Re: The Nelson-Pick Data Model

Laconic2 wrote:

> In the MySQL/PHP thread there was a dialogue in which Dawn responded to
> erk's precis about what the issues were.
>
> 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?
>
>
>
>
>

Some dated but still useful information can be found at http://www.jes.com/cdp/ . Particularly interesting (to me, anyway), is the thread at http://www.jes.com/cdp/#117

Universe and Unidata are two products from IBM based on Nelson-Pick. IBM offers a fair amount of information at http://www-306.ibm.com/software/data/u2/ and a decent overview at ftp://ftp.software.ibm.com/software/data/u2/pubs/whitepapers/nested_rdbms.pdf

jBASE, one of the newer players in the Nelson-Pick arena, gives an overview of their system at http://www.jbase.com/products/jbase.html

Raining Data (the successor to Pick Systems), offers this overview of the model: http://www.rainingdata.com/products/dbms/d3/d3datamodel.html

Hope this helps.

Steve Lancour Received on Sat Nov 06 2004 - 17:49:03 CET