Learning UML

Alphabets, Words, and Sentences

Because requirements and implementation technologies are complex and constantly changing, a language must not only facilitate communication about a subject, but also enable us to better manage change and complexity when we communicate about the subject. A language is based on a paradigm, a way of viewing a subject, that defines the types of concepts that may be used in the language and the principles of why they are useful. A language’s syntax specifies the notation used for communication and is determined by the language’s alphabet. A language’s semantics specify the meaning that is communicated and is determined by the language’s words and sentences. The syntax of the UML involves diagrams, and its semantics are based on the object-oriented paradigm.

To communicate using a language, we must understand its alphabet, how its alphabet is used to form words, and how its words are used to form sentences. We must also understand the concepts and principles of its underlying paradigm.

Alphabet

An alphabet defines the simplest parts of a language: letters, characters, signs, and marks. For example, the English language has 26 letters. The UML’s alphabet consists of symbol fragments (rectangles, lines, and other graphical elements) and strings of characters. These don’t have meaning by themselves; the smallest units of meaning in a language are its “words.”

Words

A word is a grouping of elements from a language’s alphabet that defines a unit of meaning. For ...