Schedules in traditional project plans

Some projects require detailed scheduling for project tasks that must be completed sequentially and in adherence to defined start and finish dates. A schedule defines the timing and sequence of work items in a release or an iteration plan. Projects that follow a formal, or traditional, planning model usually require this type of scheduling. When you save a plan, the plan schedule is calculated based on the information that you supply. As the plan progresses and you change the schedule information, the schedule is adjusted and recalculated.

Schedule calculation

A plan schedule indicates the start and end dates and the sequence for the work items in a plan. The plan schedule is determined by the following information:
  • Effort estimate or duration of work items
  • Start and end date of the plan
  • Schedule constraints and dependencies of work items
  • Project working days and hours
  • Availability of resources who are assigned to work items

Example: A work item is assigned to a future iteration that has a start date of Tuesday, June 1. The work item effort estimate is 40 hours. The project area work environment specifies 8 working hours per day, and 5 days of work, Monday through Friday, in a week. The project working hours are specified as 9 AM to 5 PM. The start date of the work item is Tuesday, June 1 at 9 a.m. The finish date is 7 days after the start date, considering the interim non-working days. The finish date is calculated as Monday, June 7 at 5 p.m.

If the work item starts on June 1 at 2 p.m., then the finish date is calculated as June 8 at 2 p.m.

When a resource is assigned to a work item, the schedule of the work item is calculated by using the resource calendar and availability information, such as work time, absences, and project allocation dates and percentages. If a resource who does not work on Fridays is assigned, and the work item starts on June 1 at 9 a.m., the finish date of the work item is extended by a day to June 9.

Errors and warnings in a plan: Any schedule violations in the plan are indicated and explained with errors and warnings in the Plan Check column on the Planned Items tab of the plan view. The Plan Check column is available by default in the plan Work Breakdown and Schedule view for projects that use the Formal Project Management process.

To learn how different factors affect the calculation of the plan schedule, see the following sections.

Plan start dates

When work items in a plan have no dependencies or constraints, the plan start date determines the scheduled start date of the work items. If the plan start date is in the future, the start dates of the work items for that plan are the plan start date. If the plan start date is in the past and work items are assigned to the plan, the start date of the work items is the current date. If a work item is assigned to a plan that is complete, an error is displayed in the plan.

Examples:

The start date of a phase plan is August 1.

  • A work item is assigned to the plan on June 1. Because the plan start date is a future date, the scheduled start date of the work item is the same as the plan start date, August 1.
  • A work item is assigned to the plan after the plan starts. Because the plan start date has passed, the work item start date is the current date.
  • A work item is assigned to the plan after the plan is complete. The work item start date is the current date. A warning is displayed in the plan.

Dependencies

Dependencies between work items determine the schedule and sequence of the work items in a plan. To learn more about dependencies, see Schedule dependencies

When a work item is dependent on or is a successor of another work item, the start date of the dependent or successor work item is after the finish date of its predecessor work item.

Examples:

Task B is the successor of Task A. In the plan, Task A is scheduled to finish on June 15, and Task B is scheduled to start on June 16.

  • When Task B has no constraints: If Task A ends earlier than June 15, the scheduled start date of Task B moves to a date before June 16.
  • When Task B has a Start no earlier than constraint: If the constraint date is June 16 and Task A finishes early, the start date of Task B cannot be moved to before June 16.
  • When Task B has a Finish no later than constraint: If the constraint date is June 16 and the duration is 2 days, Task A must finish by June 14 so that Task B can be finished by June 16. If Task A finishes later than June 14, an error is displayed in the plan.
Note: If a successor task starts before its predecessor is completed, the dependency relationship is ignored by the scheduling process. In this case, the actual start date determines the work item schedule, irrespective of the schedule of the predecessor work item.

Constraints

Schedule constraints impose fixed start or finish dates on work items and are given precedence in the scheduling process. If a work item with dependencies has a Start no earlier than or a Finish no later than constraint, the constraint is given precedence in the scheduling process. For information about constraints, see Schedule constraints.

Work items with a Start no earlier than constraint

If a work item has a Start no earlier than constraint, the scheduled start date of the work item is on or after the specified constraint date.

Examples:

  • The current date is June 1, and the Start no earlier than constraint for the work item is June 15. The scheduled start date of the work item is the same as the constraint date, June 15. If the work item starts before the constraint date, an error is displayed in the plan.
  • The current date is June 20, and the Start no earlier than constraint for the work item is June 15. The scheduled start date of the work item is the current date, June 20.

Work items with a Finish no later than constraint

If a work item has a Finish no later than constraint and is scheduled to finish after the constraint date, an error is displayed in the plan.

Example:

A work item is scheduled to start on the plan start date of June 15. The work item has an effort estimate of 4 days, and a Finish no later than constraint of June 18. If the work item does not start on June 15, the scheduled finish date becomes June 19, which is later than the finish date constraint. In the plan, an error is displayed that states that the scheduled finish date is later than the constraint date.

Work items with a Start no earlier than constraint and a dependency

If a work item with a start date constraint is a successor of another work item, the scheduled start date of the successor work item is whichever date is later: after the end date of the predecessor work item or on or after the constraint date.

Example:

Task B is the successor of Task A. Task B has a Start no earlier than constraint of June 20.

  • If Task A is scheduled to finish on June 22, Task B is scheduled to start on June 23, which is after the constraint date.
  • If Task A is scheduled to finish on June 15, the scheduled start date of Task B cannot be June 16, which is earlier than the constraint date. As a result, the start date of Task B is set to the constraint date, June 20.

Work items with a Finish no later than constraint and a dependency

If a work item with a Finish no later than constraint is a successor of another work item, the scheduled finish date of the successor work item must be on or before the constraint date.

Example:

Task B is the successor of Task A. Task B has a duration of 2 days and a finish date constraint of June 16. Task A must finish by June 14 so that Task B can be finished by the constraint date of June 16.

  • If Task A finishes on June 13, Task B is scheduled to start on June 14 and finish on June 15.
  • If Task A finishes later than June 14, an error is displayed in the plan.

Resource assignments

When a work item is assigned to a resource, the resource calendar is used to calculate the schedule of the work item. The work item is scheduled for the days and hours for which the resource is available.

Example:

Task A has an estimate of 32 hours and is assigned to a resource who works on Thursdays and Fridays for 8 hours each. The plan start date is Monday, June 1 and the calculated start date of the work item is Thursday, June 4. To allow 4 working days to complete the task, the calculated finish date is Friday, June 12.

Basic resource leveling

The basic resource leveling process affects the scheduling of work items. For more information about basic resource leveling, see Basic resource leveling.

Actual start and finish dates

When a plan is in progress and the states of work items change, the actual start date and finish dates for the work items are determined by those changes.

The actual start and finish dates for a work item are determined by the dates on which the state of the work item is changed. The actual start date is the date when the state of a work item is changed to In Progress. The actual finish date is the date when the state of a work item is set to Resolved.

Note: If you change the status of a work item to In Progress on a non-working day, the non-working date is set as the actual start date. If you change the status of a work item to Resolved on a non-working day, the non-working date is set as the resolution date.

Example:

A work item is scheduled to start on June 1, with an estimate of 16 hours and a finish date of June 2. On June 2, the state of the work item is set to In Progress. The actual start date of the work item is June 2. On June 5, the time spent is entered as 16 hours, and the state of the work item is set to Resolved. The actual finish date of the work item is June 5.

Time spent

When the time spent is entered for work items, the scheduled finish date for the work items is calculated by using the current date and the remaining estimate. The remaining estimate is the estimate minus the time spent.

Note: If a work item is started and the time spent is entered without changing the state of the work item, the scheduled start date is always the current date.

Example:

The scheduled start date of a work item is June 1, its estimate is 40 hours, and the calculated finish date is June 5. The work item is started on May 31, and the work item state is changed to In Progress. On June 3, a time spent value of 32 hours, which is equal to 4 days of work, is entered. The scheduled finish date is calculated by using the remaining estimate and the current date. The time spent value of 32 hours is subtracted from the estimate value of 40 hours. The remaining estimate is 8 hours, which is equal to one day of work. If the current date is June 3, and one day of work remains, the scheduled finish date is June 4.


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