- YaCy
Infobox Software
name = YaCy
caption =
developer =Michael Christen
latest_release_version = 0.61
latest_release_date =October 2 ,2008
operating_system = Platform independent
programming_language = Java
genre =Search engine
license = GPL
website = http://yacy.netYaCy (read "ya see") is a free distributed
search engine , built on principles ofpeer-to-peer (P2P) networks. Its core is acomputer program written in Java distributed on several hundred of computers,as of September 2006 , so-calledYaCy-peers . Each YaCy-peer independently crawls through the Internet, analyses and indexes found web pages and stores indexing results in a common database (so called index) which is shared with other YaCy-peers using principles of P2P networks.Compared to semi-distributed search engines, the YaCy-network has a decentralised architecture. All YaCy-peers are equal and no central server exists. It can be run either in a crawling mode or as a local
proxy server , indexing web pages visited by the person running YaCy on his or her computer. (Several mechanisms are provided to protect user's privacy).Access to the search functions is made by a locally running web server which provides a search box to enter the query and returns results of the search in form of a web page as usual on other search portals and engines
The program is released under the GPL license.
Architecture
YaCy search engine is based on five elements:Fact|date=January 2008;Crawler: A search robot which traverses from web page to web page and analyses their context.;Indexer: Creates a Reverse Word Index (RWI) i.e. each word from the RWI has its list of relevant URLs and Ranking information. Words are saved in form of word hashes.;Search and Administration interface: Made as a web interface provided by a local
HTTP servlet with servlet engine.;P2P network: Used to store the Reverse Word Index Database utilizing aDistributed Hash Table .Advantages
* As there is no central server, the results cannot be
censored , and the reliability is (at least theoretically) higher.
* Because the engine is not owned by a company, there is no centralised advertising or manipulated ranking.
* Because of the design of YaCy, it can be used to index the 'hidden web', like Tor,I2P orFreenet .Disadvantages
* As there is no central server and the YaCy network is open to anyone, malicious peers are (theoretically) able to insert inaccurate or commercially biased search results.
* At present, YaCy returns on the average significantly fewer results and is much slower than large commercial search engines.
* the YaCy protocol uses HTTP-Requests, which is much slower than UDP-Protocols or TCP-Protocols with persistent connections.See also
*
Sciencenet , a search engine for scientific knowledge, based on YaCyExternal links
* Download the Search engine software [http://yacy.net/Download.html Yacy client]
* [http://yacy.net/ YaCy website]
* [http://www.yacy-forum.org English forum]
* [http://forum.yacy-websuche.de/ German forum]
* [http://www.yacy-websuche.de/wiki/index.php/Hauptseite The YaCy-Wiki]
* [http://developer.berlios.de/projects/yacy/ developer page] atBerlios
* [http://www.yacyweb.de/ Demo - search the internet through a random YaCy-member]
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