Abstract:
A computer program product for crawling URLs that are encoded and highly dynamic, the computer program product includes a non-transitory computer readable storage medium having computer readable program code embodied therewith. The computer readable program code includes computer readable program code configured to retrieve navigational state information corresponding to a URL and compare the navigational state information to previously stored navigational state information corresponding to one or more previously visited URLs. The computer readable program code also includes computer readable program code configured to determine if the URL has been previously visited and retrieve content associated with the URL if the URL has not been previously visited.

Description:
BACKGROUND 
       [0001]    The present disclosure relates to automatic crawling of web content, and more specifically, to automatic crawling of web content having encoded and dynamic URLs. 
         [0002]    A web-crawler searches, or spiders, websites in an automated way to gather and analyze information for different purposes. The automatic navigation is based on identification of visited webpage, also referred to uniform resource locators (URLs), and discovering new ones. Many sites, in particular search engines, use automatic crawling, as a means of providing up-to-date data. Web-crawlers can also be used for automating maintenance tasks on websites, such as checking links or validating HTML code. 
         [0003]    A web-crawler starts with a list of URLs to visit, generally called seeds. As the crawler visits these URLs, it identifies all the hyperlinks in the pages and adds them to the list of URLs to visit. These URLs are recursively visited according to a set of policies. Web-crawlers are used to create a copy of all the visited pages for later processing by a search engine that will index the downloaded pages to provide fast searches. Web-crawlers often need to determine if a particular webpage, or URL, is unique. This information is used to determine if a subsequently visited webpage, or URL, being visited is new or a duplicate of one visited before. 
       SUMMARY 
       [0004]    According to one embodiment of the present disclosure, a method of crawling URLs that are encoded and highly dynamic includes retrieving navigational state information corresponding to a URL; comparing the navigational state information to previously stored navigational state information corresponding to one or more previously visited URLs; determining if the URL has been previously visited; and retrieving content associated with the URL if the URL has not been previously visited. 
         [0005]    According to one embodiment of the present disclosure, a computer program product for crawling URLs that are encoded and highly dynamic, the computer program product including: a non-transitory computer readable storage medium having computer readable program code embodied therewith, the computer readable program code includes: computer readable program code configured to retrieve navigational state information corresponding to a URL; compare the navigational state information to previously stored navigational state information corresponding to one or more previously visited URLs; determine if the URL has been previously visited; and retrieve content associated with the URL if the URL has not been previously visited. 
         [0006]    Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure. For a better understanding of the disclosure with the advantages and the features, refer to the description and to the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0007]    The subject matter which is regarded as the disclosure is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The forgoing and other features, and advantages of the disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0008]      FIG. 1  is a flow diagram illustrating the operation of a web-crawler; 
           [0009]      FIG. 2  is a flow diagram illustrating a method of crawling URLs that are encoded and highly dynamic in accordance with an embodiment of the disclosure; 
           [0010]      FIG. 3  is a table of exemplary navigation state information used by the methods depicted in  FIGS. 2 and 4 ; 
           [0011]      FIG. 4  is a flow diagram illustrating a method of uniquely identifying an encoded URL in accordance with another embodiment of the disclosure; and 
           [0012]      FIG. 5  illustrates one example of a processing system for practice of the teachings herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Referring now to  FIG. 1 , a flow diagram illustrating the operation of typical web-crawler is shown. At block  100 , the web-crawler retrieves the contents of a webpage or URL. Next, the web-crawler applies a similarity algorithm to the contents of the URL, as shown at block  102 . Once the similarity algorithm has been applied, the web-crawler determines if the URL has been visited before, as shown at decision block  104 . If the URL has been visited before, the web-crawler skips parsing of the URL, as shown at block  106 . Otherwise, the web-crawler analyzes the content of the URL and explores any additional URLs found in the content of the webpage, as shown at block  108 . As illustrated, typical web-crawlers download content referred to by an URL in order to detect whether the URL has been previously explored or not. 
         [0014]    URLs may be encoded, meaning that they do not provide any information about the content that they refer to. In addition, URLs for a single webpage may be dynamic or frequently changed. Furthermore, in some cases different URLs may refer to same content. Due to the nature of encoded and dynamic URLs, web-crawlers, such as the one depicted in  FIG. 1 , may fail to accurately identify that a URL has been previously visited, which results in the web-crawler repeatedly scanning and downloading the content of a single URL multiple times. 
         [0015]    URLs can refer to web portal applications that often contain portlets that can be rearranged in a webpage. Portlets are pluggable user interface software components that are managed and displayed in a web portal. Typically, a web portal page is displayed as a collection of non-overlapping portlet windows, where each portlet window displays a portlet. Accordingly a portlet, or collection of portlets, resembles a web-based application that is hosted in a portal. Some examples of portlet applications are email, weather reports, discussion forums, and news. Many web-crawlers treat web portal pages that contain identical portlets in different arrangements as distinct web pages because the web-crawlers assign each page a different identification code. In addition some web portal applications, such as IBM&#39;s WebSphere Portal application, use encoded and/or highly dynamic URLs. 
         [0016]    Referring now to  FIG. 2 , a flow diagram illustrating a method of crawling URLs that are encoded and highly dynamic in accordance with an embodiment of the disclosure is shown. The first step in the method, as illustrated at block  200 , is to retrieve navigational state information for the URL. Once the navigational state information has been retrieved, then a URL detection algorithm is applied to the navigational state information, as shown at block  202 . At decision block  204 , it is determined if the URL, or webpage, has already been visited by the web-crawler. If the URL has been visited, the contents of the URL are not downloaded, parsed or analyzed, as shown at block  206 . Otherwise, the contents of the URL are downloaded, as shown at block  208 . Once the URL content has been downloaded, the URL content is analyzed and any additional URLs found on the page are explored, as shown at block  210 . As illustrated, the web-crawler does not require retrieving content referred by an URL to detect whether that URL has been visited or not. Instead, the web-crawler only retrieves navigational state information of the encoded URL and applies a URL detection algorithm on it. Thus, the web-crawler avoids downloading redundant content, which saves network bandwidth and enables faster crawling of web sites. 
         [0017]    In an exemplary embodiment, the web-crawler uses navigational state information to identify encoded and dynamic URLs. Navigational state information can include, but is not limited to, navigational path, selected page, target portlets and additional information which specify the view associated with a specific client. In exemplary embodiments, one or more pieces of navigation sate information are required for URL identification. The web-crawler not only uses navigational state information of web portal URLs to identify the URL, it may also identify which piece of navigational state information to consider for the purpose of identifying the URL. 
         [0018]    In exemplary embodiments, the web-crawler is also capable of identifying URLs that have various arrangements of the same portlets. For example, a webpage has three portlets (A, B and C) and a java script action on the webpage changes the location of portlet A and C. Although the location of the portlets has changed, the content of the webpage remains unchanged. Therefore, the webpage will be detected as the same by the web-crawler. 
         [0019]    Web portal services, such as IBM&#39;s WebSphere Portal framework, include a representational state transfer (REST) service, or application program interface (API), which decodes and encodes navigational state information to and from URLs. In exemplary embodiments, the web portal REST API also provides navigational state information for a URL. The dynamic nature of URLs can also present in some of the navigational state information. For example, different pieces of navigational state information can point to the same content or view. Therefore, not all navigational state information can be used to uniquely identify URLs. Accordingly, to uniquely identify URLs the web-crawler will not consider the dynamic part of the navigational state information and will only incorporate relevant navigational state information in the URL identification process. 
         [0020]    Referring now to  FIG. 3 , a table illustrating exemplary navigational state information that can be used to uniquely identify URLs and extend scan coverage is shown. The navigational state information may include: selection-node information, which is the object ID of the currently selected node a URL refers to; resource-ID information, which is the object ID of a resource type URL; portlet-ID information, which is an ID of the portlet node which specifies the object-ID (OID); portlet-mode information that allows a portlet to display different user interface; window-state information that allows a user to change how portlet window will be displayed within portal; and action-type information which specifies that action on this link causes login status at server. In an exemplary embodiment, the selection-node and resource-ID information enable the web-crawler to detect if a URL has been previously visited. For a particular URL, these two pieces of information remain unchanged regardless how a user navigates to that page. Therefore, the web-crawler can use this information to detect visited content during automatic crawling. Moreover, the web-crawler can use portlet-mode and window-state information to discover new links. In addition, action-type information can be used to detect whether the web-crawler is about to explore a logout link. Detecting a logout link allows the web-crawler to continue a current scan session. 
         [0021]    Referring now to  FIG. 4 , a flow diagram illustrating a method of uniquely identifying a URL that is encoded and/or dynamic in accordance with an embodiment of the disclosure is shown. The first step in the method, shown at block  300 , is to receive an encoded URL as input. Next, various variables used by the method are initialized, as shown at block  302 . In an exemplary embodiment, a variable list which is used to store navigation state information corresponding to the input URL is initialized. Next, a URL to representational state transfer (REST) service is created which decodes the input URL, as shown at block  304 . Once the REST service URL is created, the navigational state information for the input URL is retrieved as shown at block  306 . In exemplary embodiments, the navigation state information may be provided in an application or XML format. Once the navigational state information is received, the URL type is determined, as shown at decision block  308 . In exemplary embodiments, the URL type may indicate whether the URL represents a resource URL or a portlet URL. In an embodiment, the URL type may be determined by checking for the presence of the state-node variable in the navigational state information. If the URL is a resource URL, the resource-ID is added to the variable list which represents navigation state information of the input URL, as shown at block  312 . 
         [0022]    Continuing with reference to  FIG. 4 , if it is determined that the URL is a engine URL, the selection-node-ID is added to the variable list which represents navigation state information of the input URL, as shown at block  310 . Next, at decision block  314 , the navigational state information is checked for the presence of a portlet node. In exemplary embodiments, the presence of a portlet node in the navigational state information indicates that the URL is portlet generated and information about portlet needs to be collected. At decision block  316 , the method includes determining whether the portlet is actually part of the URL content. In exemplary embodiments, determining whether the portlet is actually part of the URL content can be done by requesting layout information about the webpage from the web portal application and checking the existence of the portlet in the response feed. If the URL does contain a portlet that is actually part of the webpage, portlet information is added to the variable list which represents navigation state information of the input URL, as shown at block  318 . At block  320 , the variable list which represents navigation state information of the input URL is output and used to uniquely identify the encoded URL. 
         [0023]    Referring to  FIG. 5 , there is shown an embodiment of a processing system  400  for implementing the teachings herein. In this embodiment, the system  400  has one or more central processing units (processors)  401   a,    401   b,    401   c,  etc. (collectively or generically referred to as processor(s)  401 ). In one embodiment, each processor  401  may include a reduced instruction set computer (RISC) microprocessor. Processors  401  are coupled to system memory  414  and various other components via a system bus  413 . Read only memory (ROM)  402  is coupled to the system bus  413  and may include a basic input/output system (BIOS), which controls certain basic functions of system  400 . 
         [0024]      FIG. 5  further depicts an input/output (I/O) adapter  407  and a network adapter  406  coupled to the system bus  413 . I/O adapter  407  may be a small computer system interface (SCSI) adapter that communicates with a hard disk  403  and/or tape storage drive  405  or any other similar component. I/O adapter  407 , hard disk  403 , and tape storage device  405  are collectively referred to herein as mass storage  404 . A network adapter  406  interconnects bus  413  with an outside network  416  enabling data processing system  400  to communicate with other such systems. A screen (e.g., a display monitor)  415  is connected to system bus  413  by display adaptor  412 , which may include a graphics adapter to improve the performance of graphics intensive applications and a video controller. In one embodiment, adapters  407 ,  406 , and  412  may be connected to one or more I/O busses that are connected to system bus  413  via an intermediate bus bridge (not shown). Suitable I/O buses for connecting peripheral devices such as hard disk controllers, network adapters, and graphics adapters typically include common protocols, such as the Peripheral Components Interface (PCI). Additional input/output devices are shown as connected to system bus  413  via user interface adapter  408  and display adapter  412 . A keyboard  409 , mouse  410 , and speaker  411  all interconnected to bus  413  via user interface adapter  408 , which may include, for example, a Super I/O chip integrating multiple device adapters into a single integrated circuit. 
         [0025]    Thus, as configured in  FIG. 5 , the system  400  includes processing means in the form of processors  401 , storage means including system memory  414  and mass storage  404 , input means such as keyboard  409  and mouse  410 , and output means including speaker  411  and display  415 . In one embodiment, a portion of system memory  414  and mass storage  404  collectively store an operating system such as the AIX® operating system from IBM Corporation to coordinate the functions of the various components shown in  FIG. 1 . 
         [0026]    It will be appreciated that the system  400  can be any suitable computer or computing platform, and may include a terminal, wireless device, information appliance, device, workstation, mini-computer, mainframe computer, personal digital assistant (PDA) or other computing device. 
         [0027]    Examples of operating systems that may be supported by the system  400  include Windows 95, Windows 98, Windows NT 4.0, Windows XP, Windows 2000, Windows CE, Windows Vista, Macintosh, Java, LINUX, and UNIX, or any other suitable operating system. The system  400  also includes a network interface  416  for communicating over a network. The network can be a local-area network (LAN), a metro-area network (MAN), or wide-area network (WAN), such as the Internet or World Wide Web. Users of the system  400  can connect to the network through any suitable network interface  416  connection, such as standard telephone lines, digital subscriber line, LAN or WAN links (e.g., T1, T3), broadband connections (Frame Relay, ATM), and wireless connections (e.g., 802.11(a), 802.11(b), 802.11(g)). 
         [0028]    As disclosed herein, the system  400  includes machine readable instructions stored on machine readable media (for example, the hard disk  404 ) for capture and interactive display of information shown on the screen  415  of a user. As discussed herein, the instructions are referred to as “software”  420 . The software  420  may be produced using software development tools as are known in the art. Also discussed herein, the software  420  may also referred to as a “command line testing tool”  420 , an “a testing interface”  420  or by other similar terms. The software  420  may include various tools and features for providing user interaction capabilities as are known in the art. 
         [0029]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one more other features, integers, steps, operations, element components, and/or groups thereof. 
         [0030]    The flow diagrams depicted herein are just one example. There may be many variations to this diagram or the steps (or operations) described therein without departing from the spirit of the disclosure. For instance, the steps may be performed in a differing order or steps may be added, deleted or modified. All of these variations are considered a part of the claimed disclosure. 
         [0031]    The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiment was chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated 
         [0032]    While the preferred embodiment to the disclosure had been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the disclosure first described.