  Executable scientific papers contain not just layouted text for reading. They
contain, or link to, machine-comprehensible representations of the scientific
findings or experiments they describe. Client-side players can thus enable
readers to "check, manipulate and explore the result space". We have realized
executable papers in the STEM domain with the Planetary system. Semantic
annotations associate the papers with a content commons holding the background
ontology, the annotations are exposed as Linked Data, and a frontend player
application hooks modular interactive services into the semantic annotations.
