What Engineers Do
Before they build the real thing...
…they first build models …and then learn from them
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Engineering Models
Engineering model: A reduced representation of some system
Characteristics of Useful Models
Abstract
Emphasize important aspects while removing irrelevant ones
Understandable
Expressed in a form that is readily understood by observers
Accurate
Faithfully represents the modeled system
Predictive Purpose: To help us understand a complex problem or solution To communicate ideas about a problem or solution To drive implementation
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Modeled system Modeled system
Model Model
Can be used to derive correct conclusions about the modeled system
Inexpensive
Much cheaper to construct and study than the modeled system
To be useful, engineering models must satisfy all of these characteristics!
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How Models are Used
To detect errors and omissions in designs before committing full resources to full implementation
Through (formal) analysis and experimentation Investigate and compare alternative solutions Minimize engineering risk
A Problem with Models
.. .. ..
To communicate with stakeholders
Clients, users, implementers, testers, documenters, etc.
Semantic Gap due to: Semantic Gap due to: Idiosyncrasies of actual Idiosyncrasies of actual construction materials construction materials Construction methods Construction methods Scaling effects Scaling effects Skill sets Skill sets Misunderstandings Misunderstandings Can lead to serious errors Can lead to serious errors and discrepancies in the and discrepancies in the realization realization
To drive implementation
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Models of Software
A description of the software which

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