| OCL statement in a class diagram | can specify what the values of attributes and associations must be |  |
| can state the preconditions and postconditions of operations | |
| is a subtopic of 5.6 - More Advanced Features of Class Diagrams | |
| is a kind of OCL statement | |
| OCL statement | can be used for automatic code generation | |
can consist of - References to role names, association names, attributes and the results of operations.
- The logical values true and false
- Logical operators such as and, or, =, >, < or <> (not equals)
- String values such as: 'a string'
- Integers and real numbers (the latter having a decimal point)
- Arithmetic operations *, /, +, -
| |
| can navigate from class to class using a dot to separate components. For example, in LinearShape, to refer to the length of the edges you can refer to edge.length. | |
| can refer to all the values in a collection using the forall operator | |
| can refer to special OCL properties of a collection itself using the -> operator | |
| can use the {ordered} constraint to indicate that an OCL collection is a sequence, which allows you refer to special properties such as first and last | |
| can use the implies operator which is true if either the left hand side is false or if both sizes are true | |
| does not have to be written on a UML diagram but can be written separately with a context specified | |
| has example {startPoint <> endPoint} constrains the two ends of a LineSegment to be different | |
| is not compiled | |
| is not executed | |
| statement | should be not more than one line long if possible | |
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