Using Schedule Dependencies and Constraints

This chapter provides overviews of schedule dependencies, activity constraints, integration of dependencies and constraints with Microsoft Project, and project schedule indicators, and discusses how to:

Click to jump to parent topicUnderstanding Schedule Dependencies

This section provides overviews of:

Click to jump to top of pageClick to jump to parent topicDependency Types and Relationships

A dependency is a logical relationship between two project activities in which the start or end date of one activity depends on the start or end date of another activity. The activity that depends on the other activity is the successor, and the activity that it depends on is the predecessor. The system calculates the successor activity's start date, end date, or duration based on the dependency relationship, dependency type, and calculation method that you establish.

You can define multiple activity successors and activity predecessors for each project activity. The system sets the start and end dates of new activities that are equal to the project start date. You can manually update the dates and duration, or use dependencies and constraints to determine the activity start and end dates.

The best practice for project activity scheduling is to set dependencies and constraints on all activities to drive the project schedule rather than manually updating every activity date. When you specify a dependency on an activity, the predecessor activity schedule might affect the successor activity schedule. If that successor activity has additional related dependencies, there can be a cascading effect on many activity dates. You can select the activity date cascade calculations option on the Project General - Program Management page to specify when to calculate activity dates and roll them up to summary activities. Delaying the summary date rollup can help you manage system performance.

This table identifies the system calculation processing based on the activity date cascade calculations options.

Activity Date Cascade Calculations Option

System Calculation Processing

Manual

The system does not calculate any of the activity schedule. You must manually enter the activity's start date, end date, and duration. The system does not roll up activity start and end dates to summary activities.

Delay Calculations Until Save

Certain date processing occurs immediately upon field edits, and other date processing and summary roll-ups occur when you save.

At save, the system rolls up the activity start and end dates to summary activities. Additionally, the system updates the successor activity dates as a result of dependencies, constraints, or changes to predecessor activities.

Realtime Calculation

Activity dependency changes and predecessor date changes flow through the schedule as soon as the changes are made. Summary activity date processing occurs immediately.

Define dependencies on the Activity Predecessors page where you specify predecessor projects, predecessor activities, dependency types, and lead or lag time. Dependency types that you can establish include:

Additionally, you can define a lag time or lead time for dependency relationships. Lag time is the delay between activities that have a dependency. Lead time is the overlap between activities that have a dependency.

Activity Date Calculation Methods

The system calculates activity start date, end date, and duration based on the calculation method that you specify at the activity level and the lag or lead time that you specify when you create the dependency.

You specify the calculation method in the Calculate field on the Project Activities page or the Activity Definitions - General Information page. The available options are:

Specify lead or lag time, in whole work days, in the Lag field on the Activity Predecessors page.

Lag time is the delay between activities that have a dependency. For example, if you need a two-day delay between the end of one activity and the start of another, you can establish an end-to-start dependency and specify a lag time of two days. Lag time is expressed with a positive whole number in the Lag column of the Activity Predecessors page.

Lead time is the overlap between activities that have a dependency. For example, if an activity can start when its predecessor is two weeks from its end date, you can establish and end-to-start dependency with a lead time of ten days for the successor activity. Lead time is expressed with a negative whole number in the Lag column of the Activity Predecessors page.

End-to-Start Dependencies

For an end-to-start dependency, the system sets the start date of the successor activity to the next working day after the predecessor's end date plus or minus any lag or lead time. When the calculation method is:

Note. You cannot set an end-to-start dependency on an activity that has the start date calculation method.

This table shows activities, durations, start dates, and end dates before you establish the end-to-start dependency:

Activity

Duration

Start Date

End Date

Develop

15 days

June 1 (Monday)

June 19 (Friday)

Unit Test

5 days

June 1 (Monday)

June 5 (Friday)

This table shows the effect on the successor activity start and end dates based on the end-to-start dependency with an end date calculation method:

Dependency Relationship

Dependency Type

Lag

Activity

Duration

Start Date

End Date

Predecessor

   

Develop

15 days

June 1 (Monday)

June 19 (Friday)

Successor

End-to-Start on Develop Activity

2 days

Unit Test

5 days

June 24 (Wednesday)

June 30 (Tuesday)

Note. For the examples in this chapter, the duration, start date, and end date are based on the work days in a business calendar with Monday-Friday work weeks.

End-to-End Dependencies

For an end-to-end dependency, the system sets the successor activity's end date to the predecessor activity's end date plus or minus any lag or lead time. When the calculation method is:

Note. You cannot set an end-to-end dependency on an activity that has the end date calculation method.

This table shows activities, durations, start dates, and end dates before you establish the end-to-end dependency:

Activity

Duration

Start Date

End Date

Develop

15 days

June 1 (Monday)

June 19 (Friday)

Unit Test

5 days

June 1 (Monday)

June 5 (Friday)

This table shows the effect on the successor activity start and end dates based on the end-to-end dependency and start date calculation method:

Dependency Relationship

Dependency Type

Lag

Activity

Duration

Start Date

End Date

Predecessor

   

Develop

15 days

June 1 (Monday)

June 19 (Friday)

Successor

End-to-End on Develop Activity

–1 day (Lead)

Unit Test

5 days

June 12 (Friday)

June 18 (Thursday)

Start-to-Start Dependencies

For a start-to-start dependency, the system sets the successor activity's start date to the predecessor activity's start date plus or minus any lag or lead time. When the calculation method is:

Note. You cannot set a start-to-start dependency on an activity that has the start date calculation method.

This table shows activities, durations, start dates, and end dates before you establish the start-to-start dependency:

Activity

Duration

Start Date

End Date

Develop

15 days

June 1 (Monday)

June 19 (Friday)

Unit Test

5 days

June 15 (Monday)

June 19 (Friday)

This table shows the effect on the successor activity start and end dates based on the start-to-start dependency and an end date calculation method:

Dependency Relationship

Dependency Type

Lag

Activity

Duration

Start Date

End Date

Predecessor

   

Develop

15 days

June 1 (Monday)

June 19 (Friday)

Successor

Start-to-Start on Develop Activity

2 days

Unit Test

5 days

June 3 (Wednesday)

June 9 (Tuesday)

Start-to-End Dependencies

For a start-to-end dependency, the system sets the successor activity's end date to the predecessor activity's start date plus or minus any lag or lead time. When the calculation method is:

Note. You cannot set a start-to-end dependency on an activity that has the end date calculation method.

This table shows activities, durations, start dates, and end dates before you establish the start-to-end dependency:

Activity

Duration

Start Date

End Date

Develop

15 days

June 1 (Monday)

June 19 (Friday)

Unit Test

5 days

June 1 (Monday)

June 5 (Friday)

This table shows the effect on the successor activity start and end dates based on the start-to-end dependency and Start Date calculation method:

Dependency Relationship

Dependency Type

Lag

Activity

Duration

Start Date

End Date

Predecessor

   

Develop

15 days

June 1 (Monday)

June 19 (Friday)

Successor

Start-to-End on Develop Activity

0 days

Unit Test

5 days

May 26 (Tuesday)

June 1 (Monday)

Click to jump to top of pageClick to jump to parent topicActivities with Multiple Dependencies

You can set one or more dependencies on a successor activity. Each of these dependencies can consist of different types, such as an end-to-end dependency with a predecessor activity along with an end-to-start dependency with another predecessor activity. Each dependency can yield different effects on the successor's start and end dates. The system sets the successor dates and duration based on the predecessor activity that drives the successor dates to the latest date.

Example One of a Successor Activity with Multiple Dependencies

This table shows activities, durations, start dates, and end dates before you establish dependencies:

Activity

Duration

Start Date

End Date

Functional Design

10 days

June 1 (Monday)

June 12 (Friday)

Usability Design

2 days

June 1 (Monday)

June 2 (Tuesday)

Develop

15 days

June 1 (Monday)

June 19 (Friday)

This table shows the effect on the successor activity start and end dates based on the dependency relationships and types and an end date calculation method:

Dependency Relationship

Dependency Type

Activity

Duration

Start Date

End Date

Predecessor

 

Functional Design

10 days

June 1 (Monday)

June 12 (Friday)

Predecessor

 

Usability Design

2 days

June 1 (Monday)

June 2 (Tuesday)

Successor

  • End-to-Start on Functional Design

  • Start-to-Start on Usability Design

Develop

15 days

June 15 (Monday)

July 3(Friday)

The Functional Design and Usability Design activities are both predecessors to the Develop activity, However, the system uses the Functional Design activity end date to determine the Develop activity start and end dates. The next working day after the Functional Design activity end date drives the Develop activity dates to be later than if it was driven by the Usability Design activity start date.

Example Two of a Successor Activity with Multiple Dependencies

This table shows activities, durations, start dates, and end dates before you establish dependencies:

Activity

Duration

Start Date

End Date

Functional Design

10 days

June 1 (Monday)

June 12 (Friday)

Usability Design

2 days

June 1 (Monday)

June 2 (Tuesday)

Develop

15 days

June 1 (Monday)

June 19 (Friday)

Unit Test

7 days

June 1 (Monday)

June 9 (Tuesday)

This table shows the effect on the successor activity start and end dates based on the dependency types and relationships and an end date calculation method:

Dependency Relationship

Dependency Type

Activity

Duration

Start Date

End Date

Predecessor

 

Functional Design

10 days

June 1 (Monday)

June 12 (Friday)

Predecessor

 

Usability Design

2 days

June 1 (Monday)

June 2 (Tuesday)

Predecessor

 

Develop

15 days

June 1 (Monday)

June 19 (Friday)

Successor

  • End-to-Start on Functional Design

  • Start-to-Start on Usability Design

  • End-to-Start on Develop

Unit Test

7 days

June 22 (Monday)

June 30 (Tuesday)

The system uses the Develop activity to determine the Unit Test activity's dates. The end date for the Develop activity drives the Unit Test activity dates to be later than the Functional Design activity end date and the Usability Design activity start date.

Click to jump to top of pageClick to jump to parent topicDependencies Across Projects

Use the Activity Predecessors page to define a dependency between a successor activity on one project and a predecessor activity on a different project. You can define dependencies across projects as long as the projects are within the same business unit.

The system uses the scheduling calculation method that is specified at the project level of the successor activity if the successor’s dates must change to align with the new dependency relationship. The system allows multiple levels of cross-project dependencies.

The system automatically triggers Change Request workflow for cross-project dependencies. If you change the dates for a predecessor activity that affect the dates for the successor activity, the system automatically sends a change request to the project manager of the project with the successor activity. If the project manager approves the change request, the system uses date processing rules for dependencies to update the successor activity dates or remove the dependency if there is a conflict. If the project manager rejects the change request, the system leaves the successor activity dates as they were and removes the dependency between the two projects’ activities.

See Also

Change Requests for Cross-Project Dependencies

Click to jump to top of pageClick to jump to parent topicCopying Projects with Dependent Activities

On project templates, you can set up dependencies within a single project. The system calculates the correct activity start dates and end dates for the new project based on the dependency. If you create projects from copies of existing projects, the system copies dependencies within that project to the target project.

Click to jump to parent topicUnderstanding Activity Constraints

This section provides overviews of activity constraints and copying activities with constraints.

Click to jump to top of pageClick to jump to parent topicActivity Constraints

A constraint is a restriction that you place on an activity to control the activity's start date or end date. You can define flexible, moderately flexible, or inflexible constraints.

Each activity can have only one constraint type, which determines when the activity can start or end. For summary activities, you can select only As Soon As Possible, End No Later Than, or Start No Earlier Than constraint types.

If users try to change detail activities to summary activities, and the detail activities have constraints that are not valid for summary activities, the user must either remove the constraint or leave the activity as a detail activity.

If no constraint type is specified for an activity, users can enter any start and end dates, as long as the dates do no violate any existing dependencies for the activity, and the activity is a detail activity.

On the Project General - Program Management page, you can select a project-level option that requires that activities always honor the constraint. If you select this option:

If you do not require activities to honor the constraint, users can change activity start and end dates manually or through dependency relationships. The constraint remains on the activity but the system allows the activity dates to change even if they violate the constraint.

As Soon As Possible Constraint

Use the As Soon As Possible constraint for the system to schedule the activity as early as it can, based on these rules:

Note. You cannot enter an As Soon As Possible constraint if the calculation method is Start Date.

As Late As Possible Constraint

Use the As Late As Possible constraint for the system to schedule the activity as late as it can, based on these rules:

Note. You cannot enter an As Late As Possible constraint if the calculation method is End Date.

End No Earlier Than

Use the End No Earlier Than constraint to establish the earliest possible date that an activity could end. The activity cannot finish any time before the date you specify. The system determines the schedule based on these rules:

Start No Earlier Than

Use the Start No Earlier Than constraint to establish the earliest possible date that an activity can begin. The activity cannot start any time before the date you specify. The system determines the schedule based on these rules:

Start No Later Than

Use the Start No Later Than constraint to establish the latest possible date that an activity could start. The activity can start anytime on or before the date that you specify. The system determines the schedule based on these rules:

End No Later Than

Use the End No Later Than constraint to establish the earliest possible date that an activity could end. The activity can end on or before the date you specify. The system determines the schedule based on these rules:

Must Start On

Use the Must Start On constraint to specify the exact date when an activity must start. The system determines the schedule based on these rules:

Must End On

Use the Must End On constraint to specify the exact date for which the activity must be completed. The system determines the schedule based on these rules:

Click to jump to top of pageClick to jump to parent topicCopying Activities with Constraints

If you create a project activity from a copy of an existing activity, the system copies the constraint on that activity to the target activity. However, if you create a project activity from a template, the constraint on that activity does not copy to the target activity.

See Also

Creating and Maintaining Projects

Click to jump to parent topicUnderstanding Integration of Dependencies and Constraints with Microsoft Project

Microsoft Project 2002 has dependencies and constraints that are similar to PeopleSoft Program Management's dependencies and constraints. All dependencies and constraints that you establish in Microsoft Project will transfer to PeopleSoft, and vice versa. It is possible for an activity schedule that you imported from Microsoft Project to differ in PeopleSoft and vice versa, because of differences in activity schedule calculations between PeopleSoft and Microsoft Project. You should maintain your smaller projects (less than one hundred activities) in PeopleSoft. However, for larger projects, you should use Microsoft Project as the master for the activity schedule. The system handles the integration process differently based on the source and target applications.

PeopleSoft to Microsoft Project Integration

The system uses these rules to assign constraints during the integration from PeopleSoft to Microsoft Project, because Microsoft Project requires a constraint on every activity, but PeopleSoft does not:

This diagram shows the logic that the system uses to export dependency and constraint information from PeopleSoft to Microsoft:

Exporting PeopleSoft activity dependency and constraint data to Microsoft

The integration process uses PeopleSoft's project-level date calculation method to determine the calculation method in Microsoft Project. This table displays the mapping between the PeopleSoft and Microsoft Project calculation method mapping to the Microsoft Project calculation method:

Activity Date Cascade Calculation Option In PeopleSoft

Microsoft Project Calculation Method

Manual

Manual

Delay Calculations Until Save

Manual, then, once in Microsoft Project, select Calculate Now

Realtime Calculations

Automatic

Microsoft Project to PeopleSoft Integration

When you import projects from Microsoft Project to PeopleSoft, the integration process sets the activity date cascade calculation option to Manual . The system imports the activity schedule into PeopleSoft exactly as it was in Microsoft Project. The system does not recalculate the schedule in PeopleSoft. You can change the Activity Date Cascade Calculation option on the Project General - Program Management page after you import the project. However, if you change the activity date cascade calculation option, it is possible for an activity schedule that you imported from Microsoft Project to differ in PeopleSoft, because of differences in activity schedule calculations between PeopleSoft and Microsoft Project.

Additionally, the systems assigns the value in the Calculate field based on the project's default value in PeopleSoft for all activities without dependencies. The system assigns the duration calculation method for all activities with dependencies.

Since summary activities in PeopleSoft cannot have dependencies on other activities, if there are any summary activities with dependencies in Microsoft Project, the import process does not bring the dependencies into PeopleSoft. The system issues a warning to indicate that the dependencies on summary activities will not be imported into PeopleSoft. The schedule dates that Microsoft Project assigned as a result of dependencies that were set on summary tasks will not change during the import. You can view the details of this process on the Integration Session Log that you can view on the Create Project from Microsoft page.

See Also

Integrating with Microsoft Project 2002

Click to jump to parent topicUnderstanding Project Schedule Indicators

During project planning and execution, project managers need to be alerted to various conditions that are associated with each activity. A column on the Project Activities page shows warning and informational visual indicators to alert project managers to attributes about each activity.

The Project Activities page displays a warning visual indicator if:

The Project Activities page displays an informational visual indicator if:

You can move the mouse across the indicator to view alternate text about the nature of these conditions. If more than one condition exists, click the indicator to access the Activity Alerts page to view the alert messages.

See Also

Creating and Maintaining Activities

Click to jump to parent topicSpecifying Schedule Dependencies

This section discusses how to specify activity predecessors.

Click to jump to top of pageClick to jump to parent topicPage Used to Specify Schedule Dependencies

Page Name

Object Name

Navigation

Usage

Activity Predecessors

PGM_ACT_DEP_SEC

  • Program Management, Activity Definitions, General Information, General Information

    Click the Create Predecessors link.

    Click the Review Predecessors link.

  • Program Management, Activity Definitions, Project Activities, Project Activities

    Click the Create Predecessors icon.

    Click the Review Predecessors icon.

Select the project, activity, and dependency type to define the dependency.

Click to jump to top of pageClick to jump to parent topicSpecify Activity Predecessors

Access the Activity Predecessors page.

The project, activity, and descriptions come from the successor activity for which you are defining this dependency.

Predecessor Project ID

Enter the project ID that contains the predecessor activity. The system defaults the project ID from the project from which you are entering this dependency. You can select a different project to create a cross-project dependency.

Predecessor Activity

Enter the activity ID for the predecessor activity.

Dependency Type

Enter the dependency type from these options:

  • End-to-End: The system sets the successor activity's end date to the predecessor activity's end date plus or minus and lag or lead time.

  • End-to-Start: The system sets the start date of the successor activity to the next working day after the predecessor's end date plus or minus any lag or lead time.

  • Start-to-End: The system sets the successor activity's end date to the predecessor activity's start date plus or minus and lag or lead time.

  • Start-to-Start: The system sets the start date of the successor activity to the predecessor's start date plus or minus and lead or lead time.

Lag (Days)

Enter a number to determine the lead or lag time in whole work days between the dependency. Enter a positive number to specify lag time. Enter a negative number to specify lead time.

Click to jump to parent topicSpecifying Activity Constraints

This section discusses how to specify activity constraints.

Click to jump to top of pageClick to jump to parent topicPage Used to Specify Activity Constraints

Page Name

Object Name

Navigation

Usage

Activity Definitions - General Information

PROJ_ACT_DESCR

Program Management, Activity Definitions, General Information, General Information

Create an activity, specify a constraint, and assign the activity to a project.

Click to jump to top of pageClick to jump to parent topicSpecifying Activity Constraints

Access the Activity Definitions - General Information page.

The Activity Definitions - General Information page is documented in the PeopleSoft Project Costing PeopleBook. The fields documented here are specific to constraints.

Constraint Type

Select the type of constraint from these options:

  • blank: Leave the field blank if you do not want to define a constraint for this activity.

  • As Late As Possible: This option is not available for summary activities.

  • As Soon As Possible

  • End No Earlier Than: This option is not available for summary activities.

  • End No Later Than

  • Must End On: This option is not available for summary activities.

  • Must Start On: This option is not available for summary activities.

  • Start No Earlier Than

  • Start No Later Than: This option is not available for summary activities.

Constraint Date

Enter the date for the constraint. This field appears only if you select one of these constraint types:

  • End No Earlier Than

  • End No Later Than

  • Must End On

  • Must Start On

  • Start No Earlier Than

  • Start No Later Than

See Also

Entering Activity General Information