for example activities dimensionally affect each other. this is to remind me of dimensional coordination required. or access / staging area of one thing affecting other task. these are not schedule calculation. it is extra info for the whole thing. or for example there may be risks to be taken into account or certain codes, which are not even tasks, and they are entered as additional info. many other variables like extra info such as environmental factors, clean up , safety, equipment... to show all picture all in one place, which has the advantage of being on a scheduling program so that everything can be shown time related and info can be searched when desired.