SterlingPorter.net

We’ve loosely defined the idea of a “rules engine” in 601R for a reputation framework. The gist is that an application that wants to use the reputation framework can define a set of rules upon which its own custom reputation scores can be defined and calculated. For example, a blogging reputation system might want to provide a reputation score for its participants. The score might be based on a number of variables: numberOfPosts, LengthOfPosts, NumberOfComments, RelevancyOfPosts, ContentCategory, etc. The blogging system has its own “special formula” for computing the reputation score. This formula is some sort of mathematical expression like:

(numberOfPosts + numberOfComments) * RelevancyOfPosts

Of course, this example might not make any sense. The point is that the rules engine needs a way for the blogging system to define such a mathematical expression. I envision an XML based approach that includes nodes representing basic operators like <add>,<subtract>,<multiply>,
<divide>, and others like <sum>,
<product>,<average>,<median>, and even more complicated ones like <standardDeviation>, etc. Nested within these nodes would be variables representing attributes that the blogging system defines such as <numberOfPosts>, <spellingMistakes>, etc. These can be of various types: INTEGER, BOOLEAN, ENUM (good, better, best), etc. The structure of the XML expression could then be evaluated in the same way a functional expression is evaluated in languages like Scheme or Lisp.

Here is an example:

<expression>
	<multiply>
		<add>
			<attribute id="numberOfPosts"/>
			<attribute id="numberOfComments"/>
		</add>
		<attribute id="relevancyOfPosts"/>
	</multiply>
</expression>

The attributes “numberOfPosts” and “numberOfComments” would be INTEGERS while “relevancyOfPosts” might be FLOATING-POINT or DECIMAL. Of course, the types aren’t defined in the expression above but are defined in a separate XML document which is loaded when the expression is evaluated.

Assuming the simplest model possible for reputation system (Reputation server and many clients), I brainstormed 4 basic types of messages that such a reputation framework might have:

• ReputationReport
• ReputationReportResponse
• ReputationQuery
• ReputationQueryResponse

The ReputationReport is sent by a client to the Reputation Server and includes identifiers for the Reporter and the Reportee (the client being reported on). It also includes a report-type (e.g., in a blogging reputation system, “Comment” or “Post”). The report would also contain whatever attributes the Reporter wishes to report on and the values. Click here to see a mockup XML ReputationReport.

This semester I’m taking a class titled “Middleware” taught by Phil Windley. Middleware perhaps is too broad a name for this class. We are focusing on building a framework for a reputation system. For more about the class, click here.

More about reputation systems later…