The IntelliGantt App for SharePoint 2013 introduces a huge improvement over its predecessor, the IntelliGantt Web Part for SharePoint 2010: Scheduling! Now you can have real duration and work values in your project plans, though we still try to keep things simple. We've created special in-place editors to handle these duration and work fields so that it combines the number and the unit of measurement together. In other words, a number field and a minute, hour, day, Week, Month, Year dropdown.
As your schedule is updated, IntelliGantt will update these fields for you as well. You can change the duration to make a task longer or shorter. Or drag the endpoint of a task in the gantt chart to see durations change. Summary tasks will use the least start and most finish dates to compute their duration. A kind of 'psuedo rollup'.
Work fields are in fact rolled up as a summation. The top level work field in your view is the sum of all work values in your view, so you can quickly see how much work a particular view of tasks contains. Also, the Work field number portion isn't editable, just the units. Instead, Work is computed to be (Resources * Duration). Each Work field starts out as 0 value. Add an assignment and you will see the Work field match the task's duration. Add another assignment and the Work field will be double the duration, and so on. Yes, Level of Effort is in the works, and that will be another blog post coming soon!
Of course, the basic SharePoint task list doesn't come with a Duration or Work field, so how do we add them? Simple, create a 'Single line of text' field named 'Duration' and a 'Single line of text' field named 'Work'. IntelliGantt will treat these as reserved words and, even though they are really text fields in SharePoint, display and interact with them as Duration and Work.