Task Dependencies
After you build your project schedule and add associated tasks, you can set up relationships between the tasks. These relationships are also known as dependencies.
You can structure dependencies logically, such that certain tasks rely on the start or completion of other tasks before they can be accomplished. Establishing task dependencies makes it possible to keep close track of your project's critical path and overall schedule and to identify potential schedule risks.
Schedule Tab of Project Planning
Use the Schedule tab of Project Planning to set up dependencies between tasks. This tab provides an interactive Gantt chart that displays a timeline for each task on your project's Work Breakdown Structure (WBS). This provides a quick way to see, and work with, the project schedule, tasks, relationships between the tasks, and critical path.
Predecessor and Successor Tasks
- Predecessor — The predecessor task determines when another task will start or finish based on the established relationship.
- Successor — The successor task's start or finish date is determined by a relationship established with another task.
The most common relationship is when the predecessor task's finish date determines the successor task's start date. This, along with the other relationships that you can establish between tasks, is detailed below in the Types of Dependency Relationships section.
You can only create dependent relationships for items that are at the lowest level of the Work Breakdown Structure (WBS). These are the lowest child-level, or lowest leaf nodes, of the WBS. They display under a parent level but have no WBS children of their own. For the purpose of task dependencies, these are referred to as "tasks" but they may be phases, tasks, labor codes, or lower indent levels, depending on the WBS structure.
When you select predecessor or successor for your dependent relationship, it is also possible to select a group of tasks (black bracket on Gantt chart). Because the items must be at the lowest child-level, the dependencies are then created for the individual tasks within the group.
Types of Dependency Relationships
Vision supports four types of task dependency relationships:
- Finish to Start — The successor task cannot begin until the predecessor task is complete. This is the most common relationship used when planning projects. You can also use the right-click shortcut menu to select Set FS Relationship to build this type of relationship between two or more tasks.
- Start to Start — The successor task cannot begin until the predecessor task begins. You can also use the right-click shortcut menu to select Set SS Relationship to build this type of relationship between two or more tasks.
- Finish to Finish — The successor task cannot be completed until the predecessor task is completed. You can also use the right-click shortcut menu to select Set FF Relationship to build this type of relationship between two or more tasks.
- Start to Finish — The successor task cannot be completed until the predecessor task has begun. You can also use the right-click shortcut menu to select Set SF Relationship to build this type of relationship between two or more tasks.
You can create dependent relationships between tasks on the Schedule tab by using any of the following methods:
- Edit Dependency Dialog Box — To display this dialog box, double-click a task bar, or right-click a task bar to open the shortcut menu and then select Edit Dependency. Select the predecessor task and then use the Relationship field to select a relationship for the predecessor and successor tasks. You can also enter the number of days and specify the direction for defining the lag or lead time for the dependency.
- Right-click menu — On the interactive Gantt chart, select two or more tasks (or groups of tasks) for which you want to create a relationship. The first item (a group or task) selected will be the predecessor(s) to all subsequent tasks selected. The predecessor task bar turns blue when selected, while all subsequent task bars selected remain green. This is a visual way to identify which tasks will be predecessors and which will be successors when creating the dependency. When you right-click to open the shortcut menu and select Set FS Relationship,Set SS Relationship, Set FF Relationship, or Set SF Relationship from the shortcut menu, the respective relationship is applied.
In each of these cases, an arrow from the predecessor to the successor displays between the tasks. If you change the dates for a predecessor task, all successor tasks change accordingly. Updates on the Schedule tab automatically update corresponding information on the Labor, Expense, Consultant, and Unit Planning tabs.
Task Dates
The Start and Finish dates of the parent WBS level that displays on the Planning tabs can begin earlier than the earliest start date of its child WBS level task or end later than the latest end date of the last child WBS level task. However, when using the Schedule tab of Project Planning to schedule task dependencies, the parent WBS start and end dates must align with the start and end dates of the child WBS level tasks. If there is a discrepancy, Vision requires that you collapse the parent start and end dates on the Planning tabs before you can use the Schedule tab. Collapsing the dates means that the parent WBS level start and/or end dates will be adjusted to match the start and/or end of the child dates.
Task Duration and Spreading Data
The duration of the task is the span of time between the start and finish dates. If you resize the task bars on the Gantt chart to change the start dates, finish dates, or both, Vision recalculates and spreads the task's data evenly on all Planning tabs. For example, if the task has 44 hours of work over the duration of one week and you resize the task bar to change the duration to two weeks, Vision automatically changes the task's dates accordingly and spreads the 44 hours evenly over two weeks' time.
Whenever you resize a task bar to change its duration, Vision prompts you to confirm the change and the resulting spread of the data. The confirmation dialog box includes a check box that you can select to turn off the Re-spread Data When Resize Gantt Bar prompt. When you select this option, Vision will automatically re-spread the data on the Labor, Expenses, and Consultants Planning tabs each time that you change the duration of a task bar on the Schedule tab and will no longer prompt you with the confirmation dialog box. You can toggle this feature on and off for each plan with the Re-Spread Data When Re-Size Gantt Bar option on the Options menu.
Dependent Task Indicator on the Labor Tab
After task dependencies are created on the Schedule tab, the Labor tab of Project Planning displays a
in the Dependency column on the task row to indicate that the task has a dependent relationship. You can right-click the row and select
Dependencies to open a dialog box that displays the dependent predecessor or successor tasks for the current row. Refer to this information when building task dependencies or before changing dates for one or more task rows.
Your system administrator configures the Dependency column to display in .