Message.sequence: wording mistake?

[omegacoleman]

Description

Hi, I'm trying to implement a mcap-compatible bag facility for a self-driving system. While I appreciate your hard work, I suspect a wording mistake in spec/index.md:

### Message (op=0x05)

...

| 4     | sequence     | uint32    | Optional message counter assigned by publisher. If not assigned by publisher, must be recorded by the recorder. |

It says the sequence is optional, but "If not assigned by publisher, must be recorded by the recorder.", wouldn't that contradict with 'optional'?

It seems like a wording mistake of "If assigned by publisher, must be recorded by the recorder."

[foxhubber]

Internal tracking ticket: FG-4352

[omegacoleman]

I proposed a fix in #927

[jtbandes]

Hi, I believe this is not really a wording mistake per se... it's trying to say that since the field is required, if the publisher does not provide a sequence number then the recorder will have to come up with one. However, I agree that the wording is unclear. We will discuss internally.

[omegacoleman]

Hi, I believe this is not really a wording mistake per se... it's trying to say that since the field is required, if the publisher does not provide a sequence number then the recorder will have to come up with one.

Thanks for clarifying that out, this is important to me.

However, I agree that the wording is unclear. We will discuss internally.

I'll leave this open for a while, since that would still contradict with the Optional part.

My suggestions would be:

• if the recorder MUST come up with a sequence, then the field is not optional, it's mandatory
• Add the the recorder will have to come up with one part to the specs to let everybody know

[wkalt]

@omegacoleman I have raised a PR here to propose some new wording if you're interested: #938