Re: Information Preserving and ISSUE-42

On 18 May 2011, at 06:59, Juan Sequeda wrote:

> So does that mean that you would translate all NULL values to a triple with rdb2rdf:NULL? That makes sense and would make the current direct mapping information preserving. 

Definitely not. 
Take the case of a RDB with a Person table, having ID, name, and age.
If you query (in SQL with a simple conjunctive query) all the people with the same age of a specific person in the table having a NULL value as age, you do *not* get the people whose age is a NULL value. However, with your naive translation in RDF of this database, you would get the wrong answer with the same query translated in SPARQL.

Received on Wednesday, 18 May 2011 07:30:44 UTC