8.3. What Is a Performance Model?

A model is a representation of a system. It could be a physical, logical, or functional one. While a model represents a system, it should be as simple as possible and it should be capable of capturing the most relevant characteristics of the system under study. Often, a model of a system helps one understand some fundamental characteristics of the system. Let us take Zipf's Law [16] as an example. It was originally applied to the relationship between a word's popularity in terms of rank and its frequency of use. Zipf observed that the distribution of word frequencies in English, if the words are ordered according to their ranks, is an inverse power law with the exponent close to one. Thus, Zipf's Law states that ...

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