Re: Consistency of fuzzy rules

From: WSiler@aol.com
Date: Wed Oct 24 2001 - 11:28:10 MET DST

  • Next message: Jay Rakholiya: "CFPs:ICMLA 2002"

    In a message dated 10/23/01 4:16:04 AM Central Daylight Time,
    aegawe01@brain.spd.louisville.edu writes:

    > How about these two rules:
    >
    > R1: IF obstacle is straight ahead THEN turn left
    > R2: IF obstacle is straight ahead THEN turn right

    It is fairly obvious what the antecedent means, but less clear what the
    consequent means. Consequents are not instructions to the user - they are
    instructions to the computer shell program. Rules of the type

    R1: IF obstacle is straight ahead THEN message "turn left"
    R2: IF obstacle is straight ahead THEN message "turn right"

    do issue instructions to the reader, and are quite inadvisable. However, the
    user would immediately be aware that the computer was having trouble making
    up its mind, and could take appropriate action.

    Since this is a decision problem, a much better rule set would be

    R1: IF obstacle is straight ahead THEN turn is left
    R2: IF obstacle is straight ahead THEN turn is right

    where turn is a discrete fuzzy set, in which left and right are members.
    Presumably if the obstacle is indeed straigh ahead, then either action woul
    be acceptable.

    In the next rule block, we check for contradictions. In this case we could
    write

    R3: IF turn is left AND turn is right THEN message "turn left or right"

    Of course, avoiding obstacles is a lot more complex than that, since we must
    consider other obstacle locations than just "straight ahead" as well as
    obstacle distance, size and speed of car, but I don't think the point is
    worth writing a whole obstacle-avoiding program.

    Best - William Siler

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    Content-Type: text/html; charset="US-ASCII"
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    <HTML><FONT FACE=arial,helvetica><FONT SIZE=2>In a message dated 10/23/01 4:16:04 AM Central Daylight Time, aegawe01@brain.spd.louisville.edu writes:
    <BR>
    <BR>
    <BR><BLOCKQUOTE TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">How about these two rules:
    <BR>
    <BR>R1: IF obstacle is straight ahead THEN turn left
    <BR>R2: IF obstacle is straight ahead THEN turn right</FONT><FONT COLOR="#000000" SIZE=3 FAMILY="SANSSERIF" FACE="Arial" LANG="0"></BLOCKQUOTE>
    <BR></FONT><FONT COLOR="#000000" SIZE=2 FAMILY="SANSSERIF" FACE="Arial" LANG="0">
    <BR>It is fairly obvious what the antecedent means, but less clear what the consequent means. Consequents are not instructions to the user - they are instructions to the computer shell program. Rules of the type
    <BR>
    <BR>R1: IF obstacle is straight ahead THEN message "turn left"
    <BR>R2: IF obstacle is straight ahead THEN message "turn right"
    <BR>
    <BR>do issue instructions to the reader, and are quite inadvisable. However, the user would immediately be aware that the computer was having trouble making up its mind, and could take appropriate action.
    <BR>
    <BR>Since this is a decision problem, a much better rule set would be
    <BR>
    <BR>R1: IF obstacle is straight ahead THEN turn is left
    <BR>R2: IF obstacle is straight ahead THEN turn is right
    <BR>
    <BR>where turn is a discrete fuzzy set, in which left and right are members. Presumably if the obstacle is indeed straigh ahead, then either action woul be acceptable.
    <BR>
    <BR>In the next rule block, we check for contradictions. In this case we could write
    <BR>
    <BR>R3: &nbsp;IF turn is left AND turn is right THEN message "turn left or right"
    <BR>
    <BR>Of course, avoiding obstacles is a lot more complex than that, since we must consider other obstacle locations than just "straight ahead" as well as obstacle distance, size and speed of car, but I don't think the point is worth writing a whole obstacle-avoiding program.
    <BR>
    <BR>Best - William Siler
    <BR></FONT></HTML>

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