06.03.2013 Views

Artificial Intelligence and Soft Computing: Behavioral ... - Arteimi.info

Artificial Intelligence and Soft Computing: Behavioral ... - Arteimi.info

Artificial Intelligence and Soft Computing: Behavioral ... - Arteimi.info

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

against the data items of the WM. In case all the variable instantiation of the<br />

antecedent parts of a rule are consistent, then the rule is fired <strong>and</strong> the new<br />

consequents are added to the WM. In some production systems, the righth<strong>and</strong>-side<br />

of the rule indicates which data are to be added to or deleted from<br />

the WM. Normally, new consequents are added to the WM <strong>and</strong> some old<br />

data of WM, which are no longer needed, are deleted from the WM to<br />

minimize the search time required for matching the antecedent parts of a rule<br />

with the data in WM. OPS5 is a production language that offers the addition /<br />

deletion features highlighted above.<br />

3.4 The Control Unit / Interpreter<br />

The control unit / interpreter for a production system passes through three<br />

steps, which together is called the recognize-act cycle [4].<br />

Recognize-Act Cycle<br />

1. Match the variables of the antecedents of a rule, kept in a knowledge<br />

base, with the data recorded in the WM.<br />

2. If more than one rule, which could fire, is available then decide<br />

which rule to fire by designing a set of strategies for resolving the<br />

conflict regarding firing of the rules.<br />

3. After firing of a rule, add new data items to WM or delete old (<strong>and</strong><br />

unnecessary) data, as suggested by the fired rule from the WM <strong>and</strong><br />

go to step (1).<br />

Generally, a start-up element is kept at the working memory at the<br />

beginning of a computation to get the recognize-act cycle going. The<br />

computation process is terminated if no rule fires or the fired rule contains an<br />

explicit comm<strong>and</strong> to halt.<br />

The conflict resolution process helps the system by identifying which<br />

rule to fire. It is, however, possible to construct a rule-set where only one rule<br />

is firable at any instant of time. Such systems are called deterministic. Since<br />

most of the real world problems contain a non-deterministic set of rules, it<br />

becomes difficult for many systems to present the rule-set in a deterministic<br />

manner.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!