kindly remove me from this mailing list Thomas Beale <thomas at deepthought.com.au> wrote:
Tim Churches wrote: >On Tue, 2003-08-05 at 07:27, Thomas Beale wrote: > > >>Not sure what you mean by "inefficient".. >> >> > >Well, I have changed my address several times during my life, but not my >sex or my name. This can be modelled by either keeping an address >history within my demographic record (that is, explicitly modelling the >time domain), or by keeping timestamped versions of my entire >demographic record. openEHR seems to adopt the latter approach. > Actually, it doesn't, but it's not obvious I agree. If you look at the common RM (http://www.openehr.org/Doc_html/Model/Reference/common_rm.htm) you will see that there is a class VERSION_REPOSITORY and a class VERSION. The former is a functional interface to the stack of versions for one versioned entity, which might be a PARTY, a TRANSACTION of whatever. But it does not say how to implement this. A space-inefficient, but simple, implementation would be to just have successive complete copies. A more efficient way would be to adopt the algorithm used in versioning object databases which only stores new objects in each version, and uses special markers for deleted objects. Normally this would be done backwards, so that it is always the most recent version that is complete, since it is the one most likely to be retrieved all the time. >That >approach is less efficient space-wise, but that hardly matters these >days. It is more efficient if the (medico-legal) query is "what was my >demographic record at date yyyy-mm-dd?" Much less efficient if the query >is "how many times did I change my address?". > for a single patient, neither of these is much work - it's trivial, regardless of the representation of versions > Very, very inefficient if >the query is "what is the mean number of address changes in the entire >population?". I am thinking from an aggregate epidemiological POV, not a >clinical/medico-legal individual patient POV. But then, satisfying the >former POV is what data warehouses, populated from EHRs, are for... > sure - and I agree - this is what data warehouses are for. This kind of querying requires forethought. If you know you are going to be collecting say 50 statistica, including "number of times change address", then you start designing software agents to capture the data as they go into the EHR, e.g. a simple address change counter for your query. Then generating the result is trivial. - thomas - If you have any questions about using this list, please send a message to d.lloyd at openehr.org Dr.N.S.Shivam MS,FRCS,DNB Head Healthcare Business development (Provider) HCL Perot Systems Plot No3, Sector 125, Noida Ph: 09811901903 --------------------------------- Want to chat instantly with your online friends??Get the FREE Yahoo!Messenger -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.openehr.org/mailman/private/openehr-technical_lists.openehr.org/attachments/20030805/2f4fde5b/attachment.html>
