[DDI-users] greeting mail

I-Lin Kuo ikuo at icpsr.umich.edu
Sun Jan 11 23:44:11 EST 2004


Hello Csaba,

> Therefore, I would like to ask you to direct me to anyone who could help us 
> in this transition with answering our annoying questions about some 
> problematic DDI elements ;-).

I would advise that you direct your questions to this list, as all the members
of the DDI Expert Committee should be on this list. Also, the questions that
you have may be shared by many people, so the answers to your questions will
probably be helpful to others as well.

> we have to face several problems. Moreover, it is also a problem that some 
> of the IT solutions we prefer are not automatically compatible with DDI. for
> example we store our databases in MySQL that we manage via an ODBC frontend,
> Perl CGI (using DBD DBI Apache modul). Our first goal is that our fields are
> completely DDI-compatible but we want not to use xml files at all. At the 
> same time we would like to have the possibility of generating xml data 
> descriptions from SQL by using CGI scripts. (It would be useful if our data 
> were included in international cooperation of databanks such as EDAN 
> [http://www.gesis.org/en/cooperation/data_service/eastern_europe/].)

There are a number of problems in general with translating the DDI to SQL
tables, of which I think the most important is the lack of an abstract data
model for the DDI. Some other databases such as Oracle can generate a complete
database from a schema, but the sheer size of the DDI and the lack of clear
foreign key referential relationships make the resulting auto-generated table a
nightmare to work with. For my own projects, I've had to pare down the DDI and
use only the parts relevant to my work. Currently, the DDI Structural Reform
Group is working towards a data model, which would be more amenable to a direct
translation to a database design.

>From your comment about not wanting to use xml files at all, I suspect you may
also have a bias against xslt. Another thing I'd advise is that you DO use xslt
to transform the DDI into flat files which can be loaded into your database.
Processing xml by using a procedural language such as Perl to walk the DOM is
very development-intensive and the resulting solution is fragile. XSLT was
designed to do general purpose xml processing and no other language does nearly
as well.


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