Akbar Keshavarzpour - Department of Computer Engineering, Apadana Institute of Higher Education, Shiraz, Iran
Haleh Homayouni - Department of Computer Engineering, Apadana Institute of Higher Education, Shiraz, Iran
Mansoor Amini Lari - Assistant Professor of Information Technology, Department of Computer and InformationTechnology, Faculty of Engineering, Islamic Azad University, Marvdasht, Iran
Seraj Dean Katebi - Ph.D in Computer Aided Design of Nonlinear Control Systems, Department of Electrical andComputer Engineering , Faculty of Engineering , Shiraz University , Shiraz , Iran

As we know, in general IR1 is a finding tool for retrieving lots of documents which haveunstructured nature (that we call it text), that satisfies an information need from within largedata collections that we can store them on computer. As defined in this way, informationretrieval used to be an activity that only a few people engaged in for example referencelibrarians, paralegals, and similar professional searchers. Now a day the world has changed,and hundreds of millions of people are using information retrieval every day when they areusing a web search engine or search their email. Information retrieval is fast becoming thedominant form of information access, overtaking traditional database style searching. One ofthe most important topics in IR is Index or Data Compression. In this paper we have anoverview on index compression and their techniques in information retrieval.

Information Retrieval, documents, traditional database, Data Compression Index Compression