SV: When to Validate XML?
Hi Mike > Actually I think a lot of people use database-level > validation during normal > running, and then duplicate most of the checks at application > level. The Again, db level check is still just the syntax / structure. When you need to do a Semantical check, you need to implement this in the application. An example is a CRM system I designed before coming to SAG, where we used DB level checks (triggers and rules) a lot to ensure the _integrety_ of the database, i.e. to ensure that the database wouldnt corrupt. A very simple example: "You couldn't delete a customer if that customer had open orders" (Dont ask me to show you the clean-up script that we used during testing to clean the database, it was quite big, since it had to cleanup everything, starting at the "edges" and ending with the central tables, in order not to create integrety violations.) So you could say, that the table structure itself, guarantees structural validation on table level. I.e. trying to insert ('Mike Kay', 'Software AG', 'XML',10) in the table Emp[Name, Company] will generate a SQL error. Triggers and rules guarantees relational integratiy, as well as "scope": I.e. trying to insert ('Jens Jakob Andersen', 'Post Danmark', 'XML',10) in the table Emp[Name, Company, Speciality, Number_Of_Keynotes] will generate a SQL error, if there is a rule for Emp.Keynote saying that all numbers inserted here must be between 20 and 100. So you can use RDBMS triggers and rules to handle a lot of those checks that you otherwise would have to write in every application. Great. On the other hand, there are application specific rules, that cannot be implemented in the DB. (And yet, using e.g. Oracle and PL-SQL, you can create some very nifty rules and triggers...) I also agree a lot with the other statements, about using triggers and rules in the DB is the only way to ensure integrety on the DB level, which is especially important in e.g. a n-tier architecture, where the DB is accessed from many different applications. Hmmm. Any read the book "Business Component Factory" by Pter Herzum and Oliver Sims? It touches some of these issues from a CBD viewpoint. All the best JJ
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