====== P4-REQ-21-9-008 ======

[[dido:99_annexes:annex-d-requirements:part-04:start| Return to Requirements]]

===== Statement =====

Each QoS profile mapping SHALL identify the expected ordering behavior.

===== Source =====

Part 4, Section 21.9: QoS Profile Requirements.

===== Rationale =====

Ordering behavior determines whether communication sequence must be preserved when downstream processing or lifecycle progression depends on event order.

Explicitly identifying ordering expectations allows Phase 0 participants to implement compatible sequencing behavior for applicable exchanges.

===== Applies To =====

This requirement applies to:

  * QoS profile mappings;
  * DDS Topic exchanges;
  * publishers;
  * subscribers; and
  * sequence-dependent implementation flows.

===== Verification =====

Verification SHALL confirm that each QoS profile mapping identifies its expected ordering behavior.

Verification activities should include review checks confirming that:

  * ordering expectations are stated;
  * sequence-dependent exchanges preserve required ordering;
  * publisher and subscriber behavior is compatible; and
  * the selected ordering behavior supports the interaction purpose.

===== Traceability =====

This requirement establishes the ordering expectation associated with each Phase 0 QoS profile mapping.

Related requirement identifiers:

  * [[dido:99_annexes:annex-d-requirements:part-04:p4-req-21-9-007]]
  * [[dido:99_annexes:annex-d-requirements:part-04:p4-req-21-9-010]]

Related source section:

  * [[fxdemo:04-part:21-phase-0-implementation-requirements:21-9-qos-profile-requirements:start]]

===== Status =====

Draft

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