I thought these systems were all accredited and tested - therefore they should operate in one defined way?
They're tested and accredited, yes, but it's not like RDG get a full code listing and go through all your logic with a fine tooth comb.
There's a big list of tests which must pass for a TIS to be accredited, but it doesn't mean they cover every single potential eventuality or every single potential combination of industry data. Maybe a new requirement will be added after this! The fact that the data has been rolled back
suggests that RDG understand the data causes and issue, and that the TISes affected aren't at-fault for behaving in the way they did (no matter which way that was).
The spec in question is public, so you can go and read it if you'd like:
https://www.rspaccreditation.org/do...Data+Feed+Interface+Specification.pdf&ID=1301
That, and the fact that RDG managed to screw up and release the data, implies the process is shoddy and uncontrolled. Really not good enough from an industry that treats its paying customers so badly.
Not only that, but the first rollback initially failed and resulted in fares data being provided to TISes about 10 or 11am instead of overnight as normal, without the needed fix. At the end of the day, though, it's humans editing this data (through a GUI thankfully), and humans can make mistakes.