4. Model

The following table lists the most important model classes for populating a Gantt chart with data.

Activities represent objects that will be displayed below the timeline in the graphics view of the Gantt chart control. Activities can be added to a specific layer on a row.
An activity reference is used to precisely identify the location of an activity where the location is a combination of row, layer, and the activity itself.
An activity link can be used to express a dependency between two activities.
Activity repositories are used by rows to store and lookup activities.
A (model) row object is used to store the activities found on a (visual) row of the Gantt chart.
Layers are used to create groups of activities.
A lines manager is used to control the layout of (inner) lines inside a row.
Each row and each inner line of a row are associated with a layout. The layout influences several aspects during rendering and editing of activities. Additionally several of the system layers used for drawing the row background also utilize the layout information. 
A calendar is an extension of an activity repository with the addition of a name and a visibility property.