Object Database (ODBMS) for Python

Paul D. Fernhout pdfernhout at kurtz-fernhout.com
Mon Sep 1 16:36:32 EDT 2003


Niki-

Thanks for the pointer to e4graph. I found more info about it here:
   http://www.marshallbrain.com/robotic-freedom.htm

There are several similarities -- and conceptually the ideas are very 
related (to the same extent the ER model is related to graphs).

A few comments on part of their blurb on that page:

"The e4Graph library allows you to model any kind of relationship 
between data that can be represented by a directed graph, including 
circular graphs of connections between data items. e4Graph is unique in 
that it allows these circular relationships to be represented directly 
rather than implicitly or through meta-data, as is necessitated by other 
approaches such as relational databases. A bi-directional link between 
two data items can be represented by two directed connections between 
those data items."

The Pointrel Data Repository System allows circular relationships. All 
links in the Pointrel System are bi-directional (well, sort of quad 
directional in a way).

Differences include:
* The Pointrel System is in pure Python (e4graph is in C++ and uses a 
C++ database).
* The Pointrel System suports the notion of "spaces" which could be seen 
as somewhat like "graphs" -- except query operations can span spaces (or 
even multiple archives for that matter).
* The Pointrel System focuses more on complete history (e.g. tracking 
many versions of a linked node as it were in the e4graph metaphor).

These comments are all off the top of my head after persuing the e4graph 
site for a few minutes; perhaps after looking more at e4graph I may 
realize some of these comments are incorrect or there may other 
important differences or similarities.

Thanks again for pointing e4graph out.

In general, the Pointrel System bears a resemblance to any system that 
implements something related to Peter Chen's "Entity Relational" (ER) 
model.
   http://bit.csc.lsu.edu/~chen/display.html
   http://www.cs.sfu.ca/CC/354/zaiane/material/notes/Chapter2/node1.html
The Pointrel System is not quite the same as pure ER in some 
implementation details (e.g. it embeds the notion of a space, it focuses 
on triads not arbitrary relationships, the newer version doesn't have 
relations as first class objects, it doesn't seperate attributes from 
relations, etc.), but otherwise has many of the same features.

--Paul Fernhout
http://www.pointrel.org

Niki Spahiev wrote:
> 8/29/2003, 19:11:51, Paul D. Fernhout wrote:
> 
> [...]
> PDF> Well, to chime in here, in a "friendly" competition / cooperation sort 
> PDF> of way, the Pointrel Data Repository System,
> PDF>    http://sourceforge.net/projects/pointrel/
> PDF> while not quite an object database (and admittedly its case being 
> PDF> easier) has a simple API in the bare minimum use case (it has more 
> PDF> complex variants). Here is an example of its use (with fragments 
> PDF> inspired in response to an earlier c.l.p poster's use case a few days ago):
> 
> How it compares with e4graph?
> 



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