This article outlines everything you need to know to work with logic ties in ALICE:

• Hard Logic vs. Soft Logic
• Precedence Relationships in ALICE
• Detect and Resolve Circular Dependency Cycles 
• How to Add/Remove Relationships in bulk
• How to add Predecessors and Successors
• How to Review Relationship Details

Hard Logic vs. Soft Logic

There are two types of logic ties: hard logic and soft logic (or preferential logic).

Hard logic, also known as mandatory dependencies, is based on physical or logical relationships that require one activity to be completed before another can begin. For example, excavation must be complete before drainage pipes can be installed. Hard logic is often based on contractually required items or physical limitations.

Soft logic, also known as preferential logic or discretionary dependencies, is based on best practices, preferences, resource availability, or your expert judgment. Soft logic allows for more flexibility, and the order of activities can be adjusted based on needs and priorities. For example, paving lane 1 before lane 2, or lane 2 before lane 1, or paving both at the same time are 3 different soft logic dependencies.

In ALICE, upon import of your schedule, all logic comes in as "hard logic." Using the different functionalities within ALICE, select soft logic can be removed to allow ALICE the flexibility to explore different options.

Precedence Relationships in ALICE

The dependencies between activities in a schedule are defined by precedence relationships. 
ALICE supports the 4 standard precedence types most commonly used in scheduling software: FS, SS, FF, and SF.

In addition, ALICE supports more strict precedence definitions that allow users an increased degree of control in defining dependencies. We call these ALICE custom precedence types. Read on to learn more.

Standard Precedence Types

The most common types of dependencies are the following four (4):

1. Finish-To-Start (FS): Activity B can begin after A is finished.

In other words: Finish A ≤ Start B

2. Start-To-Start (SS): Activity B can start at the same time as A.

In other words: Start A ≤ Start B

3. Finish-To-Finish (FF): Activity B can finish at the same time as A.

In other words: Finish A ≤ Finish B

4. Start-To-Finish (SF): Activity B can finish at the same time as A starts.

In other words: Start A ≤ Finish B

ALICE Custom Precedence Types

In ALICE, the above relationship types are extended by adding the "At" type, which imposes the type of dependency. Therefore, the additional precedency types are transformed to:

1. Finish - At - Start (FaS): Activity B must begin after A is finished.

Or: Finish A = Start B

2. Start - At - Start (SaS): Activity B must start at the same time as A.

Or: Start A = Start B

3. Finish - At - Finish (FaF): Activity B must finish at the same time as A finishes.

Or: Finish A = Finish B

4. Start - At - Finish (SaF): Activity B must finish at the same time as A starts.

Or: Start A = Finish B

Be mindful when using the custom precedence types, as they impose a very strict relationship between activities, which can render your schedule infeasible. 

Detect and Resolve Circular Dependency Cycles 

Cycles in construction schedules can occur at any point during project planning. For example, when starting the schedule from scratch and assigning task dependencies, or during program rescheduling. 

ALICE automatically detects and visually displays the total number of cycles and groups tasks involved in each cycle. Additionally, the platform checks in real-time if the user is trying to create a cycle and notifies the user if one is detected. 

Navigate through the player for an interactive walk-through to see cycle detection in action:

How to Add/Remove Relationships in Bulk

To add and remove logic ties in bulk, use the Add Contained Relationships or the Remove Relationships feature. 

For a more hands-on experience, navigate through the player for an interactive walk-through, or if you prefer a more detailed approach, scroll down for a step-by-step guide:

Remove Relationships 

1. On the Task List on the Plan page, bulk select the tasks for which you want to remove the common relationships.
   • Check the box of the WBS summary to select all tasks within that WBS
2. Right click and select Remove Relationships from the menu
   1. Select Remove contained relationships to remove only relationships between selected tasks
   2. Select Remove uncontained relationships to remove ALL relationships tied selected those tasks
3. In the subsequent window, you can see the relationships and manually select or deselect if you wish to remove some but not all relationships.
4. Click Remove to complete the action.

Add Contained Relationships:

1. On the Task List on the Plan page, bulk select the tasks you want to add to the common relationships.
   • Check the box of the WBS summary to select all tasks within that WBS
2. Rick-click and select Add Contained Relationships 
3. In the appeared window, select the category of relationships to add:
   • Predecessor
   • Successor
4. Check the task's boxes to add relationships to the initially selected tasks
5. Define the relationship type and lag: FS, SS, FF, SF, FaS, SaS, FaF, SaF 
6. Click Add Relationships to complete the action.

How to assign Predecessors and Successors

Predecessors and successors can be added or modified via the assignment panel or by drawing lines on the Gantt view or within the 2D canvas.


image of the assignment panel, the header will indicate predecessor or successor

Open the Assignment Panel
The assignment panel from the task list view in the following ways:

1. Click on the task to open the relationship details panel and click Edit Predecessor or Edit Successor, or
2. Right-click the task, select edit/assign, and select predecessor or successor, or
3. Double-click in the predecessor or successor column of the task list

Assign Predecessors & Successors from the assignment panel:

1. Select one or multiple tasks or milestones by checking the boxes
2. Select the Relationship Type and define the duration of the Lag 
3. Click Save to complete the action
4. Click Re-Schedule to recalculate the schedule with new changes

Assign Predecessors & Successors from the Gantt view:

1. On the timeline view on the Plan page, hover the mouse cursor on the activity bar to highlight the connection dots 
2. Click and hold the circle and drag it to connect to the beginning or end of the required task. 
   1. ALICE will assume relationship type based on what you select. If you draw a line from the end of one task to the beginning of another, a Finish to Start relationship will be defined. If you draw from the start of one task to the start of another, a Start to Start relationship will be defined. If the ends of two tasks are connected a Finish to Finish relationship will be defined.
3. Once connected, you may click on the links to modify details such as Relationship Type and define the duration Lag.
4. Click X to close the assignment window
5. Click Re-Schedule to recalculate the schedule with new changes

Using the Task Relationship Details Panel

The Task Relationship Details Panel lets you view and modify logic details for each activity. For a more hands-on experience, navigate through the player for an interactive walk-through, or if you prefer a more detailed approach, scroll down for a step-by-step guide:

1. On the Task List in either the Plan or Analyze page, select a task to activate the Task Relationship Details Panel
   • Once selected, the panel will appear at the bottom of the page
   • From the Plan page, you can edit task relationships. From the Analyze page, they can only be reviewed.
2. The Task Relationship Details Panel shows: 
   • Free and Total Float in workdays
   • Predecessors and Successors 
   • Driving and Critical tasks
   • Detail: why a given task is listed as a predecessor or successor
     • Precedence is the standard relationship type defined by users such as FS, SS, FF, and SF.
     • Resource is the resource link generated by ALICE based on resource assignment. This applies to crews, equipment, materials, and milestones.
   • Time Gap is a calculated value that represents the number of workdays between tasks depending on the type of relationship and amount of lag.
   • Go to the previous (predecessors) or next (successor) of the selected task by clicking on that task in the panel.
3. If accessing the Task Relationship Details panel from the Plan page, users can edit or remove predecessors or successors
   1. Click the red trash can icon to remove relationships
   2. Click the edit button to modify relationships, including changing relationship type or lag.