[Allegro] Structure of .ald file ?

Thomas Berger ThB at Gymel.com
Mi Aug 25 15:11:55 CEST 2010

Hash: SHA1

Hello Sylvain,

> Hello all (sorry for writing in english but I swear it's much better !),
> one library in our network is going to join the main system and I need to
> get their datas into our ILS. The librarian has sent to me all its allegro
> directory (binary + katalog). The first thing I'd like is to extract ISBN
> from this catalog to match them against our ILS. It seems I can find them in
> the *.ald file containing my database using a regexp like \x0087 (\d*)\x00,
> am I right ? Is there a better way ?

Right in a sense.

The .ald files are the binary storage format for the bibliographic records,
you'll have to pay attention that they also contain "deleted" records whose
storage is waiting to be recycled. "Deleted" not in the sense of actively
deleted: Storage is simply invalidated because records grew and hat to
be stored elsewhere in the file.

> Then I'd like to be able to match records without isbn using a key like
> "Title / Author / Date" for example. But with the .ald file I can't
> understand how to do (some records seem to be on two lines for example, all
> records don't start with same characters ...). That's why I tried to export
> in iso2709, a format I know, but all datas aren't exported (ISBN for
> examples aren't in the .iso file). And this file does'nt seem to be real
> iso2709 file (delimiters used aren't the officiel iso2709 delimiters). To
> export the datas, I started Allegro (the interface says "Allegro-Routinen
> (Version 18) / Stand: 13.8.1999", it's running under dos), then selected "9
> Besondere (und lokale) Einstellungen / Sonstiges", then "Datenexport nach
> ISO 2709".

There seems to be an added user interface (menus etc.) uncommon to me.
The correct version number might be "Version 16"? Your quote of field "87"
for ISBNs shows that the internal format of the records is (or is derived
from) the common "$A" format, cf. http://www.allegro-c.de/doku/form2004/
(there might be an english digest for it somewhere)

ISO2701 per se is just an encoding for fielded data, commonly employed for
MARC21 or UNIMARC, to a certain extend also for the german MAB format.
Since the export you tried not even exports ISBN numbers to the "ISO 2701"
(BTW: did you check the file itself? It might simply have been exported to
a different field than your understanding of / your tools handling ISO 2701
expected: MAB 540 corresponds to MARC21 020 and UNIMARC 011 for the ISBN)
it is probably not worth investigating any further with respect to what
kind of export really hides behind "Datenexport nach ISO 2709".

> If someone can help me to find a better way to export my datas or extract
> datas from the .ald file, it would help me a lot !

To get *all* valid data out of the database you should probably look for an
export in allegro-C's "external format": Maybe your user interface permits
a more freely configurable export giving you the choice to select "E-1" (.apr)
as export ruleset (Parameterdatei): This would give you all records in a
flat text file, each line containing a datafield prefixed by the field number
#kkf. Character coding would be according to the internal one of the database,
probably CP850.

Thomas Berger

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