Table of Contents
Isn't DCI just another software design pattern?
As you may have guessed, no. 
Organization
The difference between DCI and traditional object orientation is that the latter organizes concepts at the extremes either of a rather free-form network structure or of a single, punitive hierarchy of forms. The DCI paradigm strives to express a network model rather than a hierarchy, but provides disciplines for intentionality of form rather than leaving it to emergence.1)
More information about the network model differences in this FAQ entry
Execution model
DCI has a different execution model than the traditional OO model. The RoleMethods in a Context are only available to a Role-playing object during the Context execution, nowhere else.
The DCI Contexts live on a stack and their Roles can carry Role-specific behavior (RoleMethods)2)