Situatedness is a fundamental requirement for today’s complex software systems, as well as for the computational models and programming languages used to build them. Spatial and temporal situatedness, in particular, are essential features for AI, enabling actors of the system to take autonomous decisions contextual to the space-time they live in. To support spatio-temporal awareness in distributed pervasive systems, we adopt the standpoint of Logic Programming (LP) by focussing on the Logic Programming as a Service (LPaaS) approach, promoting the distribution of situated intelligence. Accordingly, we provide an interpretation about what it means to make LP span across space and time, then we extend the LPaaS model and architecture towards spatio-temporal situatedness, by identifying a set of suitably-expressive spatio-temporal primitives.

1. Logic Programming in Space-Time:
The Case of Situatedness in LPaaS
Roberta Calegari1 Giovanni Ciatto1 Stefano Mariani2
Enrico Denti1 Andrea Omicini1
{roberta.calegari, giovanni.ciatto, enrico.denti,
andrea.omicini}@unibo.it
stefano.mariani@unimore.it
1Dipartimento di Informatica, Scienza e Ingegneria—Universit`a di Bologna
2Dipartimento di Scienze e Metodi dell’Ingegneria, Universit`a di Modena e Reggio Emilia
Talk @ 19th Workshop From Objects to Agents (WOA 2018)
Palermo, June 29, 2018
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 1 / 20

2. Outline
1 Motivations & Context
2 Logic Programming as a Service
Vision & Architecture
3 Spatio-temporal awareness in LPaaS
Spatio-temporal awareness in LPaaS
Interface & API
4 Example
5 Conclusion & Further Work
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 2 / 20

3. Motivations & Context
Next in Line. . .
1 Motivations & Context
2 Logic Programming as a Service
3 Spatio-temporal awareness in LPaaS
4 Example
5 Conclusion & Further Work
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 3 / 20

4. Motivations & Context
Motivation & Context
Need for intelligence for the IoT:
Not only smart, inter-connected things
Internet of Intelligent Things (IoIT) [Ars´enio et al., 2014]
Things need to be:
Interoperable — interact with each other with no prior knowledge
Context-aware — observe the environment and react accordingly
Goal-oriented — understand us and our goals
Understandable — explain their decision and actions
Within open environments and in a distributed fashion
spatial locality does matter
temporal reference does matter, too
! reasoning capabilities still missing in nowadays Things
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 4 / 20

5. Motivations & Context
Motivation & Context
Need for intelligence for the IoT:
Not only smart, inter-connected things
Internet of Intelligent Things (IoIT) [Ars´enio et al., 2014]
Things need to be:
Interoperable — interact with each other with no prior knowledge
Context-aware — observe the environment and react accordingly
Goal-oriented — understand us and our goals
Understandable — explain their decision and actions
Within open environments and in a distributed fashion
spatial locality does matter
temporal reference does matter, too
! reasoning capabilities still missing in nowadays Things
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 4 / 20

6. Motivations & Context
Motivation & Context
Need for intelligence for the IoT:
Not only smart, inter-connected things
Internet of Intelligent Things (IoIT) [Ars´enio et al., 2014]
Things need to be:
Interoperable — interact with each other with no prior knowledge
Context-aware — observe the environment and react accordingly
Goal-oriented — understand us and our goals
Understandable — explain their decision and actions
Within open environments and in a distributed fashion
spatial locality does matter
temporal reference does matter, too
! reasoning capabilities still missing in nowadays Things
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 4 / 20

7. Motivations & Context
Motivation & Context
Logic Programming as a Service (LPaaS): [Calegari et al., 2017]
our proposal endowing IoT with logic programming
reasoning capabilities for IoT devices, provided as-a-Service
to possibly heterogeneous clients
interested in reasoning results
only making sense somewhere and for a while
LP re-interpreted within the service perspective:
Encapsulation of theories accesses and updates
Stateless interface for stateful interaction
Acceptance of locality of the logic service
! APIs letting clients focus on specific regions & time intervals
proposed in this work
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 5 / 20

8. Motivations & Context
Motivation & Context
Logic Programming as a Service (LPaaS): [Calegari et al., 2017]
our proposal endowing IoT with logic programming
reasoning capabilities for IoT devices, provided as-a-Service
to possibly heterogeneous clients
interested in reasoning results
only making sense somewhere and for a while
LP re-interpreted within the service perspective:
Encapsulation of theories accesses and updates
Stateless interface for stateful interaction
Acceptance of locality of the logic service
! APIs letting clients focus on specific regions & time intervals
proposed in this work
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 5 / 20

9. Motivations & Context
Motivation & Context
Logic Programming as a Service (LPaaS): [Calegari et al., 2017]
our proposal endowing IoT with logic programming
reasoning capabilities for IoT devices, provided as-a-Service
to possibly heterogeneous clients
interested in reasoning results
only making sense somewhere and for a while
LP re-interpreted within the service perspective:
Encapsulation of theories accesses and updates
Stateless interface for stateful interaction
Acceptance of locality of the logic service
! APIs letting clients focus on specific regions & time intervals
proposed in this work
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 5 / 20

10. Motivations & Context
Motivation & Context
Logic Programming as a Service (LPaaS): [Calegari et al., 2017]
our proposal endowing IoT with logic programming
reasoning capabilities for IoT devices, provided as-a-Service
to possibly heterogeneous clients
interested in reasoning results
only making sense somewhere and for a while
LP re-interpreted within the service perspective:
Encapsulation of theories accesses and updates
Stateless interface for stateful interaction
Acceptance of locality of the logic service
! APIs letting clients focus on specific regions & time intervals
proposed in this work
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 5 / 20

11. Logic Programming as a Service
Next in Line. . .
1 Motivations & Context
2 Logic Programming as a Service
3 Spatio-temporal awareness in LPaaS
4 Example
5 Conclusion & Further Work
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 6 / 20

12. Logic Programming as a Service Vision & Architecture
LPaaS Overview
Several situated logic services may participate to the system
possibly moving, possibly leaving/entering
They provide an abstract view of a LP inference engine
implementing the SLD resolution [Robinson, 1965]
through a technology-agnostic, network-enabled interface
Each service encapsulates its logic theories (or Knowledge Base,
KB)—which therefore represent truth from the service p.o.v.
sensors are assumed to be providing fresh & local information
[Calegari et al., 2018a]
Two roles for users:
client — may query a particular version of the service
requesting goals to be solved
configurator — may arbitrarily alter the KB
Implementation exists wrapping tuProlog [Denti et al., 2013] within a
RESTfull Web-Service, internally organized through micro-services
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 7 / 20

13. Logic Programming as a Service Vision & Architecture
LPaaS Overview
Several situated logic services may participate to the system
possibly moving, possibly leaving/entering
They provide an abstract view of a LP inference engine
implementing the SLD resolution [Robinson, 1965]
through a technology-agnostic, network-enabled interface
Each service encapsulates its logic theories (or Knowledge Base,
KB)—which therefore represent truth from the service p.o.v.
sensors are assumed to be providing fresh & local information
[Calegari et al., 2018a]
Two roles for users:
client — may query a particular version of the service
requesting goals to be solved
configurator — may arbitrarily alter the KB
Implementation exists wrapping tuProlog [Denti et al., 2013] within a
RESTfull Web-Service, internally organized through micro-services
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 7 / 20

14. Logic Programming as a Service Vision & Architecture
LPaaS Overview
Several situated logic services may participate to the system
possibly moving, possibly leaving/entering
They provide an abstract view of a LP inference engine
implementing the SLD resolution [Robinson, 1965]
through a technology-agnostic, network-enabled interface
Each service encapsulates its logic theories (or Knowledge Base,
KB)—which therefore represent truth from the service p.o.v.
sensors are assumed to be providing fresh & local information
[Calegari et al., 2018a]
Two roles for users:
client — may query a particular version of the service
requesting goals to be solved
configurator — may arbitrarily alter the KB
Implementation exists wrapping tuProlog [Denti et al., 2013] within a
RESTfull Web-Service, internally organized through micro-services
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 7 / 20

15. Logic Programming as a Service Vision & Architecture
LPaaS Overview
Several situated logic services may participate to the system
possibly moving, possibly leaving/entering
They provide an abstract view of a LP inference engine
implementing the SLD resolution [Robinson, 1965]
through a technology-agnostic, network-enabled interface
Each service encapsulates its logic theories (or Knowledge Base,
KB)—which therefore represent truth from the service p.o.v.
sensors are assumed to be providing fresh & local information
[Calegari et al., 2018a]
Two roles for users:
client — may query a particular version of the service
requesting goals to be solved
configurator — may arbitrarily alter the KB
Implementation exists wrapping tuProlog [Denti et al., 2013] within a
RESTfull Web-Service, internally organized through micro-services
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 7 / 20

16. Logic Programming as a Service Vision & Architecture
LPaaS Overview
Several situated logic services may participate to the system
possibly moving, possibly leaving/entering
They provide an abstract view of a LP inference engine
implementing the SLD resolution [Robinson, 1965]
through a technology-agnostic, network-enabled interface
Each service encapsulates its logic theories (or Knowledge Base,
KB)—which therefore represent truth from the service p.o.v.
sensors are assumed to be providing fresh & local information
[Calegari et al., 2018a]
Two roles for users:
client — may query a particular version of the service
requesting goals to be solved
configurator — may arbitrarily alter the KB
Implementation exists wrapping tuProlog [Denti et al., 2013] within a
RESTfull Web-Service, internally organized through micro-services
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 7 / 20

17. Spatio-temporal awareness in LPaaS
Next in Line. . .
1 Motivations & Context
2 Logic Programming as a Service
3 Spatio-temporal awareness in LPaaS
4 Example
5 Conclusion & Further Work
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 8 / 20

18. Spatio-temporal awareness in LPaaS Spatio-temporal awareness in LPaaS
Situatedness in LPaaS
Resolution process takes into account the service spatio-temporal context
a goal is demonstrated against a logic theory considered true within a
(possibly open) interval of time, and a region of space
resolution process could span over time and space
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 9 / 20

19. Spatio-temporal awareness in LPaaS Spatio-temporal awareness in LPaaS
The temporal/spatial dimensions
Time in LPaaS
time-dependant computations, e.g. periodic
temporal validity of logic theories, individual facts and clauses
requests may restrict the temporal scope of the expected solutions
Space in LPaaS
space-dependant computations
spatial validity of logic theories, individual facts and clauses
requests may restrict the spatial scope of the expected solutions
High-level, situation-aware APIs must be provided to clients
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 10 / 20

20. Spatio-temporal awareness in LPaaS Spatio-temporal awareness in LPaaS
The temporal/spatial dimensions
Time in LPaaS
time-dependant computations, e.g. periodic
temporal validity of logic theories, individual facts and clauses
requests may restrict the temporal scope of the expected solutions
Space in LPaaS
space-dependant computations
spatial validity of logic theories, individual facts and clauses
requests may restrict the spatial scope of the expected solutions
High-level, situation-aware APIs must be provided to clients
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 10 / 20

21. Spatio-temporal awareness in LPaaS Spatio-temporal awareness in LPaaS
The temporal/spatial dimensions
Time in LPaaS
time-dependant computations, e.g. periodic
temporal validity of logic theories, individual facts and clauses
requests may restrict the temporal scope of the expected solutions
Space in LPaaS
space-dependant computations
spatial validity of logic theories, individual facts and clauses
requests may restrict the spatial scope of the expected solutions
High-level, situation-aware APIs must be provided to clients
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 10 / 20

22. Spatio-temporal awareness in LPaaS Interface & API
API – Temporal dimension
Clients choose when they want a solution
Timely solutions — solve(?Goal, ..., -Results ) predicates with a
within(Time ) argument constraining resolution duration
Periodic solutions stream — solve predicates with a every(Time ) arg.
Time aware resolution process
Axiom in theories decorated with time interval, defining their validity
Clients’ queries could specify a(n open?) TimeInterval of interest
Only axioms valid at Instant ∈ TimeInterval affect resolution
? reason about the future?
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 11 / 20

23. Spatio-temporal awareness in LPaaS Interface & API
API – Temporal dimension
Clients choose when they want a solution
Timely solutions — solve(?Goal, ..., -Results ) predicates with a
within(Time ) argument constraining resolution duration
Periodic solutions stream — solve predicates with a every(Time ) arg.
Time aware resolution process
Axiom in theories decorated with time interval, defining their validity
Clients’ queries could specify a(n open?) TimeInterval of interest
Only axioms valid at Instant ∈ TimeInterval affect resolution
? reason about the future?
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 11 / 20

24. Spatio-temporal awareness in LPaaS Interface & API
Spatial dimension
Clients specify where solutions should make sense
Local solutions — solveNeighborhood(?Goal, -Results, ?Region )
predicate provide a solution from a neighborhood of logic
services
implicit interaction between service instances may occur
Solutions stream across space — e.g. by widening/narrowing the region
considered at consecutive resolution cycles
Space aware resolution process
Distribution is a premise per se to spatial situatedness
Logic services are (assumed to be) aware of their positions
w.r.t. some custom notion of locality (GPS lat/long, network hops, etc)
They keep track of what is true in their surroundings
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 12 / 20

25. Spatio-temporal awareness in LPaaS Interface & API
Spatial dimension
Clients specify where solutions should make sense
Local solutions — solveNeighborhood(?Goal, -Results, ?Region )
predicate provide a solution from a neighborhood of logic
services
implicit interaction between service instances may occur
Solutions stream across space — e.g. by widening/narrowing the region
considered at consecutive resolution cycles
Space aware resolution process
Distribution is a premise per se to spatial situatedness
Logic services are (assumed to be) aware of their positions
w.r.t. some custom notion of locality (GPS lat/long, network hops, etc)
They keep track of what is true in their surroundings
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 12 / 20

26. Example
Next in Line. . .
1 Motivations & Context
2 Logic Programming as a Service
3 Spatio-temporal awareness in LPaaS
4 Example
5 Conclusion & Further Work
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 13 / 20

27. Example
Testbed Scenario
User looking for a parking in proximity of a metro station in London
distance = num. of stations between LPaaS server and parking place
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 14 / 20

28. Example
Testbed Scenario
?- solve( station with parking(X ), S )
no.
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 14 / 20

29. Example
Testbed Scenario
?- solveAllNeighborhood( ( station with parking(X ),
free places(X, N ) ), S, region( , distance(1, Line ) ) )
yes. S = (X /‘LondonBridge’, N /5, Line /black)
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 14 / 20

30. Example
Testbed Scenario
?- solveAllNeighborhood( ( station with parking(X ),
free places(X, N ) ), S, region( , distance(1, brown) ) )
no.
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 14 / 20

31. Example
Testbed Scenario
?- solveAllNeighborhood( ( station with parking(X ),
free places(X, N ) ), S, region( , distance(2, Line ) ) )
yes. S = [ (X /‘LondonBridge’, N /5, Line /black),
(X /‘Charing Cross’, N /1, Line /brown),
(X /‘Canada Water’, N /2, Line /[black, gray]) ]
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 14 / 20

32. Conclusion & Further Work
Next in Line. . .
1 Motivations & Context
2 Logic Programming as a Service
3 Spatio-temporal awareness in LPaaS
4 Example
5 Conclusion & Further Work
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 15 / 20

33. Conclusion & Further Work
Conclusion
Pervasive and situated IoIT scenarios may take advantage of
context-aware intelligence
LPaaS aims at satisfying such a challenging requirement
exposing logic reasoning capabilities as-a-Service
to heterogeneous clients moving around
It supports spatio-temporal awareness while reasoning, thus
supporting the distribution of situated intelligence
through suitably-expressive set of spatio-temporal primitives
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 16 / 20

34. Conclusion & Further Work
Conclusion
Pervasive and situated IoIT scenarios may take advantage of
context-aware intelligence
LPaaS aims at satisfying such a challenging requirement
exposing logic reasoning capabilities as-a-Service
to heterogeneous clients moving around
It supports spatio-temporal awareness while reasoning, thus
supporting the distribution of situated intelligence
through suitably-expressive set of spatio-temporal primitives
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 16 / 20

35. Conclusion & Further Work
Conclusion
Pervasive and situated IoIT scenarios may take advantage of
context-aware intelligence
LPaaS aims at satisfying such a challenging requirement
exposing logic reasoning capabilities as-a-Service
to heterogeneous clients moving around
It supports spatio-temporal awareness while reasoning, thus
supporting the distribution of situated intelligence
through suitably-expressive set of spatio-temporal primitives
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 16 / 20

36. Conclusion & Further Work
Further Work
Designing & developing a specialised logic-based middleware
Tests in pervasive deployment scenarios are required, mainly in the
IoT landscape
e.g. testing directly LPaaS over BLE or Wifi-Direct connections
Integrating LPaaS with Labelled LP [Calegari et al., 2018b] for
domain-specific logic-based computation
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 17 / 20

37. Conclusion & Further Work
Further Work
Designing & developing a specialised logic-based middleware
Tests in pervasive deployment scenarios are required, mainly in the
IoT landscape
e.g. testing directly LPaaS over BLE or Wifi-Direct connections
Integrating LPaaS with Labelled LP [Calegari et al., 2018b] for
domain-specific logic-based computation
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 17 / 20

38. Conclusion & Further Work
Further Work
Designing & developing a specialised logic-based middleware
Tests in pervasive deployment scenarios are required, mainly in the
IoT landscape
e.g. testing directly LPaaS over BLE or Wifi-Direct connections
Integrating LPaaS with Labelled LP [Calegari et al., 2018b] for
domain-specific logic-based computation
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 17 / 20

39. References
References I
Ars´enio, A., Serra, H., Francisco, R., Nabais, F., Andrade, J., and Serrano, E. (2014).
Internet of Intelligent Things: Bringing Artificial Intelligence into Things and
Communication Networks, pages 1–37.
Springer Berlin Heidelberg, Berlin, Heidelberg.
Calegari, R., Ciatto, G., Mariani, S., Denti, E., and Omicini, A. (2018a).
Micro-intelligence for the iot: Se challenges and practice in lpaas.
In 2018 IEEE International Conference on Cloud Engineering (IC2E 208), pages 292–297.
IEEE Computer Society.
Calegari, R., Denti, E., Dovier, A., and Omicini, A. (2018b).
Extending logic programming with labelled variables: Model and semantics.
Fundamenta Informaticae, 161:53–74.
Special Issue CILC 2016.
Calegari, R., Denti, E., Mariani, S., and Omicini, A. (2017).
Logic Programming as a Service (LPaaS): Intelligence for the IoT.
In Fortino, G., Zhou, M., Lukszo, Z., Vasilakos, A. V., Basile, F., Palau, C., Liotta, A.,
Fanti, M. P., Guerrieri, A., and Vinci, A., editors, 2017 IEEE 14th International Conference
on Networking, Sensing and Control (ICNSC 2017), pages 72–77. IEEE.
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 18 / 20

40. References
References II
Denti, E., Omicini, A., and Calegari, R. (2013).
tuProlog: Making Prolog ubiquitous.
ALP Newsletter.
Robinson, J. A. (1965).
A machine-oriented logic based on the resolution principle.
Journal of the ACM, 12(1):23–41.
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 19 / 20

41. Logic Programming in Space-Time:
The Case of Situatedness in LPaaS
Roberta Calegari1 Giovanni Ciatto1 Stefano Mariani2
Enrico Denti1 Andrea Omicini1
{roberta.calegari, giovanni.ciatto, enrico.denti,
andrea.omicini}@unibo.it
stefano.mariani@unimore.it
1Dipartimento di Informatica, Scienza e Ingegneria—Universit`a di Bologna
2Dipartimento di Scienze e Metodi dell’Ingegneria, Universit`a di Modena e Reggio Emilia
Talk @ 19th Workshop From Objects to Agents (WOA 2018)
Palermo, June 29, 2018
Calegari, Ciatto, Mariani, Denti, Omicini LPaaS: Logic Programming in Space-Time WOA 2018, June 29 20 / 20