Field-based coordination is a model for expressing the coordination logic of large-scale adaptive systems, composing functional blocks from a global perspective. As for any coordination model, a proper toolchain must be developed to support its adoption across all development phases. Under this point of view, the ScaFi toolkit provides a coordination language (field calculus) as a DSL internal in the Scala language, a library of reusable building blocks, and an infrastructure for simulation of distributed deployments. In this work, we enrich such a toolchain by introducing ScaFi-Web, a web-based application allowing in-browser editing, execution, and visualisation of ScaFi programs. ScaFi-Web facilitates access to the ScaFi coordination technology by flattening the learning curve and simplifying configuration and requirements, thus promoting agile prototyping of field-based coordination specifications. In turn, this opens the door to easier demonstrations and experimentation, and also constitutes a stepping stone towards monitoring and control of simulated/deployed systems. Repository: https://github.com/scafi/scafi-web

1. ScaFi-Web
A Web-Based Application for Field-based Coordination Programming
Gianluca Aguzzi, Roberto Casadei, Niccolò Maltoni, Danilo Pianini,
Mirko Viroli
ALMA MATER STUDIORUM–Università di Bologna, Cesena, Italy
September 1, 2021
Talk @
COORDINATION 2021
23rd International Conference on Coordination Models and Languages

2. Introduction
Field Based Coordination [Vir+19]
A coordination model that leverages computational fields to
orchestrate large scale systems.
Aggregate Programming [BPV15]
A top-down and global-to-local approach to the specification of the
collective adaptive behaviour of a distributed system.
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3. Aggregate Programming
Benefits:
I Abstract over technologies and network topologies
I Describe behaviour in a functional and compositional manner
I Proved to have, in certain circumstances, relevent properties such as eventual
consistency [Bea+16] and self-stabilisation [BV14]
I Used in different scenario such as crowd management [BPV15], UAVs [Cas+19a] and Smart
cities [Cas+19b]
Problem: Hard to use
I High learning curve
I Plethora of tools involved
I Need of simulations
I Lack of tools for real-system monitoring
G.Aguzzi Introduction Contribution Conclusion Future Work References 2/12

4. Starting point and inspiration
Tool-chain
ScaFi [CV16]: a modular Scala-based toolchain for aggregate programming
comprising an inner-DSL, a simulator and actor-based platfrom
Protelis [PVB15]: a Java-interoperable stand-alone DSL
FCPP [Aud20]: a lightweight native implementation
Playgrounds
WebProto [UB13]: a pioneer no longer maintained playground for Proto
ScalaFiddle Scastie: well-known Scala playgrounds
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5. Goals
Reducing the learning time of SCAFI
Inject different aggregate programming languages
Zero-install distribution
Support also remote program execution
Reuse as much as possible the SCAFI codeline
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6. Architecture
A language-agnostic web interface to visualize aggregate systems
Support abstraction language and system dependent
Local SCAFI simulator
Remote Scala code compilation
javascript interpreter
scala.js
aggregate program
html rendering
scafi core scafi simulator scafi web
in-browser executor
transcompilation service /compile
/getCode
scala.js compiler + linker
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7. Current Usage Scenario
Learning and education
Exposing an environment with minimal requirements
Sequence of guided example
Simplified access to the simulated sensors and actuators
Fast Prototyping
Aggregate programming require an iterative, incremental process of program
refinement
Our approach supports this workflow proving a simulated enviroment with zero
instalation overhead
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8. Demo
https://scafi.github.io/web/
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9. Conclusion
SCAFI-WEB enables:
I Fast prototyping
I Exploratory testing
I Easy application deployment
I Pedagogical support for learning
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10. Future work
Support of remote aggregate programming execution
Support other aggregate programming languages
Extend SCAFI-WEB for monitoring and control of deployed systems
Middleware
UI
Distributed
support
node data
command
scripts Hybrid System
Simulator
node data
command
scripts
Local
support
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11. Bibliography (1/3)
[Aud20] Giorgio Audrito. “FCPP: an efficient and extensible Field Calculus framework”. In: IEEE
International Conference on Autonomic Computing and Self-Organizing Systems,
ACSOS 2020, Washington, DC, USA, August 17-21, 2020. IEEE, 2020, pp. 153–159.
DOI: 10.1109/ACSOS49614.2020.00037.
[Bea+16] Jacob Beal et al. “Self-Adaptation to Device Distribution Changes”. In: 10th IEEE
International Conference on Self-Adaptive and Self-Organizing Systems, SASO 2016,
Augsburg, Germany, September 12-16, 2016. Ed. by Giacomo Cabri, Gauthier Picard,
and Niranjan Suri. IEEE Computer Society, 2016, pp. 60–69. DOI:
10.1109/SASO.2016.12.
[BPV15] Jacob Beal, Danilo Pianini, and Mirko Viroli. “Aggregate Programming for the Internet
of Things”. In: IEEE Computer 48.9 (2015), pp. 22–30. DOI: 10.1109/MC.2015.261.
[BV14] Jacob Beal and Mirko Viroli. “Building Blocks for Aggregate Programming of
Self-Organising Applications”. In: IEEE SASO Workshops. 2014, pp. 8–13. DOI:
10.1109/SASOW.2014.6.
G.Aguzzi Introduction Contribution Conclusion Future Work References 10/12

12. Bibliography (2/3)
[Cas+19a] Roberto Casadei et al. “Aggregate Processes in Field Calculus”. In: Coordination
Models and Languages - 21st IFIP WG 6.1 International Conference,
COORDINATION 2019, Held as Part of the 14th International Federated Conference
on Distributed Computing Techniques, DisCoTec 2019, Kongens Lyngby, Denmark,
June 17-21, 2019, Proceedings. Ed. by Hanne Riis Nielson and Emilio Tuosto.
Vol. 11533. Lecture Notes in Computer Science. Springer, 2019, pp. 200–217. DOI:
10.1007/978-3-030-22397-7_12.
[Cas+19b] Roberto Casadei et al. “Engineering Resilient Collaborative Edge-Enabled IoT”. In:
2019 IEEE International Conference on Services Computing, SCC 2019, Milan, Italy,
July 8-13, 2019. Ed. by Elisa Bertino et al. IEEE, 2019, pp. 36–45. DOI:
10.1109/SCC.2019.00019.
[CV16] Roberto Casadei and Mirko Viroli. “Towards Aggregate Programming in Scala”. In:
First Workshop on Programming Models and Languages for Distributed Computing,
PMLDC@ECOOP 2016, Rome, Italy, July 17, 2016. ACM, 2016, p. 5. DOI:
10.1145/2957319.2957372.
[PVB15] Danilo Pianini, Mirko Viroli, and Jacob Beal. “Protelis: practical aggregate
programming”. In: ACM Symposium on Applied Computing. 2015, pp. 1846–1853. DOI:
10.1145/2695664.2695913.
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13. Bibliography (3/3)
[UB13] Kyle Usbeck and Jacob Beal. “Web Proto: Aggregate Programming for Everyone”. In:
7th IEEE SASOW, 2013. IEEE Computer Society, 2013, pp. 17–18. DOI:
10.1109/SASOW.2013.12.
[Vir+19] Mirko Viroli et al. “From distributed coordination to field calculus and aggregate
computing”. In: J. Log. Algebraic Methods Program. 109 (2019). DOI:
10.1016/j.jlamp.2019.100486.
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