The document discusses experiments with logic programming as a service (LPaaS) using tuProlog. It proposes an LPaaS architecture with local APIs for creating engines, loading theories, and querying. It also describes implementing tuProlog as a service (2PaaS) on iOS, where tuProlog is embedded in an app and provides an API via URL schemes for other apps to interface with it. Example application scenarios are presented, including using tuProlog for symbolic derivatives and multi-language programming. Further work is outlined to better define and extend the LPaaS paradigm.

1. Towards Logic Programming as a Service
Experiments in tuProlog
Roberta Calegari Enrico Denti Stefano Mariani Andrea Omicini
{roberta.calegari, enrico.denti, s.mariani, andrea.omicini}@unibo.it
Dipartimento di Informatica – Scienza e Ingegneria (DISI)
Alma Mater Studiorum – Universit`a di Bologna
XVII Workshop “From Objects to Agents” (WOA 2016)
Catania, Italy, 29 July 2016
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 1 / 26

2. Outline
1 Scope & Goals
2 Logic Programming as a Service (LPaaS)
3 tuProlog as a Service (2PaaS) on iOS
4 Application Scenarios
5 Related Work
6 Conclusion & Further Work
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 2 / 26

3. Scope & Goals
Outline
1 Scope & Goals
2 Logic Programming as a Service (LPaaS)
3 tuProlog as a Service (2PaaS) on iOS
4 Application Scenarios
5 Related Work
6 Conclusion & Further Work
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 3 / 26

4. Scope & Goals Context & Motivation
Context
Challenges of today’s pervasive system [MO15]
complex distributed situated intelligent
distributed situated intelligence
light-weight, effective intelligence chunks
placed where and when needed
to locally tackle the specific reasoning needs
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 4 / 26

5. Scope & Goals Context & Motivation
Motivations
Complex Internet-of-Things (IoT) scenarios
mobility/cloud ecosystem
infrastructure, platforms, and software as a service
enabling people to benefit from ubiquitous information access
Role of logic-based languages
Multiple, distributed Prolog engines
intelligence providers
technology integrators [OZ04]
Logic Programming as a Service (LPaaS)
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 5 / 26

6. Scope & Goals tuProlog in a Nutshell
tuProlog [DOR01, DOC13]
light-weight, minimal, easily deployable
dynamically configurable
inter-operable
multi-paradigm, multi-language, multi-platform
Java, .NET, Android, iOS
open-source @ http://tuprolog.unibo.it
Minimality
tuProlog core contains just the Prolog engine essentials
↑ other features via libraries
Easy deployability
e.g., JAR archive/.NET assembly made available at the desired
location – Android/iOS app (via the Android/iOS installer)
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 6 / 26

7. Logic Programming as a Service (LPaaS)
Outline
1 Scope & Goals
2 Logic Programming as a Service (LPaaS)
3 tuProlog as a Service (2PaaS) on iOS
4 Application Scenarios
5 Related Work
6 Conclusion & Further Work
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 7 / 26

8. Logic Programming as a Service (LPaaS) Architecture
LPaaS Architecture
Logic Programming as a Service (LPaaS)
Presumably at the SaaS level
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 8 / 26

9. Logic Programming as a Service (LPaaS) Interface & API
LPaaS Interface & API
(Local) API
create engine to instantiate a dedicated engine
reset engine to reset the engine to the initial state and possibly the empty
knowledge base
set theory to load the knowledge base into the engine
query to submit queries and retrieve (possibly multiple) results
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 9 / 26

10. tuProlog as a Service (2PaaS) on iOS
Outline
1 Scope & Goals
2 Logic Programming as a Service (LPaaS)
3 tuProlog as a Service (2PaaS) on iOS
4 Application Scenarios
5 Related Work
6 Conclusion & Further Work
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 10 / 26

11. tuProlog as a Service (2PaaS) on iOS Architecture
2PaaS Architecture
tuProlog as a Service (2PaaS) on iOS
is embedded in a tuProlog app
acting as the service provider for all other applications running on the
mobile device
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 11 / 26

12. tuProlog as a Service (2PaaS) on iOS Interface & API
2PaaS Interface & API I
API
create engine implicit—just embedded in the first call to the service
reset engine mapped onto the 2P reset primitive
set theory mapped onto the 2P theory primitive
query mapped onto a set of 2P primitives—namely, query to issue
the query, result and solution to retrieve the query
result, and nextSol to explore further solutions
iOS built-in URL scheme functionality
simple and effective way for application inter-communication
↑ via a user-defined, URL-based protocol
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 12 / 26

13. tuProlog as a Service (2PaaS) on iOS Interface & API
2PaaS Interface & API II
tuProlog app URL scheme
tuPrologMobile://?src=srcURL&command=argument&dst=dstURL
srcURL is the client URL scheme
command is one of theory, query, nextSol, reset, with argument
respectively being theory, query (the text of the query)
dstURL is the URL scheme of the client to which the result should be
sent, possibly different from srcURL
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 13 / 26

14. tuProlog as a Service (2PaaS) on iOS Interface & API
2PaaS Interface & API III
Query result returned by the tuProlog service
dstURL://command=commandresult
dstURL is the URL scheme of the client receiving the result
command is either result, solution, nextSol, or reset, with the
respective commandresult
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 14 / 26

15. Application Scenarios
Outline
1 Scope & Goals
2 Logic Programming as a Service (LPaaS)
3 tuProlog as a Service (2PaaS) on iOS
4 Application Scenarios
5 Related Work
6 Conclusion & Further Work
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 15 / 26

16. Application Scenarios The “Derivative” Case Study
The “Derivative” Case Study
The symbolic derivative query, and its result on iPhone and iWatch
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 16 / 26

17. Application Scenarios The Multi-language Case Study
The Multi-language Toy Example
exploiting tuProlog multi-paradigm programming support (OOLibrary)
Swift or Objective-C apps interacting with Java entities
Swift app creates Java objects, calls methods, and elaborates the (Java)
result back in Swift
Example query
a Java string member(X,[a,d]). is bound to the Prolog var Q
then a Java Prolog engine is bound to the Prolog var P
P is used to solve the query Q
the result is bound to the Prolog var S
the result is converted to a Java string via toString
then it is bound to the final result to the Prolog var SOL
the result is printed by the Swift app on its console
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 17 / 26

18. Application Scenarios Complex Pervasive Systems
Towards Home Intelligence
need for situatedness—i.e., smart fridge, geo-localised reasoning
instability of the connection
limits to the availability of bandwidth and computational power
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 18 / 26

19. Related Work
Outline
1 Scope & Goals
2 Logic Programming as a Service (LPaaS)
3 tuProlog as a Service (2PaaS) on iOS
4 Application Scenarios
5 Related Work
6 Conclusion & Further Work
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 19 / 26

20. Related Work
Related Work
[CH01] — PiLLoW library (Programming in Logic Languages on the
Web): developed in Ciao Prolog and available for
SWI-Prolog, SICStus Prolog, and YAP and Ciao
[MS02] — Logic programming for the composition of Semantic Web
Services
[BGHK97] — ALP-Prolog library aiming at embedded HTTP servers for
controlling appliances
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 20 / 26

21. Conclusion & Further Work
Outline
1 Scope & Goals
2 Logic Programming as a Service (LPaaS)
3 tuProlog as a Service (2PaaS) on iOS
4 Application Scenarios
5 Related Work
6 Conclusion & Further Work
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 21 / 26

22. Conclusion & Further Work
Conclusions
Distributed light-weight logic programming engines for pervasive and
situated systems
→ modular, multi-platform, and multi-language logic engine
→ LPaaS
→ tuProlog as a service (2PaaS) on iOS
Further Work
precisely defining and further extending the LPaaS paradigm
providing logic engines within SOA – e.g., tuProlog as a RESTful web
service
designing the architecture of a general-purpose Prolog middleware
building a full-fledged specialised tuProlog middleware
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 22 / 26

23. References
References I
Manfred Bathelt, Ulrich Gall, Bernd Hindel, and Christian Kurzke.
Accessing embedded systems via WWW: The ProWeb toolset.
Computer Networks and ISDN Systems, 29(8-13):1065–1073, September 1997.
Papers from the 6th International World Wide Web Conference.
Daniel Cabeza and Manuel V. Hermenegildo.
Distributed WWW programming using (Ciao-) Prolog and the PilloW library.
Theory and Practice of Logic Programming, 1(3):251–282, May 2001.
Enrico Denti, Andrea Omicini, and Roberta Calegari.
tuProlog: Making Prolog ubiquitous.
ALP Newsletter, October 2013.
Enrico Denti, Andrea Omicini, and Alessandro Ricci.
tuProlog: A light-weight Prolog for Internet applications and infrastructures.
In I.V. Ramakrishnan, editor, Practical Aspects of Declarative Languages, volume 1990 of
Lecture Notes in Computer Science, pages 184–198. Springer Berlin Heidelberg, 2001.
3rd International Symposium (PADL 2001), Las Vegas, NV, USA, 11–12 March 2001.
Proceedings.
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 23 / 26

24. References
References II
Stefano Mariani and Andrea Omicini.
Coordinating activities and change: An event-driven architecture for situated MAS.
Engineering Applications of Artificial Intelligence, 41:298–309, May 2015.
Sheila Mcilraith and Tran Cao Son.
Adapting GOLOG for composition of Semantic Web Services.
In Dieter Fensel, Fausto Giunchiglia, Deborah L. McGuinness, and Mary-Anne Williams,
editors, 8th International Conference on Principles and Knowledge Representation and
Reasoning (KR-02), pages 482–493. Morgan Kaufmann, 22–25 April 2002.
Andrea Omicini and Franco Zambonelli.
MAS as complex systems: A view on the role of declarative approaches.
In Jo˜ao Alexandre Leite, Andrea Omicini, Leon Sterling, and Paolo Torroni, editors,
Declarative Agent Languages and Technologies, volume 2990 of Lecture Notes in
Computer Science, pages 1–17. Springer, May 2004.
1st International Workshop (DALT 2003), Melbourne, Australia, 15 July 2003. Revised
Selected and Invited Papers.
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 24 / 26

25. Extras
URLs
Slides
on APICe
→ http://apice.unibo.it/xwiki/bin/view/Talks/LpaasWoa2016
on SlideShare
→ http://www.slideshare.net/andreaomicini/
towards-logic-programming-as-a-service
Paper
on APICe
→ http://apice.unibo.it/xwiki/bin/view/Publications/LpaasWoa2016
on CEUR
→ http://ceur-ws.org/Vol-????/paper ?.pdf
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 25 / 26

26. Towards Logic Programming as a Service
Experiments in tuProlog
Roberta Calegari Enrico Denti Stefano Mariani Andrea Omicini
{roberta.calegari, enrico.denti, s.mariani, andrea.omicini}@unibo.it
Dipartimento di Informatica – Scienza e Ingegneria (DISI)
Alma Mater Studiorum – Universit`a di Bologna
XVII Workshop “From Objects to Agents” (WOA 2016)
Catania, Italy, 29 July 2016
Calegari, Denti, Mariani, Omicini (UniBo) Towards Logic Programming as a Service WOA 2016, 29/07/2016 26 / 26