which open-source frameworks exist for fact-extraction
I don't know many examples but I'm aware of at least one such tool, specialized for the medical domain: SemRep


  SemRep is a UMLS-based program that extracts three-part propositions,
  called semantic predications, from sentences in biomedical text.
  Predications consist of a subject argument, an object argument, and
  the relation that binds them. For example, from the sentence in (1),
  SemRep extracts the predications in (2).
  
  1.We used hemofiltration to treat a patient with digoxin overdose that was complicated by refractory hyperkalemia.
  
  
  Hemofiltration-TREATS-Patients,
  Digoxin overdose-PROCESS_OF-Patients,
  hyperkalemia-COMPLICATES-Digoxin overdose,
  Hemofiltration-TREATS(INFER)-Digoxin overdose
  


In general, this is closely related to the problem of semantic role labeling:


  semantic role labeling (also called shallow semantic parsing) is the process that assigns labels to words or phrases in a sentence that indicate their semantic role in the sentence, such as that of an agent, goal, or result.


Apparently there are some implementations available: https://framenet.icsi.berkeley.edu/fndrupal/ASRL