Hallöchen!

Sebastian Kraft writes:

> [...] 
>
> Ok, I fully agree. That would really make sense. What scheme could
> we use to set the IDs? Simple enumeration is too error prone and
> we always have to keep track of the last ID. Maybe a combined
> format:
>
> "PX1755-1" for a Pentax 17-55mm lens. If there are several with
> the same focal length we can increase the last part by one.

I was hoping for a purely numerical format so that the calling
program only has to store an int.  We could assure integrity in our
database with a script.  Values < 1000 would be reserved for local
use.

However, this has the problem that intra-database links are not
legible.  I think of two cases where they occur:

<calibration cropfactor="1.534" camera="1342">

Here, the "camera" attribute is purely informational (like the XML
comments with currently used).  And the second case is to avoid
compact camera mounts:

<lens>
  <camera>1065</camera>

So, one uses <camera> instead of <mount>.  In both cases, a
non-numerical ID would make the database much more legible for human
eyes.

I think if we guarantee that the length never exceeds, say, 63
characters, this is almost as easy as an int for the calling
program?  Still, a numerical ID is possible, and the drawbacks could
be dealt with.  Besides, making up all the string IDs for lenses is
no fun either.

> Or maybe hashing the attributes?

I thought of hashing the attributes for local entries which do not
yet have an ID; definitely not for the main database.  But maybe it
is better to discard all entries without an ID and force the user to
update their local files?

Tschö,
Torsten.

-- 
Torsten Bronger    Jabber ID: [email protected]
                                  or http://bronger-jmp.appspot.com


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