Re: [rules-users] Guvnor web based decision table

Greetings: Jarek, Mark, Edson, Wolfgang and others are far better at the specific, in-depth details in Drools than myself. However, I did notice two things that called attention to themselves in the email below: (1) Priority (or specificity) should be used, if at all, sparingly. More than three levels of priority indicate a possibility that a procedural program is being done with declarative rules. Five levels and you definitely need to use Java or C++ or something else rather than a rulebase. (2) Global variables in a rulebase, as in Java or C or C++, should be avoided whenever possible. They are a death trap that has killed off many an excellent idea. Most vendors point these things out when they explain how to implement global variables and/or specificity. It's almost as bad (really close) as using a GOTO in BASIC. Yes, it's there. But don't use it. One other thing: External code should never change the value of an element being used by the rulebase in the condition part of the rules. If the datum is used by the action element it still MIGHT not be a good idea and should be used very carefully. However, returning a boolean is the normal use of external code that does not modify data - that's about the only SAFE way to use them. SDG jco "This above all: to thine own self be true, And it must follow, as the night the day, Thou canst not then be false to any man." Hamlet, Act 1, Scene III http://www-tech.mit.edu/Shakespeare/hamlet/hamlet.1.3.html On Jul 14, 2009, at 3:16 PM, Jaroslaw Kijanowski wrote: