Spatial issues are essential in new classes of complex software systems, such as pervasive, multi-agent, and self-organising ones. Understanding the basic mechanisms of spatial coordination is a fundamental issue for coordination models and languages in order to deal with such systems, governing situated interaction in the spatio-temporal fabric. Along this line, in this talk we make space-aware coordination media out of ReSpecT tuple centres, by introducing the few basic mechanisms and constructs that enable the ReSpecT language to face most of the main challenges of spatial coordination in complex software systems. [Talk @ WOA 2013]

1. Space-aware Coordination in ReSpecT
Stefano Mariani
Andrea Omicini
{s.mariani, andrea.omicini}@unibo.it
DISI
Alma Mater Studiorum—Universit` di Bologna
a
WOA 2013
Torino, Italy
2 December 2013
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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2. Outline
1
Motivations & Goals
2
Space-aware Coordination Media
Spatial issues
Space-aware tuple centres
3
Spatial ReSpecT
Basic ReSpecT
Language extension
Virtual Machine extension
4
Expressiveness via Examples
5
Conclusion, Ongoing & Future Work
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
2 / 42

3. Motivations & Goals
Outline
1
Motivations & Goals
2
Space-aware Coordination Media
Spatial issues
Space-aware tuple centres
3
Spatial ReSpecT
Basic ReSpecT
Language extension
Virtual Machine extension
4
Expressiveness via Examples
5
Conclusion, Ongoing & Future Work
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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4. Motivations & Goals
The Need for Spatial Coordination
Spatial issues are fundamental in many sorts of complex software systems,
including intelligent, multi-agent, adaptive, and self-organising ones
[Beal et al., 2011].
Spatial coordination
Understanding the basic mechanisms of spatial coordination is a
fundamental issue for coordination models and languages in order to
govern situated interaction in the spatio-temporal fabric.
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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5. Motivations & Goals
Goal of the Work
In this work we aim at
devising out
the fundamental abstractions
the basic mechanisms
the linguistic constructs
required to generally enable and promote space-aware coordination
defining their embodiment in terms of
the tuple centre coordination medium
the ReSpecT coordination language
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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6. Motivations & Goals
Outline of the Work
Along this line, we
discuss the issues of spatial coordination
devise out the general requirements for space-aware coordination
media
introduce the specific notion of space-aware tuple centre
show how the ReSpecT coordination language can be extended so as
to support space-aware coordination
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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7. Space-aware Coordination Media
Outline
1
Motivations & Goals
2
Space-aware Coordination Media
Spatial issues
Space-aware tuple centres
3
Spatial ReSpecT
Basic ReSpecT
Language extension
Virtual Machine extension
4
Expressiveness via Examples
5
Conclusion, Ongoing & Future Work
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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8. Space-aware Coordination Media
Spatial issues
Outline
1
Motivations & Goals
2
Space-aware Coordination Media
Spatial issues
Space-aware tuple centres
3
Spatial ReSpecT
Basic ReSpecT
Language extension
Virtual Machine extension
4
Expressiveness via Examples
5
Conclusion, Ongoing & Future Work
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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9. Space-aware Coordination Media
Spatial issues
Situatedness & Awareness I
Spatial coordination requires
spatial situatedness
spatial awareness
of the coordination media
This translates in a number of technical requirements
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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10. Space-aware Coordination Media
Spatial issues
Situatedness & Awareness II
Situatedness
A space-aware coordination abstraction should at any time be associated
to an absolute positioning, both physical and virtual
In fact,
software abstractions may move along a virtual space – typically, the
network – which is usually discrete
whereas physical devices move through a physical space, which is
mostly continuous
However, software abstractions may also be hosted by mobile physical
devices, thus share their motion.
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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11. Space-aware Coordination Media
Spatial issues
Situatedness & Awareness III
Awareness
The position of the coordination medium should be available to the
coordination laws it contains in order to make them capable of reasoning
about space—so, to implement space-aware coordination laws.
Also, space has to be embedded into the working cycle of the coordination
medium:
a spatial event should be generated within a coordination medium,
conceptually corresponding to changes in space
then, such events should be captured by the coordination medium,
and used to activate space-aware coordination laws
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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12. Space-aware Coordination Media
Space-aware tuple centres
Outline
1
Motivations & Goals
2
Space-aware Coordination Media
Spatial issues
Space-aware tuple centres
3
Spatial ReSpecT
Basic ReSpecT
Language extension
Virtual Machine extension
4
Expressiveness via Examples
5
Conclusion, Ongoing & Future Work
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
12 / 42

13. Space-aware Coordination Media
Space-aware tuple centres
Tuple Centres
Technically, a tuple centre is a programmable tuple space, i.e., a tuple
space whose behaviour in response to (coordination) events can be
programmed so as to specify and enact any coordination policy
[Omicini and Denti, 2001b, Omicini, 2007].
General-purpose coordination media
Tuple centres can then be thought as general-purpose coordination
abstractions, which can be suitably forged to provide specific coordination
services.
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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14. Space-aware Coordination Media
Space-aware tuple centres
Space-aware Tuple Centres I
The location of a tuple centre is obtained through the notion of
current place
i.e., the absolute position of the computational device where the
coordination medium is running, or the domain name of node hosting
the tuple centre
Motion is conceptually represented by two sorts of spatial events:
leaving from a starting place
stopping at an arrival place
in any sort of space / place
Analogously to (coordination) operation and time events, it is
possible to specify reactions triggered by spatial events—the so-called
spatial reactions
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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15. Space-aware Coordination Media
Space-aware tuple centres
Space-aware Tuple Centres II
Space-aware coordination policies
As a result, a spatial tuple centre
can be programmed to react to motion in either a physical or a virtual
space
so as to enforce space-aware coordination policies.
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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16. Spatial ReSpecT
Outline
1
Motivations & Goals
2
Space-aware Coordination Media
Spatial issues
Space-aware tuple centres
3
Spatial ReSpecT
Basic ReSpecT
Language extension
Virtual Machine extension
4
Expressiveness via Examples
5
Conclusion, Ongoing & Future Work
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
16 / 42

17. Spatial ReSpecT
Basic ReSpecT
Outline
1
Motivations & Goals
2
Space-aware Coordination Media
Spatial issues
Space-aware tuple centres
3
Spatial ReSpecT
Basic ReSpecT
Language extension
Virtual Machine extension
4
Expressiveness via Examples
5
Conclusion, Ongoing & Future Work
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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18. Spatial ReSpecT
Basic ReSpecT
ReSpecT I
ReSpecT tuple centres
ReSpecT tuple centres are based on first-order logic (FOL), which is
adopted both for the communication language (logic tuples), and for the
behaviour specification language (ReSpecT) [Omicini and Denti, 2001a].
Basically, reactions in ReSpecT are defined as Prolog-like facts
(reaction specification tuples) of the form
reaction(Activity , Guards , Reactions )
A reaction specification tuple specifies the list of the operations
(Reactions ) to be executed when a given event occurs (called
triggering event, caused by an Activity ) and some conditions on the
event hold (Guards evaluate to true).
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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19. Spatial ReSpecT
Basic ReSpecT
ReSpecT II
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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20. Spatial ReSpecT
Language extension
Outline
1
Motivations & Goals
2
Space-aware Coordination Media
Spatial issues
Space-aware tuple centres
3
Spatial ReSpecT
Basic ReSpecT
Language extension
Virtual Machine extension
4
Expressiveness via Examples
5
Conclusion, Ongoing & Future Work
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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21. Spatial ReSpecT
Language extension
Spatial Observation Predicates
current place(@S ,?P ) succeeds if P unifies with the position of the node
which the tuple centre belongs to
event place(@S ,?P ) succeeds if P unifies with the position of the node
where the triggering event was originated
start place(@S ,?P ) succeeds if P unifies with the position of the node
where the event chain that led to the triggering event was
originated
The node position can be specified as either
S =ph its absolute physical position
S =ip its IP number
S =dns its domain name
S =map its geographical location—as typically defined by mapping services
like Google Maps
S =org its organisational position—that is, a location within an
organisation-defined virtual topology
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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22. Spatial ReSpecT
Language extension
Spatial Guard Predicates
at(@S ,@P ) succeeds when the tuple centre is currently executing at the
position P , specified according to S
near(@S ,@P ,@R ) succeeds when the tuple centre is currently executing at
the position included in the spatial region with centre P and
radius R , specified according to S
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Space-aware ReSpecT
WOA 2013, 2/12/2013
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23. Spatial ReSpecT
Language extension
Spatial Event Descriptors
from(?S ,?P ) matches a spatial event raised when the device hosting the
tuple centre starts moving from position P , specified
according to S .
to(?S ,?P ) matches a spatial event raised when the device hosting the
tuple centre stops moving and reaches position P , specified
according to S .
As a result, the following are admissible reaction specification tuples
dealing with spatial events:
reaction(from(?Space ,?Place ), Guards , Reactions ).
reaction(to(?Space ,?Place ), Guards , Reactions ).
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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24. Spatial ReSpecT
Language extension
Spatial Extension
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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25. Spatial ReSpecT
Virtual Machine extension
Outline
1
Motivations & Goals
2
Space-aware Coordination Media
Spatial issues
Space-aware tuple centres
3
Spatial ReSpecT
Basic ReSpecT
Language extension
Virtual Machine extension
4
Expressiveness via Examples
5
Conclusion, Ongoing & Future Work
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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26. Spatial ReSpecT
Virtual Machine extension
Extended Event Model I
The first fundamental extension to the event model is clearly depicted
in Table II: a new sort of spatial Activity is introduced
! In particular, the notion of Situation activity is extended with the two
spatial activities from( Space Place ), to( Space Place )
Another issue is represented by spatial qualification of events, that is,
making all ReSpecT events featuring spatial properties—in the same
way as for temporal properties in [Omicini et al., 2005]
! This is represented by the Space:Place property featured by Cause
– and StartCause , of course –, as shown in Table III, where the
extended ReSpecT event model is depicted.
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Space-aware ReSpecT
WOA 2013, 2/12/2013
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27. Spatial ReSpecT
Virtual Machine extension
Extended Event Model II
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
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28. Spatial ReSpecT
Virtual Machine extension
Extended Transition System I
The operational semantics of a ReSpecT tuple centre is expressed by
a transition system over a state represented by the labelled triple
OpE ,SitE Tu, Re, Op OutE [Casadei and Omicini, 2009]—abstracting
n
away from the specification tuples Σ
OutE is automatically emptied by emitting the outgoing events
In the same way, OpE and SitE are automatically extended whenever
a new incoming (either operation or situation) event enters a tuple
centre
! In particular, SitE is added new environment events by the associated
transducers [Casadei and Omicini, 2009], new time events by the flow
of time [Omicini et al., 2005], and also new spatial events whenever
some sort of motion takes place
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Space-aware ReSpecT
WOA 2013, 2/12/2013
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29. Spatial ReSpecT
Virtual Machine extension
Extended Transition System II
The behaviour of a ReSpecT tuple centre is modelled by a transition
system composed of four different transitions
[Casadei and Omicini, 2009]: reaction (−→r ), situation (−→s ),
operation (−→o ), log (−→l )
! Quite intuitively, spatial events are handled – in the same way as time
and environment events – by the situation transition, which triggers
ReSpecT spatial reactions
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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30. Expressiveness via Examples
Outline
1
Motivations & Goals
2
Space-aware Coordination Media
Spatial issues
Space-aware tuple centres
3
Spatial ReSpecT
Basic ReSpecT
Language extension
Virtual Machine extension
4
Expressiveness via Examples
5
Conclusion, Ongoing & Future Work
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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31. Expressiveness via Examples
Spheric Broadcasting I
Requirements:
a message has to be locally spread in the environment (e.g. network
of nodes), so as to be perceived only by nearby agents
you want to do so through a distributed, collaborative dissemination
process
the distance defining “locally” can be thought of as a “straight-line”
radius, identifying a three-dimensional sphere around the point where
the message is firstly created
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
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32. 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Expressiveness via Examples
Spheric Broadcasting II
% 1) Get agent message
% 1.1) Delete garbage tuple
...
% 1.2) Check range then forward
reaction ( out ( spheric ( Msg,Radius )) ,
( operation,completion ),
( current_place ( ph,RecPos ) ,
% Current position
start_place ( ph,SendPos ) ,
% Starting position
in_range ( R e c P o s , S e n d P o s , R a d i u s ) , % Prolog computation
start_source ( Sender ) , start_time ( Time ) ,
out ( msg ( Ms g, Se n de r, Ti m e )) ,
rd ( neighbours ( Nbrs )) , List of neighbours
out ( forward ( N b rs ,M sg , Ra di us )) )).
% 2) Forward to every neighbour
% 2.1) Delete garbage tuple
...
% 2.2) Neighbour list not empty
reaction ( out ( forward ([ Nbr | Nbrs ] ,Msg,Radius )) ,
internal,
( Nbr ? out ( spheric ( Msg,Radius )) ,
% Forward
out ( forward ( N b rs ,M sg , Ra di us )) )). % Iterate
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Space-aware ReSpecT
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33. Expressiveness via Examples
Spheric Broadcasting III
Given a virtual topology is reified in the tuple neighbours, we get
that any message embedded in a spheric tuple is autonomously
spread solely to Radius-reachable neighbouring tuple centres
This is made possible by the start place/1 observation predicate,
inspecting the place where the first spheric broadcast request was
issued—regardless of the number of tuple centre hops taken to
forward the request
“Basic”, spatial-coordination mechanisms
? What if we replace current place(ph,RecPos) with
current place(dns,RecPos)?
? What if we replace start place with event place?
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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34. Expressiveness via Examples
Monitored Motion I
Requirements:
you have an autonomous mobile device – e.g. a simple
wheel-equipped robot – that has to reach a given destination
this implies that the mobile device should
start moving when asked to do so
monitor its own position so as to understand when given destination is
reached, if obstacles are on its way, etc.
finally stop when due
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Space-aware ReSpecT
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35. 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Expressiveness via Examples
Monitored Motion II
% 1) Compute motion vector then start moving
reaction ( out ( move ( Dest,TStep )) , ( o p e r a t i o n , c o m p l e t i o n ) ,
( current_place ( ph,Here ) , current_time ( Now ) ,
Check is Now + TStep,
direction ( Dest,Here,Vec ) ,
% Prolog computation
out_s ( ... ) ,
% Schedule monitoring ( Reaction 2)
curre nt_targ et ( _@Node ) ,
% Get node id
m ot io n_ d ev @N od e <- env ( dir,Vec ) ,
% Set direction
m ot io n_ d ev @N od e <- env ( engine, ’ on ’) )). % Move on
% 2) Monitor destination arrival
reaction ( time ( Check ) , internal, % Time to check
( current_place ( ph,Here ) ,
rd ( move ( Dest,TStep )) ,
( check ( Here,Dest ) ,
% Prolog computation
curr ent_targ et ( _@Node ) ,
% Get node id
m ot io n_ d ev @N o de <- env ( engine, ’ off ’)
; % Prolog ’ if-then-else ’
current_time ( Now ) , Check is Now + TStep,
out_s ( ... ) ))).
% Schedule monitoring ( Reaction 2)
% 3) Arrival clean-up
reaction ( to ( Dest ) , internal, in ( move ( Dest,_ )) ). % Dest . reached
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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36. Conclusion, Ongoing & Future Work
Outline
1
Motivations & Goals
2
Space-aware Coordination Media
Spatial issues
Space-aware tuple centres
3
Spatial ReSpecT
Basic ReSpecT
Language extension
Virtual Machine extension
4
Expressiveness via Examples
5
Conclusion, Ongoing & Future Work
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
36 / 42

37. Conclusion, Ongoing & Future Work
Conclusion
Spatial situation is a requirement for many advanced application
scenarios
Coordination models should be enhanced to handle situated
interaction
Coordination media should be enhanced to address all the need of
space-aware coordination
Tuple centres can be extended to become space-aware coordination
media
ReSpecT can be extended to enable space-aware coordination policies
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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38. Conclusion, Ongoing & Future Work
Ongoing & Future Work
Implementation of space-aware ReSpecT tuple centres completed
ReSpecT tuple centres provided as coordination media of the
TuCSoN coordination middleware [TuCSoN, 2013]
Android version in beta version
Experiments on Android devices and mobile computers
Spatial transducers for a range of diverse mobile sensors & devices
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
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39. References
References I
Beal, J., Michel, O., and Schultz, U. P. (2011).
Spatial computing: Distributed systems that take advantage of our geometric
world.
ACM Trans. Auton. Adapt. Syst., 6(2):11:1–11:3.
Casadei, M. and Omicini, A. (2009).
Situated tuple centres in ReSpecT.
In Shin, S. Y., Ossowski, S., Menezes, R., and Viroli, M., editors, 24th Annual
ACM Symposium on Applied Computing (SAC 2009), volume III, pages
1361–1368, Honolulu, Hawai’i, USA. ACM.
Omicini, A. (2007).
Formal ReSpecT in the A&A perspective.
Electronic Notes in Theoretical Computer Science, 175(2):97–117.
5th International Workshop on Foundations of Coordination Languages and
Software Architectures (FOCLASA’06), CONCUR’06, Bonn, Germany,
31 August 2006. Post-proceedings.
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Space-aware ReSpecT
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40. References
References II
Omicini, A. and Denti, E. (2001a).
Formal ReSpecT.
Electronic Notes in Theoretical Computer Science, 48:179–196.
Declarative Programming – Selected Papers from AGP 2000, La Habana, Cuba,
4–6 December 2000.
Omicini, A. and Denti, E. (2001b).
From tuple spaces to tuple centres.
Science of Computer Programming, 41(3):277–294.
Omicini, A., Ricci, A., and Viroli, M. (2005).
Time-aware coordination in ReSpecT.
In Jacquet, J.-M. and Picco, G. P., editors, Coordination Models and Languages,
volume 3454 of LNCS, pages 268–282. Springer-Verlag.
7th International Conference (COORDINATION 2005), Namur, Belgium,
20–23 April 2005. Proceedings.
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41. References
References III
TuCSoN (2013).
Home page.
http://tucson.unibo.it/.
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42. Space-aware Coordination in ReSpecT
Stefano Mariani
Andrea Omicini
{s.mariani, andrea.omicini}@unibo.it
DISI
Alma Mater Studiorum—Universit` di Bologna
a
WOA 2013
Torino, Italy
2 December 2013
Mariani, Omicini (DISI, Alma Mater)
Space-aware ReSpecT
WOA 2013, 2/12/2013
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