Dave Caroline <[log in to unmask]> a écrit :
> The questions seem related to search engines or should you be googling for
> full text indexes or the other more correct name inverted index.
> Because in the normal scheme of events databases return exactly what
> you ask for.

One could argue that the same thing happens with search engines. After  
all, both databases and search engines are deterministic programs that  
provide a set of records in response to a query.

Precision and recall are not determined by what you ask - what defines  
them is how relevant the output records are with respect to a  
real-life question. It isn't tied to a technology. Of course, it can  
be more or less difficult to translate this question into a query, and  
the program might be more or less "smart" while processing the query.  
Both aspects affect precision and recall, in my opinion.

Anybody who ever used a bibliographic database using Google-like  
queries can testify that a database can have extremely poor precision  
and recall in some use cases ;-)

Best regards,
Alain Borel
EPFL Bibliothèque
Rolex Learning Center
1015 Lausanne (Switzerland)