Glossary
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
B
Backward pass: A calculation in a schedule network that determines late start dates by subtracting durations from late finish dates
Baseline schedule: Represents the original configuration of the program plan and signifies the consensus of all stakeholders regarding the required sequence of events, resource assignments, and acceptable dates for key deliverables
Basis document: A single document that defines the organization of the IMS, describes the logic of the network, describes the basic approach to managing resources, and provides a basis for all parameters used to calculate dates
C
Consolidated schedule: An IMS that aggregates multiple project files in a single master file for reporting or management purposes, even if those projects are immaterially related. Also known as a portfolio schedule, although portfolio schedule and consolidated schedule are often synonymous with IMS
Contingency: A margin or a reserve of extra time to account for known and quantified risks and uncertainty
Critical activity: An activity on the critical path. When the network is free of date constraints, critical activities have zero float, and therefore any delay in the critical activity causes the same day-for-day amount of delay in the program forecast finish date
Critical path: The longest continuous sequence of activities in a schedule. Defines the program’s earliest completion date or minimum duration
D
Dangling logic: Scheduling logic that is not properly tied to an activity’s start or end date. Also referred to as hanging logic
Date constraint: An override of the calculated start or finish dates of activities by imposing calendar restrictions on when an activity can begin or end
Detail activity: Activities at the lowest level of the WBS representing the performance of actual discrete work that is planned in the project. Logically related paths of detail activities are linked to milestones to show the progression of work that is planned
Detail schedule: The lowest level of schedule. The detail schedule lays out the logically sequenced day-to-day effort to reach program milestones
Deterministic critical path: The critical path as defined by the initial or current set of inputs in the schedule model
Duration: The estimated time required to complete an activity—the time between its start and finish. Durations are expressed in business units, such as working days, and are subjected to the project calendar
F
Finish no earlier than (FNET): A date constraint that schedules an activity to finish on or after a certain date. That is, FNET constraints prevent an activity from finishing before a certain date. Also called finish on or after constraints
Finish no later than (FNLT): A date constraint that schedules an activity to finish on or before a certain date. That is, FNLT constraints prevent an activity from finishing after a certain date. FNLT constraints are also called finish on or before constraints
Finish-to-finish (F-F): A logic relationship that dictates that a successor activity cannot finish until the predecessor activity finishes
Finish-to-start (F-S): A logic relationship that dictates that a successor activity cannot start until the predecessor activity finishes
Float: See total float or free float. Also referred to as slack
Forward pass: A calculation in a schedule network that determines the early start and early finish times for each activity by adding durations successively through the network, starting at day one. The forward pass will derive the total time required for the entire project by calculating the longest continuous path through the network
Fragnet: A fragmentary, or subordinate, network that represents a sequence of activities typically related to repetitive effort. Subordinate networks can be inserted into larger networks as a related group of activities
Free float: The portion of an activity’s total float that is available before the activity’s delay affects its immediate successor. Depending on the sequence of events in the network, an activity with total float may or may not have free float
G
Giver/receiver: Represents dependencies between schedules, such as hand-offs between integrated product teams and delivery and acceptance of government-furnished equipment
H
Horizontal traceability: Demonstrates that the overall schedule is rational, has been planned in a logical sequence, accounts for the interdependence of detailed activities and planning packages, and provides a way to evaluate current status. Schedules that are horizontally traceable depict logical relationships between different program elements and product handoffs
I
Integrated master schedule (IMS): A program schedule that includes the entire required scope of effort, including the effort necessary from all government, contractor, and other key parties for a program’s successful execution from start to finish. The IMS should consist of logically related activities whose forecasted dates are automatically recalculated when activities change. The IMS includes summary, intermediate, and detail-level schedules
Intermediate Schedule: The intermediate schedule includes all information displayed in the summary schedule, as well as key program activities and milestones that show the important steps in achieving high-level milestones
L
Lag: Denotes the passage of time between two activities. Lags simply delay the successor activity—no effort or resources are associated with this passage of time
Lead: A negative lag used to accelerate a successor activity. Leads imply the unusual measurement of negative time and exact foresight about future events
Level-of-effort (LOE) activity: An activity that represents effort that has no measurable output and cannot be associated with a physical product or defined deliverable. LOE activities are typically related to management and other oversight that continues until the detailed activities they support have been completed
Longest path: Theoretically, the longest path is equal to the critical path. As a schedule becomes more complex, total float values may not necessarily represent a true picture of schedule flexibility. In those cases, the longest path is the sequence of activities directly affecting the estimated finish date of the key milestone, ignoring the presence of any date constraints
M
Merge bias: The additional risk at points in the schedule where parallel paths merge
Milestone: Points in time that have no duration but that denote the achievement or realization of key events and accomplishments such as program events or contract start dates. Because milestones lack duration, they do not consume resources
Must finish on (MFON): A date constraint that schedules an activity to finish on a certain date. That is, MFON constraints prevent an activity from finishing any earlier or later than a certain date, thereby overriding network logic. MFON constraints are also called mandatory finish constraints
Must start on (MSON): A date constraint that schedules an activity to start on a certain date. That is, MSON constraints prevent an activity from starting any earlier or later than a certain date, thereby overriding network logic. MSON constraints are also called mandatory start constraints
N
Near-critical activity: An activity with total float within a narrow range of the critical path. Near-critical activities can quickly become critical if their small amount of total float is used up in a delay
O
Out-of-sequence logic: The result of progress on an activity performed in a different order from that originally planned
P
Path convergence: Several parallel activities joining with a single successor activity
Performance measurement baseline: A time-phased budget plan for accomplishing work. Performance is measured against the PMB
Predecessor: Activities that are logically related within a schedule network are referred to as predecessors and successors. A predecessor activity must start or finish before its successor
Probabilistic branching: The addition of new activities in a schedule that occur only with some probability. Probabilistic branching is used to model the random choice between two alternatives
Progress override: When out-of-sequence progress occurs, managers and schedulers may choose to override the existing network logic. Work on the activity that began out of sequence is permitted to continue, regardless of original predecessor logic. Actual progress in the field supersedes the plan logic, and work on the out-of-sequence activity continues
R
Resource: Anything required to perform work, such as labor, materials, travel, and facilities
Resource leveling: Adjusts the scheduled start of activities or the work assignments of resources to account for their availability. Leveling is used primarily by the organization that has control of the resources to smooth spikes and troughs in resource demands created by the sequencing of activities in the schedule network
Retained logic: When out-of-sequence progress occurs, managers and schedulers may choose to retain existing network logic. Work on the activity that began out of sequence is stopped until its predecessor is completed. As much as possible of the original network logic is preserved because the remainder of the out-of-sequence activity is delayed until the predecessor finishes, to observe its original sequence logic
Risk: An uncertain event that could affect the program positively or negatively. Risk and its outcomes can be quantified in some definite way
Rolling wave planning: The incremental conversion of work from planning packages to detailed work packages. Rolling wave planning with portions of effort that align to significant program increments, blocks, or updates is sometimes referred to as block planning
S
Schedule narrative: A document that accompanies the updated schedule to provide a log of changes and their effect, if any, on the schedule time
Schedule risk analysis: An analysis that uses statistical techniques to predict a level of confidence in meeting a program’s completion date. A schedule risk analysis focuses on uncertainty and key risks and how they affect the schedule’s activity durations
Slack: A synonym for float
Start no earlier than (SNET): A date constraint that schedules an activity to start on or after a certain date, even if its predecessors start or finish earlier. That is, SNET constraints prevent an activity from beginning before a certain date. SNET constraints are also called start on or after constraints
Start no later than (SNLT): A date constraint that schedules an activity to start on or before a certain date. That is, SNLT constraints prevent an activity from starting any later than a certain date. SNLT constraints are also called start on or before constraints
Start-to-finish (S-F): A theoretical logic relationship that has the bizarre effect of directing a successor activity not to finish until its predecessor activity starts
Start-to-start (S-S): A logic relationship that dictates that a successor activity cannot start until the predecessor activity starts
Statement of work (SOW): Defines, either directly or by reference to other documents, performance requirements for a contractor’s effort. The SOW specifies the work to be done in developing the goods or services to be provided by a contractor
Status date: Denotes the date of the latest update to the schedule and thus defines the demarcation between actual work performed and remaining work. Also called a data date or time-now date
Statusing: The process of updating a plan with actual dates, logic, and progress and adjusting forecasts of the remaining effort
Successor: Activities that are logically related within a schedule network are referred to as predecessors and successors. A predecessor activity must start or finish before its successor
Summary activity: A grouping element that shows the time that activities of lower levels of detail require. Summary activities derive their start and end dates from lower-level activities
Summary schedule: Provides a strategic view of the activities and milestones necessary to start and complete a program. Summary schedules are roll-ups of lower-level intermediate and detail schedules
T
Total float: The amount of time an activity can be delayed or extended before delay affects the program’s finish date. If positive, it indicates the amount of time that an activity can be delayed without delaying the program’s finish date. If negative, it indicates the amount of time that must be recovered so as not to delay the program’s finish date beyond the constrained date. Zero total float means that any amount of activity delay will delay the program finish date by an equal amount
V
Vertical traceability: Demonstrates the consistency of dates, status, and scope requirements between different levels of a schedule—summary, intermediate, and detailed. When schedules are vertically traceable, lower-level schedules are clearly consistent with upper-level schedule milestones, allowing for total schedule integrity and enabling different teams to work to the same schedule expectations
W
Work breakdown structure: Deconstructs a program’s end product into successively greater levels of detail until the work is subdivided to a level suitable for management control
Work package: An activity or grouping of activities at the lowest level of the work breakdown structure, where work is planned and progress is measured