1. Industrial Avionics Working Group 18/04/07 AL Partitioning (1) – Physical Domain Application Layer P 1 P 2 P 3 P n App P S 1 S 2 S 3 S n App S R 1 R 2 R 3 R n App R Q 1 Q 2 Q 3 Q n App Q P 1 P 2 Q 3 Q 2 R 2 R 1 P 3 Q 1 R 3 Application Layer CELL: All the inter-cell interactions are via the architecture

2. Industrial Avionics Working Group 18/04/07 Extensible Core Low Assurance Low Change High Assurance Low Change High Assurance High Change Low Assurance High Change Regions:Blocks: Block Susceptibility to ChangeLow High Low Assurance Region AL Partitioning (2) – Safety Domain Cell Block Interactions – Contracted Behaviour

3. Industrial Avionics Working Group 18/04/07 AL Partitioning (3) – Logical Partitioning Rationale Too many blocks - Very Extensible - Expensive to set-up contracts between blocks Too Coarse - Limited Extensibility - Reduced set-up costs Compromise - Extensible in HC/HA - Some extensibility in HC/LA & LA/HC Change Assurance Change Assurance Change Assurance

4. Industrial Avionics Working Group 18/04/07 AL Partitioning (4) – Partitioning Guidelines Assurance – Each LA cell, map to block in LA regions – HA/mixed assurance cells, map to blocks in HA regions Susceptibility to Change – Each LC cell, map to block in LC regions – HC/mixed susceptibility to change cells, map to blocks in HC regions All cells that are LC & LA, map to one Block in LCLA region Example considerations for grouping cells into Blocks –Impact of Change Scenario Isolate sets of cells that are affected by groups of changes Likelihood of future change in assurance Impact of future change uncertain –Synergy

5. Industrial Avionics Working Group 18/04/07 AL Partitioning (5) – Example Partitioning Susceptibility To Change Assurance LCHA1 LCHA2 LCHA3 LCLA1 HCHA1 HCHA5HCHA4HCHA3HCHA2HCHA{N}HCHA6HCLA4HCLA3HCLA2HCLA1