Beginnings of design documentation for party services.

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@93 542714f4-19e9-0310-aa3c-eee0fc999fb1

docs/crowd/design.txt

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+Cocktail: Party Design -*- outline -*-
+
+* Introduction
+The Party layer builds upon the Cher layer through the addition of a few
+key services. These services are based around the concept of bodies and
+places. A client of the system is represented by a body and that body can
+occupy a place. Bodies can communicate with one another through two
+mechanisms: they can speak which broadcasts their message to all other
+bodies that occupy the same place, or they can tell which delivers their
+message specifically to one target body regardless of place.
+
+Services are provided for switching from place to place as a body can only
+occupy one place at a time (or no places at all). A framework is provided
+for management of places on the server. Most applications will likely want
+to specialize the place concept and extend it with functionality specific
+to their needs.
+
+* Components
+Wherein the individual classes and components that make up the Party
+framework are described.
+
+** BodyObject
+The body object extends the client object from the Cher framework and
+tracks information like the current place occupied by the body.
+
+** PlaceObject, PlaceManager
+An instance of place object represents a particular place and tracks
+information pertinent to that place, like what bodies currently occupy it.
+Every place has an associated place manager which lives on the server and
+coordinates services for that place. It can be extended to coordinate
+services for place specializations.
+
+** ChatService, ChatProvider, ChatReceiver
+These three classes coordinate and manage communication between bodies.