The smallest amount of work defined in a critical path method schedule. Typically an activity is defined as a single type of work completed by a single crew in one specific area of work. Non-work activities are included in a schedule when they significantly constrain production activities.
actual cost of work performed
(also ACWP) The total cost incurred within a given time period. A cumulative ACWP reflects the total costs incurred since the start of the project.
actual finish date
The date that an activity finished. See also the section on cost vs. time completion and out-of-sequence progress.
actual start date
The date that an activity actually began.
Arrow Diagramming, or "activity-on-the-arrow" scheduling, is a method of CPM scheduling that shows an activity as an arrow. Sequence between activities is identified by the activities that merge at the head or tail of the arrow. Combining activity duration and sequence on the same arrow results in the need for two types of "dummy" logic relationships. These dummy relationships are the numbering dummy and the logic dummy.
The backward pass is the second part of the CPM calculation procedure. The backward pass answers the question, "How late can I start any activity without delaying the project?"
A schedule that has been agreed upon by all parties to be the basis upon which to calculate time and earnings progress. The originally approved schedule is the first baseline schedule. New baselines will typically be establised following agreements of cost and time as issued in construction contract modifications.
budgeted cost of work performed
(also BCWS) The estimated costs for work that has been actually accopmlished. This value may be compared directly to the actual cost of work performed to determine if the project is meeting contractor direct cost goals. Some text link 'cost' and 'earned value', this is not correct since earned value calculations include overheads and profits not included in direct construction costs.
budgeted cost of work scheduled
(also BCWS) The expected cost that should be incurred at a given time in the future, if the project proceeds as scheduled. Some text link 'cost' and 'earned value', this is not correct since earned value calculations include overheads and profits not included in direct construction costs.
Adding the budgeted cost, actual cost, and earned value to the schedule can signficantly improve a project managers ability to detect cost overruns as the project progresses. Cost-Time Tradeoff analysis and cash flow analysis may also be accomplished if a schedule is loaded with the direct costs of each activity. Also see value loading
(also CV) The difference between the budgted cost of work performed and the actual cost of work performed. This can be used to calculate the accuracy of the original estimates and/or the efficience of the construction work. Some texts describe cost variance as related to 'earned values' to be precise about such language this is not correct since direct project costs, from a contractors point of view, does not include overheads and profit that is included in 'earned value' calculations.
The critical path is that set of activities from the start of the project through to the end, that have the minimum total float. This total float is a shared property of all activities on the critical path.
critical path method (CPM)
The Critical Path Method is a project model that reflects work to be accomplished and shows the sequence of work. CPM Calculations assist the project manager to identify how soon the project can be completed, and identify those critical set of activities that, if delayed, also delay the entire project. In CPM, “work” is defined as “activities.” “Sequence” is defined differently in each of the two types of CPM scheduling, Arrow Diagramming and Precedence Diagramming
The amount that the contactor must pay for labor, materials, and equipment to complete a specific production activity. Direct costs must not include the cost of project trailers, home office staff, transportation, permits and other indirect costs.
The amount that the contactor must charge the owner to recoup direct costs, indirect costs, and profit. In the CPMtutor I have tried to be very clear about the difference between the "costs" incurrec by construction contractors and the "costs" (i.e. "earned value") incurred by the project owner. Great care must be taken when discussing "costs" with owners since they will typically be talking about "earnings" and not the contractor's actual cost.
The Finish Date is that date that governs the completion of a given activity. There are at least two Finish Dates for every activity in a CPM network. The first Finish Date is the "Early Finish". Early Finish is the earliest date on which the activity can finish. The second Finish Date is the "Late Finish." Late Finish is the latest date on which the activity can finish without delaying the overall project.
Finish-to-Finish is one of the ways to model of the underlying physical constraints of work to be accomplished in CPM. Identifying the sequence between two activities as a Finish-to-Finish sequence indicates that the prior activity must end prior to the end of the following activity. Finish-to-Finish is typically found in Precedence Diagrams only since the modeling Finish-to-Finish using the Arrow Diagram requires the addition of partially complete activities and, often, logical dummies. In general, two activities with a Finish-to-Finish sequence will also have a complementary Start-to-Start sequence.
Finish-to-Start is one of the ways to model of the underlying physical constraints of work to be accomplished in CPM. Identifying the sequence between two activities as a Finish-to-Start sequence indicates that the prior activity must be completed prior to the start of the following activity. Finish-to-Start is the most commonly used sequence in CPM. Finish-to-Start sequence is easily modeled in both Arrow and Precedence Diagramming.
Float or Slack typically refers to the CPM value of "Total Float." Total float is the time difference between the earliest possible start of an activity, derived from the forward pass, and the latest possible start of an activity, derived from the backward pass. Float may have one of three types of values. A positive float indicates that the activity may be delayed without delaying the project. A zero float indicates that the activity cannot be delayed without delaying the project. A negative float value indicates that the project is behind schedule and the negative time value indicates the amount of that delay. Float is a property of a series of tasks within a network path. As a result changes to the start time or duration of any of the activities in that path will result in a corresponding change in total float to all activities in the path.
The forward pass is the first part of the CPM calculation procedure. The forward pass answers the question "how early can I complete this project?"
The costs incurred by the contractor to be able to perform the actual construction work. Indirect costs include, but are not limited to, the cost of project trailers, computers, telephones, home office staff, transportation, permits, etc... Allocation of indirect costs to determine an appropriate value to charge the owner for the task ('earned value') by adding a percentage increase to each product tasks.
When two activities have a Finish-to-Finish sequence, there may be time delay between the time when the first activity ends and the second activity ends. This time delay on the Finish-to-Finish sequence is called "Lag" time.
When two activities have a Start-to-Start sequence, there may be time delay between the time when the first activity starts and the second activity begins. This time delay on the Start-to-Start sequence is called "lead" time
See unlimited resource leveling
limited resource allocation
When there are insufficent resources to complete your project, then you should conduct the limited resource allocation analysis. This procedure can be used to determine when the project might be finished under different resource constraints.
A milestone is a date that is included in a schedule to override standard CPM scheduling calculations. There are several different types of milestone dates. Due to the differences in calculations related to these dates, and the associated difficultly of the project team to clearly discuss the results of such calculations, only two dates that should be typically used. The first of these dates impacts the earliest that an activity can start. An example of such a milestone would be the project start date. The second of these dates impacts the latest that an activity can finish. An example of such a milestone is the project end date.
Precedence Diagramming, or "activity-on-the-node" scheduling, is a method of CPM scheduling that shows an activity as a box. The sequence among activities is shown as arrows. Separating sequence from the definition of the activity eliminates the need for "dummy" logic as and unique as is required in the Arrow Diagramming Method.
A project is any undertaking with a defined start and end. Projects have defined objectives that when completed, demonstrate the completion of the project. Most projects are required to be completed with limited time, labor, equipment, funds, and other resources.
Project management is art and science of using limited time, labor, equipment, funding, and other resources to complete a project to the satisfaction of all project stakeholders. Stakeholder satisfaction may be defined by a variety of tangible and intangible goals. Of tangible concern of project managers is completing a project within budget and on-schedule. Somewhat less tangible concerns of project managers include management of project scope changes and issues of quality control.
(or SV). The difference beween the actual cost of work performed and the budgeted cost of work scheduled. This shows if the project is ahead of schedule, or behind schedule, with respect to cost. Some text link 'cost' and 'earned value', this is not correct since earned value calculations include overheads and profits not included in direct construction costs.
In CPM the order, or precedence, of activities is typically identified in a table that lists each activity and the activities that precede that activity.
The Start Date is that date that governs the starting of a given activity. There are at least two Start Dates for every activity in a CPM network. The first Start Date is the "Early Start". Early Start is the earliest date on which the activity can start given it’s prior activities. The second Start Date is the "Late Start." Late Start is the latest date on which the activity can start without delaying the overall project.
Start-to-Start is one of the ways to model of the underlying physical constraints of work to be accomplished in CPM. Identifying the sequence between two activities as a Start-to-Start sequence indicates that the prior activity must begin prior to the start of the following activity. Start-to-Start is typically found in Precedence Diagrams only since the modeling Start-to-Start using the Arrow Diagram requires the addition of partially complete activities and, often, logical dummies. In general, two activities with a Start-to-Start sequence will also have a complementary Finish-to-Finish sequence.
Time-Cost Tradeoff is the procedure used to evaluate the impact of direct versus indirect costs. In many projects increasing the cost of some activities on the critical path, by increasing resources or working additional shifts, could result in an overall decrease of project cost. This technique should always be used when there are completion incentives. The technique should also be used when there are liquidated damages on the project.
unlimited resource leveling
When you have enough resources (typically labor) to complete the project but the levels of required resources vary over time, you should consider performing the unlimited resource leveling analysis. This analysis technique will reduce the churn of workers on your site, and will promote higher quality work and improved productivity.
Owner requirements for "cost-loaded" schedules are actually requirements to assign the proportional "bugeted earned value." As the work is completed, the owner and contractor agree on the fiscal percent for each activity and thus determine the payment owed to the contractor. Also see cost loading
work breadkown structure
(or WBS) Work breakdown structure defines the way in which you will need to decompose actual work into the models of the work activities in the CPM schedule. Typically you should have multiple types of classifications to develop a work breakdown schedule. For example crew type and work area are two of the most critical categories you can use to create a WBS. CPMtutor also recommends use of activity type (non-work vs production acivity) and bid item codes as the for components of any useful WBS.