Re: Confused betwen user cases and user stories

Hello Thanks for answering my questions, it is helping to put user
stories and use cases into context, but I have some more questions.
see below.....

Cheers.


On Aug 15, 6:46 pm, "H. S. Lahman" <h.lah...@xxxxxxxxxxx> wrote:
Responding to Kong...

I am wondering if you can sort out my confusion concerning user
stories and use cases:
1. When is appropriate to develop user stories, instead of use cases?

Use cases are a form or requirements specification. They will be
invariant regardless of the way the software will be developed (e.g.,
how one breaks up the development into increments).

A user story describes the functionality of what will be developed in a
particular IID increment. To that extent it reflects design and project
decisions. That may or may not map directly to a use case, depending on
a variety of factors that mostly involve how the project is broken up.
Thus in certain types of agile development environments where there are
no formal requirements, the user stories /are/ the use cases.

1.1 Does that mean, before you define the user stories, you will need
to define the high level iterations, and then the high level functions/
services to be delivered in each iteration, for which you can then
define the relevant user story corresponding to each system function
you want to define/develop?

1.2 When scoping the project, could you first define on the first
iteration the user stories as place holders for later elaboration as
more detailed use cases in another project iteration of the
requirements definition phase, as well as deciding what user stories
would be elaborated in what iteration as use cases?

1.3 I am planning to develop a web base CRM system, what would be the
appropriate number of user stories for it?

1.4 For a small project, such as a recent project that I worked on
such as a web base search engine, user stories seem to be appropriate,
because we were not too concerned as to the background business
processes. Yet what happens in a large project such as developing a
new hospital clinical information systems, in which the developed
software system must map to a business process? How do you relate a
user story to a business process modelled as an UML activity diagram?

1.5 It concerns me that there would be certain situations there would
be no formal requirements, is that not asking for trouble? I have read
that they are meant to be used in place of formal Software
Requirements Specifications, is that correct? I know that as one
captures requirements that they do tend to change, and the intent of
iterative development is to deliver something in small chunks, so the
stakeholders are getting something as soon as possible, rather than
waiting for the requirements to be 100% right [which is never the
case!] Yet not having some formal requirements documents on a large
project is hoping to to "wing it", and one of the reasons for the
failure of large software development projects is very poorly written
requirements documents. Could relying on user stories as the basis of
requirements definition in large software development projects be bad
software engineering practice?




2. When is appropriate to develop use cases, instead of user stories?

When there is a need to preserve the requirements beyond the initial
development or there is need to provide arm's length communications
among different development teams. However,...

2.1 Would you capture user stories as part of the project scoping and
planning phases [RUP: Inception], as a way of defining the system
services on the high level, while performing the business modelling
and defining the business processes, and in the Requirements phase
then define the system requirements as system use cases?
2.2 Because from what I understand of user stories, they are meant to
be written by the customer, and therefore would the acceptance tests
associated with each user story be the basis of the later user
acceptance testing?




3. Can one capture the business requirements [stakeholder requests] as
user stories, as part of the process of elaborating the business
problem domain, and then define the solution requirements with use
cases? Or for the first iteration, capture user stories, and for the
second, more detailed iteration, define use cases from the user
stories?

3.1 One difference I see between a use case and a user story is the
functional scope: a use case contains a number of scenarios, pre and
post conditions, triggers, and some non-functional requirements
[supplementary requirements]; where as a user story may correspond to
a single scenario, is that correct?
3.2 Because a use case contains a number of different scenarios, could
you develop your user stories to correspond to each scenario?
3.3 One aspect that I do see user stories simplify things is in RUP
you have a typical hierarchy of requirements as: Stakeholder Requests
[typically equivalent to IEEE803-1998 requirements, but maybe user
stories??], [Product] Features, and then [System] Use Cases, and trace-
ability between. How I see user stories working as simplying things by
eliminating [Product] Features as a requirement type [which confuses
stakeholders], and just have Stakeholder requests elaborated as user
stories [and mapping to business processes modelled as UML activity
diagrams..], and [System] Use Cases. The User stories would be
elaborated in the RUP Business Modelling/Inception project phase, and
then [System] Use Cases being elaborated in the RUP Elaboration/
Requirements projects phase: would that be a good way to use User
Stories/Use Cases together?
3.4 Another difference that I understand between a user story and use
case is time: it was put to me you can a write user story 'quick and
dirty' in about two hours, whereas writing a fully dressed user story
may take up to three days.





The content of use cases and user stories in total will be the same
because both define requirements. So the differences are primarily
cosmetic and scope. That is, the content of individual uses cases and
user stories may not map 1:1 on an individual basis and they may be
formatted differently, but the set of use cases and the set of user
stories have equivalent overall content.

If one does both, then the use cases will usually be done first because
they represent the customer view of the system that is independent of
development. The user stories will be developed second because that
involves design and project level decisions about things like allocation
of resources.

3. Can one develop UML models from user stories?

Yes. The only limitations are completeness and precision of
specification. Quite often user stories are inadequate because they are
not rigorous enough. That's because agile processes usually provide
additional mechanisms (e.g., feedback) to define requirements.

4. How do user stories fit into an RUP framework?

You should be able to use a user story anywhere you would use a use
case, provided the story is complete and precise.

5. When one is capturing user stories, should one also define the
acceptance test for that user story at the same time?

That's a process issue that depends upon the particular development
environment.

6. What are the limitations for user stories?

In theory, none. In practice, though, there may be issues about
completeness and precision, depending on what sort of other mechanisms
are available for communicating requirements. (Use cases are usually
design to be standalone requirements specifications while user stories
may not be.)

7. How does user stories work with requirements management tools such
as Rational RequisitePro: do you need to define special requirement
types and attributes for them?

7.1 The question was more about requirements management. Recently I
had to write user stories for web portal search engine, and these
consisted of the following:

As a <business stakeholder in this user storiy> I want to <intent of
business representative in this user story> ; So that <reason of
business stakeholder in this user story>;

Acceptance Criteria: <insert the user acceptance test testing the
validity of this requirement expressed as a user story>

Comments
Priority
Complexity

It appeared that they only way to manage these user-story-requirements
was in a MS Word document which is fine if you only a small number of
requirements and a single analyst; but what happens if you have
hundreds, or thousands of requirements as user stories, and many
analysts? How do you manage these? It appears that user stories as
fine for informal 'quick and dirty' small project development, but
they may be a major risk on large rigous software development
projects: is that your view?



I don't know enough about the tool to answer that. I would hope not, but
it will depend on how informal the user stories are.

*************
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not be cured by a capful of Drano.

H. S. Lahman
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Pathfinder Solutionshttp://www.pathfindermda.com
blog:http://pathfinderpeople.blogs.com/hslahman
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