General talk about software patterns

[Donald McLean <dmclean AT stsci.edu>]

I'm working on an application that will be storing family history 
information.

Some of the data is precise and well known (such as my birthday), and 
some is not. For example, a precise month and day may be known, but not 
necessarily the precise year.

Is anyone aware of any library or libraries that support the encoding of
information with different levels of determinateness? Is anyone aware of 
any research into the representation and/or encoding of such information?

Time (dates and intervals) are one of the types of data involved and I 
am working on getting (and then digesting) Martin Fowler's Analysis 
Patterns as well as several works referenced by him (i.e. Snodgrass) for 
insight into that part of the general problem but if anyone knows of any 
other relevant references, I would be greatly appreciative.

Thank you,

Donald McLean