Systematic uncertainties and RDataFrame:

• People want to be able to vary the computation graph in an easy way
• Seems to be a bit counter-intuitive to define a full graph for each variation

Collections and RDataFrame:

• TTree::Draw can operate on collections more seamlessly than current dataframe, e.g. explosion of two arrays. Can we reach a feature set similar to this?
  https://root.cern.ch/doc/master/classTTree.html#a73450649dc6e54b5b94516c468523e45
• Example: Plot something which is not a column, but an expression in a column, e.g. "muons[0]"?
• In RDF, these things have to be written down a bit more explicitly
• RVec functions are a way out, but maybe not sufficiently advertised / missing features, specifically operating on multiple collections like explosion/join

Domain-specific language:

• Not our immediate goal, but probably worth to make RDF accessible enough to facilitate this if people want to do this