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Crawl Frontier
A crawl frontier is a data structure used for storage of URLs eligible for crawling and supporting such operations as adding URLs and selecting for crawl. Sometimes it can be seen as a priority queue. Overview A crawl frontier is one of the components that make up the architecture of a web crawler. The crawl frontier contains the logic and policies that a crawler follows when visiting websites. This activity is known acrawling The policies can include such things as what pages should be visited next, the priorities for each page to be searched, and how often the page is to be visited. The efficiency of the crawl frontier is especially important since one of the characteristics of the Web that make web crawling a challenge; is that it contains such a large volume of data and it is constantly changing. Architecture The initial list of URLs contained in the crawler frontier are known as seeds. The web crawler will constantly ask the frontier what pages to visit. As the crawl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uniform Resource Locator
A Uniform Resource Locator (URL), colloquially termed as a web address, is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifier (URI), although many people use the two terms interchangeably. URLs occur most commonly to reference web pages (HTTP) but are also used for file transfer (FTP), email (mailto), database access (JDBC), and many other applications. Most web browsers display the URL of a web page above the page in an address bar. A typical URL could have the form http://www.example.com/index.html, which indicates a protocol (http), a hostname (www.example.com), and a file name (index.html). History Uniform Resource Locators were defined in in 1994 by Tim Berners-Lee, the inventor of the World Wide Web, and the URI working group of the Internet Engineering Task Force (IETF), as an outcome of collaboration started at the IETF Living Documents birds of a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Priority Queue
In computer science, a priority queue is an abstract data-type similar to a regular queue or stack data structure in which each element additionally has a ''priority'' associated with it. In a priority queue, an element with high priority is served before an element with low priority. In some implementations, if two elements have the same priority, they are served according to the order in which they were enqueued; in other implementations ordering of elements with the same priority remains undefined. While coders often implement priority queues with heaps, they are conceptually distinct from heaps. A priority queue is a concept like a list or a map; just as a list can be implemented with a linked list or with an array, a priority queue can be implemented with a heap or with a variety of other methods such as an unordered array. Operations A priority queue must at least support the following operations: * ''is_empty'': check whether the queue has no elements. * ''insert_wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Web Crawler
A Web crawler, sometimes called a spider or spiderbot and often shortened to crawler, is an Internet bot that systematically browses the World Wide Web and that is typically operated by search engines for the purpose of Web indexing (''web spidering''). Web search engines and some other websites use Web crawling or spidering software to update their web content or indices of other sites' web content. Web crawlers copy pages for processing by a search engine, which indexes the downloaded pages so that users can search more efficiently. Crawlers consume resources on visited systems and often visit sites unprompted. Issues of schedule, load, and "politeness" come into play when large collections of pages are accessed. Mechanisms exist for public sites not wishing to be crawled to make this known to the crawling agent. For example, including a robots.txt file can request bots to index only parts of a website, or nothing at all. The number of Internet pages is extremely large; ev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crawler Frontier Architecture
Crawler may refer to: * Web crawler, a computer program that gathers and categorizes information on the World Wide Web * A first-instar nymph of a scale insect that has legs and walks around before it attaches itself and becomes stationary * Crawler (BEAM) in robotics * A type of crane on tracks * "Crawlers" (''Into the Dark''), an episode of the second season of ''Into the Dark'' *''The Crawler'', an episode of the cartoon ''Extreme Ghostbusters'' * ''Crawler'' (album), an album by IDLES * Crawler (band), a British rock band * Crawlers (band), a British rock band * A fictional creature in the video game ''Fable III'' * A fictional creature in the movie ''The Descent'' See also * Bottom crawler, an underwater exploration and recovery vehicle * Crawl (other) * Crawler-transporter, a large tracked vehicle used by NASA to transport spacecraft * Nightcrawler (''Lumbricus terrestris ''Lumbricus terrestris'' or the ''common earthworm'' is a large, reddish worm specie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Middleware
Middleware is a type of computer software that provides services to software applications beyond those available from the operating system. It can be described as "software glue". Middleware makes it easier for software developers to implement communication and input/output, so they can focus on the specific purpose of their application. It gained popularity in the 1980s as a solution to the problem of how to link newer applications to older legacy systems, although the term had been in use since 1968. In distributed applications The term is most commonly used for software that enables communication and management of data in distributed applications. An IETF workshop in 2000 defined middleware as "those services found above the transport (i.e. over TCP/IP) layer set of services but below the application environment" (i.e. below application-level APIs). In this more specific sense ''middleware'' can be described as the dash ("-") in '' client-server'', or the ''-to-'' in ''peer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
