This book uses the following typeface conventions:
All OCL expressions and context definitions are printed in a monospaced font .
All OCL keywords are printed in a monospaced bold font .
At the first introduction or definition of a term, the term is shown in italics .
All references to classes, attributes, and other elements of a UML diagram are shown in italics .
All references to types start with a capital letter and are shown in italics . All references to instances of that type start with a lowercase letter. For instance, in the sentence "The value of a boolean expression is an instance of type Boolean ," the first occurrence of the word boolean refers to a value, the second refers to the type.