dawn schrieb:

Yes, in the RM we need to do almost everything manually (numerous joins
and restrictions, hundreds of options) so it is nowadays a low level
data manipulation and access technique rather than a high level data
model. The RM knows almost nothing about our data and hence it cannot
help us in many important tasks. If earlier (say, 10-20 years ago) it
was used really as a high level data model then now it is used to model
other data models. And for this purpose it is very efficient because of
its powerful record matching, manipulation and transformation
mechanisms. In particular, complete absence of *logical navigation*
means (for example, by using links or automatic constraint propagation)
is actually a verdict and restricts its use to the level of
implementation of other models. In other words, the RM with respect to
other (conceptual) data models is like assembly language or machine
codes for OO languages. Data modelists and designers do not think now in
terms of relations -- instead they use them (or other means) to
implement higher level constructs. Indeed, if you have hundreds or even
thousands of tables then will you build yourself an access path
consisting of 10 or 20 tables? Even if you are an expert it will take a
couple of pages of code and nobody will be able to understand and edit
it in future. Conceptual models with *logical navigation* allow doing it
in a couple of lines with absolutely predictable and clear result.

I wonder which decade they mean, the fifties or the sixties?

How often do you find what you're looking for via clicking on a link,
and how often via a search engine?

Marshall