Data Structure for logic tree

[Michael Arnett]

All,
I am attempting to design a solution for filtering messages. Essentially, I am looking for a data structure that I can map into a database schema which will allow users to define their own filters such as:

if ( c1 AND c2 ) OR ( c3 AND c4 AND ( c5 OR c6 ) ) OR c7 then filter message
Any suggestions would be greatly appreciated. Are there any existing standards, libraries, or design patterns to tackle this task? Seems like it would be a common problem albeit a complex one.
Thanks in advance,
-MLA

[Neil Laurance]

Perhaps use XML? Then you could use XSL to transform your structure to an SQL or other query to decide on the filtering:

<filter type="exclude">
  <description>Some description</description>
  <logic>
    <or>
      <and>
        <expr>C1</expr>
        <expr>C2</expr>
      </and>
      <and>
        <expr>C3</expr>
        <expr>C4</expr>
        <or>
          <expr>C5</expr>
          <expr>C6</expr>
        </or>
      </and>
      <expr>C7</expr>
    </or>
  </logic>
</filter>

Hope this helps

[Neil Laurance]

And the XSL to transform this back to the original text:

<xsl:stylesheet
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  version="1.0">
<xsl :-o	 utput method="text"/>
<xsl:template match="description"></xsl:template>
<xsl:template match="and|or">
  <xsl:text>(</xsl:text>
  <xsl:apply-templates select="*"/>
  <xsl:text> :wink: </xsl:text>
  <xsl:if test="not(position()=last()) and not(name(..) = 'logic')">
    <xsl:text> </xsl:text>
    <xsl:value-of select="name(..)"/>
    <xsl:text> </xsl:text>
  </xsl:if>
</xsl:template>
<xsl:template match="expr">
  <xsl:value-of select="."/>
  <xsl:if test="not(position()=last())">
    <xsl:text> </xsl:text>
    <xsl:value-of select="name(..)"/>
    <xsl:text> </xsl:text>
  </xsl:if>
</xsl:template>
</xsl:stylesheet>

[Neil Laurance]

Don't you just love the way UBB formats your code sections :roll: :roll: