The progressive divergence over time between an intended requirement or design intent and its formalization, implementation, or maintained specification, resulting in loss of semantic fidelity or increased ambiguity.

Principle

Human factors, incremental changes, ambiguous wording, and mismatches between stakeholders' mental models and formal representations cause specification artifacts to drift; the organizing idea is that specification is a socio-technical artifact that must be actively synchronized with intent.

Demonstration

An API's informal contract states a function should not expose internal identifiers, but subsequent releases modify types and add fields without updating the formal spec; implementers begin to rely on the exposed identifiers, causing the realized system to drift from the original intent.

Misapplication

Attributing every mismatch between doc and code to 'drift' ignores deliberate evolution and versioned changes; calling deliberate requirement changes 'drift' conflates change management with unintended divergence.

Consequence

Awareness of drift leads to practices like continuous specification review, traceability between requirements and artifacts, and automated checks; unchecked drift produces interoperability failures, security gaps, and user-visible regressions.

Reversal

Specification Convergence: the active, coordinated process of aligning artifacts, implementations, and stakeholder expectations so that formalizations remain faithful to intent.

Boundary

Concerns evolving specifications and their artifacts over time; does not apply to a one-off mismatch caused by a single mistake nor to intentional refactorings that include coordinated updates to specifications.

Semantic Tension

Tension with underspecification and over-specification: drift can arise from underspecified areas that later acquire accidental constraints, or from over-specified parts that are relaxed over time; the concept focuses on temporal divergence rather than initial completeness.

Synthesis

Specification Drift is the temporal misalignment of intent and artifact that emerges from human, technical, and organizational processes; managing it requires traceability, governance, and tooling to keep formalization and implementation synchronized with requirements.