Hello Andy,
My implementation of version 4 (random-number-based) guids may not be unique in space and time. It is based on boost::mt19937 to generate random numbers and it is seeded with std::time(0). Cryptographic-quality random numbers would reduce the probability of repeated values.
Using version 5 (name-based) guid can be used to ensure that guids are unique in space (guids generated on several computers at the same time) and time. Generate a guid for each computer as the namespace_guid and pass a counter as the name to the create function.
Because creating uuid v5 seams too expensive for me I could let one special computer (in my project == master) generate guids (unique in space). So I've make a decision wether uuid v4 or v1 should be used in order to be uinque in time?! Or do you have another suggestion? Regards,Oliver