07 Feedback

Question 1

what are the information needs

Answer 1

the underlying cause of the query that a person submit to the search engine
- can be categorised into type of information or type of task

Question 2

how is query related to information need

Answer 2

queries is a representation off very different information needs
- but it can be a poor representation as users find it difficult to express
- encouraged to enter short queries
- ambiguous: the same query may represent different needs

Question 3

what is the query formulation problem

Answer 3

difficult to generate well formulated queries without
- knowledge of collection
- knowledge of retrieval environments

can learn which one is relevant, first query is trial run

Question 4

what is the key aspect of effective retrieval

Answer 4

users cant change the ranking algorithm but can change the result through interaction. IR is an iterative process

Question 5

what is the ASK hypothesis

Answer 5

you don’t know what you don’t know:
you can’t search for it if you don’t know about it, therefore there is a need for search engines to show users a list of relevant documents

Question 6

what are some examples of explicit interaction

Answer 6

1. relevance feedback
   - allow user to provide feedback, add terms from relevant document into query
   - use feedback information to reformulate query and produce result
   - allow more interactive process
2. query expansion
3. query term suggestion

Question 7

how does relevance feedback using vectors work

Answer 7

1. document that are relevant to one another resemble one another in similar vectors
2. move query closer towards those vectors by
   - adding vectors for relevant documents to the query vector
   - subtract vectors for the non-relevant documents to the query vector

variations
- add positive weights to relevant terms
- add negative weights to words found in non-relevant document
- remove terms that only appear in non-relevant document

Question 8

relevance feedback performance

Answer 8

positive feedback is more valuable than negative feedback
penalise, not remove

Question 9

why is relevance feedback seldom used

Answer 9

users generally reluctant to provide explicit feedback
long queries

Question 10

types of user feedback

Answer 10

explicit
- relevance feedback
- query suggestion
- similar pages

implicit
- click tracking
- mouse tracking
- user behaviour

Question 11

pseudo relevance feedback

Answer 11

assume the top retrieved documents are relevant and do rocchio method/ automatic query expansion
need to reweight the query terms
might drift away from optimal query
eg. homepage of glasgow information retrieval has only 1 unique document, not useful to expand query

Question 12

thesaurus based query expansion

Answer 12

for each term in query, expand with related words and synonyms
weight the added terms less than original