[Year 12 SofDev] Use Cases, context diagrams

Wed Feb 8 22:11:38 EST 2012

Hi Mark,

   Yes, a number of interesting statements in the articles ( and linked
articles from those pages including "The pros and cons of use case diagrams,
<http://searchsoftwarequality.techtarget.com/news/1273406/The-pros-and-cons-
of-use-case-diagrams> ",  "Five use case traps to avoid:
<http://searchsoftwarequality.techtarget.com/tip/Software-requirements-analy
sis-Five-use-case-traps-to-avoid> " , "How to document use cases
<http://searchsoftwarequality.techtarget.com/news/1264767/How-to-document-us
e-cases> "  etc.  

  The other  statements I picked up that made me think and it makes sense
is:

1)      It is worth keeping in mind that actor is a slight misnomer. In UML
an actor is a role rather than something that plays a role. For roles
carried out by humans the term user role is an increasingly common
alternative term to actor. Although it's clearer, the term is not a drop-in
substitute for actor because not all actors are human roles, and not all
human roles would necessarily be classed as users in a context diagram. The
common stick-figure notation for actors makes sense for human roles, but it
looks a little strange for nonhuman roles such as devices and other software
systems. For those kinds of actors consider using an alternative icon or
simply a box stereotyped with <actor>.   

Displaying external systems such as a video system or a Credit Card System
as a stick figure does make it look strange. 

2)      There is little point in drawing a diagram if you don't know what
you want from it   -  true. What are students doing with the ucd they are
given ?

As far as the text based use cases vs the diagrammatic representation, this
is my first year teaching it so I would like to hear what others have done.

Kind Regards

Kevork Krozian

Edulists Creator Administrator

www.edulists.com.au

tel: 0419 356 034

From: sofdev-bounces at edulists.com.au [mailto:sofdev-bounces at edulists.com.au]
On Behalf Of Mark KELLY
Sent: Wednesday, 8 February 2012 1:14 PM
To: Year 12 Software Development Teachers' Mailing List
Subject: Re: [Year 12 SofDev] Use Cases, context diagrams

Thanks, Kevork.

The second link raises an interesting point when it says "For reasons that
remain a mystery to me, many people focus on the stick figures and ellipses
in use case writing since Jacobson's first book, Object-Oriented Software
Engineering (1993) came out, and have neglected to notice that use cases are
fundamentally a text form."

I must admit I've mainly stressed use case DIAGRAMS (UCD) with kids and
spent little time on the textual descriptions of the use cases in the SRS.
For the simple use cases we handle, I've found the UCD alone conveys all the
necessary info, and giving textual use cases as well is mere duplication of
the UCD. In the SRS, I tend to gloss over the textual use cases section.  My
outcomes last year took this approach and VCAA said nothing about that being
a problem when they were audited.

The study design does not give much of a clue about the relative balance of
use case text/diagrams, apart from requiring students to know use cases (SD
U3O1 KK10) and the composition of an SRS (SD U3O1 KK12). 

The detailed example for U3O1 mentions drawing a UCD. The assessment
handbook's rubric for U3O1 says that "all relationships between users, the
network, including data flows, and the proposed solution are accurately and
clearly represented *diagramatically*" (which to me suggests a CD/DFD and a
UCD).

Do you guys stress the textual descriptions of use cases in the SRS, or
mainly rely on the UCD? 

Just curious.

Cheers
Mark

On 8 February 2012 11:16, Kevork Krozian <kevork at edulists.com.au> wrote:

Hi Folks,

A couple of really good links covering use cases and context diagrams.
http://searchsoftwarequality.techtarget.com/definition/use-case

http://searchsoftwarequality.techtarget.com/news/1280295/From-use-case-diagr
ams-to-context-diagrams?asrc=EM_NLN_2495725
<http://searchsoftwarequality.techtarget.com/news/1280295/From-use-case-diag
rams-to-context-diagrams?asrc=EM_NLN_2495725&track=NL-498&ad=607290&>
&track=NL-498&ad=607290&

Kind Regards

Kevork Krozian
Edulists Creator Administrator
www.edulists.com.au<http://www.edulists.com.au>
tel: 0419 356 034 <tel:0419%20356%20034> 

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-- 
Mark Kelly
Manager of ICT, Reporting, IT Learning Area
McKinnon Secondary College
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