Latent Semantic Indexing

Latent Semantic Indexing

Author: Aamod Bhor

LSI or Latent Semantic Indexing is a method used by the search engines for viewing and ranking pages on the web in a human and natural way. The algorithms of LSI analyze from behind the scene. These algorithms look not only for the keywords, but also for related words and synonyms which may be present on the page. An example of this can be a page which has the word visitor and analyzed by LSI method, has to have the words such as tourist, guest, sightseer etc on the page.

History

Google purchased Applied Semantics in the year 2003. The software technology of this company was used to organize and extract information from the websites in a way which is similar to the method used by humans while acting. The sole purpose of this exercise was to aid Google in matching the advertisements of AdSense with the relevant web pages wherein these adverts would be displayed. In the initial stages, the AdSense ads matched the keywords present on the pages with the keywords present in the ads. This resulted in millions of pages having the similar purpose of displaying keywords for generating traffic to their website. The content which was present on these websites was virtually non-realistic. This resulted in most of the pages searched to be spam.

Problems such as keyword stuffing and the use of reciprocal links for increasing the web traffic were increasing in such a scenario. This was leading to compounding of the already existent problems. This led Google and partially MSN and Yahoo to discontinue to method of reciprocal linking for search engine rankings of pages. This gave rise to the inbound links becoming important for the ranking purpose.

Evolution of LSI

Some of the methodologies which were incorporated with the advent of LSI are listed below.
Themed sites:

Shifting from the use of keyword based sites to theme based sites for the purpose of search engine ranking was one of the major changes brought about by Latent Semantic Indexing. This necessitates the use of synonyms and other related words while developing or building websites.

Anchor Text:

In the initial days, the techniques of SEO were focused on single keywords or phrases for internal as well as external links. It was a general feeling that if a particular keyword is generating the traffic to the website; it has to be used extensively throughout. But, after the introduction of LSI by Google, the websites which had a higher ranking initially on account of inbound links pertaining to single keywords, have now lost in the rankings race. Hence, varieties of anchor texts have to be used while designing of websites.

Summary

To summarize things, LSI favors theme based sites rather than single keyword centered sites. Naturally worded pages have to be written for optimizing the sites. Synonyms, plurals and tenses have to be used wherever possible for getting better results from search engines.