Formalisms I

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SIMULATION MODELS FORMALIZATION
Pau Fonseca i Casas; pau@fib.upc.edu
The need of a conceptual model
Advantages of use a conceptual model
 
Textual specification is less precise. Conceptual model have in a detailed manner, the dynamical relations between the different elements of the interest process.

Constitutes an specification by itself.
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Simplifies the dialog between the different parts that are involved in the project. Constitutes a representation of the simulation model independent of the selected tool used to build the model.
Conceptual model formalization
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Formalism must be independent from the simulation tools. The formalized model must allow some analysis.
 To
determine relations between components.
Conceptual model formalization

Formalism ,must allow an easy transformation to the representations supported by the existing simulation frameworks.
Simplify the implementation process.  To evaluate alternatives.

Conceptual model formalization
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Some aspects of the model can be no specified, without causing problems in the transformation to other representations. MODULARITY The model must be defined in terms that no constrain its codification in a particular mechanism of simulation clock update.
Modularity

The capacity to describe the behavior of each subsystem, independent from the other subsystems that compose the model
 Incremental
design of the model.  Simplifies the verification and the validation of the model.  Each different stage  implementation stage.
Assure the Modularity
1.
2.
A module cannot access directly to the state of other modules or components. A module must own a set of ports (input/output) to allow the interaction with the other parts of the model.
Conceptual models
   
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Flow models. Queue networks. Petri nets Colored Petri nets. SDL language DEVS Causal and Forrester diagrams.
Flow models
Simulation models formalization
Flow models (data)
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Magnetic disc
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Document
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Multiple document
Flows models (Processes)
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State Process
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Decision point
Pediatrics example
 
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Models a pediatrics example. If a new emergency arrives a special process takes cure of it. If X ray is needed, or blood analysis, is done in a second visit Finally the patient release the system.
Flows models
Flows models (best)
 
Simple Allows to describe the system faster.
Flows models (worse)
   
No description about the implementation. No description about the events. Is not calculable. Not structured methodology, not specific of the OR.
Queue networks
Simulation models formalization
Queue networks
Queue networks (M|M|S)
Queue networks (best)
  
Simple Allows to understand the system faster. Specific to describe queue models.
Queue networks (worse)
 

No description about the implementation. Do not describe too much about the events management. Is not always calculable.
 Some
models can be calculated following the queue theory.