Unresolvable edit conflict scenario

[enikao]

Model state at start, synchronized between client 1, client 2, and repo

• Node A
  • [contains] Node B
• Node C [parallel to A]

Described below as

• A
  • B
• C

1. Based on start state, client 1 moves A under C

results in model state:

• C
  • A
    • B

2. Based on start state, client 2 moves C under B

results in model state:

• A
  • B
    • C

3. Repo handles both commands

Variant a: Repository chooses one command, discards the other

sends event "moved C under B", resulting in:

• A
  • B
    • C

Effectively discarding client 1's command, applying client 2's command.

Variant b: Applies both updates with additional conflict resolution event

1. sends event "moved A under C", resulting in:

   • C
     • A
       • B

2. sends conflict resolution event "moved C next to A" (not sent by any client, invented by repo to resolve conflict), resulting in:

   • A
     • B
   • C

3. sends event "moved C under B", resulting in:

   • A
     • B
       • C

Variant c: Just apply in order

1. sends event "moved A under C", resulting in:

   • C
     • A
       • B

2. refuses command from client 2