Axiom is  a general purpose Computer Algebra system. It is useful for research and development of mathematical algorithms. It defines a strongly typed, mathematically correct type hierarchy. It has a programming language and a built-in compiler.
Polybutylene is simply a type of plumbing material that was manufactured between the late 70's and early 90's. It is thought that it was installed in over 6 million homes during that time period.
The previous three plastic pipe variants are all rigid whereas PB (polybutylene) and PE (polyethylene) are flexible; the former being rigid and used for the same purposes as CPVC and the latter being low cost. Both of these types are not joined with solvents but are instead formed with mechanical and clamped couplings.