ISO = "International Organization for Standardization"
As in the general case of ISO's, ISO's for Weld metallurgical qualification originate in Europe. These documents are known as "Standards".
The North-American Weld metallurgical qualifications are more frequently known as "Codes" (but are Standards) originating from respected Industry bodies like the American Welding Society (AWS), the American Society of Mechanical Engineers (ASME), the American Petroleum Institute (API), etc.
ISO's tend to be less wordy so are smaller, but are changed or replaced frequently. They do not contain explanation of the top-level objective which must be achieved or catch-all general statements to ensure no specific issues can "leak past" the Standard by reason of not being individually identified.
The North-American Codes tend to be very large, with explanations of why they exist and what overall must be achieved (good catch-alls for any unforeseen issues which inevitably occur); but have very long continuous gestations over many decades, so they are easy and useful to learn by reason of their durability and constancy of the thread of logic running through them. The North-American Codes tend to be more pragmatic than the ISO's, with a very strong "flavour" of how the job can be done in a practical way.
(R. Smith, 06Oct2015)