[Openid-specs-fapi] "SHALL" vs. "MUST"

Preibisch, Sascha H Sascha.Preibisch at ca.com
Wed Dec 7 00:57:19 UTC 2016

Thanks Brian and Mike!

I checked RFC https://www.ietf.org/rfc/rfc2119.txt, and, as Mike said, according to that MUST and SHALL are exactly the same.

My feeling tells me though they are understood as you said, Brian.

With that it is just important to always reference the RFC 2119 when using the terms:

1. MUST   This word, or the terms "REQUIRED" or "SHALL", mean that the
   definition is an absolute requirement of the specification.

Now I feel better.


From: Brian Costello <BCostello at yodlee.com<mailto:BCostello at yodlee.com>>
Date: Tuesday, December 6, 2016 at 4:03 PM
To: Sascha Preibisch <sascha.preibisch at ca.com<mailto:sascha.preibisch at ca.com>>, Financial API Working Group List <openid-specs-fapi at lists.openid.net<mailto:openid-specs-fapi at lists.openid.net>>
Subject: RE: "SHALL" vs. "MUST"

I ran this by a couple of contract lawyers I trust.

They use "shall" to create ambiguity because it can mean "may" or "will". "Must" has no ambiguity. It also connects with rights and responsibilities. "Must" is a responsibility and "shall" is a right, which is why there can be ambiguity. One doesn't have to do the "shall" thing, even if there a right to do so.

It also really hinges on jurisdiction and how they have interpreted shall.


-----Original Message-----
From: Openid-specs-fapi [mailto:openid-specs-fapi-bounces at lists.openid.net] On Behalf Of Preibisch, Sascha H via Openid-specs-fapi
Sent: Tuesday, December 06, 2016 9:01 AM
To: Financial API Working Group List <openid-specs-fapi at lists.openid.net<mailto:openid-specs-fapi at lists.openid.net>>
Subject: [Openid-specs-fapi] "SHALL" vs. "MUST"

Hi all!

I just had a chat with a colleague and he said:

- you know Sascha, I hate to read 'shall' in specifications. I then never know if a product supports it

So my question is: what is the reason for using "shall" instead of "must"?


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