ChatStates only provides a change notification, and no way to download the initial state. This is clearly silly, if your UI exposes more than just a boolean state (Composing vs. the rest).

In practice I expect that most UIs will only care about Composing anyway, but for completeness, I propose:

mapping Chat_State_Map : a{uu}
    A map from contacts to their chat states.

    Contact: u, Contact_Handle
        A contact
    State: u, Channel_Chat_State
        The chat state corresponding to that contact

property ChatStates : a{uu}, Chat_State_Map
    A map containing the chat states of all contacts in this
    channel whose chat state is not Inactive.

    Contacts in this channel, but who are not listed in this map,
    may be assumed to be in the Inactive state.

    In implementations that do not have this property, its value may be
    assumed to be empty.

    | This property was not present in older versions of telepathy-spec.
    | In CMs that follow those older versions, following this rule will
    | mean that initial chat states will always be assumed to be Inactive,
    | which is the best we can do here.

Tagging this as patch to get it in the review queue, since the wording shown above is effectively a patch :-)