Emerging Challenges for Long Term Archiving and Retrieval of Product Authority Data
Terrence J. McGowan, Boeing, ECMA TC43 U3D Co-Chairman

Authority product data must be retrievable and usable with explicit representation of digital product authority for many years. How can this be accomplished?

Situation
As aerospace product development advances into the 21st Century, new methods and practices will be needed to meet the challenges associated with long term retention of digital product definitions. The days of simply storing documents on various media types and cataloging them is no longer sufficient. Digital product definitions, derived from computer based tools, possess complex data structures with explicit and semantic data representations. Type certification of the product authority is established from this structured authority data.

Regulatory agencies require guaranteed longevity for a variety of digital data objects, (i.e. aircraft type design data, etc.). This type of data must be preserved and be accessible in a usable form during the operational life of the product. Failure to meet this requirement can result in litigation costs associated with the inability to retrieve and use the type certified data. The preservation and accessibility of this design and PDM data is very important for data re-use in the future. Structured data must maintain its integrity and be accessed with appropriate security layers established. Also, it is vital to ensure that the retrieved data is in a usable form for the life of the type certificate.

Additionally, OEMs are required to demonstrate to an official authority, the proper functioning of the product records system. Non-standard or program specific PDM schemas present many challenges for storing structured data in a perpetual state. Standardization brings congruency to these processes.

Archiving requirements are very specific and must be adhered to for continued readability, authenticity, and traceability. Archiving considerations include: What is the purpose of the archived data? What process will be used to archive? What level of data quality is required? Any archival process needs to be well defined and well documented. Digital archiving requirements demand open and neutral standards for storing process data, format data content, and data quality requirements. Some of the open standards which address these requirements are:

• OAIS –Open Archival Information System (ISO 14721.4)
• STEP –file formats (ISO 10303-21, ISO 10303-28)
• STEP –product models (ISO 10303-2xx, ISO 15926)
• LOTAR -Long Term Archiving and Retrieval (EN9300)

What are Open Standards?
A standard for product data interoperability (exchange, visualization, sharing, and long term data archiving) is open if:

• The data model is fully described according to state of the art practices.
• The format and the services implementing the data are described explicitly.
• The use of the standardized data is free of charge.
• The updating process of the associated components are described and well accepted by the community of involved parties.
• Companies using the standard participate in the ballot for updates.

The advantages of using open standards include the following:  broader tool selection, freedom from licensing restrictions, control of data destiny, interoperability and rigid conformance. Some of the disadvantages of open standards are: slow development pace, incompleteness of specification, lack of user support and inadequate vendor adoption.
In a document centric environment the difficulties associated with archiving are limited to document management and document quality. In a highly structured digital environment the data archiving requirements increase exponentially.

Conclusion
As more and more product design data is generated using 3D tools, robust and complex structured digital data needs to be managed in a predictable and intelligible manor. A standardized consumable open format for archiving and retrieval will need to be adopted. CAD tool vendors must be a part of this agreement. The modern parametric software tools used in creating three dimensional models produce complex structured file formats which are controlled by the tool vendor. Data is locked to a proprietary format. An irony is that the derivative data belongs to the customer but it is held captive by CAD vendor proprietary formats. This situation must be addressed to meet the challenges of future data archival.
In summary, digital data must be archived in a digital form. Structured data can not be represented outside of the digital domain. To ensure a reliable archival architecture, a digital archival solution must use open standards. Proprietary standards can disappear over time as market competition replaces weaker technology companies. Open standards will require industry involvement and are vital for archival system development and implementation. An industry consensus between CAD vendors and users must occur for any meaningful archival system implementation.