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add some clarifications

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Hubert Chathi 2018-08-30 11:24:39 -04:00
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specification/server_server_api.rst
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@ -515,8 +515,9 @@ is at the top)::
Suppose E3 and E4 are both ``m.room.name`` events which set the name of the
room. What should the name of the room be at E5?
Servers should follow one of the following recursively-defined algorithms to
determine the room state at a given point on the DAG.
Servers should follow one of the following recursively-defined algorithms,
depending on the room version, to determine the room state at a given point on
the DAG.
State resolution algorithm for version 2 rooms
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@ -549,11 +550,12 @@ Power events
``state_key``. The idea behind this is that power events are events that have
may remove someone's ability to do something in the room.
Unconflicted and conflicted state maps
Unconflicted state map and conflicted state set
The *unconflicted state map* is the state where the value of each key exists
and is the same in each state :math:`S_i`. The *conflicted state map* is the
set of all other state events. Note that the conflicted state map is a set of
events, rather than a map of ``(event_type, state_key)`` to ``event_id``.
and is the same in each state :math:`S_i`. The *conflicted state set* is the
set of all other state events. Note that the unconflicted state map only has
one event per ``(event_type, state_key)``, whereas the conflicted state set
may have multiple events.
Auth difference
The *auth difference* is calculated by first calculating the full auth chain
@ -563,7 +565,7 @@ Auth difference
the auth difference is :math:`\cup C_i - \cap C_i`.
Full conflicted set
The *full conflicted set* is the union of the conflicted state map and the
The *full conflicted set* is the union of the conflicted state set and the
auth difference.
Reverse topological power ordering
@ -594,12 +596,11 @@ Mainline ordering
such that :math:`P` is last. Given another event :math:`e`, the *closest
mainline event to* :math:`e` is the first event encountered in the mainline
when iteratively descending through the ``m.room.power_levels`` events in the
``auth_events`` starting at :math:`e`. If :math:`e` is not an
``m.room.power_levels`` event, and does not have an ``m.room.power_levels``
event in its ``auth_events`` (this happens if the :math:`e` is sent before
the first ``m.room.power_levels`` event), then the closest mainline event to
:math:`e` can be considered to be a dummy event that is before any other
event in the mainline of :math:`P` for the purposes of condition 1 below.
``auth_events`` starting at :math:`e`. If no mainline event is encountered
when iteratively descending through the ``m.room.power_levels`` events, then
the closest mainline event to :math:`e` can be considered to be a dummy event
that is before any other event in the mainline of :math:`P` for the purposes
of condition 1 below.
The *mainline ordering based on* :math:`P` of a set of events is the
ordering, from smallest to largest, using the following comparision relation
@ -628,9 +629,9 @@ Algorithm
The *resolution* of a set of states is obtained as follows:
1. Take all *power events* and any events in their auth chains that appear in
the *full conflicted set* and order them by the *reverse topological power
ordering*.
1. Take all *power events* and any events in their auth chains, recursively,
that appear in the *full conflicted set* and order them by the *reverse
topological power ordering*.
2. Apply the *iterative auth checks algorithm* on the *unconflicted state map*
and the list of events from the previous step to get a partially resolved
state.