Abstract:
A system determines a freshness of a first document. The system determines whether a freshness attribute is associated with the first document. The system identifies, based on the determination, a set of second documents that each contain a link to the first document. The system assigns a freshness score to the first document based on a freshness attribute associated with each document of the set of second documents or the freshness attribute associated with the first document.

Description:
RELATED APPLICATION 
     The present application is a continuation of U.S. application Ser. No. 12/854,727, filed Aug. 11, 2010, which is a continuation of U.S. application Ser. No. 10/879,503, filed Jun. 30, 2004 (now U.S. Pat. No. 7,797,316), which is a continuation-in-part of U.S. application Ser. No. 10/748,664, filed Dec. 31, 2003 (now U.S. Pat. No. 7,346,839), which claims priority under 35 U.S.C. §119 based on U.S. Provisional Application No. 60/507,617, filed Sep. 30, 2003, the disclosures of which are incorporated by reference herein in their entirety. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     Systems and methods consistent with the principles of the invention relate generally to information searching and, more particularly, to determining the freshness of retrieved documents and possibly using this freshness to score the retrieved documents. 
     2. Description of Related Art 
     Existing information searching systems use search queries to search through aggregated data to retrieve specific information that corresponds to the received search queries. Such information searching systems may search information stored locally, or in distributed locations. The World Wide Web (“web”) is one example of information stored in distributed locations. The web contains a vast amount of information, but locating a desired portion of that information can be challenging. This problem is compounded because the amount of information on the web and the number of new users inexperienced at web searching are growing rapidly. 
     Search engines attempt to return hyperlinks to web documents in which a user is interested. Generally, search engines base their determination of the user&#39;s interest on search terms (called a search query) entered by the user. The goal of the search engine is to provide links to high quality, relevant results to the user based on the search query. Typically, the search engine accomplishes this by matching the terms in the search query to a corpus of pre-stored web documents. Web documents that contain the user&#39;s search terms are “hits” and are returned to the user. 
     Frequently, web documents that are returned as “hits” to the user include out-of-date documents. If the freshness of web documents were reliably known, then the known freshness could be used in the ranking of the search results to avoid returning out-of-date web documents in the top results. Currently, however, a reliable freshness attribute for web documents does not exist. HTTP supports a “last-modified-since” attribute that indicates the day a last modification was made to a corresponding web document. This attribute, however, is optional in HTTP and is not used by all web documents. Additionally, the data indicated in the HTTP “last-modified-since” attribute may not be correct. 
     SUMMARY OF THE INVENTION 
     According to one aspect consistent with the principles of the invention, a method of determining the freshness of a first document is provided. The method may include identifying a set of second documents that each contains a link to the first document and determining a freshness attribute associated with each document of the set of second documents. The method may further include assigning a freshness score to the first document based on the freshness attribute associated with each document of the set of second documents. 
     According to another aspect, a method of determining the freshness of a first document is provided. The method may include determining whether a freshness attribute is associated with the first document and identifying, based on the determination, a set of second documents that each contain a link to the first document. The method may further include assigning a freshness score to the first document based on a freshness attribute associated with each document of the set of second documents or the freshness attribute associated with the first document. 
     According to a further aspect, a method of assigning a freshness score to a first document is provided. The method may include identifying a set of second documents that each contains a link to the first document and determining a freshness associated with each document of the set of second documents. The method may also include assigning a first freshness score to the first document if more documents of the set of second documents correspond to documents that are not fresh. The method may further include assigning a second freshness score to the first document if more documents of the set of second documents correspond to documents that are fresh, where the first freshness score is different than the second freshness score. 
     According to yet another aspect, a method of determining the freshness of a first document is provided. The method may include identifying a set of second documents that each contains a link to the first document and determining times at which each of the links to the first document existed. The method may also include assigning a freshness score to the first document based on the determined times. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, explain the invention. In the drawings, 
         FIG. 1  is a diagram of an overview of an exemplary aspect of the invention; 
         FIG. 2  is a diagram of an exemplary network in which systems and methods consistent with the principles of the invention may be implemented; 
         FIG. 3  is an exemplary diagram of a client and/or server of  FIG. 2  in an implementation consistent with the principles of the invention; and 
         FIGS. 4A and 4B  are flowcharts of exemplary processing for determining the freshness of one or more documents according to an implementation consistent with the principles of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description of the invention refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. Also, the following detailed description does not limit the invention. 
     A “document,” as the term is used herein, is to be broadly interpreted to include any machine-readable and machine-storable work product. A document may include an e-mail, a web site, a file, a combination of files, one or more files with embedded links to other files, a news group posting, a blog, a web advertisement, etc. In the context of the Internet, a common document is a web page. Web pages often include textual information and may include embedded information (such as meta information, images, hyperlinks, etc.) and/or embedded instructions (such as Javascript, etc.). A “link” as the term is used here, is to be broadly interpreted to include any reference to or from a document. 
     Exemplary Overview 
       FIG. 1  illustrates an overview of determining the freshness of a document according to an exemplary aspect of the invention. As shown in  FIG. 1 , a freshness score of a document p  105  may be based on freshness attributes  115  associated with each linking document  110  of a set of documents  100  that each have a link  120  pointing to document p  105 . Set of documents  100  may include at least a portion of documents from a group of documents that each include at least one link  120  to document p  105 . Each linking document  110  may have associated with it a freshness attribute  115  that provides some indication of when the respective linking document  110  was last modified, or updated. In some implementations consistent with principles of the invention, the freshness attribute may include an HTTP “last-modified-since” attribute. Other freshness attributes, however, may be used. Each linking document  110  may further include a link  120  that points to document p  105 . Each link  120  may include, for example, a hypertext link. Each link  120  may exist during a time period and may, thus, have associated with it a creation time and a removal time. 
     A freshness score (F r ), that, in some implementations, may be used in ranking document p  105  when document p  105  is returned at a result of an executed document search, may be assigned to document p  105  based on the freshness attributes  115  associated with each linking document  110  of the set of documents  100 , and/or based on times at which each link  120 , pointing to document p  105 , existed. 
     Exemplary Network Configuration 
       FIG. 2  is an exemplary diagram of a network  200  in which systems and methods consistent with the principles of the invention may be implemented. Network  200  may include multiple clients  210  connected to multiple servers  220  and  215  via a network  230 . Network  230  may include a local area network (LAN), a wide area network (WAN), a telephone network, such as the Public Switched Telephone Network (PSTN), an intranet, the Internet, a memory device, another type of network, or a combination of networks. Two clients  210  and two servers  220  and  215  have been illustrated as connected to network  230  for simplicity. In practice, there may be more or fewer clients and servers. Also, in some instances, a client may perform the functions of a server and a server may perform the functions of a client. 
     Clients  210  may include client entities. An entity may be defined as a device, such as a wireless telephone, a personal computer, a personal digital assistant (PDA), a laptop, or another type of computation or communication device, a thread or process running on one of these devices, and/or an object executable by one of these devices. Servers  220  and  215  may include server entities that gather, process, search, and/or maintain documents in a manner consistent with the principles of the invention. Clients  210  and servers  220  and  215  may connect to network  230  via wired, wireless, and/or optical connections. 
     In an implementation consistent with the principles of the invention, server  220  may include a search engine  225  usable by users at clients  210 . Server  220  may implement a data aggregation service by crawling a corpus of documents (e.g., web pages) hosted on data server(s)  215  and store information associated with these documents in a repository of crawled documents. The data aggregation service may be implemented in other ways, such as by agreement with the operator(s) of data server(s)  215  to distribute their hosted documents via the data aggregation service. Search engine  225  may execute a search, received from a user, on the corpus of documents hosted on data server(s)  215 . Server  220  may assign freshness scores to documents retrieved as a result of the executed search based on freshness attributes associated with each linking document of a set of documents that includes a link to the documents retrieved as a result of the executed search. 
     Server(s)  215  may store or maintain documents that may be crawled by server  220 . Such documents may include data related to published news stories, products, images, user groups, geographic areas, or any other type of data. For example, server(s)  215  may store or maintain news stories from any type of news source, such as, for example, the Washington Post, the New York Times, Time magazine, or Newsweek. As another example, server(s)  215  may store or maintain data related to specific product data, such as product data provided by one or more product manufacturers. As yet another example, server(s)  215  may store or maintain data related to other types of web documents, such as pages of web sites. 
     While servers  220  and  215  are shown as separate entities, it may be possible for one or more of servers  220  and  215  to perform one or more of the functions of another one or more of servers  220  and  215 . For example, it may be possible that two or more of servers  220  and  215  are implemented as a single server. It may also be possible for a single one of servers  220  or  215  to be implemented as two or more separate (and possibly distributed) devices. 
     Exemplary Client/Server Architecture 
       FIG. 3  is an exemplary diagram of a client or server entity (hereinafter called “client/server entity”), which may correspond to one or more of clients  210  and servers  220  and  215 , according to an implementation consistent with the principles of the invention. The client/server entity may include a bus  310 , a processing unit  320 , an optional main memory  330 , a read only memory (ROM)  340 , a storage device  350 , an input device  360 , an output device  370 , and a communication interface  380 . Bus  310  may include a path that permits communication among the components of the client/server entity. 
     Processing unit  320  may include any type of software, firmware or hardware implemented processing device, such as, a microprocessor, a field programmable gate array (FPGA), combinational logic, etc. Main memory  330  may include a random access memory (RAM) or another type of dynamic storage device that stores information and instructions for execution by processing unit  320 , if processing unit  320  includes a microprocessor. ROM  340  may include a conventional ROM device or another type of static storage device that stores static information and/or instructions for use by processing unit  320 . Storage device  350  may include a magnetic and/or optical recording medium and its corresponding drive. 
     Input device  360  may include a conventional mechanism that permits an operator to input information to the client/server entity, such as a keyboard, a mouse, a pen, voice recognition and/or biometric mechanisms, etc. Output device  370  may include a conventional mechanism that outputs information to the operator, including a display, a printer, a speaker, etc. Communication interface  380  may include any transceiver-like mechanism that enables the client/server entity to communicate with other devices and/or systems. For example, communication interface  380  may include mechanisms for communicating with another device or system via a network, such as network  230 . 
     As will be described in detail below, the client/server entity, consistent with the principles of the invention, may perform certain searching-related operations. The client/server entity may, in some implementations, perform these operations in response to processing unit  320  executing software instructions contained in a computer-readable medium, such as memory  330 . A computer-readable medium may be defined as one or more physical or logical memory devices and/or carrier waves. 
     The software instructions may be read into memory  330  from another computer-readable medium, such as data storage device  350 , or from another device via communication interface  380 . The software instructions contained in memory  330  may cause processing unit  320  to perform processes that will be described later. Alternatively, hardwired circuitry may be used in place of, or in combination with, software instructions to implement processes consistent with the principles of the invention. Thus, implementations consistent with principles of the invention are not limited to any specific combination of hardware circuitry and software. 
     Exemplary Processing 
       FIGS. 4A and 4B  are flowcharts of exemplary processing for determining the freshness of one or more documents according to an implementation consistent with the principles of the invention. As one skilled in the art will appreciate, the processing exemplified by  FIGS. 4A and 4B  can be implemented in software and stored on a computer-readable memory, such as main memory  330 , ROM  340  or storage device  350  of server  220 . In other implementations, the processing exemplified by  FIGS. 4A and 4B  can be implemented in hardwired circuitry, such as combinational logic, within processing unit  320  of server  220 . 
     Processing may begin with performance of a search through a corpus of documents (act  405 ). Search engine  225  of server  220  may use one or more search queries to perform the search. The documents returned as a result of the search may be analyzed to identify any associated freshness attributes (act  410 ). In one implementation, search engine  225  may identify a HTTP “last-modified-since” attribute as a freshness attribute for each document. For each document p returned as a result of the search, it may be determined whether an associated freshness attribute (e.g., a HTTP “last-modified-since” attribute) has been identified (act  415 ). If document p does have a freshness attribute associated with it, then the freshness attribute may be used as a basis for assigning a freshness score to document p (act  420 )( FIG. 4B ). In some implementations, for example, the freshness attribute may be used directly as a freshness score for document p. 
     If document p does not have a freshness attribute associated with it, or, optionally, even if document p does have a freshness attribute associated with it, then a freshness attribute associated with each document (e.g., linking document  110 ) of a set of documents that each currently contains, or previously contained, links to document p may be determined (act  425 )( FIG. 4A ). The set of documents that currently contain, or previously contained, links to document p may be selected randomly, or selected based on any appropriate criteria, from a group of documents containing a link to document p. A certain portion of the documents of the set of documents containing links to document p may include out-of-date documents (i.e., “not fresh”), while another portion of the documents of the set of documents containing links to document p may include “fresh” documents (i.e., documents that have been updated or modified within a configurable period of time relative to a current time). Optionally, times at which each link (i.e., link  120 ), associated with each document of the set of documents containing links to document p, existed may be determined (act  430 )( FIG. 4B ). A certain portion of the documents of the set of documents may have had a link to document p during a time period T, where T can be any specified length of time (e.g., the past two years). For each link to document p, the creation time and removal time of the link can be determined. 
     A freshness score (F r ) may be assigned to document p based on the freshness attribute of each linking document  110  pointing to document p and/or based on the times at which each link, pointing to document p, existed (act  435 ). For example, if the number of “not fresh” documents of the set of documents containing links to document p is greater than the number of “fresh” documents of the set of documents containing links to document p (i.e., as determined by freshness attribute(s) associated with each document of the set of documents), then document p can be considered “not fresh,” and a corresponding “low” freshness score F r  may be assigned to document p. As an illustrative example, if each document of a set of  100  documents containing a link to document p each has a freshness attribute, such as, for example, a HTTP “last-modified-since” attribute, that indicates that  80  of the documents have been not been recently modified or updated (i.e., modified or updated within a configurable period of time relative to a current time) and, thus, are not fresh, then a “low” freshness score F r  can be assigned to document p. 
     As another example, if the number of “fresh” documents of the set of documents containing links to document p is greater than the number of “not fresh” documents of the set of documents containing links to document p (i.e., as determined by freshness attribute(s) associated with each document of the set of documents), then document p can be considered “fresh,” and a corresponding “high” freshness score F r  may be assigned to document p. To illustrate, if each document of set of 100 documents containing a link to document p has a freshness attribute, such as, for example, a HTTP “last-modified-since” attribute, that indicates that 70 of the documents have been recently modified or updated and, thus, are fresh, then a “high” freshness score F r  can be assigned to document p. 
     As a further example, if the number of links that currently point to document p is smaller than the number of links that pointed to document p at some time t in the past (e.g., one year ago), then document p can be considered to be “not fresh” and a corresponding “low” freshness score F r  may be assigned to document p. As another example, if the number of links that pointed to document p at some time t in the past is smaller than the number of links that currently point to document p, then document p can be considered “fresh” and a corresponding “high” freshness score F r  may be assigned to document p. 
     As yet another example, if a ratio of a number of recent, or “new,” links to document p to a number of not recent, or “old,” links to document p is larger than a threshold value T h , then document p can be considered “not fresh” and a corresponding “low” freshness score F r  may be assigned to document p. If the ratio of the number of “new” links to document p to the number of “old” links to document p is smaller than a threshold value T h , then document p can be considered “fresh” and a corresponding “high” freshness score F r  may be assigned to document p. Acts  415 - 435  may be performed for each document p returned as a result of the performed search to assign a freshness score F r  to each document p. 
     The freshness scores assigned to each of the documents returned as a result of the performed search may be one factor of a set of factors used to rank the results of the search (act  440 ). 
     Conclusion 
     The foregoing description of preferred embodiments of the present invention provides illustration and description, but is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. For example, while a series of acts has been described with regard to  FIGS. 4A and 4B , the order of the acts may be modified in other implementations consistent with the principles of the invention. Also, non-dependent acts may be performed in parallel. 
     It will also be apparent to one of ordinary skill in the art that aspects of the invention, as described above, may be implemented in many different forms of software, firmware, and hardware in the implementations illustrated in the figures. The actual software code or specialized control hardware used to implement aspects consistent with the principles of the invention is not limiting of the present invention. Thus, the operation and behavior of the aspects of the invention were described without reference to the specific software code—it being understood that one of ordinary skill in the art would be able to design software and control hardware to implement the aspects based on the description herein. Further, certain portions of the invention have been described as “logic” that performs one or more functions. This logic may include hardware, such as an application specific integrated circuit or a field programmable gate array, software, or a combination of hardware and software. 
     No element, act, or instruction used in the present application should be construed as critical or essential to the invention unless explicitly described as such. Also, as used herein, the article “a” is intended to include one or more items. Where only one item is intended, the term “one” or similar language is used. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.