Introduction To Information Rertrieval Answer

z=( * z ) . n e x t & z=n u l l

Exercise 1.11 ow should the boolean 0uery x *D + y be handled6 8hy is naive evaluation of this 0uery normally very expensive6 8rite out a postings merge algorithm that evaluates this 0uery efficiently% *nswer: 'ind any terms of x that not matched with terms of y% +he algorithm may be lie this: I N V E R T E D _ I N D E X* p x=x I N V E R T E D _ I N D E X* p y=y I N V E R T E D _ I N D E X* z=a l l o c a t e ( ) w h i l ep x! =n u l l : i f( * p x ) . d o c I d<( * p y ) . d o c I d : ( * z ) . d o c I d=( * p x ) . d o c I d p x=( * p x ) . n e x t  e l s e : p y=( * p y ) . n e x t ( * z ) . n e x t=a l l o c a t e ( ) z=( * z ) . n e x t & z=n u l l

Exercise 1.12 8rite a 0uery using 8estlaw syntax which would find any of the words professor& teacher& or lecturer in the same sentence as form of the verb explain% *nswer: (professorE +eacherE
Exercise 1.13 +ry using boolean search features on a couple of major web search engines% 'or instance& choose a word& such as burglar& and submit the 0ueries (.# burglar& (ii# burglar *D burglar& and (iii# burglar   burglar%
Exercise 2.1 *re the following statetemnts true or false6 a# .n a 5oolean retrieval system& stemming never lowers precision% ('alse#  b# .n a 5oolean retrieval system& stemming never lowers recall% (+rue#

c# =temming increases the si!e of the vocabulary% ('alse# d# =temming should be invoed at indexing time but not while processing a 0uery% ('alse#

Exercise 2.2 =uggest what normali!ed form should be used for these words (including the word itself as a  possibility#: a# FCos& cos& because  b# =hiite& shiite c# cont d& count down& counting down d# awaii& hawai e# oure& o roure& roure

Exercise 2.3 +he following pairs of words are stemmed to the same form by orter stemmer% 8hich pairs would you argue shouldnt be conflated% Give your reasoning: a# *bandon , abandoment% +his associative is good because term abandoment is clearly adjective form of verb abandon%  b# *bsorbency , absorbent% +his associative loos fine% c# Hareting , marets% +his associative loos not relevant because marets refer to place& while mareting refer to job function% d# Iniversity , universe% +his associative clearly not relevant& because term universe has general meaning while term university refers to place% e# Jolume , volumes% +his associative loos really good%

Exercise 2.4 'or the orter stemmer rule group shown in (2%1#: a# 8hat is the purpose of including an identity rule such as == K ==6 +o identify such term belong to adjective%  b# *pplying just this rule group& what will the following words be stemmed to6 circus canaries boss circus canari boss c# 8hat rule should be added to correctly stem pony6 ./== K 7 d# +he stemming for ponies and pony might seem strange% Does it have a deleterious effect on retrieval6 8hy or why not6  o& it does not have high deleterious effect on retrieval result because poni as result of stemming of ponies and pony have been stored at index at first will always matched with poni from post processed term of 0uery%