Juliano <jju...@gmail.com> writes: > We've been working with an ontology at my department […] I have been > being pushed towards changing the basic plan and build a DB so that > data access will be faster and easier for both the desktop GUI and the > web app. Right now, I'm trying to work with sqlite, since it can be > used as a separate file for the GUI and as a DB for Django (which may > be the choice for the web interface).
You're also working with a relational database system, which will make it relatively easy to migrate your database structure to a different relational database system if that proves necessary. > I have been redaing some books on DBs but I kind of get stuck when it > comes to the normalization and the planning of the tables. No shame in that; it's somewhat counter-intuitive, though it's an essential topic when working with databases. Try the Wikipedia article <URL:http://en.wikipedia.org/wiki/Database_normalization>. > The problem is that we have basically four fields that can be arranged > in a tree- like structure. Tree-like structures don't fit into table-like relations very well; but it's not hopeless. > So, for ONE *concept*, we have, usually, MANY *slots*, each *slot* has > ONE *facet*, and each *facet* can have MORE THAN ONE *filler*. > Besides, some *slots* and *fillers* are themselves *concepts*, > creating a sort of recursive reference. Recursive references, on the other hand, are deadly to storing data sanely in a relational database: while recursion is algorithmically elegant, it makes for hideously slow operations querying, and especially modifying, the database. The focus, then, should be on teasing out a non-recursive, declarative schema for the data. This is a well-known problem, with many possible solutions. Several popular approaches (each with different trade-offs) are “Adjacency list” , “Materialized path”, and “Nested sets”. Use those terms in database-savvy circles and you'll get lots of explanations. > What would be a good way to create tables for this situation? > In fact, this is the first time I've ever tried to create a DB, so I'm > completely lost. This topic is rather orthogonal to Python. You would do well to seek further guidance from a Usenet group such as <URL:news:comp.databases>. Good fortune, and persist; you're going into databases off the deep end with a problem domain like this :-) -- \ “I distrust those people who know so well what God wants them | `\ to do to their fellows, because it always coincides with their | _o__) own desires.” —Susan Brownell Anthony, 1896 | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
