Page 24 - DCAP601_SIMULATION_AND_MODELING

Simulation and Modelling

Notes refinements.) In fact, some refinement of the goals is most certainly necessary. (What exactly are
the performance data that would enable a meaningful decision to be made?)
It is also important to observe that the model’s features as outlined above have an orientation
that is specific to the stated goal of the project. There is very little in the presentation that would
allow a model formulated from the given description to be useful in, for example, an
environmental assessment of the gas station’s operation or indeed in an analysis of its financial
viability.

1.4 Types of Models

System Modelling

1. System modelling helps the analyst to understand the functionality of the system and
models are used to communicate with customers
2. Different models present the system from different perspectives
(a) External perspective showing the system’s context or environment
(b) Behavioural perspective showing the behaviour of the system
(c) Structural perspective showing the system or data architecture
Structured Methods

1. Structured methods incorporate system modelling as an inherent part of the method
2. Methods define a set of models, a process for deriving these models and rules and guidelines
that should apply to the models
3. CASE tools support system modelling as part of a structured method
Method Weaknesses

1. They do not model non-functional system requirements
2. They do not usually include information about whether a method is appropriate for a
given problem

3. The may produce too much documentation
4. The system models are sometimes too detailed and difficult for users to understand
Model Types
1. Data processing model showing how the data is processed at different stages
2. Composition model showing how entities are composed of other entities
3. Architectural model showing principal sub-systems
4. Classification model showing how entities have common characteristics
5. Stimulus/response model showing the system’s reaction to events

Context Models

1. Context models are used to illustrate the boundaries of a system
2. Social and organisational concerns may affect the decision on where to position system
boundaries
3. Architectural models show the system and its relationship with other systems

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