Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
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Glossary · Change, versions and configuration

Forward compatibility

German: Vorwärtskompatibilität

In systems engineering, forward compatibility is the controlled ability of a current system to handle future or extended interface and data versions. It requires a defined rule for what the system does with content it does not recognize.

  • Data and interfaces
  • Systems engineering

In one sentence

Forward compatibility defines how today's system treats future or extended data and interfaces, including unknown fields and newer versions.

Example

An HMI on a CNC machine ignores unknown optional fields in status messages but rejects unknown safety-relevant status codes and shows a defined fault message instead.

How it applies

  • Integrated systems: Specify the handling of unknown content: ignore, log, reject or fall back. The rule may differ between optional information and safety-relevant values.
  • Machine safety: Silently ignoring an unknown value is acceptable only where it cannot hide a hazardous state. For safety-relevant data, a safe default or a defined fault reaction is usually required.
  • Evidence: Test forward compatibility with deliberately extended messages. Data validation rules are part of the verified behavior.
  • Technical documentation: Interface documents should state the extension rules, so that future versions can be designed against them.

Forward vs. backward compatibility

Backward compatibility looks back: the new version supports the old. Forward compatibility looks ahead: the current version tolerates the new in a defined way. Neither is automatic; both have to be specified and tested.

Not to be confused with forward and backward versioning

Forward compatibility is a property of a system or interface. Forward and backward versioning are something else: two conventions for publishing documentation versions.

  • Forward versioning keeps the current version at the published location, always under the same URL. Each time a new version is released, the older one is moved to an archive with its date stamp.
  • Backward versioning gives each new release a new version number (v1, v2, v3 …), so the newest version always carries the highest number and every version stays addressable by that number.

For docs-as-code publishing and static HTML websites, only forward versioning makes sense: links, bookmarks, search results and references from other documents always lead to the current content, while dated archive copies keep the older versions traceable. A document can therefore describe a backward-compatible interface and still be published with forward versioning — the terms answer different questions.

By knowledge.aitechdoc.world · Published September 25, 2026 · Last reviewed

Source: AI TechDoc Blog editorial definition, based on systems engineering practice

Definitions follow the cited standards and specifications. Where a source is a copyrighted publication, such as an ISO, IEC or EN standard, the definition is a close paraphrase, not a verbatim quotation, so as not to infringe copyright. We recommend reading the original publication. The sections “How it applies” are editorial commentary by AI TechDoc Blog and are not part of any standard.

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