See also precedence relationship. A dependency between two project schedule activities, or between a project schedule activity and a schedule milestone. The four possible types of logical relationships are: • Finish-to-Start. Start of activity depends on finish of preceding activity, either immediately or after a lapse of time • Finish-to-Finish. Finish of activity depends on finish of preceding activity, either immediately or after a lapse of time • Start-to-Start. Start of activity depends on start of preceding activity, either immediately or after a lapse of time • Start-to-Finish. Finish of activity depends on start of preceding activity, either immediately or after a lapse of time