break / stop execution in UML sequence diagram mid-way inside alt / opt
<p>In a UML Sequence Diagram - If a flow should stop if a condition is met midway, how would it be best represented with alternate / optional fragments? </p>

<p>i.e. - 
If the stop condition is not met then the flow is continued for several more steps. 
Should the alternate fragment cover all of the steps since the stop condition, making all steps past it part of the alternate fragment, or is there a notation to handle the stop inside a small alternate fragment (confined only to the condition)? </p>