Permaculture Database

[jedd <jedd@progsoc.org>]

On Thursday 05 April 2007 9:41 am, Paul Cereghino wrote:
> This has been repeated by others.  I know I am confused and others may
> be as well.  Is there a specific table and relationship structure that
> you db-designers think of when I say hierarchy?  Are there basic
> alternative models of adding attributes to objects that need to be
> selected among?!
>
> for example..... [The Chicken]
>
> what are the different data structure choices... not for describing the
> relationship of the chicken to other objects... but of describing the
> characteristics of the chicken.... size, longevity, lifeform, breed, etc...

 The latter isn't hierarchical - the attributes of the object are
 what you're talking about there - average | max life, size ranges,
 egg productivity, feed requirements, placidity, etc.

 I'm not a db expert, but I can't conceive of creating a schema
 that would be inherently hierarchical.

 The nature of family/genus/species is hierarchical, f.e., but the way
 you'd represent it in a db isn't, at least not to my mind.  I'm
 intending to write some thoughts up about schema design soon,
 anyway, as it happens.

 Oh, when you say adding attributes to objects, do you mean the
 values of those attributes, or adding new attributes?  The problem
 with the latter is that although the db can be designed to cope with
 this (though it takes a lot of effort to abstract things out to do so)
 the application suite that uses that db needs to know the attributes,
 so it can start doing sensible things with the data (attributes and
 values).  Adding attributes typically is a couple of lines of SQL,
 but a non-trivial change at the application layer.

 Have I misunderstood your question?

 Jedd.