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Design Methods for Reactive Systems, R.J. WieringaPart V: Communication Notations
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Outline
Data flow diagrams (DFDs)Communication diagramsContext modellingRequirements-level architectures
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Where are we?
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Data flow diagrams (DFDs): heating controller example
A collection of communicating data stores and processes
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Data flow diagrams (DFDs): hierarchical structuring; tank control process
Data processspecification:
Lower-levelDFD
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Data flow diagrams (DFDs): basic concepts (1)
Flow: Instantaneous and reliable communication channel
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Data flow diagrams (DFDs): basic concepts (2)
Stores: Remembers the data written to it
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Data flow diagrams (DFDs): basic concepts (2)
Process: Some system activity Data process Control process Composite process
Stateless or stateful processesSyntax:
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Data flow diagrams (DFDs): control process specification; STD for heater control process
Note consistency with DFD
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Communication diagrams: basics
DFDs instance-level; communication diagrams possibly type-level
Used to represent requirements-level architectures ”Language”
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Communication diagrams: heating controller example
Nodes ~ componentsEdges ~ communication channels
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Communication diagrams: heating controller; instance-level
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Communication diagrams: components
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Communication diagrams: decomposition
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Communication diagrams: decomposition and closely coupled components
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Communication diagrams: decomposition and closely coupled components; elevator controller
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Communication diagrams: allocation of functions to components (allocation table)
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Communication diagrams: flowdown
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Context modelling: motivation
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Context modelling: alternative system boundaries for the elevator controller
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Contex modelling: context boundary
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Context modelling: context diagram for the training information system
We need not only worry about the system boundary,but also about the context boundary … see guidelines
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Context modelling: structuring the context
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Context modelling: structure in the context of a information-provision system
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Context modelling: structure in the context of a directive system
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Context modelling: structure in the context of manipulative system
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Requirements-level architectures: architectures in general
We now move from modelling what is given to designing the SuD
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Requirements-level architectures: input sources
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Requirements-level architectures: encapsulation versus layering
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Requirements-level architectures: architectural styles
Data flow style: Not applicable to reactive
systems
Von Neumann style Strict separation of data
storage and data processing Database and
applicationprograms
Object-oriented style Processing and storage
encapsulated in objects
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Requirements-level architectures: comparison with implementation-level architectures
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Requirements-level architectures: main decomposition approaches
Functional decomposition each system function is allocated to a different component
Subject-oriented decomposition each group of subject domain entities corresponds to a
system component
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Requirements-level architectures: functional decomposition, object-oriented style; the ticket system example
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Requirements-level architectures: subject-oriented decomposition, object-oriented style; the ticket system example
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Requirements-level architectures: mixed architecture
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Requirements-level architectures: communication-oriented decomposition
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Requirements-level architectures: evaluation criteria
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Summary
Data flow diagrams (DFDs)Communication diagramsContext modellingRequirements-level architectures