Sure that it would add value to have the speaker's note but I found it actually helpful. The duck typing part interested me as it seems a good fit for the prob

Sure that it would add value to have the speaker's note but I found it actually helpful. The duck typing part interested me as it seems a good fit for the problem I'm trying to solve: I have to work with a bunch of objects retrieved from a key/value store, some keys are simple attribute but others define the object class, required keys, value constraints, etc. while keeping the code generic. Are there any good references on this ?