[Esip-preserve] On Earth Science Data File Uniqueness

[Curt Tilmes]

On 02/09/11 11:50, Lynnes, Christopher S. (GSFC-6102) wrote:
> I thought UUID was designed to answer only the question: are data
> items A and B bitwise-identical?

Absolutely not.  You're thinking of digital signatures or hashes such
as MD5 or SHA-1 which can be used to verify file content
integrity/fixity.

UUID is just a way to make an identifier that is globally unique
forever [1] and easily recognizable as a UUID.

> If they have the same UUID, then the answer is yes.  If they have
> different UUIDs, then the answer is that there is no evidence to say
> that they are bitwise identical.

They can be assigned to the object arbitrarily without regard to
content.

For example, here is one: 0cdf7b24-f374-419e-8cce-9758432cfdfa
It's totally unique in the world (go ahead, google it)

You could assign it to some chunk of data (some object) as you will.
Of course, if two of us tried to assign it to different data, we'd
have a problem, but we wouldn't do that.

Curt

[1] Ok, ok.  Practically globally unique forever, like really really
likely to be globally unique forever.  Almost perfect.  Like it is
"Hitchhiker's Guide to the Galaxy" improbable that you would get a
conflict.