CiteSeer was a public search engine and digital library for scientific and academic papers, primarily in the fields of computer and information science that has been replaced by CiteSeerX. Many consider it to be the first academic paper search engine. It became public in 1998 and had many new features unavailable in academic search engines at that time. These included:
- Autonomous Citation Indexing automatically created a citation index that can be used for literature search and evaluation.
- Citation statistics and related documents were computed for all articles cited in the database, not just the indexed articles.
- Reference linking allowing browsing of the database using citation links.
- Citation context showed the context of citations to a given paper, allowing a researcher to quickly and easily see what other researchers have to say about an article of interest.
- Related documents were shown using citation and word based measures and an active and continuously updated bibliography is shown for each document.
It is often considered to be the first automated citation indexing system and was considered a predecessor of academic search tools such as Google Scholar and Microsoft Academic Search. CiteSeer-like engines and archives usually only harvest documents from publicly available websites and do not crawl publisher websites. As such authors whose documents are freely available are more likely to be represented in the index.
CiteSeer's goal is to improve the dissemination and access of academic and scientific literature. As a non-profit service that can be freely used by anyone, it has been considered as part of the open access movement that is attempting to change academic and scientific publishing to allow greater access to scientific literature. CiteSeer freely provided Open Archives Initiative metadata of all indexed documents and links indexed documents when possible to other sources of metadata such as DBLP and the ACM Portal. To promote open data, CiteSeerX shares its data with other researchers under a Creative Commons license.
The name can be construed to have at least two explanations. As a pun, a 'sightseer' is a tourist who looks at the sights, so a 'cite seer' would be a researcher who looks at cited papers. Another is a 'seer' is a prophet and a 'cite seer' is a prophet of citations.
CiteSeer and CiteSeer.IST 
It was created by researchers Lee Giles, Kurt Bollacker and Steve Lawrence in 1997 while they were at the NEC Research Institute (now NEC Labs), Princeton, New Jersey, USA. CiteSeer's goal was to actively crawl and harvest academic and scientific documents on the web and use autonomous citation indexing to permit querying by citation or by document, ranking them by citation impact.
After NEC, in 2004 it was hosted as CiteSeer.IST on the World Wide Web at the College of Information Sciences and Technology, The Pennsylvania State University, and had over 700,000 documents. For enhanced access, performance and research, similar versions of CiteSeer were supported at universities such as the Massachusetts Institute of Technology, University of Zürich and the National University of Singapore. However, these versions of CiteSeer proved difficult to maintain and are no longer available. Also, CiteSeer is not so accurate in its search on authors and their papers. In fact, for the same author, one gets fewer citation counts than other sites, such as Google Scholar.
CiteSeer had not been comprehensively updated since 2005 due to limitations in its architecture design. It had a representative sampling of research documents in computer and information science but was limited in coverage because it only has access to papers that are publicly available, usually at an author's homepage, or those submitted by an author. To overcome some of these limitations, a modular and open source architecture for CiteSeer was designed - CiteSeerX.
CiteSeerX replaced CiteSeer and all queries to CiteSeer were redirected. CiteSeerX is a public search engine and digital library and repository for scientific and academic papers primarily with a focus on computer and information science. Released in 2008, it was loosely based on the previous CiteSeer search engine and digital library and is built with a new open source infrastructure, SeerSuite, and new algorithms and their implementations. It was developed by researchers Dr. Isaac Councill and Dr. C. Lee Giles at the College of Information Sciences and Technology, Pennsylvania State University. It continues to support the goals outlined by CiteSeer to actively crawl and harvest academic and scientific documents on the public web and to use a citation index to permit query by citations and ranking of documents by the impact of citations. Currently, Lee Giles, Prasenjit Mitra, Susan Gauch, Min-Yen Kan, Pradeep Teregowda, Juan Pablo Fernández Ramírez, Pucktada Treeratpituk, Jian Wu, Douglas Jordan, Steve Carman, Jack Carroll, Jim Jansen, and Shuyi Zheng are or have been actively involved in its development. Recently, a table search feature was introduced. It has been funded by the National Science Foundation, NASA and Microsoft Research.
CiteSeerX continues to be rated as one of the world's top repositories and was rated number 1 in July 2010. It currently has over 2 million documents with nearly 2 million unique authors and 40 million citations.
CiteSeerX also shares its software, data, databases and metadata with other researchers, currently by Amazon s3 and by rsync. Its new modular open source architecture and software (available on SourceForge) is built on Apache Solr and other Apache and open source tools which allows it to be a testbed for new algorithms in document harvesting, ranking, indexing, and information extraction.
Other SeerSuite-based search engines 
The CiteSeer model had been extended to cover academic documents in business with SmealSearch and in e-business with eBizSearch. However, these were not maintained by their sponsors. An older version of both of these could be once found at BizSeer.IST but is no longer in service.
Other Seer-like search and repository systems have been built for chemistry, ChemXSeer and for archaeology, ArchSeer. Another had been built for robots.txt file search, BotSeer. All of these are built on the open source tool SeerSuite, which uses the open source indexer Lucene.
See also 
- Google Scholar
- Microsoft Academic Search
- The Collection of Computer Science Bibliographies
- DBLP (Digital Bibliography & Library Project)
- List of academic databases and search engines
- Disciplinary repository
- "About CiteSeerX". Retrieved 2010-05-07.
- "The CiteSeerX Team". Pennsylvania State University. Retrieved 2010-07-24.
- "Ranking Web of World Repositories: Top 800 Repositories". Cybermetrics Lab. July 2010. Retrieved 2010-07-24.
- "About CiteSeerX Data". Pennsylvania State University. Retrieved 2012-01-25.
Further reading 
- C. Lee Giles; Kurt D. Bollacker; Steve Lawrence (1998). "CiteSeer: an automatic citation indexing system". Proceedings of the third ACM conference on Digital libraries (DL '98).