Apparel Product Data Exchange Standard

                                Y. Tina Lee

                    Factory Automation Systems Division
                   Manufacturing Engineering Laboratory
              National Institute of Standards and Technology
                          Gaithersburg, MD 20899

ABSTRACT

     The apparel industry is increasingly reliant on computer technologies to support activities
throughout the product life cycle. As computers become more widely used in design, pattern
making, grading, and automated manufacturing, the industry is becoming more aware of the
potential benefits of exchanging information electronically. A standard for communication among
different CAD/CAM systems is also becoming a very important issue. The Standard for the
Exchange of Product Model Data (STEP) is an emerging international standard, the result of an
effort to develop a mechanism for digitally representing the physical and functional
characteristics of a product throughout a product's life cycle. In recent years, the National
Institute of Standards and Technology (NIST), under the Defense Logistics Agency's
sponsorship, has been working on extending STEP to include apparel product data to support
computer integration of the apparel life cycle. The work is continuing to be carried out with
support from, and in cooperation with, standards organizations, the apparel manufacturing
industry, and academia. NIST recently proposed to the American Apparel Manufacturers
Association (AAMA) that they establish a task group to develop formal application protocols as
extensions to STEP for apparel. The AAMA has agreed to this proposal. This paper describes
the proposed activities.

KEY WORDS

APDES; apparel; apparel PDES; application protocols; CIM; pattern; PDES; product data;
product data exchange; STEP

INTRODUCTION

     The apparel industry is in a transition from a labor-intensive, manually operated
technology base to a more competitive computer technology base. Apparel companies are using
an increasingly larger number of computer systems in all phases of design, analysis,
manufacture, and support of their products. This increasing role of computer systems in
manufacturing, logistic support and system integration is leading to a greater need for standards.
The apparel industry, through the American Apparel Manufacturers Association (AAMA), has
recognized the importance of computer-integrated manufacturing (CIM) and has started to
develop standards in this area.
     The objective of the CIM Subcommittee of the AAMA Apparel Research Committee,
(formerly the CIM Committee or CIM/COM), is to promote the utilization of CIM concepts in
the apparel industry through the development and establishment of standards and protocols. Over
the last several years, the CIM Subcommittee has accomplished several tasks, such as the
establishment of a standard for numerically controlled (N/C) fabric cutting machines, the
recommendation of a standard for a CIM network protocol, and the development of a pattern
data exchange standard. Currently, there are six task groups for standards development within
the CIM Subcommittee: CIM Architecture, Cutter, Pattern Data Interchange, Spreading, N/C
Stitching, and Education/Publication.
     In November, 1989, the CIM/COM asked the University of Southwestern Louisiana
(USL) and the National Institute of Standards and Technology (NIST) to recommend a strategy
for developing a neutral data format for the representation and exchange of pattern piece data.
The resulting report [1] recommended a two-phase approach. The initial effort would be to
develop a standard based on some file format already in widespread use. The report
recommended using the popular DXF format defined by AutoDesk, Inc. For the second phase
of work, the report recommended that the Standard for the Exchange of Product Model Data
(STEP), an international standard still under development, be extended to support apparel
applications. This second phase would result in a standard that would have capabilities beyond
those envisioned for DXF. The CIM/COM accepted these recommendations, and work was
begun within the Pattern Data Interchange (PDI) Task Group to standardize the use of DXF to
exchange pattern data. At the same time, NIST began an effort to define how STEP could be
extended to support apparel manufacturing.
     The first phase of work is now nearly complete and it is time for the Task Group to enter
the second phase of work. A set of conventions for using DXF as a pattern data exchange
standard has been developed, and USL, under contract to the AAMA, is preparing these
conventions for consideration as a U.S. national standard under guidelines of the American
National Standards Institute (ANSI). Meanwhile, NIST has prepared a road map for how the
new work should proceed.
     This paper describes the work that the Task Group is starting. The next section presents
some background information about STEP and the history of the CIM/COM activities in product
data exchange. We then describe STEP application protocols: the established framework for
extending STEP to new application areas. Following that, we discuss how the Task Group will
use this framework to extend STEP to support the apparel industry. The final section of the
paper reports the current status of these activities.

BACKGROUND

     STEP is an emerging standard, the result of an international effort to develop a
mechanism for the exchange of product data among all stages of the life cycle of a product.
STEP is considered by many to be a critical technology for improving America's
competitiveness in manufacturing [2]. Product Data Exchange Using STEP (PDES) is the United
States' organizational activity that supports the development and implementation of STEP. A
National PDES Testbed, under the sponsorship of the Computer-aided Acquisition and Logistic
Support program of the Department of Defense, has been established at NIST. This facility
provides testing and validation for the emerging standard [3]. The applications addressed by
PDES to date include mechanical piece parts; mechanical assemblies; architecture, engineering,
and construction; finite element models; manufacturing applications; drafting applications; and
electrical printed wiring board products. A software toolkit for manipulating PDES data has been
developed at the Testbed [4]. The apparel industry can greatly leverage its own efforts by joining
in the PDES effort. An Apparel Pattern Information Model was developed at NIST to
demonstrate the feasibility of extending STEP to include the exchange of apparel pattern data
[5]. A computer program, an implementation of the Apparel Pattern Information Model, has also
been developed at NIST [6]. It demonstrates the exchange of two-dimensional pattern data
between different industry formats.
     In recent years, NIST, under the Defense Logistics Agency (DLA) sponsorship, has been
working on developing the apparel product data exchange standard (APDES). Both NIST and
DLA have a strong interest in encouraging the development of apparel PDES. However, the
work can only be achieved with support from, and in cooperation with, standards organizations,
the apparel manufacturing industry, government, and academia. The AAMA can provide the
industry leadership needed to make this effort succeed. 
     In May 1991, NIST proposed a strategy for APDES implementation by formally
establishing an APDES task group within the CIM Subcommittee. The mission of this task group
would be to extend STEP to include apparel product data. The final goal of this task group
would be to provide STEP application protocols for specific apparel application systems required
to design and manufacture a garment. The proposed activities are reiterated in a later section of
this paper. The AAMA CIM Subcommittee accepted the proposal and decided that the PDI Task
Group that developed the DXF pattern exchange standard would be the best organization to work
on APDES. 
      The PDI Task Group will be restructured. The group will continue the work to complete
the DXF standardization procedure. It will also begin the longer term work of developing
APDES. The restructured Task Group will be more in the nature of a technical working group
rather than a review committee for technical work done outside of the organization. An expanded
scope statement of the Task Group's new mission is now under development. 

STEP AND STEP APPLICATION PROTOCOLS

     STEP provides a neutral mechanism for representing product data throughout the life
cycle of a product. STEP defines the information that describes products within different
computer applications and across different enterprises. STEP application protocols are essentially
subsets of STEP. STEP application protocols are themselves standards that define the context,
the use, and the kind of product data for a particular data sharing scenario. An application
protocol is a standardized way of implementing a portion of STEP for a specific application. The
concept of an application protocol allows vendors to build an application system that can
interface with STEP data in a standard manner. The expectation is that there will be many STEP
application protocols. Our APDES project is aimed at developing application protocols for
different apparel applications. For example, an application protocol for apparel pattern design
may be developed to address the use of a pattern design system to provide pattern pieces of
garments to a marker system.
     Application protocols employ three types of models: an application activity model, an
application reference model, and an application interpreted model [7]. These models are defined
as follows: 

     - Application activity model: A representation of one or more activities which use
                                   product data in a specific application context. The
                                   model defines the scope and information
                                   requirements that the application protocol will
                                   address. It is used to establish an understanding of
                                   an agreement on the application activities and
                                   processes.

     - Application reference model:     A model that describes the information requirements
                                        and constraints for an application domain. The
                                        model uses application-specific terminology and
                                        rules familiar to an expert from the application
                                        domain.

     - Application interpreted model:   A specification of standardized STEP data that
                                        match the requirements described in the application
                                        reference model. This model ties the application
                                        reference model to the rest of STEP.

     An application protocol also includes a complete set of abstract test cases to support
conformance testing and a validation report. An abstract test case is a complete and
implementation-independent specification of the actions required to achieve a specific test
purpose. (For example, one of the abstract test cases for marker-making may be to find all the
pattern pieces in the garment.) Validation testing is the process to ensure that the application
protocol is complete, unambiguous, and functional. Validating an application protocol is a
complex process that includes: evaluating the scope and requirements; validating the application
reference model and the application interpreted model; evaluating conformance requirements and
test purposes; and implementing prototype systems to test the application protocol.

APDES ACTIVITIES

     The work to develop APDES includes administrative and technical activities. NIST,
under DLA sponsorship, will provide administrative guidance to coordinate the work of the PDI
Task Group with the national and international activities. NIST will also provide technical
support in STEP development methods and tools. This work will be a formal and active
standards-development effort. 

Administrative Activities

     (1) Restructure the PDI Task Group. A new charter and scope of the work will be
drafted, reviewed by the CIM Subcommittee, and documented. A chairman will be selected from
group members. This group will be expanded to include experts from the CIM Subcommittee,
ARC, and other interested parties. The Task Group needs recruits and more participation,
including non-AAMA members. 
     (2) Obtain recognition from the IGES/PDES Organization (IPO). The IPO is the body
of volunteers who have developed IGES and are participating in the development of STEP. The
IPO is working with other standards-making organizations, both foreign and domestic, to achieve
the formal adoption of STEP as an international standard [8]. The IPO is the U.S. liaison to the
International Organization for Standardization (ISO). The IPO comprises three components:
Steering Committee, General Assembly, and Administration Office. The Steering Committee
provides management direction, policies, and procedures. The General Assembly is a working
body that is charged by the Steering Committee to develop standards and specifications and gain
consensus approval for them. The Administration Office provides administrative services and
professional staff to support the work of the IPO. The General Assembly comprises a Chairman,
Standing Committees, Technical Committees, and Interest Groups that together perform the
technical development and validation work required to create and approve standards and
specifications. To start development of APDES, the PDI Task Group will propose to the IPO
Chairman that the Task Group should serve as an Interest Group within IPO to undertake
specific technical projects in its domain of interest. Once the project activity is ongoing for a
long enough period of time, the Task Group may seek recognition as a Technical Committee.
     (3) Participate in the IPO meetings. The General Assembly of the IPO will meet in
regular session four times a year. In addition to the quarterly meetings, special meetings may
be called as needed. Task Group representatives will participate in the IPO meetings as needed. 
     (4) Provide PDES/STEP training courses to group members. NIST will help to establish
training courses as needed.
     (5) Hold Task Group meetings. The Task Group will meet quarterly or as determined by
the Task Group chairman. The CIM Subcommittee will accommodate this Task Group activity
in its meeting agenda. The Task Group will also meet independently as needed. These group
meetings will be used to define objectives, identify topical areas, develop plans, discuss technical
and non-technical issues, perform technical reviews, and generally manage the evolution of the
apparel standards based on STEP.
     (6) Perform the standardization process. STEP is being developed by the ISO Technical
Committee 184 (Industrial Automation Systems and Integration). Subcommittee 4 of ISO
Technical Committee 184 (ISO TC184/SC4) is responsible for manufacturing data and
languages. The Task Group will follow established procedures of ISO TC 184/SC4 for obtaining
an international standard. 

Technical Activities

     The technical activities are aimed at developing application protocols within the
procedural guidelines for international standardization. The APDES work will parallel the
existing work in other STEP application areas. Prior to developing application protocols, the
Task Group will define a glossary of terms used in apparel design and production. To begin
with, the Task Group will identify specific topical areas and their corresponding application
systems for application protocol development. Other topical areas will be started at a later date.
The process of producing an application protocol includes five steps [7]:
     (1) Develop and document an application protocol summary. This defines the scope and
requirements of the application protocol. The task group will clearly define what the application
protocol applies to and what the application protocol's functionality includes. This activity will
be performed using the IDEF0 modeling methodology [9] and will produce an application
activity model. Definition of scope and information requirements shall be reviewed by experts
in the application. 
     (2) Develop and document an application reference model. The application reference
model, a data model that defines the information requirements in terms familiar to an expert in
the relevant application area, will be developed using the EXPRESS [10] or the IDEF1X
information modeling methodology [11]. This model shall be reviewed by both expert modelers
and application experts.
     (3) Develop and document an application interpreted model. When the application
reference model has been developed and reviewed, the model must be integrated with the STEP
resource models. This integration process maps the application specific data requirements from
the application reference model to the general STEP data models where applicable. The activity
will generate an application interpreted model using EXPRESS. This model shall be reviewed
by both STEP experts and application experts to ensure that it is complete and correct.
     (4) Develop conformance requirements and test purposes. This defines simulations or
prototype systems and evaluation criteria for the purpose of evaluating implementation concerns
and performing tests using actual data. A complete set of abstract test cases shall be provided
in the application protocol. These are derived from three areas: scope and requirements, the
application reference model, and the application interpreted model. The Task Group will recruit
organizations to implement simulations or prototype systems that will be used to perform
conformance testing. 
     (5) Validate the application protocol. This process leads to the development and execution
an application protocol validation plan. The scope and requirements evaluation, application
reference model validation, application interpreted model validation, conformance requirements
and test purposes evaluation, and application protocol validation via prototypes will be
performed. The development and validation of a STEP application protocol is an iterative
process. Each step in this process provides critical feedback for the next iteration.

STATUS OF APDES

     The PDI Task Group of the CIM Subcommittee is now moving toward a long-term goal:
the development of a comprehensive standard for sharing apparel product data throughout the
entire product life cycle using the STEP technology. The Task Group is now seeking recognition
as a Special Interest Group from the IPO. The Task Group has been compiling a glossary of
terms used in the apparel design and manufacturing arenas. The Task Group has also begun to
develop an informal application protocol for apparel pattern making. The informal application
protocol will be developed using the STEP methodology, but will not include development of
an application interpreted model. This informal application protocol will be used to study the
STEP methodology within the context of the apparel industry. Based on a successful evaluation,
the next phase will be the development of formal application protocols for the apparel industry.
     APDES is an on-going project which was initiated by DLA and is being carried out by
NIST. APDES provides a neutral mechanism capable of completely representing product data
throughout the entire apparel life cycle. Recently, the CIM Subcommittee of the AAMA
endorsed and began actively participating in the effort. The APDES standard is for the apparel
industry; therefore, the engagement of the industry is critical. Broader participation in this effort
will help the work proceed more quickly and will improve the value of APDES to the industry.

REFERENCE

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     Formats for the Representation of 2-D Pattern Pieces," USL A-CIM Technical Report
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[2]  Carver, G. P., and Bloom, H. M., "Concurrent Engineering Through Product Data
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[3]  McLean, C., "National PDES Testbed Strategic Plan 1990," NISTIR 4438, NIST,
     October, 1990.

[4]  Clark, S. N., "An Introduction to the NIST PDES Toolkit," NISTIR 4336, NIST, May,
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[5]  Lee, Y. T., "On Extending the Standard for the Exchange of Product Data to Represent
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[6]  Moncarz, H. T., and Lee, Y. T., "Apparel STEP Translator," NISTIR 4612, NIST,
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[7]  Palmer, M., "Guidelines for the Development and Approval of STEP Application
     Protocols," ISO TC184/SC4/WG4 N 25 (P5), ISO, September, 1991.

[8]  IGES/PDES Organization, "IGES/PDES Organization Reference Manual," National
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[9]  U.S. Air Force Wright Aeronautical Laboratories, "Function Modeling Manual
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     Volume IV, Materials Laboratory, U.S. Air Force Wright Aeronautical Laboratories,
     June, 1981.

[10] Spiby, P., "EXPRESS Language Reference Manual," ISO TC184/SC4/WG5 Document
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[11] U. S. Air Force Wright Aeronautical Laboratories, "Information Modeling Manual
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