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Probabilistic Question Answering On The Web - Clair

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Probabilistic Question Answering on the Web Dragomir Radev, Weiguo Fan, Hong Qi, Harris Wu, Amardeep Grewal The University of Michigan Ann Arbor, MI, 48105 USA          ABSTRACT                                                                              !  "                         #  $                                                              %           &            #  '(()*                       #  +,    )-. /   &               0$) Categories and Subject Descriptors 12 3       4" 5   6 7+ 3  4" 0 -   6 7+/ 3      4" 5  8    General Terms 9    7   -     (     Keywords                                    1. INTRODUCTION TO WEB-BASED Q&A                                                                  9 : ;90                                                   -                        <   =  >?  <  Copyright is held by the author/owner(s). , May 7–11, 2002, Honolulu, Hawaii, USA. ACM 1-58113-449-5/02/0005.         9   >?         <' &)   &)  * 97 '@=  :*?             #                                                        #      A   9   'A9* $                    (    (   ) #  '(()* $       B    5           0$) '   < ?*     A9             ()  9 # C  5 3D4   $  3+4 9 # C       :                       5               $                  !    :                                                     < ?  < ?                                 !    A9 '          * 1                       ;      #      <          9   >?                 # '             *                                      ! "#  $" $        %#&&&   '%         ( )      *   + ,        #       "#      -  ""           &#& & &      "EE #  "EE  "EE  "/2,,E  "EE                             $                           #        $    !       :                 #                                        9      9   ;   D 9        #               A9  (()   '(    (   ) # *                    #                (()              #      #                         '   *      ' *        #               0   9                  9              0 F  +,,D 2. RELATED WORK 0 9) 3G4      !  A9    1                 5$ $  9   #             9       5B)9H 324         #                     5B)9H                                          9    A9       (          "           )-. AI9 3J4                                 6                                                                               #     2.1 Related work from TREC  )-.         3J4                       0      )-.           +K                    3L M4                        #                                     #                                                       #       #                       3/4   AI9         $)   (    9      !               #       #                # (                 #                                    !                                    9    3+4                 !     ;                        !    ! 9                     K                   !   !        &                              #                   .#   3N4                       #     O                 $7; #                               9                              #                               #           9  %            %              #      3D,4 ;                                                     (                                     P  !                              ;         )-. AI9      3J4 2.2 Related work on the Web  )-.    %                 A   9   1               !    )-.     Q  %              AI9         8       &    3DD4                            #  %             9     3D+4                !             9           3DG4                                                K                      !             !                  9                                               #                                   $                          9     #          3D24 9   DJ        !         -5                         %          !                           9         AI9        3D4 0      )-.             ;                       $           #    !   #           !      "        0          3D+ M4                                                             O  $7; '                            *                                                                                      &    %   3D4                9          5                           E      $    5     D,, #    '& -O    7  0  (   .    +,,+*  #    $                      !           #                0 #    9             %                # 3. A PROBABILISTIC APPROACH TO PHRASE RERANKING 3.1 The general architecture of our system &          "     8                                     3D24 $              :                        8                        "       O            8              #               ' *                     '   *   8                                   8                                              ' *  #  8               #                             3.2 Evaluation metric 9               # ' *                    #            ' *      "   R  D   'D*            '         * ;          D,        "                                   S  S  R M+J )7)   !                  $              #        '     *  )7)              )-.      %        )-.      #                              !                                       B  )7)           )-.     #  !        9       )-.                     P           %                            '        *  #          '  P  !*                <  ?      3J4 $                                                                )-. / N   D,   $0 3J4          D,,,    E     B                +,,     )-./  5       %                            !       !                        )-. 3.3 Manual vs. automatic evaluation consistency                            ;  ?        .    DM         2          O    "         )  3DJ4            D+,,     )-./ )-.N   )-.D,             !                      ;            <   $ 5 ?    #         !                <                        .1B= 3DL4       & (     9        2D      #       : )  )  ) 4  )  ) 4  5) # +5 # +52   +53  +5.  +52 +56  +50 +5+" +" 1+.   0          )          !   A    )-.N )-./   )-.D,             $         GM                    ;  <              - 1"2?            <   ?     <  ?     O   <  ?               )                 ;       )               <- 1 J , $; '  $   $=- * 97 '  $=-  *? 0   )                 #           <1          -    (  -  ?             )     )              G  $ !  %    &    !    '   #       $0/ $0/ ! $0/ ! $0/ > $0/ ! >     ;;<= ?>'= ;>@ =    ;<= '>=    "   #     ./01+ .2 / 3$/ +-4/0 3/5+5$51+ 106+57$51+ 3/ 05.$51+ 440/85$51+ *+1)+10 0$/ 2/+6$9 1+/ 0/1+ 3-0$51+ .-0.1/ +15+2 1$9/0 <7    ?       #              <     C  >?6       # <        >?     <(  ?  < ?                              !         O   A                <& ? 4.1 Machine learning approach )                 O   $             DG   N            4.2 Heuristic algorithm          !         O        A     O                               1        < ?     2/2 )-.N                                9      2                        <  ?   < ? < ?                 ;                        #    J K   E                 $    K :       (&0         3DM4  E          7 ' *  <     B  0      >?     (   ' '     '        A>;B  A@>B  A<>B #AB  &A;''B AB 0/1+AB +15+2A?!B .2 /A;?B 3/5+5$51+A;@B ./01+A!B 106A@B +-4/0AB +-4/0A''B 2/+6$9A@B 0$/A;B 1+/A;B 3-0$51+A'B 0/1+AB 3/ 1$9/0AB  )               !         )-.          .  +  3    A       B  1  ( '   *  <       C >?             7 < ?                                                              ;       < E7 E  E  EQKT .   E(     E0 >E?   !        <   ?   < ?            6     O      <&)9 $T9 $&? .  7 < ?       (          # ;              O     # <        U >?           6         <7-;$$ $&?                        6                       &       !                  !        ;       < :             >?             <   ?   <      ?        < ?             7 %             # <         !  )        #>?  <    :     >?                          # <  !   C  ?         :                                                 F - 1 0       < ?            O  - 1                  L                        !                   #   )-.N    6        )-./   )-.N    6         * !  %    &         '   #      $0/ $0/ ?!= $0/ ! ?<= $0/ ! > <@=  $0/ ! $0/ > C= != @= !;= CC= ?@=                   )          +,V                G,V      )-./N      )-.D, 9      L        /V         D/V $                         O             ;      # <   ?            <      ( (  DNND?         O    <     0 DN/+? 5. DOCUMENT RETRIEVAL      W         P      9                    '       *         B)                ( (""7                       E           2,          $             :                       "           &      +,,D 6. SENTENCE RANKING         #                    #   (                               #          &                    Q 0  ;                                Q                     #          '  *                     "  R   ¾  S  ½    S                ¿  'G*    ' R D + G*                      ' R D + G*                   D DJ   2                                           !    "  D  2,         2,   2, 9       #            !     &#  #            #  3D/4 $ !    "    '2*       ¾ , J S D J       S                          ' * R G        +,                           $               0$)        7. PHRASE EXTRACTION AND RANKING 7.1 Potential answer identification $                  #    %     # 3DL4 ;               2,              #               #  1          ' )-. /*             !  "  #$ D,GL,       &    D,GL,     D,        <1 X ? 1    D,          D,GL,           !                O     "                8                                                  ;  G    %              (                             activation weight 1 0 Pi-w Pi-1 pi Pi+1   $ +,      Pi+w phrase position 7.2 Phrase ranking 9  -    ) #       #                                     <     ?                  ;               5  :                 '(1)90- X(-0$*              ;               <1 X ?        #  <( (?     '(-)0&( (* 2J/              ;                                              ;  2            '(&0*                                   # 3DL4 ;   QK7              CC  P  7    ' < ?*   <(?     &  AI9               &      !             #               !     #                                               8. EXAMPLE :      +D  )-./"  %      $      <9 0 ?                         # '  ;  J*                                        2,                 D2MDM          +V         G,,   9             #       <9 0 ? $   Æ    ;  J        +           !  9       !  9                            ;  L ;  M                                 ;  / U        '     *     #        #     ;  N           #  #                          9                               + :       #    ;   M <  0 ;   &   ? $  &               =#       +   QK7 7  ( 7 CC  ( ( 7 ( & 'D,,V* & '/LMV* (-)0& 'G/V* B5K-) 'G/V* &) '+JV* (-)0& 'GM2V* (9.- '+NLV* 79 - '+DMV* & 'MLV* & 'MJLV* B5K-) 'DDDV* (9.- '22V* &) '22V* (9.- 'GMGV* (-)0& 'GJLV* & 'DLNV* &) 'D,+V* &) 'JJLV* & 'GGGV* (9.- 'JLV* 79 - 'JLV*   ( -     '    '       .                   #     #   '  / '     '    ,   '   !-     ) 0    /  !-1 2           4           @ 1 # C  @    D        *          E        E          (           (         E            "  "# #  " $ (        (    3  ( .#      E            "        5   E     F      "   .  # #   3       # C 5  @ 5            +  4      #        "  E       9   E       %       *   3 '       %  +! .    , '&    '  4                !"#"$  %%   %%  ; ' < C @ ? ! >  ; ' < C  >C !@;  3$  ++.   ++. 1  ++.   ++   >C !C@< 5  ++.  ++.  ++.  ++. >C !' ! 5  ++.  ++.  ++. >C !;C  $1 "  84 >C C ' '' + ++. D ++.  ++.  ++. >C!?<>  3   84 >C!C<> $ 3$   ++ >C?@? ?   DD   ++ >C@!>'   ++.   ++. >C@?'@  3$ "  ++ "  ++ >C@C?C?  ++. ( ( >C@;@;? ,  ++ , H  5+ >C@?>;  ++ >C@>@<  "  # +.+   5 6  7 + 4 ,    4 2     !- 1    3           (   (455      3 '    '  ,     <7 ( ( ( ?                 <(-)0&?  <(9.-? $     '<(-)0&?<7 ( ( ( ?* '<(9.-?<7 ( ( ( ?* R R , 9           , &            #  <9 0 ? !     D2MDM            JDLGL/   #                                  GMLGGL             JDLGL/       M+//D2 1      > $    '<(9.-?<( (?* S '<(-)0&?<( (?*       GM+// S GJJNG          !     )                   8           (-)0&   (9.              ;       <9 0 ?         '   *                 DNGJ          #  J,            #     &  )7)      D/ ' D2 S ,G S ,D* 9. EVALUATION 9.1 Performance by question length                                <@C>;  ++.   ++.   ><<@<@@ . / ++. 2/+30 ++.  ><' ?@   ++.   ++. >' ><' 5  ++.  ++.  ++.  ++. >' @;C>  .0.I   DD  ++  ++ >' C C@ + ++. D ++.  ++.  ++. >' <;;  3$   ++.   ++. 2 ++. 5 # ++. >' >@'  3$ 0  ++. .  ++.   >'? ? ?   ++.   ++.  #&"##"  %%   %% >'?C@@  "  # ++. >'?'?' 5  ++.  ++.  ++. >'?;;!  ++. >'? < $ ++.   ++.   ; ' < C   1 6  7 + 4 ,   7 #  4 2       3       /   8   '  ,   ' #         ; ' < C " ? ! >  ; ' < C         ><< ;';  "  # ++. ><?C 6 ++. ><'?! C  ++. ><'!'C 6 ++.  '"&$  %%   %% ><;'!CC   ++.   ++. ><;''  ++. # ++. ><>@C   ++.   ++.  ++ ><> < 2 ++.    ++. >'!C?@'  ++.  ++. 3 # ++. $@> ++ >'!!@C  3$  ++. 5  ++.  ++.  ++. >'?>>'>  ++. 0    ++.  ++.   ++. >'@@?<   ++.   ++. >'C >C! # ++. 0 ++. # ++. 0 ++.   9 6  7   7 + 4 ,   7 #  4 2          /  *       :   '   ,        5            '   /             3 ' '                /       3 #   % 4 4 (4 )4 8&    9 .   9  Y , .   9      "  0 ,/GJJ  D,2NJ +JLDV DGGLD JNN+V D2N  DLG N2,V DL2 D,,MV  1   3     !- 1 #   /   ) " +  2  6  - 2  1% - 2  1% - 2  1%  ;'' >';! >;@;; ;C;C! ><' ? ;CC;! >C<>> >< ';    - 4  !C';= !@<>=  !'= !;C =  ?!!C= !>@!=     ) "     C;''= C?'=  ?;@'= ?> = J> = ;C@=  '!<= C> =     ) "     ;;;;= ;>;>=  '!'!= '@'@=       8 <9 ?                                                   #        ;       J                        #  'DSDE+SDEGSDE2SDEJ* 9      #                      '      *                0     !          #            9       )-. /   '    /*            #           +,               0