Nick Matthews wrote: > On 21/05/2011 11:39, Ian Goddard wrote: >> Also, you have integers as PKs in the database design. This is the most >> efficient way to glue the tables together internally but if it's to meet >> the data exchange aim you need something in the external representation >> which will be unique across databases such as UUID/GUIDs. >> > I've yet to be convinced on the usefulness UUID/GUIDs, I'm never sure > what they're supposed to show. Facts should be linked to their source > and conclusions linked to the person who made them - anything else seems > to vague. > The advantage of UUIDs as part of an immutable record is that you can instantly disregard duplicates. And from that you can de-weight what might otherwise appear to be a consensus of opinion but which is just a single statement being repeated. Let me give you an instance. If you go to the old family search site and search for the baptism of Jonathan Goddard, 1779, you will get multiple hits (two IIRC) giving the mother's name as Christiana. You will also get multiple hits for the baptism of Christiana, the previous year. What I suspect has happened in each case is that one person has made a mistake re 1778, drawn an incorrect conclusion re 1779 & others have blindly copied them. If there had been a means of attaching UUIDs to original postings and copying them it would have been clear. As things stand would you believe apparently multiple claims to the above vs a single statement that the baptism of Jonathan did not give the mother's name and an alternative conclusion that it was Mary? -- Ian The Hotmail address is my spam-bin. Real mail address is iang at austonley org uk