BSI Standards PublicationAerospace series — LOTAR — Long term archiving and retrieval of digital technical product documentation such as 3D, CAD and PDM data Part 003: Fundamentals and c
Introduction
General
Different user communities have different definitions for long term archiving and retention This clause explains the major differences of both terms and their relation to the scope of EN 9300
Aerospace companies must retain data to meet business, certification, and legal obligations, with a focus on digital formats This necessity gives rise to four key considerations for the retention of digital data.
Invariance: how important is it to ensure that digital data is not altered
Objectives: why keeping of digital data is required
Length of time: the required length of time for retaining digital data
Stored Form: the stored format of the digital data
This section addresses key considerations for long-term archiving and retention, forming the foundation for the scope definition of EN 9300 The scope of EN 9300 integrates various elements related to long-term archiving and retention practices.
Invariance
Invariance ensures that information remains unchanged, providing evidential weight that the design intent is preserved Three distinct categories can be identified in this context.
Auditable – where validation methods and test suites ensure that information cannot be changed without the change being detected
The implicit system is engineered to prevent alterations, requiring oversight of activities that could modify digital data This supervision can be implemented through a separate write-protected vault Evidence of "no change" is demonstrated by the lack of recorded changes and the reliability of the system itself.
Not required – where changes to data are not explicitly controlled
Of the three, auditable invariance is the strongest, and is likely to be the most suitable where the information is used in legal proceedings.
Objectives for keeping digital data
Digital data often faces challenges due to its storage in proprietary formats, which may become unrecognizable over time To ensure long-term interpretability, it is crucial to utilize neutral archiving formats as recommended by EN 9300 This standard advocates for the adoption of standard formats for long-term archiving, along with regular migrations of both storage media and data formats To mitigate the risk of data loss during migration, it is essential to renew time stamps and digital signatures that maintain the integrity and immutability of archived data Implementing auditable archiving and retrieval processes further guarantees data readability and integrity across current and future systems.
The objectives for keeping the data are distinguished into two major subcategories:
Legal requirements/certification requirements, such as for proof of technical documentation for actions in law
Business requirements, such as keeping knowledge
Within the two subcategories EN 9300-003 offers four characteristics which describe the objectives in more detail:
To maintain the integrity of original data generated by a source system, it is essential to preserve it as evidence of its state on a specific date, aligning with the legal requirement subcategory.
To keep data available to new users over the period for which it is kept This characteristic fits with the subcategories ‘legal requirement’ and ‘business requirement’
To be able to preserve the source of the kept data This characteristic fits with the subcategory ‘business requirement’
To be able to reuse the data, for example, by modifying design data to meet new requirements This characteristic fits with the subcategory ‘business requirement’.
Length of time of keeping data
The life cycle of software and hardware is significantly shorter than that of aircraft Digital data life cycles are characterized by software versions and generations Typically, a new software version within the same generation modifies only a small portion of the software's functionalities while maintaining the existing data format In contrast, a generation change involves substantial alterations to the software, such as a shift to a new architecture, which may lead to the introduction of new data formats.
The release cycle for CAD software typically ranges from 6 to 12 months for new versions and 3 to 10 years for new generations In contrast, the life cycle of an aircraft can extend from 30 to 50 years or more This disparity leads to specific definitions outlined in EN 9300.
Short term - within one or two versions
Medium term - within one generation
Long term - over multiple generations
Additionally to the technical aspects, legal requirements have to be considered when defining archiving terms For further information see EN 9300-001 (Structure) and EN 9300-002 (Requirements).
Stored Form
A crucial difference exists between representation and presentation Representation refers to how a computer stores information about a concept, while presentation pertains to the form or appearance of that information to a human For instance, a musical score serves as a representation of a musical piece, whereas a recording of that piece acts as its presentation.
The stored form has been divided into three main subcategories:
Detail Level: the description level of model;
Representation: describing the different logical forms of data representation;
Format: describing the different physical formats of the data
An accurate representation is where data elements are described in the original level of detail, independent of whether they are represented in a native or other format;
An approximate representation is where data elements are described in a lower level of detail than the accurate representation, e.g where a curved surface is approximated by a set of small, flat faces
A native representation is that created by and private to the source system;
A derived representation transforms native data into an alternative format, such as converting a text document into an HTML version, which can be based on either a native or standardized format.
A presentation is a visualization of data to a user, e.g a drawing or a print out of product structure information as a snapshot of the current data representation
A native format refers to a proprietary data format that is specific to a particular system or interface It is closely tied to the life cycle of that system, including its versions and generations.
A standardized open format refers to a data format defined by a wide community, such as ISO, that is independent of specific systems or interfaces The term "open" indicates that the format is fully documented in both syntax and semantics, and is available for free use Furthermore, standardization processes govern the procedures for any changes to the standard.
Including both accurate and approximate representations is essential, as they can be archived simultaneously in a standard format like STEP This format is well-documented and tends to remain stable for a significantly longer duration compared to native formats.
Terminology
General
From descriptions in 4.1, the following definitions of terms are derived: Product information model, Product model, Business Application, Retention and Long Term Archiving These definitions are used within EN 9300.
Product information model
The Product information model represents an information model which provides an abstract description of facts, concepts and instructions about a product, e.g STEP 2 ) Application reference model or STEP Application interpreted model
Product model
The Product model serves as a specific instance of a product information model tailored for individual products, such as the geometric model of part a123 Companies develop various types of product models based on different life cycle stages or disciplines, including models like "space allocation mock up." Notably, product models maintain independence from their presentation formats.
As a further determination EN 9300 distinguishes:
A dynamic or temporary Product Model (in internal memory of the computer),
The static Product Model (e.g represented as a file or as a data base on permanent storage media, such as disks or tapes);
Product Models can be accessed and queried through applications by loading the static form of the Product Model into its dynamic form in memory.
Additionally there are different usages of a Product Model, optimized for different functions/users intents
The Working Form Product Model is utilized for the creation and modification processes within the native application, aligning with the design phase of the Product Model This Working Form typically exists in the native format of the COTS (Commercial Off-The-Shelf) application.
The Original Product Model is specifically designed to maintain the design intent for Long Term Archiving, ensuring compliance with certification and legal requirements for proof It can be stored in either a native or standardized format.
Based on these definitions, EN 9300 recommends the archiving for long term of the original & accurate
Product Models in a standardized static format, such as STEP, can be retrieved and subsequently loaded into applications in a temporary dynamic form This process allows for the validation of properties and the execution of specified operations, including consultation.
In the scope of EN 9300, an application is a piece of software, which allows processing the Product Model according to a dedicated purpose This purpose can be:
the visualisation with possible 3D measurement,
a type of simulation (FEA, aerodynamics, …),
Business Application
A Business Application is software that generates native Product Models for creation and modifications, which must be converted into a standardized Product Model for Long Term Archiving Relevant examples of Business Applications for CAD Product Models include Unigraphics, Catia V5, CADDS5, and Pro/Engineer For PDM Product Models, notable Business Applications include VPM, Metaphase, Enovia, and Windchill.
The Long Term Archiving process for a specific Product Model begins with defining Use Cases that the Retrieved Product Model must support For instance, Use Cases related to the Long Term Archiving of 3D Definition models focus on information visualization, while those for Finite Element Analysis models emphasize replaying simulations to validate that sub-assemblies can withstand the associated load cases.
See the next Figure 1 illustrating the types of functions of Business applications for Product Model processing
Figure 1 — Example for retrieve use case for specification of long term retention
Retention
“Retention”: Storage of data for reuse of a later date:
aiming for data re-use and to keep data available;
retaining any of the representations needed, but not the presentations;
working over medium and short term;
expecting invariance, though this is not mandatory;
migration of the data format is allowed to guaranty data quality and interpretability.
Long Term Archiving
“Long Term Archiving”: Storage of a copy of data in an appropriate way for record, certification and legal purposes
The data will be preserved and kept available for a use within the archive and possibly for further re-use
Certified conversion processes enable the transformation of native data from the source system into a format suitable for long-term archiving This ensures compliance with legal and certification requirements, allowing the stored data to be either an accurate or approximate representation of the original source.
Integrity must be ensured by a digital signature
The data is retained over the long term
Business, legal and certification requirements are covered
The relation of these two terms to the concepts is shown in the following Figure 2
Figure 2 — Retention and Long Term Archiving
Scope of EN 9300
According to definitions of previous clauses, the scope of EN 9300 can be described as follows:
The reasons for archiving of digital data include business and certification as well as legal requirements, keeping data available for re-use and preserving the original information
An accurate representation is essential, while an approximate representation can help validate the geometry of recovered files Retaining the native representation is important primarily for short to medium-term use Additionally, visualization can aid the retrieval process, although it is optional.
Retention is for the long term
Invariance must auditable to fulfil business and certification requirements
The following Figure 3 gives an overview of the scope for EN 9300
Figure 3 clearly distinguishes between the mandatory aspects of the scope, represented by a solid line with an arrow, and the optional aspects for EN 9300, indicated by a dashed line with an arrow.
Relation to Legal Admissibility Standards
"Code of Practice for Legal Admissibility and evidential weight of information stored electronically"
Existing standards like BP 0008, which outlines the "Code of Practice for Legal Admissibility and Evidential Weight of Information Stored Electronically," offer comprehensive guidance on the business practices necessary to ensure the legal validity of electronic documents While these standards provide a general framework, they are compatible with LOTAR and establish a context for LOTAR, addressing both the information life cycle stages beyond LOTAR's defined processes and the archival processes themselves.
The EN 9300 series focuses on preserving model information rather than documents, emphasizing the embedded knowledge within the software that generates and manipulates data Experience with CAD and PDM data exchanges highlights the potential for errors during data transfer between systems, which is unacceptable for high-integrity products like aircraft To address these risks, the EN 9300 series implements an explicit archive based on the OAIS standard, identifies stable and well-defined information standards such as ISO 10303, and establishes validation methods to ensure that the recovered model matches the stored model.
This EN 9300-003 is applicable to existing records, on current and earlier products, produced using previous regulations
General
EN 9300 is designed for long-term archiving in accordance with international standards, enhancing acceptance within the designated community and improving interoperability among systems and data formats By utilizing these standards, the longevity of data storage is increased, processes are simplified, and costs are reduced through modularization and component reuse Additionally, EN 9300 aims to harmonize requirements with the international aerospace community, building on the IAQG Initiative that aligns it with the SAE Aerospace document ARP9034 Adapting the OAIS ISO standard may further facilitate harmonization with other sectors, including automotive and maritime industries.
EN 9300 references extensively ISO 14721 "Open reference model for Archiving Information System" (OAIS) and ISO 10303 (STEP).
Introduction to OAIS — ISO 14721
General
OAIS is a framework describing the significant entities and relationships among entities in an archive environment
An OAIS-type archive is expected to meet certain minimum responsibilities:
negotiate and accept appropriate information from information producers;
obtain sufficient control of the information to ensure long term preservation;
determine the scope of the Designated Community;
ensure the information is understandable by the Designated Community without the assistance of the information producers;
To ensure the preservation of information against potential contingencies, it is essential to adhere to established policies and procedures This approach facilitates the dissemination of information as authenticated copies of the original or ensures traceability back to the original source.
make the information available to the Designated Community
The OAIS reference model details a conceptual design for an archive, including its primary components and their associated functions and relationships, to support these requirements.
The OAIS Environment
The OAIS environment is derived from the interaction of four roles: producers, consumers, management and the archive itself
Producers supply the information that the archive preserves
Consumers use the preserved information A special class of consumers is the Designated Community that is a subset of consumers who are expected to understand the archived information
Management plays a crucial role in setting the overarching policy objectives for the archive, such as deciding which types of information to archive and identifying relevant sources However, the daily administration of the archive is handled by a dedicated functional entity within the archive itself.
The OAIS model
OAIS standardizes a reference model for a system architecture of archiving systems and processes
The OAIS functional model is shown in Figure 5
Figure 5 — Functional Model of OAIS
The OAIS framework emphasizes five key process modules: Preservation Planning, Data Management, Access, Ingest, and Administration The Archival Storage function is considered to be adequately addressed by existing archival systems, such as databases and storage media, according to EN 9300 However, EN 9300 will enhance the Archival Storage module by incorporating the capability to set digital time signatures The other process modules, specifically Data Management and Administration, remain within the OAIS framework and are not included in the scope of the EN 9300 series.
The OAIS framework provides a structure for understanding key entities and their relationships in archiving However, it does not specify definitions for archiving formats or minimum subsets necessary for archiving elements such as 3D geometry models and PDM information, nor does it address process definitions, including activity sequences, security considerations, and business or legal requirements for long-term archiving Consequently, EN 9300 builds upon the OAIS framework rather than replacing it.
Introduction to ISO 10303
General
ISO 10303 is generally referred to as the STandard for the Exchange of Product model data (STEP)
ISO 10303 is a global standard designed for the digital representation and exchange of product data, enabling a comprehensive description of product information throughout its lifecycle, regardless of the system used This standard facilitates not only file exchanges but also serves as a foundation for developing and sharing product databases and archiving solutions.
1 implementation implementations methods for data exchange and integration
2 description method for product data (EXPRESS)
4 application-orienteddata models forproduct description(e.g AP214, AP212,AP203)
5 methods for testing of STEP implementations
Figure 6 — Overview about Structure of ISO 10303
The standard's primary strategy involves utilizing STEP methods to convert real product data descriptions into a neutral format suitable for long-term archiving, ensuring that the meaning remains intact Figure 7 demonstrates a method for mapping the mathematical representation of two circles to the STEP format.
Figure 7 — Application example, formal schema definition and mapping onto Part 21 file format
The STEP development community is dedicated to establishing standards that facilitate international product model exchange and sharing The aerospace sector is actively involved to ensure that their product model data effectively supports real business processes.
Integrated Resource parts in STEP address, geometry, materials, tolerances, configuration management, and other general requirements
The following subsections describe the most relevant Application Protocols (AP) within the development of
EN 9300 Common PARTS A further extension of the list is possible.
ISO 10303-203:1994 and Edition 2 draft, Configuration controlled 3D designs of
AP 203 facilitates the exchange of geometry, product structure, and configuration management data across various business processes It is widely supported by major CAD and Product Data Management vendors The draft of Edition 2, available since 2003, introduces a modular approach that enhances 3D exchanges by incorporating tolerances, construction history, layers, validation properties, and colors.
ISO 10303-214:2001 and ISO 10303-214:2003, Core Data for Automotive Mechanical
AP 214 (Edition 2) facilitates the exchange and sharing of essential data such as geometry, drawings, geometric tolerances and dimensions, product structure, and configuration management This standard is widely supported by all major CAD vendors and numerous Product Data Management providers It is commonly utilized in the automotive sector and the European aerospace industry, ensuring effective communication and collaboration across these fields.
AP 203 Edition 2 is compatible with AP 214 for the common scope (both are harmonized by the PDM Schema which builds the core of the new modular architecture of STEP standards).
ISO 10303-233, System engineering data representation
AP 233 emphasizes the importance of exchanging system representations for aircraft and spacecraft Its scope encompasses adherence to system concepts, configuration control, requirements and their analysis, functional allocation and analysis, as well as behavior and physical architecture.
ISO 10303-209:2001, Composite and metal structural analysis and related design
AP 209 outlines the representation of computer-interpretable data for composite and metallic structural products, including aspects such as shape, idealized analysis shape, finite element analysis (FEA) models, analysis results, and material properties This information, along with design and analysis details, is organized within a Product Data Management (PDM) structure.
ISO 10303-237, Computational fluid dynamics
AP 237 establishes a standardized data representation for the exchange of fluid dynamics information, encompassing digital flow field data, surface data, and integrated data derived from analysis and computation, ground tests such as wind tunnel tests, and flight tests The initial edition primarily emphasizes data associated with analysis and computation.
ISO 10303-210:2001 and Edition 2 draft, Electronic assembly, interconnect and packaging
AP 210 outlines the data representation standards for printed circuit card design, encompassing the physical layout of the printed circuit card assembly, detailing the connections between functional objects and packaged parts, managing configurations, and specifying actual parameters for parts and functional objects.
ISO 10303-212:2001, Electro technical design and installation
AP 212 is a STEP exchange standard that defines data representation for electrotechnical plants and industrial systems design It focuses on the essential electrical product definitions required for various applications, including current analysis, equipment specifications, lighting design, cable sizing, electrical connectivity checks, and cable tray interference detection.
Overview
The fundamentals of this standard aim to assure the integrity of data and the authenticity of the associated provenance information This is considered under four headings:
Definition of data content (EN 9300-1xx and 2xx)
Definition of data formats and description methods for data conversion (EN 9300-1xx and 2xx)
Definition of test suites and description of certification methods (EN 9300-016)
The foundation of an effective archival procedure lies in establishing a strong business case for information archiving, which is detailed through various use cases Each use case is supported by one or more core data models that encapsulate the essential information needed to fulfill the business case An overview of this process is illustrated in Figure 8.
Figure 8 — Distinction of Business requirements, Business Cases and Use Cases
The article outlines the process views for Data Preparation, Ingest, Archival Storage, and Retrieval, detailing clearly defined validation steps and methods as specified in parts EN 9300-010 to 019 These views are considered normative within their respective scopes.
To ensure the integrity of data after conversion, data content, data quality and validation properties are defined (Parts in the EN 9300-1xx and 2xx series)
Understanding data formats and their descriptive methods is crucial for maintaining the integrity of transformations between the source system, the archive, and the consumer system, as outlined in the EN 9300-1xx and 2xx series.
The test suites and certification methods (EN 9300-016) verify that the archive correctly implements the recommendations of other parts of the standard
Figure 9 — Scope definition for EN 9300 (grey marked rectangle)
EN 9300 excludes certain elements of the OAIS framework, focusing primarily on the processes of Ingest, Archival Storage, Retrieval, and specific aspects of Access While OAIS advocates for the integration of Data Management, Preservation Planning, and Administration modules, EN 9300 only addresses the views related to these core functions It encompasses the information packages, including the Submission Information Package (SIP), Archival Information Package (AIP), and Dissemination Information Package (DIP), along with their associated Descriptive Information and package metadata.
The Administration and Data Management definitions belong to OAIS The definition of Preservation Planning will be detailed within Support Process Part EN 9300-030.
Processes
OAIS creates a standardized terminology framework that facilitates the comparison of archives It offers an in-depth overview of functions, roles, and data packages, along with their functional interdependencies However, OAIS does not cover the transition from function to process, the establishment of timelines, or the specifics of data verification.
EN 9300 enhances the OAIS framework by offering detailed process views that normatively describe essential aspects of the archiving process, including roles and responsibilities It outlines necessary data format conversions, the preparation of validation information, and the execution of validation and verification tests, all aimed at establishing a certifiable archiving process.
Data
Archiving Product Models vs Archiving Documents
Historically, design information has been documented through drawings, often stored in electronic formats like TIFF The archiving community focuses on preserving these documents, addressing integrity constraints related to accidental changes, such as speckling, and substantial changes, like the loss of pages.
A key aspect of a document is that its interpretation relies solely on the human reader, while the software used for display only understands how to render the document's image data For instance, a triangle drawing consists only of information regarding which pixels are black and which are white, with the display software needing to interpret these pixel strings as an image and potentially decompress the data.
A triangle product model encompasses a defined 2-D subspace, rules for determining point inclusion, straight line boundaries, and the topology of these boundaries It may also include constraints on side lengths, angles, and tolerances for positions and straightness for manufacturing purposes This comprehensive model allows for direct manufacturing or inspection of the triangle without human intervention, although many systems also incorporate the ability to create a visual representation of the triangle.
To effectively archive a product model, it is essential to preserve the embedded product knowledge, which consists of both data representation and processing within the software Given the uncertainty of continued software availability, this knowledge must be maintained solely through the data It is crucial that the information is stored in a well-documented format, with accessible documentation for interpretation The EN 9300 standard recommends using ISO 10303 (STEP) for recording archived information.
When a source or consumer system does not directly handle STEP data, a conversion to the system's representation is necessary This conversion process can lead to four types of losses.
Losses arising from software errors
Losses arising from the representation of numbers
Loss of provenance and context information
Content losses arise from the source representation having a broader scope than the target representation
This standard defines a core model for each type of data, which defines the minimum scope for the AIP, and must be supported by the conversion processes
Software errors can lead to discrepancies between the knowledge contained in a conversion target and its source Due to the complexity of product models, it is unsafe to assume error-free conversion processes Therefore, this standard outlines various verification and validation techniques to identify conversion failures and ensure that the converted model accurately represents the original These techniques are specifically defined for the core model, which is restricted to constructs that can be reliably and verifiably converted.
Floating-point representation of real numbers poses challenges in numerical software, particularly in systems modeling product geometry To address numerical errors, it is crucial to implement verification and validation processes for converted models This ensures that the conversion and loading of product models maintain fidelity to the original, preventing significant discrepancies.
The loss of provenance can sever the connection to the contextual information from which digital content is derived Unlike physical documents, digital documents lack a true original; they exist solely as data within software environments EN 9300 outlines a series of auditable processes designed to maintain the integrity of the original design's product knowledge, ensuring it is preserved for consumers and that this preservation is verifiable.
The product model generated by a specific system typically offers only a partial view of the product's knowledge, with additional insights derived from the contextual information surrounding the model's creation For instance, while a CAD model can specify the material used for a component, comprehensive details about that material are supplied through established materials standards These standards facilitate the integration of contextual information with the product model and may require certain elements to be included.
Data content
The data content of the information packages is divided into four categories:
The engineering approvals data (as an electronic signature);
The EN 9300-1xx and 2xx series outlines the different categories for each product model, specifying the applicable data quality criteria for each category.
7.3.2.2 Definition of the core model
Core models determine the essential data needed to maintain design intent for specific purposes The domain-specific sections of EN 9300 outline these purposes through relevant use cases, establishing the core model necessary to support business cases A core model consists of a system of data elements, including their representation, interpretation, and the data quality criteria they must fulfill.
The core model allows for the archiving of supplementary information and the duplication of data in various formats, enhancing functionality by preserving design knowledge and ensuring compatibility with specific tools However, it is important to acknowledge the increased risk of this additional information becoming unusable over time The extent of such supplementary information is detailed in the ingest agreement The accompanying figure demonstrates how a core model for a single geometric part can be expanded to incorporate both extra information and formats.
1 essential information set e g Part110: shape of a single part within general tolerance
Figure 10 — Concept of a core model
Metadata is essential for managing and utilizing information packages, as outlined in EN 9300 This standard focuses on data necessary for retrieving the package and validating its data and provenance For instance, in the context of a part, metadata plays a crucial role in ensuring accurate identification and verification.
The scope of metadata is determined by specific use cases and outlined in domain-specific sections, which also include applicable data quality criteria Any additional metadata should be agreed upon in the ingest agreement Data used for internal archive management is not covered by EN 9300 Furthermore, detailed information regarding intellectual property rights may be explicitly identified and documented in the Archival Information Package during both the ingest and retrieval processes.
7.3.2.4 Definition of digital (engineering) signatures
A digital engineering signature facilitates the business release process by allowing the data producer to confirm that the prepared data meets the necessary engineering process and quality standards Like metadata, the digital signature is specific to its domain, and its usage must be mutually agreed upon by both the producer and the archive Additionally, a digital engineering signature can help identify the approver of the data.
Data formats
The standard considers different data formats within archiving processes
The native data representation is system dependent and out of scope for EN 9300
Core models data must utilize open and standardized representations and formats, ensuring complete documentation in syntax and semantics, and free accessibility ISO 10303 (STEP) is available at minimal publication costs, promoting common understanding within the designated community and ensuring long-term public availability and stability Standardization processes, as outlined in EN 9300, facilitate regulated change Preferred Application Protocols for 3D geometry and product structure data include AP 214, which focuses on "Core Data for Automotive Mechanical Design Processes," and AP 203 (Edition 2), which addresses "Configuration Controlled 3D Designs of Mechanical Parts and Assemblies." Additionally, company-specific implementations may adopt conventions like the "PDM Schema," supported by EN 9300, even if not issued by ISO 10303 Other STEP Application Protocols also fall under the scope of EN 9300, despite not being currently referenced.
EN 9300 aims to guarantee the integrity of the stored documents/data packages Therefore the following signatures will be used within EN 9300:
Digital (engineering) signatures (personal created signatures) guaranteeing the integrity of the content of digital data
Digital time signatures, which are automatically generated, play a crucial role in preserving the integrity of archived data packages throughout their storage duration The subsequent applications and uses of digital signatures will be detailed in EN 9300-005.
A digital signature serves as a digital seal for data, created using a mathematical algorithm and a private cryptographic key It can be verified at any time with the corresponding public key, ensuring the identity of the signature owner and the integrity of the data Digital signatures adhere to established regulations and standards.
3) The “PDM (Product Data Management) Schema” is an industrial agreement for a reference information model for the exchange of a central, common subset of the data being managed within a PDM system It represents the intersection of requirements and data structures from a range of STEP Application Protocols, all generally within the domains of design and development of discrete electro/mechanical parts and assemblies
Directive in 1999/93/EC of the European parliament and the council from the 13th of December, 1999 about collective basic conditions of digital signature
Digital signatures must be renewed every 5-6 years For EN 9300, these signatures are essential for ensuring data integrity during the brief interval between the producers' release and the transfer to the archive system.
A digital time signature adds an automatically generated timestamp to a digital signature, ensuring the integrity of stored data can be verified at any time Businesses must demonstrate the renewal of the digital time signature, which is legally defined to have a validity period In Germany, the production algorithm for digital time signatures requires renewal approximately every 20 years This digital time signature plays a crucial role in the Archival Storage process, as outlined in EN 9300-013.
7.3.3.7 Information packages - Preservation Description Information (PDI)
The PDI identifier (ID) is essential for maintaining the interpretation of Content Information, encompassing four key categories: Provenance, Reference, Fixity, and Context information According to OAIS, these categories provide a framework for understanding the necessary information required for effective content preservation.
Provenance describes the source of the Content Information, who has had custody of it since its origin, and its history (including processing history);
Context outlines the relationship between the Content Information and external information within the Information Package It explains the purpose behind the creation of the Content Information and may detail its connection to other Content Information objects stored in the archive.
References offer unique identifiers or systems of identifiers that allow for the distinct identification of Content Information For instance, an ISBN number can be used for books, or a specific set of attributes can differentiate one instance of Content Information from another.
Fixity provides a wrapper, or protective shield, that protects the Content Information from undocumented alteration For example, it may involve a check sum over the Content Information of a digital Information Package.
Archiving approach for complex product models
Complex and large product models can be effectively organized into sub-models, simplifying their representation and preventing duplication during ingestion This approach allows for incremental archiving of sub-models while maintaining overall context through cross-reference mechanisms, which will be defined in the relevant domain-specific sections (1xx and 2xx series).
This method is particularly relevant for archiving product structure data, as outlined in sections 115 (CAD assembly model structure) and 220 (PDM part-assembly product structure).
Data quality assurance
Data quality primarily hinges on adherence to established specifications According to the OAIS framework, this adherence is outlined in the Ingest agreement, with assurance being defined by specific characteristics.
Data quality assurance is essential and must be conducted through data validation and verification before the ingestion process Additionally, it is necessary for attested copies of archived data during the retrieval process to guarantee accurate delivery to the consumer.
EN 9300 outlines sets of Validation Properties essential for verifying data consistency during transformations between different representations and formats It specifies domain-specific validation properties, particularly for CAD and PDM, with the possibility of further extensions through user agreement The implementation of these validation properties is mandatory to maintain data integrity and process security Additionally, recommended subsets of STEP validation properties are detailed in the EN 9300-100 and EN 9300-200 series.
Validation properties should be simple to compute, compact to store, and effective at detecting critical errors It is essential to establish validation properties for both the key and global characteristics of the object in question For instance, geometric models can incorporate validation criteria like surface area, volume, or center of gravity, which are particularly sensitive to modeling errors While engineering correctness is not the focus of these validation properties, it is important to recognize that an invalid representation often signals an underlying engineering error In EN 9300, validation properties specifically assess the accuracy of the core model's representation.
7.3.5.3 Definition and application of verification rules
Validation aims to confirm the accuracy of captured information, while verification focuses on ensuring that data is accurately represented Verification rules are designed to meet quality standards within specified tolerances, and a verification is deemed successful if all rules are adhered to These rules are specific to each domain and are outlined in the EN 9300-1xx and EN 9300-2xx series, with only core model verification rules included in EN 9300 An overview of the validation and verification concepts is illustrated in the accompanying figure.
Figure 11 — Concept of validation/verification
The EN 9300-1xx and EN 9300-2xx series will include sections that outline the core model and its essential information set, as specified in EN 9103 as key characteristics Additionally, these standards will detail the quality verification and validation rules, along with a comprehensive definition of how information is assigned to the sub-packet of the AIP.
The key characteristics has to be explicitly identified, described, documented and checked in the Archival Information package during the Ingest and after Retrieval process.
Process phases and cycles
VP Validation Properties a Data conversion b Data validation c Source/Target Representation d Data definition e Archive Representation f Archive Data definition
Figure 12 — Overview of data conversion and data definitions
Due to the significant time gap of 30 to 50 years or more in the aerospace industry between submission and retrieval, direct validation of the retrieved information against the original submission is not feasible The interconnected cycles of translation and validation create a continuous chain aimed at ensuring that the submission remains unaltered throughout the archiving and retrieval process.
EN 9300 outlines a series of phases for archiving based on the OAIS standard, where data undergoes conversion from one representation to another The quality of these conversions is ensured through predefined validation properties The primary phases involved in this process include Data Preparation, Ingest, Archival Storage, and Access and Retrieval.
1) the data will be prepared for archiving The source representation (application data in native format - native representation, see 4.1.5) will be converted into the target representation SIP (Submission Information Package, defined as the source document for the archiving process) The data verification ensures the data quality for both representations Quality control of native formatted data is strongly recommended to ensure efficient data generation and data preparation The definition of data quality controls for data generation is out of scope for EN 9300
2) the source representation SIP will be converted into the target representation AIP An accurate representation of data, (see 4.1.5) will be transferred into the archives storage section The end of the conversion process (source representation into target representation) closes a domain specific release process by setting a digital time signature From this moment the data package AIP represents the digital original EN 9300 recommends the declaration of the digital original as the only relevant source representation for 3D product data, comparable with a released and signed paper for 2D drawing The validation properties ensure the integrity and consistency of both representations
3) the data selection represents the first step of the retrieval process The accurate representation (AIP) will be selected by a consumer or administrator during the access process The target representation (a selection list) will be generated, additionally a copy of the selected accurate representation may be prepared The management information ensures the available selection items meet the access rights management policy
4) during the retrieval process the target representation DIP will be generated from the requested selection list items The DIP is a derived representation (see 4.1.5) and contains a digital copy of the accurate representation The derived representation has to fulfil the requirements for the target application data and will be transferred to the consumer The validation properties ensure the integrity and consistency of both representations
The following Figure 13 gives an explicit example
During long-term archival storage, the accurate representation (AIP) may need to be converted into a new archiving format, which is a scenario that should be avoided whenever possible Adhering to established standards helps maintain consistency in the archive format throughout the storage period However, converting the archive representation poses risks, including the potential for unauthorized changes during the process Therefore, it is essential to review data consistency and reset the digital time signature to ensure integrity.
Figure 14 illustrates the unique use cases that may arise during the archiving period The standard use case, where time remains constant, indicates that the digital original representation remains unchanged throughout its storage duration However, in exceptional or special use cases, modifications to the representation may occur.
Mapping approach onto physical data representations
EN 9300 recommends a three level approach (see Figure 15)
Figure 15 — Mapping approach onto physical data representation
The first level defines the domain specific view Within this view the engineering data required for archiving will be identified
The second level outlines the data representation, which corresponds to a data schema, like the PDM Schema, tailored to meet domain-specific requirements This level will establish the schema in accordance with existing standards.
The third level defines the archiving format of the data, such as STEP Part 21 or XML.
Fundamentals for testing the LOTAR process and components
The goal of testing the LOTAR process and its components is to certify the entire LOTAR environment, ensuring that both software and hardware components are thoroughly audited as part of the testing procedure.
Ensuring high data quality is crucial for the future interpretability of archived data, making the establishment of test methods essential Defined test methods should be applied to both data and processes within the scope The testing of archiving processes and data quality can be enhanced through well-defined, certified test suites, which conduct quality checks based on verification rules and by comparing validation property values.
Within a test suite two types of functional test scenarios shall be covered:
“Good”, i.e correct test files (without any error)
“Bad” test files, which includes known errors to test the verification and validation systems
To ensure accuracy in the conversion process from SIP to AIP or AIP to DIP representations, it is essential to utilize the correct test cases Initially, validation properties are generated by the source system for the test case, followed by their generation within the target system after the data conversion The comparison of the source and target data representations is conducted using these validation properties If the results fall within a defined tolerance, the component successfully passes the "good" test scenarios.
The following Figure 16 shows the basic procedure for comparison of validation properties, following the process phase number 2 ‘transfer to archive’, (see Figure 12)
VP Validation Properties a Data conversion b Data validation c Source Representation d Data definition e Target Representation f Data definition
Figure 16 — Data validation by comparison of defined validation properties
For "bad" test scenarios, the process component must conclude with a clear error, either by pinpointing the failure in the source representation or by producing a result that falls outside the established tolerance limits.
Additional test suites will be employed to evaluate the components, ensuring that a specific data representation aligns with the established verification rules For "good" test scenarios, the component is expected to successfully pass the test files without any rule violations Conversely, in "bad" test scenarios, the component must accurately identify the object(s) that violate the verification rules and specify which rules are breached.
The establishment of EN 9300-016 (Test Suites) aims to improve the reliability of archived product data for aerospace companies adhering to certified processes The test suites are designed to demonstrate that the processes and tools can identify data quality deficits, as outlined in other sections of EN 9300, while ensuring the immutability of the data, which is a central focus of EN 9300.
Archiving system itself, (out of scope of EN 9300)
Testing shall be implemented in several levels:
The initial test level focuses on process consistency, ensuring that the processes yield accurate results at the conclusion of each step, such as AIP or SIP This level will be subject to an audit by an independent authority.
The second test level focuses on integrated archiving tools, particularly data conversion tools, which involve validating conversions from the source format to the recommended archiving format, STEP ISO 10303 It outlines the testing requirements for STEP Files, based on ISO 10303 Parts 31, 32, and 34, which establish the standards for conformance testing in STEP.
The third test level focuses on the archiving system, ensuring that key functions are properly executed This includes verifying the correct implementation of access rights, the appropriate use of storage media, and the effectiveness of search results during retrieval processes Notably, this test level is not covered by EN 9300.
System Architecture Framework
EN 9300 outlines a conceptual system architecture that details the interactions among involved IT systems, as specified in EN 9300–006 ‘System Architecture Framework’ This architecture aims to establish clear definitions of terms and ensure consistency in archived data and processes.
Establishing and interpreting standards requires a shared understanding, which is facilitated by accepted and standardized description methods EN 9300-004 outlines the methods utilized in the standard, including UML and EXPRESS.