Abstract: The World Wide Web has evolved drastically over the past decade – and the proliferation of Web APIs has turned it into the middleware of choice for most distributed systems. The recent focus on hypermedia-driven APIs together with initiatives such as the Web of Things and Linked Data are now promoting and advancing the development of a new generation of dynamic, open, and long-lived systems on the Web. These systems require agent-based solutions to the point thatWeb researchers have started to build autonomous systems on their own. It is thus both timely and necessary to investigate and align the latest developments in Web research and multi-agent systems (MAS) research. In this paper, we analyze in hindsight the factors that hindered the widespread acceptance of early Web-based MAS. We argue that the answer lies equally in a lack of practical use cases as well as the premature development and alignment of Web and agent technologies. We then present our vision for a new generation of autonomous systems on the Web, which we call hypermedia MAS, together with the research opportunities and challenges they bring. Andrei Ciortea, Simon Mayer, Fabien Gandon, Olivier Boissier, Alessandro Ricci, Antoine Zimmermann, "A Decade in Hindsight: The Missing Bridge Between Multi-Agent Systems and the World Wide Web", AAMAS 2019 Read full paper online: http://www.ifaamas.org/Proceedings/aamas2019/pdfs/p1659.pdf

1. A Decade in Hindsight: The Missing Bridge Between
Multi-Agent Systems and the World Wide Web
1 University of St. Gallen, Switzerland
2 Wimmics, Inria Sophia Antipolis, Univ. Côte D’Azur, CNRS, France
3 ETH Zurich, Switzerland
4 MINES Saint-Étienne, Univ. de Lyon, Laboratoire Hubert Curien, CNRS, France
5 University of Bologna, Italy
Andrei Ciortea1,2 Simon Mayer1,3 Fabien Gandon2
Olivier Boissier4 Alessandro Ricci5 Antoine Zimmermann4
AAMAS 2019, Blue Sky Track, May 17, Montreal

2. “(...) in fact documents on the web describe real objects and
imaginary concepts, and give particular relationships
between them. (...) This means that machines, as well as
operating on the web information, can do real things.”
Sir Tim Berners-Lee, WWW 1994
https://www.w3.org/Talks/WWW94Tim/

3. Tim Berners-Lee, James Hendler, Ora Lassila. Scientific American, 2001

4. “The rest of the ideas in that article are now seeing widespread
deployment, but I ask again: where are all the agents?”
James Hendler, IEEE Intelligent Systems, 2007
“Once dynamic and open systems become the norm,
they’ll need to adopt agent technologies as fundamental.”
Peter McBurney and Michael Luck,
IEEE Intelligent Systems, 2007
Tim Berners-Lee, James Hendler, Ora Lassila. Scientific American, 2001

5. Outline
• A Decade in Hindsight: MAS and the Web
– Availability of Practical Use Cases
– Juxtaposition of MAS and the Web
– MAS – More Than Just Agents
• Our Vision: Hypermedia MAS
• Opportunities and Challenges

6. Availability of Practical Use Cases
Recent developments in Web research unlock new practical use cases for MAS
– as dynamic, open, and long-lived systems gain adoption on the Web
[Singh and Huhns, 2005]
https://www.programmableweb.com/news/research-shows-interest-providing-apis-still-high/research/2018/02/23
[Amundsen, 2017]
The manual integration of static Web APIs becomes a pressing bottleneck:
• designing evolvable Web APIs with hypermedia (“Affordance is the key!”)
• designing general-purpose clients

7. Availability of Practical Use Cases
The Web of Things (WoT)
• core idea: to integrate devices into the Web architecture as first-class citizens
– Target: Class 1 devices [RFC 7228] (~100 KiB Flash and ~10 KiB ROM, less than $1)
• currently being standardized through combined efforts of the W3C, IETF, and IRTF
The dynamics of Web systems increase to a point where existing programming
paradigms become impractical and agent-based systems become a necessity.

8. Availability of Practical Use Cases
The Web of Things (WoT)
• core idea: to integrate devices into the Web architecture as first-class citizens
– Target: Class 1 devices [RFC 7228] (~100 KiB Flash and ~10 KiB ROM, less than $1)
• currently being standardized through combined efforts of the W3C, IETF, and IRTF
A personal view on the evolution of WoT systems:
2018 2010
[Guinard et al., 2010]
http://ifttt.com
2013
http://nodered.org
[Mayer et al., IoT 2014]
Goal-directed WoT systems
(planning + hypermedia
affordances)
2014
[Kovatsch et al., IoT 2015]
Goal-directed WoT systems
(planning + hypermedia
affordances)
2015
[Ciortea et al., IoT 2016]
JaCaMo + hypermedia
affordances
2016
[Ciortea et al., AAMAS 2018]
JaCaMo + planning + hypermedia
affordances + manufacturing
(Siemens WoT Research Group, Berkeley)

9. Availability of Practical Use Cases
Linked Data
• Linked Open Data Cloud (as of March 2019):
– 1.239 datasets and 16.147 links
• Clients can browse Linked Data, but also observe and act
on it:
– W3C Linked Data Platform, W3C Linked Data
Notifications, etc.
https://lod-cloud.net
The growing source of linked structured data on the Web now provides a
breeding ground for MAS research that was not available a decade ago.

10. Juxtaposition of MAS and the Web
Large body of literature on MAS and Web services [Singh and Huhns, 2005]
… but Web services have evolved drastically over the past decade
Roy T. Fielding, Architectural Styles and the Design of Network-based Software Architectures. Doctoral dissertation, UC Irvine, 2000
It is now well recognized that systems using the Web merely as a transport layer are misaligned with
the Web architecture and remain outside of the Web [Pautasso et al., WWW 2008]
– WS-* standards (SOAP, WSDL, etc.) use the Web for transport
– FIPA Agent Message Transport Protocol for HTTP

11. Juxtaposition of MAS and the Web
Large body of literature on MAS and Web services [Singh and Huhns, 2005]
… but Web services have evolved drastically over the past decade
It is now well recognized that systems using the Web merely as a transport layer are misaligned with
the Web architecture and remain outside of the Web [Pautasso et al., WWW 2008]
– WS-* standards (SOAP, WSDL, etc.) use the Web for transport
– FIPA Agent Message Transport Protocol for HTTP
MAS using the Web merely as a hidden transport layer are
misaligned with the Web architecture and remain outside of the Web.

12. MAS – More Than Just Agents
Environment as a first-class abstraction [Weyns et al., 2007]
– Environment for Multiagent Systems (E4MAS)
Organization as a first-class abstraction
– Coordination, Organizations, Institutions, and Norms in Agent Systems (COIN)
What about the Web?

13. Our Vision: Hypermedia MAS
Affordances:
Turn On / Off
Change color
Org. Spec.
Init.
propose
reject
Part.
Interaction
Prot. Spec.
Policies
PUT [lightbulb_IRI]
[intended state]
200 Ok
Distributed hypermedia environment
Socio-technical systems composed of people and autonomous agents situated and
interacting in a shared hypermedia environment that is distributed across the open Web.

14. Our Vision: Hypermedia MAS
Affordances:
Turn On / Off
Change color
Org. Spec.
Init.
propose
reject
Part.
Interaction
Prot. Spec.
Policies
New state
Distributed hypermedia environment
Socio-technical systems composed of people and autonomous agents situated and
interacting in a shared hypermedia environment that is distributed across the open Web.

15. Our Vision: Hypermedia MAS
Affordances:
Turn On / Off
Change color
Org. Spec.
Init.
propose
reject
Part.
Interaction
Prot. Spec.
Policies
Distributed hypermedia environment
Socio-technical systems composed of people and autonomous agents situated and
interacting in a shared hypermedia environment that is distributed across the open Web.

16. Our Vision: Hypermedia MAS
Affordances:
Turn On / Off
Change color
Org. Spec.
Init.
propose
reject
Part.
Interaction
Prot. Spec.
Policies
Distributed hypermedia environment
Socio-technical systems composed of people and autonomous agents situated and
interacting in a shared hypermedia environment that is distributed across the open Web.
• Key point: agent environments are not layered on top of the Web (technological integration), but
they are integrated into the hypermedia fabric of the Web (conceptual integration)

17. Opportunities & Challenges: the MAS Perspective
What does it mean for an agent to be situated on the Web?
How can agents leverage affordances provided by resources discovered in their
environment at run-time in order to achieve their goals?
How can agents find resources required to achieve their goals in large-scale
hypermedia environments?
What architectures, paradigms, and languages are suitable for designing and
programming agents that operate on Linked Data?
etc. (open list!)

18. Opportunities & Challenges: the Web Perspective
Interaction as a first-class abstraction on the Web
Regulation as a first-class abstraction on the Web

19. Conclusions: A Call to Action
It is both timely and necessary to create thorough conceptual and technological
bridges between MAS and Web research.
All the elements required to design and deploy Hypermedia MAS
are already available.

20. May 13, San Francisco, CA
Andrei Ciortea, Simon Mayer, Fabien Gandon, Olivier Boissier
First Workshop on Hypermedia Multi-Agent Systems
in conjunction with
@hyperagents Weaving a Web for People and Artificial Agents http://hyperagents.org

21. Thank You!
andrei.ciortea@unisg.ch
@andreiciortea

22. References
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