[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: My Daily Diary of Validation
> > Hi Folks, Hi Roger. Are these really validation? Or are they verification (I know it has other meanings too)? I think there is a difference. The difference: invalidity is a symptom of system failure or error; negative verification means the system is working OK, it just produces a result you may not want or may be exceptional. > I wake up. Before entering the bathroom I validate that it is not > occupied. You would validate that the bathroom is either empty or busy: has the roof fallen in for example. Those are its allowed states. You verify that the bathroom is empty. > I walk down stairs and get a can of V-8 juice from the 'frig. Before I > open it I validate that the expiration date hasn't passed. ditto > Tonight there's a nice movie on TV. I set the VCR to record the show. I > validate that it is programmed correctly. Validation would say "have I entered something that makes sense" while verification would be "have I entered the actual time I wanted." > I'm short on groceries. I write a list of items I need. I go to the store > and shop. When finished, I validate the items in my shopping cart against > the items on my grocery list. I'll allow this as validation. > I pay for the groceries by check. I validate that the total purchase > amount is less than the balance in my checking account. Verification. Overspending is not a system error. > Time for work. I start my car. I validate that the amount of fuel is > greater than 1/8 tank (I have a rule that I get gas when the tank gets to > 1/8 or less). Verification. > As I drive I validate that my speed doesn't exceed the posted limit. Verification > When entering the highway I validate that I am entering it in the > correct direction. Verification, unless we are robots. > When exiting the highway I validate that I am taking the correct exit. Verification, unless we are guided by GPS. > Before proceeding through the intersection I validate that the traffic > signal is green. Verification. > Before turning I validate there are no oncoming cars. Verification. > I arrive at the subway station. I need cash for the subway train. At the > ATM I validate that I got the correct amount. Validation. > Before getting on the subway train I validate that the train is for the > correct line. Verification. > Before getting off the subway I validate that I am at the correct > station. Verify, unless you have a guide dog perhaps. > I arrive at the office. The guard validates me and my badge. Verify. > I need to FAX a document. I validate that the original is face down as > required by the machine. I validate that the destination fax number is > correct. Verify. > I check my inter-office mail. I validate that I am retrieving the mail > from the correct bin. I don't understand what a bin is. > I need to send an email message. I validate that the recipient list is > correct. Verify. > Time to go home. I need to first pick up a prescription. I validate that > it is correct (it is mine and the medicine is the right one). Validate. > Time for bed. I validate that the alarm is on and set to the correct wake > up time. Verify. The practical difference is that validation and verification result in completely different kinds of responses: verification errors are user issues; validity errors are system issues. Conventional schema languages don't allow any way of representing the difference (Schematron they can be modelled as phases, or just using the @roles attribute.) They mix everything up. The conventional Fail|error|warning|caution|note kinds of error log messages show that there are these kinds of demarcations. It is a separation of concerns. Cheers Rick Jelliffe
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