network diagrams.doc

8/10/2019 network diagrams.doc

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NETWORK DIAGRAMS AND SCHEDULE ANALYSIS

Network diagrams are schematic displays of project schedule activities and theinterdependencies between these activities. When developed properly, this graphical view of a

projects activities conveys critical schedule characteristics required to effectively analyze and

adjust schedules thus resulting in accurate and feasible schedules. !his document addresseswhat should be considered in the development of a network diagram, how network diagrams are

created, and how they may be analyzed to identify necessary corrective actions and ensure

optimal schedule definition.

NETWORKDIAGRAMCREATION

Network diagrams can be created manually but are also available as project views in projectscheduling tools such as "icrosoft #roject. $%ee "icrosoft #roject, &iew' "ore &iews '

Network (iagram).

*nputs+

#roject %cope %tatement !he schedule definition required in network diagram

development must be based on the approved scope documented in the #roject %cope

%tatement. *f network diagram and schedule definition does not account for all requireddeliverables in scope, the resulting network diagram and schedule will not accurately reflect

the time necessary to complete the work.

Work reakdown %tructure $W%) !he #roject !eam must include W% project

work in the network diagram to ensure comprehensive reflection of project activities.

-istorical #roject *nformation !he accuracy of network diagramschedule

estimation is strengthened by actual schedule metrics from past projects. #roject teams

should consider past level of effort and duration for comparable project activities.

W% (ictionary !he W% (ictionary defines task durations, dependencies,predecessor and successor relationships, and resources all of which need to be defined prior

to network diagram creation to ensure that the network diagram accurately reflects the

schedule required to successfully complete the project.

/esource 0alendars !he #roject !eam should develop and utilize a resource

calendar that includes holidays and personnel availability. 0reation of this calendar prior to

network diagram creation will ensure that the schedule accounts for actual working time.

#rocedure+

0onsider all inputs and enter all activity definition, sequencing, and duration

information into a software tool such as "icrosoft #roject. *f using this tool, ensure all tasks

are linked. 0onfirm all tasks are linked with accurate dependencies and with resource names

identified for each task.

1utput+

"icrosoft #roject #lan with task dependencies, predecessors and successors defined,

and resources applied to tasks

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elow is a sample network diagram. !o illustrate the relationship between a 2antt chart and a

Network (iagram, we have provided the 2antt of activities and the Network (iagram view.

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Sample Gantt Chart

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Correlating Netor! Diagram "age #

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Correlating Netor! Diagram "age $

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SCHEDULENETWORKANALYSIS

%chedule network analysis, as defined by theProject Management Body of Knowledge

$PMBOK), is a technique used by project managers to analyze schedule information and generate

realistic and optimal project schedules. !his analysis should be performed upon completion of

the draft schedule and network diagram and after each schedule update. %chedule networkanalysis involves+

*dentifying the schedule impact of task dependencies

*dentifying critical path tasks and understanding the impact of the critical path on the

schedule. %oftware tools such as "icrosoft #roject automatically display critical path tasksonce project information such as tasks, dependencies, and durations are identified in the

tools.

3nalyzing the effects of schedule constraints and e4ternally imposed dates

5nderstanding which tasks can e4perience delays without delaying the overall

schedule

0onducting 6what if7 analysis of various activity durations $for e4ample, what if thetesting activities take twice as long as is currently planned8)

3ssessing resourceallocation and leveling to prevent resource over9allocation

3ssessing fast tracking or crashing options to ensure optimal schedule performance

Anal%ti&al Te&hni'(e)*

PMBOKdescribes the following techniques to perform schedule network analysis. :or more

detail regarding analytical techniques, which provide valuable information necessary for

effective schedule definition, seePMBOK, fourth edition, %ection ;.nowing when a project has float allows a #roject "anager to understand whattasks may slip and by how much before they have an impact on the project schedule.

Criti&al ChainMetho+ !he basis for the critical chain method is the same as the

basis for the critical path method but with one key difference? the critical chain method

accounts for resource limitations. y adding resource limits to the analysis, the result is that

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critical path is generally longer. !he resource9constrained critical path is known as the

critical chain. *f resources are allocated in the scheduling tool, the network diagram will

display the critical chain. 5sing the critical chain method involves adding duration buffers toproject schedules to protect the targeted finish date from slippage. (uration buffers are

added to the schedule as non9work schedule activities one at the end of the critical chain

and others at the end of each sequence of tasks that feeds into the critical chain. 3s a result,6buffer7 time is integrated throughout the project schedule to account for duration

uncertainty. @ater in the project, project teams monitor project progress by reviewing the

consumption rate of the buffers.

Re)o(r&e Le,eling /esource leveling is the process of changing schedule resource

allocation to resolve over9allocations or conflicts. /esource leveling is applied to a schedule

that has already been analyzed by the critical path method. !his technique is used to adjust aproject schedule if shared resources are only available at certain times, or in limited

quantities, or if a #roject "anager wants to maintain resource usage at a constant level.

/esource leveling is often used to correct resource over9allocations and will often change the

critical path. !he network diagram should be recreated after resource leveling to assess theupdated critical path.

What-I. S&enario Anal%)i) !his analysis e4amines the schedule impact of various

scenarios, such as the delayed delivery of a major deliverable. What9if scenario analysis may

include simulation that calculates multiple project durations with different sets of activity

assumptions. "ultiple network diagrams may be generated to visually convey the impact ofvarying scenarios. #roject managers can use the results of this analysis to determine

schedule feasibility under adverse conditions and prepare relevant contingency plans.

S&he+(le Compre))ion Te&hni'(e)*

3s a result of network diagram analysis, project teams may identify a need to compress theschedule. %chedule compression shortens the project schedule in order to meet schedule

deadlines without reducing the project scope. %chedule compression techniques include crashingand fast tracking. *f utilized, project teams should recreate and reassess the network diagram to

ensure that no new schedule issues have emerged.

Cra)hing 0rashing involves either adding resources or increasing work hours

$overtime, weekends) to shorten task duration. %horter task durations typically result in

higher task costs, so project teams must determine, prior to crashing, whether the total costssavings is enough to justify the higher costs. 0rashing almost always requires cost increases

because it usually necessitates new tasks. 0rashing is a controversial technique because

adding project resources can increase project comple4ity or risk and may ultimately have anegative impact on the schedule. 0rashing does not involve reducing project scope oreliminating project tasks.

/a)t Tra&!ing :ast tracking is a schedule compression technique in which project

phases or activities usually conducted sequentially are performed in parallel to reduceduration. 0are must be taken to ensure that parallel work does not create additional work or

increase risk. :ast tracking frequently results in increased comple4ities in task dependencies,

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so additional project controls must be implemented to ensure ongoing and accurate insight

into schedule performance.

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