Monday, December 4, 2006

Project Management Glossary

A Guide to the Often Confusing World of Project Management Software Terminology (Last Update: 12/4/06, by Dave Wagner)


Note: I first published this glossary in 1993 to the project management community on the Internet, when I was Vice President of Marketing for a software company in charge of technical publications. I was the editor for this glossary but other (unknown) individuals contributed to the document, including Marilyn Cantey, who has since retired. The project management glossary can now be found on dozens of websites and the company that bought the original product documents on which this glossary was based has since moved on. In sum, it seemed wise to take control of the document again, correct errors that have crept into the document over the years, and make it available to a new generation of MBAs and project management professionals.

Terms Defined (Click below)

Activity
Activity Duration
Actual_Dates
Baseline_Schedule
Calendars
Control
Critical Activity
Calculate Schedule
Critical Path
Duration
Early Finish
Early Start
Elapsed Time
Finish Float
Finishing Activity
Finish-to-Finish Lag
Finish-to-Start Lag
Float
Forced Analysis
Free Float
Gantt (Bar) Chart
Hammocks
Histogram
Lag
Late Finish
Late Start
Micro-Scheduling
Milestones
Multi-Project Analysis
Negative Float
Network Analysis
Network Diagram
Parallel Activities
Path
Positive Float
Precedence Notation
Predecessor
PERT
Project
Rescheduling
Resource
Resource Based Duration
Resource Leveling
Scheduling
Sequence
Slippage
Start Float
Start-to-Start Lag
Starting Activity
Sub-Critical Activity
Subproject
Successor
Super-Critical Activity
Target Finish -- Activity
Target Finish -- Project
Target Start -- Activity
Total Float
Work Breakdown Structure (WBS)
Work Flow
Work Load
Work Units
Zero Float


Activity

An activity is an individual task needed for the completion of a project. It is the smallest discrete block of time and resources typically handled by PM software. It is a single task that needs to be done in a project. Multiple activities are related to each other by identifying their immediate predecessors. Solitary activities, which have no predecessors or successors, are allowed. Most PM software packages are precedence-based systems that analyze schedules based on the activity relationships that are specified. Activities can also be called work packages, tasks, or deliverables.

Activity Duration

Activity duration specifies the length of time (hours, days, weeks, months) that it takes to complete an activity. This information is optional in the data entry of an activity. Workflow (predecessor relationships) can be defined before durations are assigned. Activities with zero duration are considered milestones (milestone value of 1 to 94) or hammocks (milestone value of 95 to 99).

Actual Dates

Actual dates are entered as the project progresses. These are the dates that activities really started and finished as opposed to planned or projected dates.

Baseline Schedule

The baseline schedule is a fixed project schedule. It is the standard by which project performance is measured. The current schedule is copied into the baseline schedule that remains frozen until it is reset. Resetting the baseline is done when the scope of the project has been changed significantly. At that point, the original or current baseline becomes invalid and should not be compared with the current schedule.

Calendars

A project calendar lists time intervals in which activities or resources can or cannot be scheduled. A project usually has one default calendar for the normal workweek (Monday through Friday), but may have other calendars as well. Each calendar can be customized with its own holidays and extra workdays. Resources and activities can be attached to any of the calendars that are defined.

Control

Control is the process of comparing actual performance with planned performance, analyzing the differences, and taking the appropriate corrective action.

Critical Activity

A critical activity has zero or negative float. This activity has no allowance for work slippage. It must be finished on time or the whole project will fall behind schedule. (Non-critical activities have float or slack time and are not in the critical path. Super-critical activities have negative float.)

Calculate Schedule

The Critical Path Method (Calculate Schedule) is a modeling process that defines all the project's critical activities that must be completed on time. The Calc tool bar button on the Gantt and PERT (found in most GUI-based PM software) windows calculates the start and finish dates of activities in the project in two passes. The first pass calculates early start and finish dates from the earliest start date forward. The second pass calculates the late start and finish activities from the latest finish date backwards. The difference between the pairs of start and finish dates for each task is the float or slack time for the task (see FLOAT). Slack is the amount of time a task can be delayed without delaying the project completion date. A great advantage of this method is the fine-tuning that can be done to accelerate the project. Shorten various critical path activities, check the schedule to see how it is affected by the changes. By experimenting in this manner, the optimal project schedule can be determined.

Critical Path

There may be several paths within one project. The critical path is the path (sequence) of activities that represent the longest total time required to complete the project. A delay in any activity in the critical path causes a delay in the completion of the project. There may be more than one critical path depending on durations and workflow logic.

Duration

Duration is the length of time needed to complete an activity. The time length can be determined by user input or resource usage. Activities with no duration are called Milestones that act as markers (see MILESTONES). Estimating durations for future activities is very difficult. It is recommended that the largest duration possible be used to account for possible delays.

Early Finish

The Early Finish date is defined as the earliest calculated date on which an activity can end. It is based on the activity's Early Start that depends on the finish of predecessor activities and the activity's duration. (See EARLY START) Most PM software calculates early dates with a forward pass from the beginning of the project to the end. This is done by selecting ANALYZE & PROCESS REPORTS from the Report pull-down menu.

Early Start

The Early Start date is defined as the earliest calculated date on which an activity can begin. It is dependent on when all predecessor activities finish. Most PM software calculates early dates with a forward pass from the beginning of the project to the end.

Elapsed Time

Elapsed time is the total number of calendar days (excluding non-work days such as weekends or holidays) that is needed to complete an activity. It gives a "real world view" of how long an activity is scheduled to take for completion.

Finish Float

Finish float is the amount of excess time an activity has at its finish before a successor activity must start. This is the difference between the start date of the predecessor and the finish date of the current activity, using the early or late schedule. (Early and Late dates are not mixed.) This may be referred to as slack time. All floats are calculated when a project has its schedule computed.

Finishing Activity

A finishing activity is the last activity that must be completed before a project can be considered finished. This activity is not a predecessor to any other activity -- it has no successors. Many PM software packages allow for multiple finish activities.

Finish-To-Finish Lag

The finish-to-finish lag is the minimum amount of time that must pass between the finish of one activity and the finish of its successor(s). If the predecessor's finish is delayed, the successor activity may have to be slowed or halted to allow the specified period to pass. All lags are calculated when a project has its schedule computed. Finish-to-Finish lags are often used with Start-to-Start lags.

Finish-To-Start Lag

The finish-to-start lag is the minimum amount of time that must pass between the finish of one activity and the start of its successor(s). The default finish-to-start lag is zero. If the predecessor's finish is delayed, the successor activity's start will have to be delayed. All lags are calculated when a project has its schedule computed. In most cases, Finish-to-Start lags are not used with other lag types.

Float

Float is the amount of time that an activity can slip past its duration without delaying the rest of the project. The calculation depends on the float type. See START FLOAT, FINISH FLOAT, POSITIVE FLOAT, and NEGATIVE FLOAT. All float is calculated when a project has its schedule computed.

Forced Analysis

Most PM software can force schedule analysis where a project is re-analyzed even if no new data has been entered. The feature is used for an analysis on the project by itself after it has been analyzed with other projects in multi-project processing (or vice versa). A leveled schedule may also be removed by forcing schedule analysis.

Free Float

Free float is the excess time available before the start of the following activity, assuming that both activities start on their early start date. Free float is calculated in the following way: FREE FLOAT = EARLIEST START OF FOLLOWING ACTIVITY - EARLIEST START OF PRESENT ACTIVITY - DURATION OF PRESENT ACTIVITY On the activity's calendar, free float is the length of time from the end of the activity to the earliest Early Start date from among all of its successors. If the activity has no successors, the project finish date is used. Since free float is meaningless for hammocks, it is set to zero. For the common case where all lags are finish-to-start lags of zero, the free float represents the number of workdays that an activity can be delayed before it affects any other activity in the project.

Example: The current activity has an Early Start of March 1st and a duration of 3 days. The succeeding activity has an Early Start of March 7th. Assuming everyday is a work day, then: FREE FLOAT = March 7 - March 1 - 3 days = 6 days - 3 days = 3 days Free float can be thought of as the amount of time an activity can expand without affecting the following activity. If the current activity takes longer to complete than its projected duration and free float combined, the following activity will be unable to begin by its earliest start date.

Gantt (Bar) Chart

A Gantt chart is a graphic display of activity durations. It is also referred to as a bar chart. Activities are listed with other tabular information on the left side with time intervals over the bars. Activity durations are shown in the form of horizontal bars.

Hammocks

A hammock groups activities, milestones, or other hammocks together for reporting. A hammock's milestone number ranges from 95 to 99. This allows for five levels of summation. For example, two hammocks at the 95 level can be combined in a 96 level hammock. Any numbers of hammocks are allowed within the five levels for a project. Most PM software calculates the duration of a hammock from the early and late dates of the activities to which it is linked.

Histogram

A histogram is a graphic display of resource usage over a period. It allows the detection of overused or underused resources. The resource usage is displayed in colored vertical bars.
The ideal level for a resource on the screen is indicated by another color (typically red). The vertical height is produced by the value specified in the maximum usage field of the Resource Label window. (The printed histogram uses a horizontal line to display the maximum usage set in the Resource Label window.) If the resource bar extends beyond the red area for any given day, resources need to be leveled (or spread out) for proper allocation. The resource histograms should be checked after resources are assigned to the project activities.

Lag

Lag is the time delay between the start or finish of an activity and the start or finish of its successor(s). See FINISH-TO-FINISH LAG, FINISH-TO-START LAG, and START-TO-START LAG.

Late Finish

Late Finish dates are defined as the latest dates by which an activity can finish to avoid causing delays in the project. Many PM software packages calculate late dates with a backward pass from the end of the project to the beginning. This is done by selecting ANALYZE & PROCESS REPORTS from the Report pull-down menu.

Late Start

Late Start dates are defined as the latest dates by which an activity can start to avoid causing delays in the project. Many PM software packages calculate late dates with a backward pass from the end of the project to the beginning.

Micro-Scheduling

Micro-scheduling is the scheduling of activities with duration less than one day (in hours or fractional days).

Milestones

A milestone is an activity with zero duration (usually marking the end of a period).

Multi-Project Analysis

Multi-project analysis is used to analyze the impact and interaction of activities and resources whose progress affects the progress of a group of projects or for projects with shared resources or both. Multi-project analysis can also be used for composite reporting on projects having no dependencies or resources in common.

Negative Float

Negative float indicates activities must start before their predecessors finish in order to meet a Target Finish date. All float is calculated when a project has its schedule computed. Negative float occurs when the difference between the late dates and the early dates (start or finish) of an activity are negative. In this situation, the late dates are earlier than the early dates. This can happen when constraints (Activity Target dates or a Project Target Finish date) are added to a project.

Network Analysis

Network analysis is the process of identifying early and late start and finish dates for project activities. This is done with a forward and backward pass through the project. Many PM software tools will check for loops in the network and issue an error message if one is found. The error message will identify the loop and all activities within it.

Network Diagram

A network diagram is a graphic representation of activity sequence and relationships. Activity boxes are connected together with one-way arrows to indicate precedence. The first activity is placed on the left side of the diagram with the last activity on the right side. Activity boxes are usually placed at different levels (not in a single row) to accommodate activities that are done simultaneously.

Parallel Activities

Parallel activities are two or more activities than can be done at the same time. This allows a project to be completed faster than if the activities were arranged serially in a straight line.

Path

A path is a series of connected activities. Refer to CRITICAL PATH METHOD for information on critical and non-critical paths.

Positive Float

Positive float is defined as the amount of time that an activity's start can be delayed without affecting the project completion date. An activity with positive float is not on the critical path and is called a non-critical activity. Most software packages calculate float time during schedule analysis. The difference between early and late dates (start or finish) determines the amount of float. Float time is shown at the end or the beginning of non-critical activities when a bar chart reflects both early and late schedules. Float is shown on many of the tabular reports.

Precedence Notation

Precedence notation is a means of describing project workflow. It is sometimes called activity-on-node notation. Each activity is assigned a unique identifier. Workflow direction is indicated by showing each of the activity's predecessors and their lag relationships. Graphically, precedence networks are represented by using descriptive boxes and connecting arrows to denote the flow of work.

Predecessor

An activity that must be completed (or be partially completed) before a specified activity can begin is called a predecessor. The combination of all predecessors and successors (see SUCCESSOR) relationships among the project activities forms a network. This network can be analyzed to determine the critical path and other project scheduling implications.

Program Evaluation and Review Technique (PERT)

PERT is a project management technique for determining how much time a project needs before it is completed. Each activity is assigned a best, worst, and most probable completion time estimate. These estimates are used to determine the average completion time. The average times are used to figure the critical path and the standard deviation of completion times for the entire project.

Project

A project is a one-time effort to accomplish an explicit objective by a specific time. Each project is unique although similar projects may exist. Like the individual activity, the project has a distinguishable start and finish and a time frame for completion. Each activity in the project will be monitored and controlled to determine its impact on other activities and projects. The project is the largest discrete block of time and resources handled by most PM software.

Rescheduling

Rescheduling is a feature of most PM software that recalculates the start and finish dates of all uncompleted activities based upon progress as of a specified date.

Resource

A resource is anything that is assigned to an activity or needed to complete an activity. This may include equipment, people, buildings, etc.

Resource Based Duration

Resource based duration provides the option to determine activity duration, remaining duration, and percent complete through resource usage. The resource requiring the greatest time to complete the specified amount of work on the activity will determine its duration. You may change the duration mode for an activity at any time. This feature may not be used without values in the Resource Usage fields.

Resource Leveling

Resource leveling provides the capability to adjust project schedules in order to minimize the peaks in daily resource usages. This is usually done when resources are over-allocated. Activities are moved within their available float to produce a new schedule. Resources and projects may have leveling priorities. Some activities may not have any rescheduling flexibility due to lack of float. Either resource-constrained or schedule-constrained leveling may be selected.

Scheduling

Scheduling is the process of determining when project activities will take place depending on defined durations and precedent activities. Schedule constraints specify when an activity should start or end based on duration, predecessors, external predecessor relationships, resource availability, or target dates.

Sequence

Sequence is the order in which activities will occur with respect to one another. This establishes the priority and dependencies between activities. Successor and predecessor relationships are developed in a network format. This allows those involved in the project to visualize the workflow.

Slippage

Slippage is the amount of slack or float time used up by the current activity due to a delayed start. If an activity without float is delayed, the entire project will slip.

Start Float

Start float is the amount of excess time an activity has between its Early Start and Late Start dates.

Start-To-Start Lag

Start-to-start lag is the minimum amount of time that must pass between the start of one activity and the start of its successor(s).

Starting Activity

A starting activity has no predecessors. It does not have to wait for any other activity to start. Many PM software packages permit multiple start activities if needed.

Sub-Critical Activity

A sub-critical activity has a float threshold value assigned to it by the project manager. When the activity reaches its float threshold, it is identified as being critical. Since this type of criticality is artificial, it normally does not affect the project's end date.

Subproject

A subproject is a distinct group of activities that comprise their own project that in turn is a part of a larger project. Subprojects are summarized into a single activity to hide the detail.

Successor

A successor is an activity whose start or finish depends on the start or finish of a predecessor activity. Refer to PREDECESSOR for related information.

Super-Critical Activity

An activity that is behind schedule is considered super-critical. It has been delayed to a point where its float to calculated to be a negative value. The negative float is representative of the number of units an activity is behind schedule.

Target Finish -- Activity

Target Finish is the user's imposed finish date for an activity. A Target Finish date is used if there are pre-defined commitment dates. Most PM software will not schedule a Late Finish date later than the Target Finish date. Your favorite PM software may alert you to negative float that occurs when a Late Finish date is later than a Target Finish date. This is caused by the duration of predecessors that makes it impossible to meet the Target Finish date. The negative float can be eliminated by reducing the duration of predecessors or extending the Target Finish date.

Target Finish -- Project

A user's Target Finish date can be imposed on a project as a whole. A Target Finish date is used if there is a pre-defined completion date. Most PM software will not schedule any Late Finish date later than the Target Finish date. See TARGET FINISH ACTIVITY on how to deal with negative float.

Target Start -- Activity

Target Start is an imposed starting date on an activity. Most PM software will not schedule an Early Start date earlier than the Target Start date.

Total Float

Total float is the excess time available for an activity to be expanded or delayed without affecting the rest of the project -- assuming it begins at its earliest time. It is calculated using the following formula: TOTAL FLOAT = LATEST FINISH - EARLIEST START – DURATION.

Work Breakdown Structure (WBS)

The WBS is a tool for defining the hierarchical breakdown of responsibilities and work in a project. It is developed by identifying the highest level of work in the project. These major categories are broken down into smaller components. The subdivision continues until the lowest required level of detail is established. These end units of the WBS become the activities in a project. Once implemented, the WBS facilitates summary reporting at a variety of levels.

Work Flow

Workflow is the relationship of the activities in a project from start to finish. Workflow takes into consideration all types of activity relationships.

Work Load

Workload is the amount of work units assigned to a resource over a period.

Work Units

A work unit is the measurement of resources. For example, people as a resource can be measured by the number of hours they work.

Zero Float

Zero float is a condition where there is no excess time between activities. An activity with zero float is considered a critical activity. If the duration of any critical activity is increased (the activity slips), the project finish date will slip.

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