The ExecutionSpecification is a graphical notation used in a UML Sequence diagram to represent the execution of action within a lifeline of an object. It is visualized as a thin long rectangle placed on a Lifeline. It is also referred to as a ‘Focus of Control’.
There are two types of ExecutionSpecifications:
▪Behavior ExecutionSpecification – represents the execution of a behavior.
▪Action ExecutionSpecification – represents the execution of an action.
How to draw an ExecutionSpecification
1 You may draw an ExecutionSpecification on a Sequence diagram by selecting the symbol from the Draw toolbar, and placing it on a lifeline – an ExecutionSpecification will only afix itself to a Lifeline – it cannot be drawn into space.
2 When placed on a Lifeline, you can drag on the handlebars of the ExecutionSpecification to adjust its length, to model the active length of the Lifeline representing an object.
3 The top of the ExecutionSpecification rectangle typically coincides with the receipt of a message. The bottom of the rectangle coincides with the completion of an action and can be marked with a return message.
4 You may draw an ExecutionSpecification on top of an existing ExecutionSpecification – nesting them – to denote an object sending a message to itself, or receiving a call back from another object.
5 Optionally, you can hide the name of the ExecutionSpecification by right-mouse clicking on the symbol, and then choosing Display Mode (or View > Display Mode) – then in the Display Mode dialog select either the Symbol Type On Diagram tab or the Selected Symbol tab, toggle on Enabled, and Hide Symbol Name.
