====== GPR-019 — Implementation Replacement Without Client Changes ======

[[public:00-sip-ra:99-annexes:annex-c-requirements:start|Go to Annex C: Requirements]]

===== Statement =====

An implementation SHOULD be replaceable by an alternative implementation satisfying the same applicable [[public:99_annexes:annex-b-terms-and-definitions:i:interface|Interface Contracts]] and conformance conditions without requiring changes to conforming clients.

===== Requirement Level =====

Recommended

===== Rationale =====

Replacement without client changes reduces implementation coupling, migration cost, operational disruption, and dependence on a particular product or vendor.

A conforming client should depend on standardized Interfaces, externally observable behavior, and applicable conformance conditions rather than implementation-specific behavior or internal design choices.

===== Evaluation Criteria =====

A Submission satisfying this recommendation demonstrates that:

  - Applicable Interface Contracts and conformance conditions are sufficient to support implementation replacement
  - Conforming clients depend only on standardized Interfaces and externally observable behavior
  - Replacing an implementation with a conforming alternative does not require changes to conforming clients
  - Implementation-specific extensions are distinguishable from standardized capabilities
  - Dependencies that could prevent implementation replacement are identified
  - Any departure from this recommendation is identified and justified

===== Referenced By =====

{{backlinks>public:00-sip-ra:99-annexes:annex-c-requirements:gpr-019-implementation-replacement-without-client-changes}}

===== Notes for Editors =====

This requirement uses ''SHOULD'' and is therefore a recommendation.

The requirement applies when the original and replacement implementations satisfy the same applicable Interface Contracts and conformance conditions.

A client that depends on implementation-specific extensions, undocumented behavior, or capabilities outside the proposed specification may require changes when the implementation is replaced. Such a client is not conforming with respect to those dependencies.

To transclude the authoritative Statement into another page, use:

<code dokuwiki>
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</code>

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