Overview
ISO/IEC TR 9789:1994 - "Information technology - Guidelines for the organization and representation of data elements for data interchange - Coding methods and principles" is a Technical Report that provides general guidance on how data can be expressed by codes. It explains the objectives of coding, surveys coding methods and their advantages/disadvantages, lists desirable code features, and gives guidelines for the design and representation of code values. This report is application‑neutral (Type 3 Technical Report) and intended as a practical reference for information modelling and data interchange.
Key Topics
- Definitions and principles: Core terms such as code, code element, coded set, coding scheme, identifier and delimiter; the role of coding in expressing information for processing and communication.
- Coding objectives: Primary purposes - identification, classification, and acting as a key to further information - and how objectives drive code design.
- Types of codes: Survey of coding methods including sequential, random, mnemonic, abbreviation‑based, matrix, hierarchical, juxtaposition, combination and value‑addition codes.
- Features of good codes: Practical properties such as uniqueness, expandability, conciseness, simplicity, versatility, sortability, stability, significance, size, structure/format and capacity.
- Representation of code values: Guidance on character sets and representation techniques for coded values to ensure interoperability in data interchange.
- Design of codes: Practical design aspects - number of characters, coded format, character set choices, assignment conventions, and error detection (use of check characters).
- Practical recommendations: General recommendations and example application areas without prescribing a single design method.
Applications and Who Uses It
ISO/IEC TR 9789 is useful for professionals designing or implementing structured data interchange and code lists:
- Data architects and modellers defining data element types and identifiers
- Systems integrators and EDI implementers building interoperable message formats
- Database designers and software engineers choosing code formats and validation schemes
- Standards developers, governmental agencies and statistical bodies preparing public code lists
- Sectors using coded representations (finance, transport, health, trade) seeking principles for robust code design
The report supports sound decisions on code selection and creation to improve accuracy, processing efficiency and long‑term stability in data interchange.
Related Standards