Re: How proprietary is the "COBOL file system"

On Mon, 1 Oct 2007 10:47:57 -0500, "tlmfru" <lacey@xxxxxxx> wrote:

Is there any file system or DB system - any file mechanism whatsoever that
is completely platform-independent?

Sure. Every data interchange file is, by definition, platform independent. Examples are
text files, HTML, XML, PDF, now defunct EDI. Relational databases are platform independent
at the low technical level of atomic data types.

A better question is whether the database is application independent. You can tell by
asking whether an application rewrite would require a database redesign. The answer will
be no if the database is fully normalized. If the answer is yes, as is usually the case,
the database structure is modeled after the application's procedural structure. It is not
tied to a hardware platform or language, it is tied to an application.

At first, files were tied to languages. For example, a file written by a Cobol program was
almost always a persistent image of a Cobol memory structure. Strings were padded with
spaces, numbers had implied decimal points, the location of which was known only to the
Cobol program. Most files were structured for the convenience of procedural batch
processing.

Second, we got relational databases, whose data types did not match Cobol's. Translation
between database types and Cobol types was time consuming (expensive) and LOSSY. Forcing a
database string or number into a Cobol picture can cause loss of information, which
becomes permanent if the datum is updated. At a higher level, the database structure
might or might not follow procedural structure. It does when database tables are
organized like indexed files.

Third, we got object databases, which are a return to language dependence. The difference
is that you, rather than the Standard, design the language. You define data types as
classes and access logic as methods. As with RDBMS, database structure may or may not be
modeled after procedural structure. It is more likely to be with ODBMS because .. this is
the great irony .. RDBMS is oriented toward declaratives and thus data, whereas ODBMS is
oriented toward behavior and thus procedure.
.

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