Advantages and disadvantages of permuted indexes

1
Advantages and disadvantages of permuted indexes

• Advantages
• Quick
• Easy
• Cheap

• Disadvantages
• Titles may not reflect content
• Limited terms
• May be hard to scan
• No vocabulary control

2
Concepts

• Permuted indexes are linear
• They must be ordered in a way that is clear to
  the user, e.g. alphabetically
• They represent multifaceted objects
• Facets are entry points
• Entry points may be by term in title, or by
  feature or subject

3
Combinations Permutations

• For n terms, if term proximity is not
  significant, there will be n entries
• If proximityis significant, but no redundancy and
  order is consistent, there will be 2(n-1) entries
  
• To represent all combinations, we would need 2n -
  1 entries

4
The online environment

• Precoordinate indexes are the only choice for
  printed materials
• Online retrieval systems do not depend on linear
  representation of entry points
• Value of ordering of terms is negotiable
• Online systems may use coordination level
  matching

5
The online environment (cont.)

• Representation of multiple entry points is more
  relevant to browsing than searching
• Subject or feature entry points are more useful
  than alphabetical
• A linear representation is not ideal for
  multifaceted objects