shapes
Advanced BREP Solids
Faceted BREP Solids
Manifold Surfaces with Topology
Wireframe with Topology
Surfaces and Wireframe without
Topology
Specifications
Surface Finish
Material
Design
Process
CAD Filename
Product Structure
Assemblies
Bill of Materials
Part
Substitute Part
Alternate Part

12. AP 209: Composite & Metallic Analysis & Related Design
Configuration Control, Approvals
Part, product definitions
Finite element analysis model, controls, and results
Analysis Discipline Product Definitions
Finite Element Analysis
Model (Nodes, Elements, Properties,...)
Controls (Loads, Boundary Constraints,...)
Results (Displacements, Stresses,...)
Analysis Report
Design Discipline Product Definition
Shape Representations
Assemblies
Information Shared Between Analysis & Design
3D Shape Representations
Composite Constituents
Material Specifications & Properties
Part Definitions
Ply Boundaries, Surfaces
Laminate Stacking Tables
Reinforcement Orientation
Composites
Homogeneous (metallics)
3D Shape Representation
AP202/203 Commonality Plus Composite Specific 3D Shapes
Advanced B-Representation
Facetted B-Representation
Manifold Surfaces With Topology
Wireframe & Surface without Topology
Wireframe Geometry with Topology
Composite Constituent Shape Representation

13. AP 210: Electronic Assembly, Interconnect, and Packaging Design
Part
Functionality
Termination
Shape 2D, 3D
Single Level Decomposition
Material Product
Characteristics
Product Structure/ Connectivity
Functional
Packaged
Physical
Component Placement
Bare Board Geometry
Layout items
Layers non-planar,
conductive & non-conductive
Material product
Configuration Mgmt
Identification
Authority
Effectivity
Control
Requirement Traceability
Analytical Model
Document References
Geometry
Geometrically Bounded
2-D Shape
Wireframe with Topology
Advanced BREP Solids
Constructive Solid Geometry
Requirements
Design
Allocation
Constraints
Interface
Technology
Fabrication Design Rules
Product Design Rules