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Guanotes

The concept

Guanotes application allows flockrs to post notes, called guanotes, to the ambient ( i.e any device available in the surroundings ranging from other flockr device to devices installed on public places such as KK). This is a concept similar to Stickies application in Mac but guanotes can hop from one device to another.

Flockrs can thus discover other flockrs guanotes, store them and exchange them later with other flockrs such that guanotes can be ‘percolated’ through the entire Urbiflock. Percolation of guanotes allows flockrs to receive guanotes offline without relying on infrastructure. In other words, sender and receiver of guanotes do not have to be necessary online to receive a guanote.

Flockrs can also subscribe to a particular type of guanotes such that they are automatically notified whenever they meet a flockr carrying guanotes of that particular type. Currently, flockrs can subscribe to receive guanotes sent to a particular flock. This functionality is reminiscent to the subscription to a mailing list.

Another idea is that flockrs can stop the percolation of guanotes. For example, if a flockr detects that a spam guanote or a guanote with unapropiate content, it could stop its propagation.

Design

To implement Guanotes, we are going to reuse the concepts developed by TOTA. This could be combined with the RETE engine we built for the proximities, in the future to reason about multiple tuples.

The idea is to build a framework similar to TOTA, called AmbientTOTA, to be able to exchange and percolate guanotes. Tota proposes relying on distributed tuples to coordinate distributed application nodes. Tuples are injected in the network and can autonomously propagate according to application-specific propagation rules expressed in the tuples themselves. The idea is to implement AmbienTota as a general framework so that we can then instantiate our AmbientTota with guanote objects in Guanotes. A guanote actually extends a tuple object of AmbienTota with some flockr-dependent behaviour.

AmbientTota has been designed to be independent from service discovery. So, Guanotes will also have to implement some glue codeto plug in the discovery mechanism of Urbiflock (via Flockr).

API

Here comes the public interface to interact with an AmbientTota framework:

makeTupleSpace()
makeTuple(tupleID)
extendTuple: tuple with: closure

A tuple space (ts) in AmbientTota basically consists of a local ts, an ambient ts (to inject tuples in the ambient). The public interface of an ts is the following:

// tota operations to manage a local ts
def add(tuple)
def delete(template) -> vector with the deleted tuples 
matching the template
def read(template) -> vector with the matching tuples

//publishes a tuple into the ambient ( ~ inject in TOTA)
def inject(tuple) -> subscription object to cancel the injection

// places a listener on to the local TS ( ~ subscribe in TOTA)
// it returns a publication object to be able to unsusbscribe 
when: template matches:{ | tuple |
 // code  
}
//Templates are currently boolean expressions on tuples. 
Example of template applied to guanotes:
{ |guanote|  guanote.flock == "KK" }

//methods belonging to the propagation protocol

// notifies the discovery of a remote ts
// and starts the propagation protocol (send side)
def notifyTSDiscovered(ts)
// notifies the arrival of tuples from a ts 
// receive side of the propagation protocol
def receiveTyples(tuples)

A tuple in our system is just the object contained in a local TS offering the following API to propagate itself:

// called in every tuple at pass() 
def decidePropagation() -> boolean
// specifies operations on the local TS
def doAction ();
// specifies operations on the tuple itself 
def changeTupleContent() -> tuple
// if true -> note gets added to local TS
def decideStore () -> boolean
// if true -> tuple gets unexported and deleted from local TS.
//new operation not in TOTA
def decideDie() -> boolean 

decideDie() is there for discontinuous decidePropagation functions. for example, tuples that should be only propagated every Tuesday could not implemented with TOTA because the propagation protocol only gets called once. We change this by providing decideDie() that gets called when you decide not to propagate. Like this a tuple can still be propagate at a later point in time, despite the fact that the decidePropagation function has evaluated to false at a certain moment.

uf/guanotes.1234371712.txt.gz · Last modified: 2009/11/18 15:07 by elisag
 
 
 
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