Related functional and non functional requirements

[Graham_Labdon]

Hi all

I am wondering if I should show a relationship between some of my non functional requirements and my functional requirements; and if so what sort of relationship it is.

For example I have a functional requirement that reads -

"The system shall make a list of the last 10 occasions when power to the machine was lost available to a technical user"

I have written a use case and used a realizes relationship showing that the use case realizes the requirement.

I have a non functional requirement that states

"The system shall log when a power loss is detected. The system shall store the time and date for each power loss. There shall be a maximum of 10 power losses stored"

There is obviously a link between the two - how do I show this ?

Graham

[«Midnight»]

What is the "obvious" link?

[Graham_Labdon]

In order for the system to fufill the functional req it must implement the non functional requirement.

The system has to store the data in oreder for the user to view it

[«Midnight»]

My point is that, in this case, if the connection is glaringly obvious you don't need to point it out. If the connection is difficult to express (i.e. so trivial that you cannot word it meaningfully) then there's no distinction between the two 'requirements' at all. So...

I don't think you'd create a requirement or use case just to store data.

If there is a need for the system keeps a specific record of session failures fine, but think this through. It seems that you've only got one requirement: the system must track recent session failures and provide a list of these for the user. This is a single requirement. Write it as appropriate.

You might have a (very detailed) use case to show developers that users can access this data and how you expect this to work, but remember that this is a pretty limited (i.e. low-level) scenario. If there's nothing else to add I think you could just write the whole thing into a single requirement statement.

Call it functional or non functional as you wish, perhaps based on the 'voice' you prefer to write it in; just pick one.

[Graham_Labdon]

Thanks

What I think I'll do is have one combined requirement and one use case to cover the high level user interaction with the system

Does this sound about right?

[«Midnight»]

Sure. Just keep in mind that it's a pretty simple use case from the sounds of things. [Open a menu; observe it.] You might want to just put this in the requirement itself.

Exception: If you are describing all situations where a user interacts with the system via the menu then you might want to include this in that set of use cases, even if it is trivial.