The Nelson-Pick Data Model

I'd like to focus in on the Nelson-Pick model for a little while. I did a quick google search and the first five sites were companies that were selling their expertise for big bucks. That's the sort of thing that Dawn has claimed is less necessary with Nelson-Pick than with Relational. So I'm not interested in the bucks. I'm interested in the bang.

What is the Nelson-Pick Model?
Is it a subset of the graph (or di-graph) group of data models? Is it essentially a variant on the hierarchical model, or is it inherently different? I'll point out that in the "Database Hall of Fame", it gets a separate entry from "Hierarchical".

What is the Nelson-Pick model for?
I note that the discussion seems to center on "Pick files". Does this mean that it's a data model for "files" only? Or is it also a data model that serves as a foundation for building a class of DBMS products? In other words, what is it's mission?

How does the Nelson-Pick model work?
The only discussion in here, about a year ago, seemed to suggest that the implementation was based on the following: inside a pick file is a whole pile of records. Every record has two record pointers in it, followed by data. The first pointer points to the eldest child (or nil). The second pointer points to the next younger sibling (or nil).

The above sounds, to me, to be only trivially different from the hierarchical model. But there was a lot of discussion in here about a year ago, and elsewhere on the web, that strongly opines that this is not so.

Is the Nelson-Pick model easy to learn and use? Is there less to learn? Are there fewer ways to misuse the power of the model than there are in, for instance, the Relational model? Are there obvious pitfalls? Are there well known ways to avoid them?

Is the data model intentional or accidental? At the time the Relational model was first proposed, the idea of a data model was itself something of a novelty. And the idea of proposing a model first, and then building an implementation was a radical departure from the history of the hierarchical model, which was built first, and only then modeled. That's what I mean by an "accidental model".The CODASYL model was proposed, debated and published before ever being implemented. So how central was the Nelson-Pick model of data to the product known as "Pick"?

What kind of interfaces are offered?
In addition to a query/programming language, is there a data sublanguage? is there an ODBC like connection mechanism?

Why do it's proponents like the Nelson-Pick model?

Why aren't there more proponents of the Nelson-Pick model? Received on Sat Nov 06 2004 - 16:22:15 CET