I think Yingying Chen wrote: > Dear Ernest, > > Thanks. It works. But I still don't understand why you use jess to do all the work > like recording all products information. I think database can do a better job than > jess. And Jess is better to do only the recommendation part. Though it may be quick > to find a product, it seems not feasible for a large product list. Any comments on > that?
Several times in chapter 19, the possibility of using a database is mentioned. For example, in 19.13, it says "After extensive use, writing and reading the accumulated facts from flat files could become prohibitively slow. Also, loading all the data at startup and saving it all at shutdown may incur too great a risk of data loss in the event of a crash. Instead of using a flat file, the application could be changed to use a relational database. Orders relevant to a particular user could be loaded from a database on demand by the Recommend servlet. The Purchase servlet could save those facts relevant to a particular order just as the order was being placed, and then remove all the user's facts from the Rete object." and in 19.5: "This is a book about rule-based application development, not a book about building e-commerce systems, so the web application you've developed here is lacking in many important respects... the possibility of using a relational database together with Jess to provide long-term persistence. A database would provide faster, more robust access to historical data than the flat file used here." If I were to have written the application in the book this way, it would have been longer, harder for the reader to set up because of the database dependency, and the database code would have been a distraction. --------------------------------------------------------- Ernest Friedman-Hill Science and Engineering PSEs Phone: (925) 294-2154 Sandia National Labs FAX: (925) 294-2234 PO Box 969, MS 9012 [EMAIL PROTECTED] Livermore, CA 94550 http://herzberg.ca.sandia.gov -------------------------------------------------------------------- To unsubscribe, send the words 'unsubscribe jess-users [EMAIL PROTECTED]' in the BODY of a message to [EMAIL PROTECTED], NOT to the list (use your own address!) List problems? Notify [EMAIL PROTECTED] --------------------------------------------------------------------
