Homework  Assignment  2

P

1

|

2    

Homework  Assignment  2  

Due  date:  4th  of  November  2013      

Please  note  that  even  though  the  homework  assignments  are  optional,  you’re  still  highly  encouraged   to  answer  them,  as  they  will  help  you  prepare  for  your  final  exam.  You  can  work  in  a  group  of  two  or   alone.  Solutions  can  be  dropped  off  at  the  institute’s  homework  mailbox  located  on  the  2

 floor,   next  to  room  238.  In  that  case,  please  make  sure  both  your  name  and  matriculation  number  is  noted   down.  If  your  answers  span  more  than  one  sheet,  kindly  staple  them  together.  Another  alternative  is   to  send  your  homework  via  email  to:  elmaarry@ifis.cs.tu-­‐bs.de      

L ECTURE   2:   O THER   R ETRIEVAL   M ODELS  

Given  the  following  subset  of  documents  from  a  collection  

!

=  !

, !

, !

         !

= {!

, !

, !

}  

!

=  !

, !

, !

, !

, !

                    !

= {!

, !

, !

, !

}  

!

=  !

, !

, !

, !

                    !

= {!

, !

, !

}    

E XERCISE   2.1   (I NVERTED   I NDEX )  

Create  an  inverted  index  for  the  following  terms:  !

, !

, !

, !

, !

  E XERCISE   2.2   (B OOLEAN   M ODEL )  

According  to  the  Boolean  model  we  reviewed  in  Lecture  1:  Introduction,  evaluate  the  following   queries.  

§ !

= !

!"  !

 but  not   !

!"  !

§ !

= !

!"#  !

 or   !

!"#  !

  E XERCISE   2.3   (F UZZY   L OGIC   M ODEL )  

Given  the  following  fuzzy  weights  for  !

=  !

/0.4, !

/0.8, !

/0.8, !

/0.2, !

/0.9, !

/0.6         2.3.1 Compute  the  relevance  of  document  !

 to  both  queries  !

and!

.  

2.3.2 What  is  the  motivation  behind  using  fuzzy  weights?  

2.3.3 Assuming  the  following  journal  collection:  !

, !

and  !

= !

, !

 constitute  an   entire  document  collection,  compute  the  fuzzy  membership  degree  for  the   collection’s  terms  with  respect  to  !

.  

E XERCISE   2.4   (C OORDINATION   L EVEL   M ATCHING )  

Given  the  following  query:  q  =  {  !

, !

, !

}  on  the  document  collection  defined  in  2.3.3  return   level-­‐based  matching  of  these  documents  for  q.    

Information  Retrieval  and  Web  Search  Engines  

Winter  Semester  2013/14  

Prof.  Dr.  Wolf-­‐Tilo  Balke  and  Kinda  El  Maarry  

P

2

|

2    

E XERCISE   2.5   (V ECTOR   S PACE   M ODEL )  

2.5.1 List  the  different  ways  of  representing  documents  in  a  vector  space  model.  

2.5.2 Why  do  we  normalize  the  vector  representation  of  documents  in  the  vector  space   model?  Is  it  always  a  good  idea?