Diapositiva 1

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Validating Reconfigurations of Reo Circuits
2nd General Meeting CINA Bologna
Maurice H. ter Beek, Fabio Gadducci and Francesco
Santini
ISTI-CNR, Pisa Università di Pisa IIT-CNR,
Pisa
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Intro and Motivations

• Dynamic reconfigurations of Reo circuits
• Reo circuits formally model the coordination
  among components
• Graph transformation techniques formally model
  reconfigurations
• Reconfiguration is triggered by events
• In our scenario, when system buffers become
  congested
• Applied to a critical scenario in Finance (Credit
  Suisse)
• The e-banking infrastructure can start loosing
  orders (i.e. money)
• Different infrastructures can be considered to
  save money
• A first simulation was presented at ESM12 (Risk
  Analysis)
• This research was presented at ISARCS13
  (Architecting Critical Systems)

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Simulation

• Beside a formal definition of coordination (Reo)
  and graph rewriting (DPO), we performed a
  simulation, to check how reconfiguring works in
  practice
• Modelica (for complex physical systems) and
  Dymola tool

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Outline

• Introduction
• Reo
• Graph Transformation
• Modelica Simulation Language
• Simulation
• Conclusion
• Future Work

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In a Nutshell
Reo
Modelica
Graph Rewriting
Simulation
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Reo Arbab04

• A graphical language it implements the
  composition of channels into circuits
• A circuit describes exogenous coordination
• Components (software) are not aware of how
  interaction works
• Circuits made of nodes and (open-ended set of)
  channels
• Nodes are where different channels are
  synchronized
• Components write/take data to/from circuits
  boundary nodes
• Every circuit defines an interface through its
  boundary nodes
• Semantics (also) based on constraint automata
  Baier et al.06

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Reo channels
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Example with Writer/Reader
Writer
Reader
A
B

s
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Examples
1) a XOR
2)
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Algebraic Graph Transformation

• Rewrite (parts of) circuits by manipulating
  graphical structures
• Already proposed for Reo in Krause11 and
  Krause et al.13
• Set of rewrite rules that state the objects to be
  modified
• L ? R (pattern graph ? replacement graph), K
  invariant/gluing graph
• Search occurrence of pattern graph L in G, then
  replace it to obtain H
• DPO approach a rule is a pair of morphisms l L
  ? K, r K ? R in the graphs category denoting how
  graph L is rewritten into graph R while
  intermediate graphs store connection between
  items of LHS and RHS

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Case1
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Case 2
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Rewriting Rule 1
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Rewriting Rule 2
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Rewriting Rule 3
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Modelica

• Modelica is an object-oriented, declarative,
  modeling language for component-oriented modeling
  of complex systems, e.g. systems containing
  mechanical, electrical, electronic, hydraulic,
  thermal, control, electric power or
  process-oriented subcomponents

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Modelica (2)

• An object oriented, modeling language
• Modelica classes are not compiled in the usual
  sense, but they are translated into objects which
  are then exercised by a simulation engine
• The primary content of classes are equations x
  y 3 z
• They express equalities (not assignments)
• The simulation engine discovers the order of
  execution and which components in the equation
  are inputs and which are outputs
• Algorithmic parts can be present as well
• Open (OpenModelica) and commercial front-ends
• Dymola Dynasim AB (now part of Dassault Systèmes)

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Case 1 (Modelica)
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Case 2 (Modelica)
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Aggregating Values
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Rewriting (Modelica)
fifoCongestion gt a
1) open 2) case1or2
1) fifoCongestion
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Simulation
fifoCapacity 100
When (fifoCongestion 10) then (switch from
case1 to case2)
10K orders, 1h
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Conclusion and Future Work

• Formal design of coordination among components
• Easy to verify (e.g. model check) behaviour of
  coordination
• Formal design of event-triggered rewriting of
  coordination
• Simulation through an equation-based simulation
  language
• Application to a critical e-banking system
• To stress the infrastructure and have feedback on
  e.g. risk analysis
• Test other coordination schemes
• A link to Control Theory and Hybrid Simulation

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Thank you for your time!
Contact/questions maurice.terbeek_at_isti.cnr.it