Developer Forum

Hi all,

what experiences do you have concerning non-functional requirements of
embedded systems?
Do you have examples to point these experiences out?

For a systematic representation I invite you to share your knowledge
on http://www.yqcomputer.com/ .

Thank you,
Julian Wild

I don't remember ever being asked to develop systems that are
non-functional. If I had it would have made my life a lot easier and a
considerable saving on the BOM.

Peter

On Sep 25, 9:08 am, "Peter *** erson"



I think he's referring to technical requirements as opposed to
functional requirements (in a project management sense of both terms).
However the web site to which he pointed is so broken that I can't
really be sure.

Hi,
that's right, it is about non-functional requirements as they are
known in the software-engineering.

Sorry that the server sometimes is not responding, but the link URL is
correct.

Julian

>> what experiences do you have concerning non-functional requirements of

It's true that "non-functional requirements" can lead to a non-functional
system but the OP's question is about requirements that don't *function* as
a requirements should. The litmus test for a functional requirement is Can
it be measured? If it can't be measured, you can't tell if the requirement
has been met. A more useful way to express a functional requirement is that
there can be one and only one interpretation.

Examples:

Non-functional - user friendly
Functional - user can edit data value XXX from the root menu with three or
fewer button presses

Non-functional - fast response
Functional - response screen is painted within XXX milliseconds of external
event YYY

Writing useful requirements is a skill that one learns over many years. And
I've even seen experts occasionally write non-useful requirements. But
that's where the grey area comes in. A useful requirement is as much a
function of the local departmental vernacular as it is about the writer's
native language. IOW, a useful requirement is useful only as long as
everyone who uses it interprets it the same way. The risk is you sometimes
never know who will be reading your requirements.

JJS

OTOH, and for example, reducing "user friendliness" to component metrics,
then designing to the metrics, can result in a system that's pretty darn
user hostile. I don't think that a few such guidelines in a functional
specification are off base, as long as they're delineated as such.

--
Tim Wescott
Control systems and communications consulting
http://www.yqcomputer.com/

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.yqcomputer.com/

The rules are very simple:

1. The customer provides the functional requirements.

2. Engineering generates technical requirements from the functional
requirements.


Every link I tried was 404'ing.

As one who has dealt with understanding and writing "Functional
Requirements" and "Non-functional Requirements" I can assure you all that
they can both be measured for compliance. Larwe mentioned also "Technical
Requirements" which could be a mixture of the two.

The Functional Requirements are keyed to the tasks that the equipment must
perform and will include event timings, what it must do, how errors are
expected to be managed and even the Safety Requirements.

The non-functional requirements have details like how the box in which the
equipment is mounted is fixed to the wall or specifies the rack slot
dimensions into which it might be plugged. It may even have details of the
connectors to be used (pins, style - coded orientation etc) and will also
contain the maximum expected weight of the unit and its environmental
performance.

Functional Requirements, Non-functional Requirements, Interface Control
Document, Safety Requirements and Performance Criteria may all appear in
one physical document from which you have to sift each of the appropriate
aspects of specification. Then again, they may also appear as separate
documents in their own right.

PS. While the webpage may be colourful it is not doing very much on my
browser (a list of a few disparate items and a panel stating that it is
"Loading").


--
********************************************************************
Paul E. Bennett...............<email:// XXXX@XXXXX.COM >
Forth based HIDECS Consultancy
Mob: +44 (0)7811-639972
Tel: +44 (0)1235-811095
Going Forth Safely ..... EBA. www.electric-boat-association.org.uk..
********************************************************************

On Sep 25, 10:50 am, "Paul E. Bennett" < XXXX@XXXXX.COM >



On a multichannel spectrum analyzer I had a requirement that the
signal processing be performed in a floating point format of at least
32 bits.

This was verified by inspection of code and compiler manuals rather
than a functional test.

Dale B. Dalrymple
http://www.yqcomputer.com/

I think a few people missed the joke... ;)

Regards,

--
Mark McDougall, Engineer
Virtual Logic Pty Ltd, < http://www.yqcomputer.com/ >
21-25 King St, Rockdale, 2216
Ph: +612-9599-3255 Fax: +612-9599-3266

Indeed, or have an even drier sense of humour than I.

Peter

Peter *** erson escribi?




That's what the smiley was invented for, 25 years ago...

In article < XXXX@XXXXX.COM >,



How does one categorize requirements such as "It has to use my cousin's
company's design software" or "I heard fuzzy logic is good. Use some of
that. And maybe some neural nets" ?


--
Wim Lewis < XXXX@XXXXX.COM >, Seattle, WA, USA. PGP keyID 27F772C1

A non-functional requirement. The question when responding to this is
whether or not the cousin's company's design software would allow you to
meet the goals of the project or not.

nets" ?

In a requirements specification it is borderline between functonal and
non-functional. However, this is specifying implementation details too
early really and the question here is whether or not you might specify
fuzzy logic or neural nets in the Technical Specification (a much more
detailed level).

--
********************************************************************
Paul E. Bennett...............<email:// XXXX@XXXXX.COM >
Forth based HIDECS Consultancy
Mob: +44 (0)7811-639972
Tel: +44 (0)1235-811095
Going Forth Safely ..... EBA. www.electric-boat-association.org.uk..
********************************************************************

> "I heard fuzzy logic is good. Use some of that. And maybe some neural nets" ?

I thought that if the customer wants something to be used than it is
called a constraint. It's no more a requirement, neither functional
nor non-functional. If it makes sense is then another question.

To all users in this discussion: thank you. I just wanted to say, that
I'm still following the discussion.
Concerning the above mentioned web-application: I'm about to move it
on the server of the science chair where I write my diploma thesis. I
hope their server runs more stable than the one I'm using right now.
The URL will be given in time.