Colin L. wrote in post #947005:
On 8 October 2010 21:58, Marnen Laibow-Koser [email protected]
wrote:
functionality of the current phase of development.
Which, at any given time, is all we care about.
My turn to say No! I agree that one should not do extra work to add
features that may never be required, but where choices exist that do
not add extra work then the design should be so as to provide the best
base for future extension and modification.
To the extent that we know the direction of future extension and
modification, I agree with you. However, my experience is that we
almost never do know that, so any work spent “future-proofing” now is
likely to be wasted.
In my experienced, the best future-proofing we can do is to write
maintainable code, and to refactor it as necessary so it stays that
way. After a few refactorings, the necessary generalizations will
emerge.
internals.
It’s to the developer’s advantage to structure the application so that
adding more value for the user will be as easy as possible – hence good
development practices – but the user sees and cares about none of this.
Don’t kid yourself that the user has any reason to care about what goes
on under the hood, as long as the application works as specified.
My experience does not match this. Most of my work has been in-house
developments where the customer and myself are the same company.
No. The customer is some specific department of that company –
probably one where the staff’s jobs don’t involve going through code.
In
my case management has been keen to ensure that the code base should
be well designed in order to minimise future costs.
Well, of course, but management generally has no way of verifying that
beyond asking the developers if they are following good practice.
Perhaps in the
case of contract work things are different.
It has really nothing to do with whether the work is free-lance. On
both my free-lance and (at least my current) office jobs, the customer
(my direct client in the former case; marketing, project management,
editorial, and finance people in the latter) is not particularly
technically minded. They wouldn’t know the difference between good and
bad Ruby code.
That’s why I have a job. If my customers were knowledgeable enough to
find out for themselves anything useful about the quality of the code,
they wouldn’t need me to write it!
I find it surprising
though that a customer would not be at all interested in this.
I find it surprising that a customer would have the necessary knowledge
to get any useful information from that interest.
Perhaps I should not be surprised however.
Again I will quibble, slightly tongue in cheek, though not entirely.
The purpose of the code is to provide the implementation, as you
state, however the process of developing the application has other
purposes. Â Notably to provide us with a living wage and job
satisfaction.
That adds value for the developer, not for the user. Â If all we care
about is running up the billable hours, there are lots of ways to do
that – and not all of them involve adding value for the user – and
soon the user will realize this and find a developer who can actually
add value for him.
Oh no, you completely misunderstand me, I was not suggesting in any
way ‘running up billable hours’.
Nor was I. I was saying that if we confuse our goal (making money) with
the client’s goal (having a usable application), then we make poor
decisions.
[…]
Your user’s goals are not your goals.
To a great extent I think you are wrong here. At first sight you
might say that my principle goals are to make a living and achieve job
satisfaction. However the best way to achieve that is to provide the
best product to the user with the minimum effort (always a compromise
of course) and hence minimum cost.
No, the best way to make money is to provide product with minimum effort
and maximum cost. (Minimum effort does not always translate to minimum
cost.)
Of course, neither you nor I would do that – we have too much pride in
our work. I suppose that’s where the job satisfaction comes in.
The Users goal is to receive the
best product for the minimum cost. Hence the goals are pretty much
the same.
No. You’ve found a pretty good way of aligning them – of giving
yourself incentive to meet the client’s goals – but the client’s goals
are different from yours.
That doesn’t mean I don’t see my client as a partner in the development
process, or that I don’t see my job as being the satisfaction of the
client’s dreams. Of course I do. But that’s a little different.
scenarios suggests one or the other but we code it the ‘right’ way
To a point. Â But not much. Â Do The Simplest Thing That Could Possibly
Work is an important principle.
Consider, for example, text formatting. If I want a bit of text
highlighted the STTCPW would be to use tags. It is more complex
to use css.
Arguable.
So why do we use CSS? The scenarios do not require it,
but we know that it will be easier to maintain.
CSS is not about maintainability. It is about separating logical
structure of the document from presentation.
Similary DRY is often
not the simplest way to do something. It is simpler to cut and paste
a bit of code rather than extracting it into a method.
Yes it is, and so I usually start with cutting and pasting to get tests
to pass. Then – and usually only then – do I refactor to remove the
duplication.
An oft-quoted set of steps:
- Make it work.
- Make it right.
- Make it fast.
Do them in that order.
The same could
be said, I think, about Unobtrusive Javascript.
No again. This is about document structuring same as CSS, though in
this case some DRY is involved.
These are all design
concepts that are intended to improve flexibility of the code, reduce
bugs, make the app more easy to understand and maintain and so on.
Do The Simplest Thing doesn’t mean that you throw knowledge of good
practice out the window. And the definition of “simple” is often
unclear. There’s nothing simple about maintaining 24 copies of the same
function.
Don’t bend over backwards to
generalize; let the generalizations emerge.
Agreed, but there is nothing wrong with standing up and looking around
to check there is not a better solution nearby.
Right.
and is less likely to have unnoticed
bugs.
That’s what tests are for.
Hmm, did you really mean that?
Yes.
Tests cannot ever cover every
possibility,
True, but somewhat orthogonal to the issue.
some bugs will get through.
And when they do, you write more tests.
Coding so as to minimise the
likelihood of bugs is worthwhile.
What do you mean by that? I certainly don’t code that way as such.
I write code that I can read.
I write code that I believe will be maintainable.
I write code to pass my tests.
I think those three factors, taken together, minimize the likelihood of
bugs, but I don’t feel like I’m taking that as an explicit goal when I
write code. Why rely on likelihood when your tests will establish
certainty (at least in the areas they cover)?
Also, even if the tests do point
out a bug, we have still wasted effort fixing it which would have been
saved if we had not introduced the bug in the first place.
That’s an old, old fallacy. Of course you shouldn’t be sloppy, but you
can’t always get things right the first time. That’s why we have tests
and iterative methodologies. Particularly in uncharted territory,
sometimes we have to see how things go wrong in order to make them
right.
If we were doing formal methods and proof-carrying code, this would be
somewhat less so. But unfortunately, we’re not.
 I think these ideas also apply to the larger scale design of
the app, including the models and relationships. Â The overall design
can be aesthetically pleasing, or even a thing of beauty (I know, OTT
again, sorry). Â The scenarios do not address that aspect of the
design, only the designer can do that.
And the user will not care one iota about all that beauty. Â It, in and
of itself, adds no value for him at all.
No, but it increases my job satisfaction, and if it does not cost the
customer anything then everyone is happy.
Right. Just don’t pretend that it means anything to the client, except
insofar as it makes use of the app or future development easier.
The only thing adding value for the user here is that the beautiful code
makes the app easier to maintain – that is, to extend functionality
– that is, to do things that do add value for the user.
To reiterate: there is no user value at all in elegant code, except
insofar as the elegance makes future development easier. Â There is
developer value, but no user value.
The fact that the elegance makes future development easier is of
value to the user as it will keep his future costs down. He may, or
may not, appreciate this but it is still true.
Generally so.
It also adds value for
me as it will assist me in meeting future targets (in the in-house
case) or allow tendering at a lower cost (or higher profit) in the
contract case.
That may actually decrease value for you, if it means that your paycheck
won’t be as high. 
us satisfaction in the design as discussed above.
Since we don’t know what the further phases will be, we can’t design for
them. Â Period. Â You’re deluding yourself into premature generalization,
and apparently somehow think that your clients care what the source code
looks like.
I am not talking about generalisation, but basing the model
identification on those aspects of the problem domain that are least
likely to change.
But you can’t really know which aspects those will be. You’re heading
straight into premature generalization.
That is not a more general solution
Right – it’s just a more time-consuming one, and if you guess wrong,
the extra effort is wasted. Why do it?
than purely
looking at the details of the scenarios and coming up with a set of
models that solves the problem but may not be based on those aspects
of the problem domain that is least likely to change.
I don’t care (much) what will change in the future. I care what works
today, not after the completion of the Seventeenth Five-Year Plan.
suspect that 90% of the time there will be little difference between
the two approaches.
and refactor for tomorrow’s requirements when you know what they are.
It is not gueswork, just a matter of mapping the problem domain
objects (where appropriate) to the models.
I think now our ideas are starting to diverge. Â My initial assumption
would be that there will be user and product classes because they
are domain objects (unless the scenarios show that they do not
actually exist in the app).
That would be my initial assumption as well when I start to implement,
but that’s because I follow such a programming style in general.
Apparently not everybody does.
I am not sure what we are arguing about then, we appear to be in
complete agreement.
[…]
This is an implementation detail, and as such
it is irrelevant right up till the moment we start implementing.
I am not sure what you mean here.
I mean that the nature our object model should be of no concern to us at
all till the moment we start to write actual code.
Surely you have a phase where you sit back and consider the models and
their relationships before you start typing?
Yes – about 30 seconds before I start typing.
But that is the point, if the domain objects and program objects map
onto each other closely,
Which there is no guarantee that they will.
I believe that they should.
(There was an interesting
post from Jim Coplien a while back where he said that very few bank
systems actually have any sort of Account object internally, even though
there’s a business concept of an account.)
I can’t seem to find that.
http://www.ruby-forum.com/topic/203844
Assuming it is correct I wonder why that
is. It would certainly not be my starting point. In addition just
because it is true does not mean that it is ideal. Are banking
systems renowned for their good design or are they a hotchpotch of
legacy systems lashed together over the decades to more or less work?
He seemed to be quoting them as good design, and I gather that he knows
what he’s talking about.
then since the domain objects tend not to
change dramatically the program objects will also not change
dramatically (though their behaviour will be added to and modified of
course.
Behavior is most of what program objects are about. Â That’s not really
true of domain objects. Â I guess – and I hadn’t realized this before –
that in that sense, the two are somewhat incommensurable.
Can you give examples of this? I am not sure what you mean.
Let me try to come up with some concrete examples.
But that’s not even true. �It assumes a degree of clairvoyance regarding
the future directions the project will take that we do not generally
possess.
Again, by mapping domain objects closely to program objects then
clairvoyance is not required as domain objects tend to be stable.
Really? Â What happens when your client’s business model changes?
I did not say they never change, only that they tend to be stable.
Plus I am only talking about domain objects that appear in the problem
domain. If these change then I would expect the scenarios to change.
Right – and you don’t know in what direction.
Or
when you discover domain objects your client didn’t know existed? Â (Not
so far-fetched; see http://c2.com/cgi/wiki?WhatIsAnAdvancer for a
real-world example.)
That is not a problem, it is immaterial who identifies the existence
of the objects.
Right – but it means you may have domain objects that neither you nor
your client even know exist! Advancers only emerged from refactoring 2
years into the project; if the WyCash project had not been amenable to
refactoring their object model, they’d have missed the existence of
advancers entirely (or so they say).
Colin
Best,
Marnen Laibow-Koser
http://www.marnen.org
[email protected]