Re: Sourcing Metadata for Database Independence

Hi again :-)

Dawn M. Wolthuis wrote:
> For database independent applications, such as those written by many
> application software development companies, the most basic of metadata, such
> as the names of attributes, must be sourced so it is useful with any target
> database implementation.

What do you mean with "database independent"? My guess would be "vendor independent", but last time I assumed that I turned out to be wrong. So I'm checking.

> There are many different strategies for where to
> source such metadata (as well as how extensive this metadata should be since
> all code is, itself, metadata).

Code contains and uses metadata, but it *is* not metadata, imho. Metadata: data about data. Code uses that to achieve manipulation and representation of data.

> It could be sourced in code, thereby fixing on a particular language while
> remaining database-independent.

Could you please explain what you mean by that?

> It could be sourced in the metadata
> repository of a development database from which the product is built for any
> environment. It could be sourced in XML documents (or any type of parm
> file) that serve as input for the code and for the database processes. It
> could be sourced as data in a database (rather than simply as metadata).

> This could be an embedded database in a metadata service.
I have seen this reasonably in place several times. Both in tagged textfiles (to be specific: DCF/GML, not unlike SGML/XML - but I don't think it really matters), and in some database product.

> If you figure that the specification of a data type for a given attribute is
> a business rule, of sorts, you could have a business rules repository that
> is the source of all metadata. You are then tied to a particular rules
> engine (which might then tie you to a language or database too) even if it
> is written in-house. I know there are some not-very-widely-used standards
> for metadata repositories -- are there industry standards for rules
> specifications other than SQL? There are also third party metadata
> repositories.
>
> I'm thinking more about the future than about what are the currently most
> accepted practicies. If you are not tied to a specific language or database
> up front and are developing a new software application to be deployed at
> many customer sites on many different databases, where/how would you source
> the metadata? Thanks in advance for your thoughts on this..

I don't think the where/how (i.e.: which type of metadata database) is particularly important - except of course for a solution provider. Otoh a clear investment choice from time to time does wake up the decision makers to the cost, and, more importantly the benefits of datamanagement. The deployment of a specialised tool may give the leverage to get the necessary procedures accepted :-) Received on Sun Aug 08 2004 - 23:50:21 CEST