The Target Platform State View shows the current status of the resolver state in PDE.
The view is available under Window > Show View > Other... > Plug-in Development > Target Platform State .
Any plug-ins displayed with a red X are currently unresolved. Expand an unresolved plug-in to reveal the unsatisfied constraints which result in the unresolved status.
When you open the children of a resolved plug-in, you will see its dependencies separated into imported packages and required bundles. The child of each dependency is the plug-in which satisfies the particular dependency.