Tham khảo tài liệu 'project planning control 4 episode 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Basic network principles 5 No chain of activities must be permitted to form a loop . such a sequence that the last activity in the chain has an influence on the first. Clearly such a loop makes nonsense of any logic since if one considers activities 2-3 B 3-4 C 4-5 E and 5-2 F in Figure one finds that B C and E must precede F yet F must be completed before B can start. Such a situation cannot occur in nature and defies analysis. Figure Apart from strictly following the basic rules 1 to 5 set out above the following points are worth remembering to obtain the maximum benefit from network techniques. 1 Maximize the number of activities which can be carried out in parallel. This obviously resources permitting cuts down the overall programme time. 2 Beware of imposing unnecessary restraints on any activity. If a restraint is convenient rather than imperative it should best be omitted. The use of resource restraints is a trap to be particularly avoided since additional resources can often be mustered - even if at additional cost. 3 Start activities as early as possible and connect them to the rest of the network as late as possible Figures and . This avoids unnecessary restraints and gives maximum float. Figure Figure 69 Project Planning and Control 4 Resist the temptation to use a conveniently close node point as a staging post for a dummy activity used as a restraint. Such a break in a restraint could impose an additional unnecessary restraint on the succeeding activity. In Figure the intent is to restrain activity E by B and D and activity G by D. However because the dummy from B uses node 6 as a staging post activity G is also restrained by B. The correct network is shown in Figure . It must be remembered that the restraint on G may have to be added at a later stage so that the effect of B in Figure may well be overlooked. Figure Figure 5 When drawing ladder networks see page 75 beware of the danger of .
