Indexing serves as another format of controlled vocabulary, where it can directly identify what is in its controlled vocabulary with reference to documents retrieved. The types of indexing involved, namely, derivative indexing uses synonyms for keywords found in documents as index terms; free indexing is considered to be an index with no controlled vocabulary, it might suggest there is no thesaurus; whereas assignment indexing implies the use of identifies being created for the benefit not finding terms equivalent to what exists in its controlled vocabulary environment, however identifies are not found in a controlled setting. There is no doubt there are forms of indexing that require much discussion.
The activities of indexing is a cause of much debate amongst information practitioners, in as much as to imply is its role in information retrieval. The digital age we reside in, automotive technology is still playing a leading role towards delivering making information readily available to its users. This focus has fallen on to camps as to where indexing could play a significant part in the future, this involves mechanical and intellectual elements being contributory partners to indexing using computers as main stake holder in handling both mechanical and intellectual parts of indexing, however, there would need to be significant investment in research in artificial intelligence for this to become reality. For the time being, computers with indexing systems will continue to handle mechanical operations and human focus on the intellectual portion of indexing. Automatic indexing known as machine indexing does exist, but consist of limited intellectual part of indexing using a variety of algorithms for which keyword searching is most popular and has been extensively implemented.