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CPAN Ratings and the problem of choice (was Re: About tidying upKwalitee metrics)

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Paul Fenwick
June 30, 2008 00:06
CPAN Ratings and the problem of choice (was Re: About tidying upKwalitee metrics)
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G'day Jonathan / PQA,

Jonathan Rockway wrote:

> The same could be said for CPAN Ratings also.  Why should my module have
> 1 star next to it because any goof with a web browser can write a
> review?  Why is the opinion of someone with no ties to the community
> considered relevant enough to show in the search.cpan search results?

I'm a big supporter of CPAN Ratings, because I view them as solving one of 
the biggest problems facing the CPAN today.  Choice overload.

CPAN is suffering from its own success.  One of the most common questions I 
get asked is "Which CPAN module should I use?  There's like 300 that cover 
my problem".  The worst thing is, faced with too many choices, typical 
humans are more likely to choose *none* of them, compared with if they were 
only offered one or two[1].

The results are frightening to watch.  I've seen colleagues of mine 
practically ignore the CPAN because there are too many choices.  I've even 
found myself avoiding solving certain problems because of choice overload.

It's extremely telling when one of the most popular parts of Perl Training 
Australia's courses is showing students the Phalanx 100 as a short-list. 
Even though the list is quite some years old, there's almost palpable relief 
when the students realise they can just pick XML::Parser from the Phalanx 
top 10, rather than having to examine the multitude of choices on the CPAN.

So, why do ratings make a difference here?

Well, ratings provide at least a partial way for the community to solve the 
choice overload problem.  If a search reveals a 4.5 star module with eight 
reviews, one doesn't feel compelled to look at the other options; the choice 
becomes clear.

Note that the other options may actually be *better* than the 4.5 star 
module, but that doesn't matter.  The ratings help solve the problem of 
choice overload, and increase the overall use of modules from the CPAN as a 

As an interesting aside here, low ratings don't usually solve the choice 
problem, because what most people want is a whitelist rather than a 
blacklist.  As such, high ratings are actually more valuable to the 
community than low ratings[2].



[1] For a fascinating study on choice overload, see Iyengar and Lepper's 
paper: "When Choice is Demotivating: Can One Desire Too Much of a Good 

[2] At least until we see so many over-inflated CPAN Ratings that they 
become useless, but that doesn't look like it will happen any time soon.

Paul Fenwick <> |
Director of Training                   | Ph:  +61 3 9354 6001
Perl Training Australia                | Fax: +61 3 9354 2681

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