Information retrieval context free grammar?

Indexing processes covered in this article are used by many of the popular Internet search engines as well as various software applications. This process encounters many technical obstacles, the solutions to which are still under study and academic review. This article is an introduction to the algorithm involved in creating a full-text search engine index for document retrieval, and many of the data structures involved, starting after data collection. For more information about the document collection process, see Web crawling.