[klyrs]

I've been told by at least two patent lawyers that "and" and "or" are essentially synonymous. If you want to specify "xor" it's good to say "either a foo or a bar but not both a foo and a bar". But why be so specific? "One or both of a foo and a bar" could have broader coverage, presents the opportunity to mislead the competition, and (IANAL) seems to be just as sound even if "both" is actually infeasible.

[pnw_hazor]

Claim language such as "determining foo based on x, y, and y" is leaving the door open for a judge to interpret the limitation as requiring "x, y, AND z"

Better language (assuming it is how the thing works) is: "determining foo based on one or more of x, y, or z"

The strange language in claims (and patents in general) is a response to litigation. Good patent prosecutors (the patent attorneys that draft patents) watch court cases and adjust their claim language accordingly.

Good patent litigators try to tear up or dissect the claim language (as well as everything else...). So patent prosecutors should draft with an eye toward litigation and include language that inoculates a patent from common or obvious attacks.