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+
+
+Architecture
+
+TMCast (stands for Transaction MultiCast) is an implementation of a
+transactional multicast protocol. In essence, the idea is to represent
+message delivery to members of a multicast group as a transaction - 
+atomic, consistent and isolated action. Multicast transaction can
+be viewed as an atomic transition of group members to a new state. 
+If we define Mo as a set of operational (non-faulty) members of the 
+group, Mf as a set of faulty members of the group, Ma as a set of 
+members that view transition Tn as aborted and Mc as a set of members
+that view transition Tn as committed, then this atomic transition Tn
+can be described as one of the following:
+
+Mo(Tn-1) = Ma(T) U Mf(T)
+Mo(Tn-1) = Mc(T) U Mf(T)
+
+Or, in other words, after transaction T has been committed (aborted), 
+all operational (before transaction T) members are either in 
+committed (aborted) or failed state.
+
+Thus, for each member of the group, outcome of the transaction can
+be commit, abort or member failure. It is important for a member
+to exhibit a failfast (error latency is less than transaction cycle) 
+behavior. Or, in other words, if the member transitioned into a wrong 
+state, it is guaranteed to fail instead of delivering wrong result.
+
+In order to achieve such error detection in decentralized environment,
+certain limitations should be imposed. One of the most user-visible
+limitation is the fact that the lifetime of the group with only
+one member is very short. This is because there is not way for a 
+member to distinguish "no members yet" case from "my link to the
+group is down". In such situation, the member assumes the latter case. 
+There is also a military saying that puts it quite nicely: two is one, 
+one is nothing.
+
+
+State of Implementation
+
+Current implementation is in prototypical stage. The following parts 
+are not implemented or still under development:
+
+* Handling of network partitioning (TODO)
+
+* Redundant network support (TODO)
+
+* Member failure detection (partial implementation)
+
+
+Examples
+
+There is a simple example available in examples/TMCast/Member with 
+corresponding README.
+
+
+-- 
+Boris Kolpackov <boris@dre.vanderbilt.edu>
+\ No newline at end of file