Читать книгу Cyber-physical Systems - Pedro H. J. Nardelli - Страница 22

Let me start by showing a dialogue I had with my 5‐year‐old daughter:

 What is a car?

 It is a system designed to take people from one place to another, in a faster way and with less effort than walking.

 What is a system?

 Well (…), in this case, it is a machine composed of things working together to perform some action.

 And, in the other cases?

My goal in this brief section is to provide satisfactory answers to these two questions in italics. The first step is to check which are the definitions of “system” that the dictionary gives.

Definition 2.1 System in [1] (1) A regularly interacting or interdependent group of items forming a unified whole; (2) an organized set of doctrines, ideas, or principles usually intended to explain the arrangement or working of a systematic whole; (3a) an organized or established procedure; (3b) a manner of classifying, symbolizing, or schematizing; (4) harmonious arrangement or pattern; (5) an organized society or social situation regarded as stultifying or oppressive.

It is clear the meaning I used to answer to my daughter is (1). At this point, two remarks are needed. First, not everything that is a regularly interacting or interdependent group of items forming a unified whole constitutes a system. For example, a clock, a car, or a computer are usually considered systems, while open markets or football teams are not (even though they might). This relatively arbitrary daily usage of the word shall be abandoned later in this chapter. The second remark is that the different meanings of the same word may create a series of confusion. While the meaning (1) mostly refers to the concrete reality, (2) and (3) seem to refer to symbolic domains, (4) and (5) are fuzzier and more subjective. Since this book is about engineering, (1) is the most appropriate meaning as our starting point.

With those warnings given, we are almost ready to transform the word “system” – our first raw material – into a concept that will become operational in the proposed theory of cyber‐physical systems. Before we begin, though, it is important to describe how we will proceed. The first move is to provide a descriptive technical definition of what a system is following the well‐established discipline Systems Engineering [2]. After this presentation, we can finally specify how it is possible to demarcate and articulate a particular functioning system with respect to its environment.