[TYPO3-mvc] Where are data definitios are located e.g. \TYPO3\CMS\Core\Resource\ResourceInterface

[Hans-Georg Althoff]

I am not able to find the definition of the data structures.
For example 
setOriginalResource(\TYPO3\CMS\Core\Resource\ResourceInterface $originalResource)

This function requires a parameter from type 
\TYPO3\CMS\Core\Resource\ResourceInterface

But I am to stupid to find the place, where the definition is defid.

Thanks for helping me.