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Scoped Tuples for the Ambient (TOTAM)

TOTAM is tuple space model geared towards mobile ad hoc networks which provides a dynamic scoping mechanism that limits the transportation of tuples. TOTAM adopts features of both federated tuple spaces and replication-based approaches: it combines replication of tuples for read operations while guaranteeing atomicity for remove operations. In TOTAM, tuple spaces are annotated with tuple space descriptors used to determine the scope of a tuple. The novelty of our approach lies in the use of these tuple space descriptors to determine that a tuple should be propagated before it is transmitted. This enhances privacy and decreases the burden on the network traffic in a wide range of applications.


TOTA is one of the most dynamic tuple-based solutions for coordination in mobile networks. It relies on tuples which hop from location to location to coordinate distributed application nodes. Rather than merging local tuple spaces upon network connection as other tuple-based approaches like LIME, tuples themselves decide how to propagate from a tuple space to another. This means that tuples are injected in the network with and can autonomously propagate according to application-specific propagation rules expressed in the tuples themselves. These propagation rules are crucial to provide programmers with a flexible mechanism to achieve context-awareness based not only on connectivity but also on semantic information.

However, in TOTA tuples are sent to all communication partners in range. Upon arrival at the receiver side, the tuple itself decides whether it has to be stored in that tuple space. As all devices can potentially access all information, information cannot be hidden or scoped. By transmitting tuples potential malicious or non-intended users are provided with sensitive information. Not only does sending all tuples blindly to all communication partners in range may be unacceptable for certain applications, it also creates a network traffic overhead and has performance repercussions on mobile devices which are likely to have scarce resources, such as limited battery life.

Scoped Tuples for the Ambient

TOTAM provides the programmer with means to scope the tuples themselves, i.e the tuples can dynamically adjust their scope as they hop from location to location. By means of tuple space descriptors, programmers can scope their tuples preventing them to be propagated to unwanted locations. This scope is determined before the tuple is transmitted, thus allowing the programmer to prevent the physical transportation of tuples to devices which are not targeted.


Figure above illustrates how a scoped tuple is propagated through the TOTAM network. It depicts two types of locations, the blue and red locations corresponding to two teams of a multi-player game scenario where users (blue team) can use their PDA’s to chase dangerous (virtual) gangsters (red team) in the outdoors. The scope of the propagated tuple has been limited to blue locations. Figure (a) illustrates that a tuple is injected from the location with a star. This location is connected to four blue locations and one red location. As the scope of the tuple is limited to blue locations the tuple is only sent to the four blue locations. From those four locations the tuple is transitively propagated obeying the scope of the tuple until all connected blue locations are reached without being transmitted to a red location. Note that one blue location is not transitively connected to the sending device and thus does not receive the tuple. Figure (b) illustrates that a blue location moved into the range of the isolated blue location and thus, transmits the tuple to it. Again the tuple is not transmitted to nearby red locations. It is important to note from this operational sketch that the first isolated location receives a tuple without being connected at any time with the start location in which the tuple was originally inserted.


Further Reading

TOTAM: Scoped Tuples for the Ambient, C. Scholliers, E. Gonzalez Boix, W. De Meuter. Proceedings of the Second International DisCoTec Workshop on Context-aware Adaptation Mechanisms for Pervasive and Ubiquitous Services (CAMPUS 2009), from Electronic Communications of the EASST, eds. 2009. ( pdf)

uf/totam.1287587834.txt.gz · Last modified: 2010/10/20 17:44 by elisag
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