User needs, intended use, etc

[smtka]

Hi, again, guys, your replies are invaluable and i am deeply grateful

Yodon, please, just one more clarification, to make sure i understood correctly (if i did, then your answer would be closer to my assumption (b), I assume ):

- i don't need to state requirements for each item's interface, i just need to state sys/sw requirements for the whole app
- developers write the interface requirements specification (you said ICD, which, by the examples i've gathered contains both the requirements for each interface and definitions of how these requirements are going to be fulfilled)

correct?

Bottom line, my worry was if was i going to get punished in the audit for not writing requirements for each software item/its interfaces before development starts
(except for SOUP, i understand that, for SOUP items i have to write item-level performance/safety requirements, but for other types of software items, i do not, correct?)

again, thanks a lot, you're saviors

 

[yodon]

Let me try to clarify. If a software item has an interface with another software item / system or hardware, you should have a high level requirement for that interface. Details of the interface, though, can be pushed down to the specification level. So yes, you *should* have requirements for interfaces and 62304 indicates just that:

5.5.2 c) interfaces between the SOFTWARE SYSTEM and other SYSTEMS;

At the software / system requirements level, we just establish that there is an interface (our system talks to this thing). At the ICD level, we provide the details (packet construction, rates, bounds, etc.).

 

[smtka]

Ah, I'm really sorry for the confusion; I will also try and restate my question more clearly:

imagine my system consists of 5 Items, item 1 is user-facing (UI), and item 5 is talking to some other system.
Let's imagine the communication between them goes only:

user -> 1 -> 2 -> 3 -> 4 -> 5 -> external system
and
external system -> 5 -> 4 ->3 -> 2 -> 1 -> user

In this case, do I have to state requirements for interfaces of ALL items or just items 1 and 5?
I suppose I have to state requirements for interfaces of 1 and 5, and all other interfaces' definitions get written down during development in the ICD.

Also, i suppose, if item 3 was soup, then I'd have to write requirements for 1, 3 and 5.

Again, sorry for the confusion and thanks for your patience

 

[yodon]

Without knowing more, that probably should be acceptable. Depending on the SOUP, you may or may not need "interface" requirements. If it's just library calls, probably not; if it's an external system, probably so.