# SI-T01: Interface contract

Adrian Sutherland · Version 1.0 · Refreshed September 2026

© 2005–2026 Adrian Sutherland.
Source page: https://architectureportal.org/assets/systems-integration

Complete or link the relevant existing records. Mark unanswered questions as open.

## Identity and purpose

Record the contract ID, operation, purpose, edition, decision owner and status.

## Linked decisions

Link business requirements, information definitions, roles, rationale and consumers.

## Participants and authority

Who calls, receives and checks permission? Which participant is authoritative for each fact?

## Input and meaning

Describe fields, units, identifiers, absent values, version expectations, source and sensitive information.

## Acceptance and result

What must be true? What changes together? What is returned, and what does it establish?

## Repeat and conflict

Describe how the service handles repeated operation identities, changed inputs and concurrent requests. Record how long results are retained and how callers find the current state.

## Failure and timing

Distinguish rejection, pending work and unknown outcome. Specify timeouts, retry budget and escalation.

## Data handling and support

Set access, minimum payload, logging, retention, ownership and recovery responsibilities.

## Compatibility and checks

Record schema and behaviour versions, consumers, rollout, example checks and actual results.