Hi Mithun,
Assert(), assertLogical(), modify() and retract() in DRL
are implicit functions to do the exact same as WorkingMemory's related members
(much like request and response in a JSP).
What's more there is an implicit "drools" global too that
can be used to access an instance of DefaultKnowledgeHelper.
I don't know whether there are any other implicit
objects.
With kind regards,
Mike
Hi
All,
Can anybody tell as to wat
does the assert() method do in a DRL file, like the way it is used in the
below example. I am aware of assertObject() method but not assert()
method.
Thank you,
Mithun
Krishnan,
I always
prefer to use specific tools for specific jobs. So, if I were implementing
that, I would not put the I/O code inside the DRL.
If you
want your rules to drive the parsing, I would model it like that:
1)
Create a class to "represent" your file... that would be your File
interface. It would have a method: readLine() that returns a Line object, as
well as an "eof" property (true when EOF was reached).
2) Create a
rule to drive your parsing:
rule "R1: Read one more line"
when
$f : File( eof == false
)
then
System.out.println("Generate new
line");
assert( $f.readLine()
);
modify( $f ); // as
readLine "modifies" the state of the File
end
3) Create
the rules to effectivelly "analyze" your lines. If you want to read all
lines first and then analyze them, just make rule R1 to have a greater
salience. Otherwise, if you want each line analyzed as it is parsed, make
your other rules have a greater salience as showed bellow:
rule "Rx:
analyze line"
salience 10
when
Line( content matches "xxx" )
then
// do
something
end
4. Create the rule to close your file when EOF is
reached:
rule "close file'
when
$f: File(
eof == true )
then
$f.closeFile();
end
Keeping the procedural code in
your java classes instead of DRL functions makes all your rules more clear,
makes easy to unit test each part, and reduces the overall complexity.
That is how I would do it.
Hope it
helps.
Edson
2007/5/17, Krishnan <krishiyer@gmail.com>:
Hi,
I want to parse a file and match the file
for several regular expressions. Based on what I match, I write more
rules so that based on all the rules, I can set my results.
Brute force method : Parse the entire file and add all the lines
into the working memory. Write rules that
check each line for some
regular expression. This works great.
I want to optimize the
above, as we are checking each line, if we got we are looking for, then I
want to get out.
So, I wrote a function inside the rule file like the below
function String getLine(BufferedReader fileReader)
{
String line;
try
{
if ((line =
fileReader.readLine()) != null) {
return
line.toLowerCase();
} else
{
System.out.println("This is an empty
line.");
}
} catch (Exception ex) {
}
return
line;
}
Now, I need to write the rules that will use this.
rule "Generate New Line"
when
eval (getLine(fileReader) !=
null)
then
System.out.println("Generate new
line");
//assert(getLine(fileReader)); // need to somehow assert the line
specified in the eval condition
end
Also, I am confused,
how to specify file end.
rule "File End"
when
eval (getLine(fileReader) ==
null)
then
System.out.println("Reached end of file"); // I am assuming this is not
needed since if all rules are executed, then it will get out of
fireRules() anyways ?
end
Any help is appreciated.
TIA,
Krishnan
(newbie)
Sivaramakrishna Iyer Krishnan (Anand)
Never assume the obvious is true.
- William Safire
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