Abstract:
One disclosed method includes the steps of initiating a download of a first document by a computer system, the first document having a plurality of parts according to a first predefined format; initiating a download of a second document by the computer system, the second document having a plurality of parts according to a second predefined format; determining a download priority of at least one of the plurality of parts of the first document by the computer system based at least in part on the predefined format of the first document; downloading the at least one of the plurality of parts of the first document according to the download priority; determining whether to suspend the download of the second document based on a state of a resource available to the computer system and the download priority; and suspending the download of the second document.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Patent Application is a continuation of co-pending U.S. patent application Ser. No. 11/515,627, filed Sep. 5, 2006, entitled “Methods and Apparatus for Optimizing Responsiveness of Portable Documents,” is related to U.S. Pat. No. 6,073,148 filed on Jun. 6, 2000 entitled, “DISPLAYING ELECTRONIC DOCUMENTS WITH SUBSTITUTE FONTS”, both of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     Conventional computerized devices, such as personal computers, laptop computers, and the like enable users to access (i.e., download) documents. Documents can be stored locally (i.e., on the hard drive of the a computer), or remotely, such as on a server. A server can be a local area network, available only to a particular group of users. A server can also be a publicly available server, such as the Internet. 
     When a user accesses a document residing on a server, typically a copy of that document is downloaded from the server to a cache on the user&#39;s computer. The time necessary for the download to occur can depend on a number of different factors, such as the connection speed of the user&#39;s computer, the bandwidth of the server, etc. 
     Documents can be made up of document structures. A document structure can be, for example, pages, images, annotations, structure tree, help modules, etc. Typically, document structures can be downloaded as they are needed. However, once a download begins, the download continues until it is finished, regardless of the other document structures that may be need to be downloaded. 
     A portable document is a document that is self-contained, and portable across any platform. That is, everything (i.e., document structures, etc.) needed to view the document (i.e., fonts, images, etc.) is bundled into the document. All users will see the same document even when viewed with different computers, different operating systems, different document viewers, etc. Essentially, the document appears the same on virtually any viewer or printed out on paper. A document that is in Portable Document Format (PDF) is an example of a portable document. 
     SUMMARY 
     Conventional technologies for downloading portable documents, or downloading document structures associated with portable documents, suffer from a variety of deficiencies. In particular, conventional technologies related to downloading portable documents, or downloading document structures are limited in that conventional technologies download the document structures as they are needed, requiring a user to wait until the document structure has completed the download, prior to utilizing that document structure. Conventional technologies also pre-fetch document structures when there are available resources to perform the download. Once a download has started, conventional technologies do not interrupt the download until the download has finished. Thus, a request to download a document or a document structure that may be more pressing than the current download must wait until the current download has completed. Conventional technologies base the decision of when to download documents and document structures on crude methods involving the size of file, the available speed of a user&#39;s computer, and the available bandwidth of the server. Thus, there is no coordination of prioritizing downloads when multiple documents are opened. 
     Embodiments disclosed herein significantly overcome such deficiencies and provide a system that includes a computer system executing a portable document downloading process that optimizes performance and responsiveness of portable documents on slow file systems, such as the Internet by, taking advantage of deep knowledge of document structures, connection speed, and other factors. The portable document downloading process decides the best strategy, at any point, to download a document, or document structure, with the goal of minimizing the time required to download a document in its entirety while providing the optimal user responsiveness. The portable document downloading process pre-fetches document structures that may be needed while assuring that the pre-fetching does not interfere with downloading parts of the document (i.e., document structures) that are needed immediately to respond to direct user 
     actions. The portable document downloading process coordinates which document structures are downloaded at any time, using knowledge of whether the data is needed immediately (or might be needed), the speed of the connection, and the speed of a particular server. The portable document downloading process also maintains a status of in-progress downloads in such a way as to allow the portable document downloading process to selectively pause a pre-fetched download so as to allow the full bandwidth available to be applied to download document structures that are needed immediately. 
     The portable document downloading process coordinates bandwidth usage when more than one document is open at a time, and collects information about the connection speed in order to make ad hoc decisions about the optimal use of the available bandwidth. The portable document downloading process collects information about the user&#39;s connection speed, and also of particular servers&#39; bandwidth information, when possible, on an ongoing basis. In one embodiment, this data is collected on all document types that are downloaded to the user&#39;s computer, not just portable document types. 
     When a document is opened in a portable document viewer, the portable document downloading process notes the file size and the current connection speed. In one embodiment, the speed of a particular server is noted as well. The portable document downloading process determines whether it would be optimal to download the entire document or to byte range request parts of the document. The decision is made based on heuristics associated with the file size, the connection bandwidth, and if available, the bandwidth of downloads from the targeted server. If the decision by the portable document downloading process is to download the entire document, the download is handled by the portable document downloading process, and hidden from the other parts of the portable document viewer. The portable document downloading process also notes the current document with which the user is interacting, and prioritizes its downloads accordingly. Any current downloads that are associated with documents not associated with the user&#39;s current focus are paused. It should be noted that only downloads for document structures that might be needed may be paused. The portable document downloading process maintains information associated with the paused download, and restarts the download at a later time when the download does not interfere with downloading document structures that are needed to respond to a user request. 
     The portable document downloading process maintains a status of which document structures are local in the cache (of the user&#39;s computer), and which document structures have yet to be requested. When a portable document is opened, the portable document downloading process receives requests from different parts of the portable document viewer to pre-fetch parts of the document structure. The portable document downloading process also receives requests for document structures that are needed immediately to respond to actions by the user. These requests are given a higher priority to optimize responsiveness to the user. If the portable document downloading process has determined the document should be byte range requested, the portable document downloading process opens a connection with the server, and begins to download the document structures that are needed immediately. Once those document structures are downloaded, the portable document downloading process opens another connection with the server, and begins to download document structures that may be needed (i.e., pre-fetching document structures). The portable document downloading process can also pre-fetch document structures for other documents that are currently opened. While a user is interacting with the document, if, at any point, a user&#39;s request causes document structures to be needed, that are not in the cache, the portable document downloading process can pause any pre-fetch download, freeing up the available bandwidth to download the document structures that are needed immediately. While a user is interacting with the document, if, at any point, a user&#39;s action causes structures that were needed to no longer be needed, the portable document downloading process can reclassify them as structures that might be needed, and thus, may subsequently pause the download of those structures. 
     In an example embodiment, the portable document downloading process allows for a configurable cache. As part of the speculative downloading of documents and document structures, the portable document downloading process pre-fetches documents and document structures. Some security policies prevent documents and document structures from being pre-fetched. Thus, the portable document downloading process has the capability to identify a security policy and selectively configure the cache in accordance with the security policy. 
     The portable document downloading process detects a requirement to obtain a first document by the computer system. The first document has a predefined format. The portable document downloading process identifies a sequence of portions of the first document to obtain based on analysis of the predefined format of the first document, and analysis of current operational parameters of the computer system. The portable document downloading process obtains and, and in some cases, renders a first portion of the first document from the identified sequence, and obtains successive portions of the first document in accordance with the identified sequence. 
     During an example operation of one embodiment, suppose a user downloads a portable document from a server. The portable document downloading process, anticipating the user will open the document at the first page, downloads the first page of the document such that the response time of the document download is optimized, and the user is quickly presented with the first page of the document. The portable document downloading process, anticipating that the user will ‘page down’ to request the second page of the document, begins to download the second page of the document. During the downloading of the second page of the document, the user requests the tenth page of the document. The portable document downloading process pauses the download of the second page of the document, and immediately begins downloading the tenth page of the document, in response to the user&#39;s request. At a later time, the portable document downloading process resumes the download of the second page of the document. The portable document downloading process maintains a status of which document structures have been downloaded. 
     Other embodiments disclosed herein include any type of computerized device, workstation, handheld or laptop computer, or the like configured with software and/or circuitry (e.g., a processor) to process any or all of the method operations disclosed herein. In other words, a computerized device such as a computer or a data communications device or any type of processor that is programmed or configured to operate as explained herein is considered an embodiment disclosed herein. 
     Other embodiments disclosed herein include software programs to perform the steps and operations summarized above and disclosed in detail below. One such embodiment comprises a computer program product that has a computer-readable medium including computer program logic encoded thereon that, when performed in a computerized device having a coupling of a memory and a processor, programs the processor to perform the operations disclosed herein. Such arrangements are typically provided as software, code and/or other data (e.g., data structures) arranged or encoded on a computer readable medium such as an optical medium (e.g., CD-ROM), floppy or hard disk or other a medium such as firmware or microcode in one or more ROM or RAM or PROM chips or as an Application Specific Integrated Circuit (ASIC). The software or firmware or other such configurations can be installed onto a computerized device to cause the computerized device to perform the techniques explained as embodiments disclosed herein. 
     It is to be understood that the system disclosed herein may be embodied strictly as a software program, as software and hardware, or as hardware alone. The embodiments disclosed herein, may be employed in data communications devices and other computerized devices and software systems for such devices such as those manufactured by Adobe Systems Incorporated of San Jose, Calif. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing will be apparent from the following description of particular embodiments disclosed herein, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles disclosed herein. 
         FIG. 1  shows a high level view of a document editor according to one embodiment disclosed herein. 
         FIG. 2  illustrates a flowchart of a procedure performed by the system of  FIG. 1 , when the portable document downloading process detects a requirement to obtain a first document by the computer system, the first document having a predefined format, according to one embodiment disclosed herein. 
         FIG. 3  illustrates a flowchart of a procedure performed by the system of  FIG. 1 , when the portable document downloading process evaluates current operational parameters associated with the first document and the computer system to identify at least a portion of the first document to obtain, according to one embodiment disclosed herein. 
         FIG. 4  illustrates a flowchart of a procedure performed by the system of  FIG. 1 , when the portable document downloading process evaluates current operational parameters associated with the first document and the computer system to identify at least a portion of the first document to obtain, and identifies at least one second document including at least one second document structure, according to one embodiment disclosed herein. 
         FIG. 5  illustrates a flowchart of a procedure performed by the system of  FIG. 1 , when the portable document downloading process obtains a first portion of the first document from the identified sequence, according to one embodiment disclosed herein. 
         FIG. 6  illustrates a flowchart of a procedure performed by the system of  FIG. 1 , when the portable document downloading process identifies at least one first document structure associated with the first document, according to one embodiment disclosed herein. 
         FIG. 7  illustrates a flowchart of a procedure performed by the system of  FIG. 1 , when the portable document downloading process identifies at least one first document structure associated with the first document, and anticipates receipt of a request for the at least one first document structure, according to one embodiment disclosed herein. 
         FIG. 8  illustrates a flowchart of a procedure performed by the system of  FIG. 1 , when the portable document downloading process prioritizes a download of the at least one first document structure and the at least one second document structure based on the current interaction associated with the first document, according to one embodiment disclosed herein. 
         FIG. 9  illustrates a flowchart of a procedure performed by the system of  FIG. 1 , when the portable document downloading process prioritizes a download of the at least one first document structure and the at least one second document structure based on the current interaction associated with the first document, and determines that a download involving the at least one first document structure is occurring, according to one embodiment disclosed herein. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments disclosed herein include a computer system executing a portable document downloading process that optimizes performance and responsiveness of portable documents on slow file systems, such as the Internet by, taking advantage of deep knowledge of document structures, connection speed, and other factors. The portable document downloading process decides the best strategy, at any point, to download a document, or document structure, with the goal of minimizing the time required to download a document in its entirety while providing the optimal user responsiveness. The portable document downloading process pre-fetches document structures that may be needed while assuring that the pre-fetching does not interfere with downloading parts of the document (i.e., document structures) that are needed immediately to respond to direct user actions. The portable document downloading process coordinates which document structures are downloaded at any time, using knowledge of whether the data is needed immediately (or might be needed), the speed of the connection, and the speed of a particular server. The portable document downloading process also maintains a status of in-progress downloads in such a way as to allow the portable document downloading process to selectively pause a pre-fetched download so as to allow the full bandwidth available to be applied to download document structures that are needed immediately. 
     The portable document downloading process coordinates bandwidth usage when more than one document is open at a time, and collects information about the connection speed in order to make ad hoc decisions about the optimal use of the available bandwidth. The portable document downloading process collects information about the user&#39;s connection speed, and also of particular servers&#39; bandwidth information, when possible, on an ongoing basis. In one embodiment, this data is collected on all document types that are downloaded to the user&#39;s computer, not just portable document types. 
     When a document is opened in a portable document viewer, the portable document downloading process notes the file size and the current connection speed. In one embodiment, the speed of a particular server is noted as well. The portable document downloading process determines whether it would be optimal to download the entire document or to byte range request parts of the document. The decision is made based on heuristics associated with the file size, the connection bandwidth, and if available, the bandwidth of downloads from the targeted server. If the decision by the portable document downloading process is to download the entire document, the download is handled by the portable document downloading process, and hidden from the other parts of the portable document viewer. The portable document downloading process also notes the current document with which the user is interacting, and prioritizes its downloads accordingly. Any current downloads that are associated with documents not associated with the user&#39;s current focus are paused. It should be noted that only downloads for document structures that might be needed may be paused. The portable document downloading process maintains information associated with the paused download, and restarts the download at a later time when the download does not interfere with downloading document structures that are needed to respond to a user request. 
     The portable document downloading process maintains a status of which document structures are local in the cache (of the user&#39;s computer), and which document structures have yet to be requested. When a portable document is opened, the portable document downloading process receives requests from different parts of the portable document viewer to pre-fetch parts of the document structure. The portable document downloading process also receives requests for document structures that are needed immediately to respond to actions by the user. These requests are given a higher priority to optimize responsiveness to the user. If the portable document downloading process has determined the document should be byte range requested, the portable document downloading process opens a connection with the server, and begins to download the document structures that are needed immediately. Once those document structures are downloaded, the portable document downloading process opens another connection with the server, and begins to download document structures that may be needed (i.e., pre-fetching document structures). The portable document downloading process can also pre-fetch document structures for other documents that are currently opened. While a user is interacting with the document, if, at any point, a user&#39;s request causes document structures to be needed, that are not in the cache, the portable document downloading process can pause any pre-fetch download, freeing up the available bandwidth to download the document structures that are needed immediately. While a user is interacting with the document, if, at any point, a user&#39;s action causes structures that were needed to no longer be needed, the portable document downloading process can reclassify them as structures that might be needed, and thus, may subsequently pause the download of those structures. 
     In an example embodiment, the portable document downloading process allows for a configurable cache. As part of the speculative downloading of documents and document structures, the portable document downloading process pre-fetches documents and document structures. Some security policies prevent documents and document structures from being pre-fetched. Thus, the portable document downloading process has the capability to identify a security policy and selectively configure the cache in accordance with the security policy. 
     The portable document downloading process detects a requirement to obtain a first document by the computer system. The first document has a predefined format. The portable document downloading process identifies a sequence of portions of the first document to obtain based on analysis of the predefined format of the first document, and analysis of current operational parameters of the computer system. The portable document downloading process obtains and, and in some cases, renders a first portion of the first document from the identified sequence, and obtains successive portions of the first document in accordance with the identified sequence. 
       FIG. 1  is a block diagram illustrating example architecture of a computer system  100  that includes a client  120  in communication with a server  160 . In an example embodiment, the portable document downloading process  140  resides on the client  120 . In another embodiment, the portable document downloading process  140  resides on the server  160 . In yet another example embodiment, the client  120  and server  160  reside on the same computer system  100 . The server  160  contains a plurality of portable documents, including a first document  130 B and a second document  150 B. The first document  130 B is comprised of a plurality of first document structures  135   b -N. Likewise, The second document  150 B is comprised of a plurality of document structures  155   b - 1  through  155   b -N. A request, from the client  120 , for the first document  130 B on the server  160 , results in a copy of the first document  130 B downloaded to the client  120  in the form of the first document  130 A (including copies of the plurality of first document structures  135   b - 1  through  135   b -N). Likewise, a request, from the client  120 , for the second document  150 B on the server  160 , results in a copy of the second document  150 B downloaded to the client  120  in the form of the second document  150 A (including the plurality of document structures  155   a - 1  through  155   a -N). 
     The portable document downloading process  140  may be embodied as software code such as data and/or logic instructions (e.g., code stored in the memory or on another computer readable medium such as a removable disk) that supports processing functionality according to different embodiments described herein. 
     It is noted that example configurations disclosed herein include the portable document downloading process  140  itself (i.e., in the form of un-executed or non-performing logic instructions and/or data). The portable document downloading process  140  may be stored as an application on a computer readable medium (such as a floppy disk, hard disk, electronic, magnetic, optical, or other computer readable medium). The portable document downloading process  140  may also be stored in a memory system such as in firmware, read only memory (ROM), or, as in this example, as executable code in, for example, Random Access Memory (RAM). Those skilled in the art will understand that the client  120  and server  160  may include other processes and/or software and hardware components, such as an operating system not shown in this example. 
     Further details of configurations explained herein will now be provided with respect to a flow chart of processing steps that show the high level operations disclosed herein to perform the portable document downloading process  140 . 
       FIG. 2  is an embodiment of the steps performed by the portable document downloading process  140  when it detects a requirement to obtain a first document  130  by the computer system  100 . The first document  130  has a predefined format. 
     In step  200 , the portable document downloading process  140  detects a requirement to obtain a first document  130  by the computer system  100 . The first document  130  has a predefined format. The computer system  100  detects a requirement to, for example, download a first document  130  from the server  160  to the client  120 . The request may originate from a user who performs an action within a document viewer that causes a request to be transmitted from the client  120  to the server  160 . The request may also originate from the portable document downloading process  140  for a portion of the first document  130  that the portable document downloading process  140  anticipates a user may request. For example, a user navigates to a directory on the server  160 , and performs an action (such as selecting the first document  130  from a plurality of documents within the directory) to obtain the first document  130 . In another embodiment, the user may select a hyperlink from a website to view a first document  130  that is accessed via a hyperlink on the website. 
     In step  201 , the portable document downloading process  140  identifies a sequence of portions of the first document  130  to obtain based on analysis of the predefined format of the first document  130 , and analysis of current operational parameters of the computer system  100 . The first document  130  is comprised of first document structures  135 -N. The portable document downloading process  140  collects information, for example, about the connection speed of the client  120 , and the server&#39;s  160  bandwidth information, on an ongoing basis. 
     In step  202 , the portable document downloading process  140  obtains a first portion of the first document  130  from the identified sequence. The decision to download the portion of the first document  130  is based, on, for example, heuristics associated with the file size of the first document  130 , the connection bandwidth of the client  120 , and if available, the bandwidth of downloads from the server  160 . In an example embodiment, the portable document downloading process  140  obtains and renders a first portion of the first document  130  from the identified sequence. 
     In step  203 , the portable document downloading process  140 , obtain successive portions of the first document  130  in accordance with the identified sequence. In an example embodiment, while a user is interacting with the first portion of the first document  130 , the portable document downloading process  140  obtains the remaining portions of the first document  130  such that they are available when the user requires those portions. 
       FIG. 3  is an embodiment of the steps performed by the portable document downloading process  140  when it identifies a sequence of portions of the first document  130  to obtain based on analysis of the predefined format of the first document  130 , and analysis of current operational parameters of the computer system. 
     In step  204 , the portable document downloading process  140  identifies a sequence of portions of the first document  130  to obtain based on analysis of the predefined format of the first document  130 , and analysis of current operational parameters of the computer system. For example, the portable document downloading process  140  evaluates the file size of the first document  130 , the connection bandwidth associated with the client  120 , the bandwidth of downloads from the server  160 , etc. The portable document downloading process  140  utilizes this information when determining whether to download the entire first document  130  or a portion of the first document  130 , for example, the first page of the first document  130 . 
     In step  205 , the portable document downloading process  140  assesses a size associated with the first document  130 . The portable document downloading process  140  is capable of assessing the size of the first document  130  prior to the first document being downloaded from the server  160  to the client  120 . The size of the first document  130  and the bandwidth of the client  120  factor into the portable document downloading process  140 &#39;s decision to download the first document  130  in its entirety. 
     In step  206 , the portable document downloading process  140  identifies at least one first document structure  135 - 1  associated with the first document  130 . The first document is comprised of a plurality of first document structures  135 -N. First document structures  135 -N can include objects, images, help menus, etc. 
     In step  207 , the portable document downloading process  140  collects first document structure information associated with the at least one first document structure  135 - 1 . The portable document downloading process  140  has complete knowledge of the first document structures  135 -N such as pages, annotations, structure tree, etc, including where those documents structures  135 -N are physically located. The first document structure information includes at least one of: 
     i) a location associated with the at least one first document structure  135 - 1   
     ii) a size associated with the at least one first document structure  135 - 1 . 
     Alternatively, in step  208 , the portable document downloading process  140  identifies a connection between the computer system  100  and at least one other computer system (not shown). The portable document downloading process  140  takes advantage of the computer system&#39;s  100  ability to open simultaneous connections between the client  120  and the server  160 , or between the client  120  and multiple other servers (not shown). 
       FIG. 4  is an embodiment of the steps performed by the portable document downloading process  140  when it identifies a sequence of portions of the first document  130  to obtain based on analysis of the predefined format of the first document  130 , and analysis of current operational parameters of the computer system. 
     In step  209 , the portable document downloading process  140  identifies a sequence of portions of the first document  130  to obtain based on analysis of the predefined format of the first document  130 , and analysis of current operational parameters of the computer system. 
     In step  210 , the portable document downloading process  140  identifies at least one second document  150 , including at least one second document structure  155 - 1 . When a first document  130  is opened within a document viewer on the client  120 , the portable document downloading process  140  has knowledge of any other documents that are opened on the client  120 , such as a second document  150 . A second document  150 , just like the first document  130 , is comprised of a plurality of second document structures  155 -N. 
     In step  211 , the portable document downloading process  140  identifies a request to obtain at least one second document structure  155 - 1  in conjunction with obtaining at least a portion of the first document  130 . In other words, the portable document downloading process  140  handles multiple requests on the client  120 , such as a request for a second document structure  155 - 1  associated with a second document  150 , along with requests for first document structures  130 -N associated with a first document  130 . The portable document downloading process  140  uses the identified current operational parameters, and heuristics, to prioritize the requested downloads and speculatively download (i.e., pre-fetched) those document structures that have not yet been requested. 
     In step  212 , the portable document downloading process  140  identifies a capacity associated with the computer system  100 , the capacity including at least one of: 
     i) a network availability associated with the computer system  100   
     ii) a transfer speed associated with the computer system, the transfer speed associated with obtaining at least one document. 
       FIG. 5  is an embodiment of the steps performed by the portable document downloading process  140  when it obtains a first portion of the first document  130  from the identified sequence. 
     In step  213 , the portable document downloading process  140  obtains a first portion of the first document  130  from the identified sequence. After evaluating the current operational parameters associated with the first document  130  and the computer system  100 , the portable document downloading process  140  determines whether to download the entire first document  130 , or at least one first document structure  135 - 1  or with a byte range request. 
     In step  214 , the portable document downloading process  140  identifies a current interaction associated with the first document  130 . The portable document downloading process  140  identifies that a user is currently interacting with the first document  130 . For example, the portable document downloading process  140  may have downloaded the first page of the first document  130  in response to a request from the user. 
     In step  215 , the portable document downloading process  140  identifies at least one first document structure  135 - 1  associated with the first document. For example, the user may be interacting with the first page of the first document  130  and the portable document downloading process  140  identifies first document structures  135 -N associated with the second page of the first document  130  that may be requested. 
     In step  216 , the portable document downloading process  140  identifies at least one second document structure  155 - 1  associated with at least one second document  150 . Just as the first document  130  is comprised of first document structures  135 -N, the second document  150  is comprised of second document structures  155 -N. 
     In step  217 , the portable document downloading process  140  identifies a current interaction associated with the second document  150 . The portable document downloading process  140  identifies that there are multiple documents opened on the client  120  and that a user may be interacting simultaneously with multiple documents. 
     In step  218 , the portable document downloading process  140  prioritizes a download of at least one first document structure  135 -N and at least one second document structure  155 -N, based on the current interaction associated with the first document  130 . The portable document downloading process  140  identifies that multiple documents are opened on the client  120 , resulting in multiple requests for first document structures  135 -N and second document structures  155 -N. Based on the current interaction with the first document  130  by a user, the portable document downloading process  140  prioritizes the download of the first document structures  135 -N. In other words, since the user is currently interacting with the first document  130 , the first document structures  135 -N receive download priority over the second document structures  155 -N associated with the second document  150  (that is also opened on the client  120 ). 
       FIG. 6  is an embodiment of the steps performed by the portable document downloading process  140  when it identifies at least one first document structure  135 - 1  associated with the first document  130 . 
     In step  219 , the portable document downloading process  140  identifies at least one first document structure  135 - 1  associated with the first document  130 . The first document  130  is comprised of a plurality of first document structures  135 -N, such as fonts, images, annotations, etc. 
     In step  220 , the portable document downloading process  140  receives a request from a user to retrieve at least one first document structure. For example, a user is viewing the first page of the first document  130 , and pages down to view the second page. Thus, the portable document downloading process  140  receives a request for the second page of the first document  130 . That request has originated from a user, as opposed to requests for first document structures  135 -N that originate from the portable document downloading process  140 , based on the evaluation of the current operational parameters associated with the first document  130 , and the computer system  100 . 
     In step  221 , the portable document downloading process  140  maintains a status associated with at least one first document structure  135 -N. The status identifies whether the first document structure  135 -N has begun a download (i.e., whether the first document structure  135 -N has been downloaded, or whether the download is currently occurring). The portable document downloading process  140  keeps track of which first document structures  135 -N have been pre-fetched, which first document structures  135 -N have not, and which are in the process of being fetched. 
       FIG. 7  is an embodiment of the steps performed by the portable document downloading process  140  when it identifies at least one first document structure  135 -N associated with the first document  130 . 
     In step  223 , the portable document downloading process  140  identifies at least one first document structure  135 -N associated with the first document  130 . The first document  130  is comprised of a plurality of first document structures  135 -N, such as pages, annotations, structure tree, etc. 
     In step  224 , the portable document downloading process  140  anticipates receipt of a request, for at least one first document structure  135 - 1 . In an example embodiment, the user has requested the first document  130  and is viewing the first page of the first document  130 . The portable document downloading process  140  anticipates that the user will request the second page of the first document  130 , and the portable document downloading process  140  identifies those first document structures  135 -N associated with the second page of the first document  130 . 
     In step  225 , the portable document downloading process  140  anticipates receipt of a request from a user based on a request history associated with the user. The portable document downloading process  140  determines which first document structures  135 -N to download for the user, based on the user&#39;s access history. For example, the user frequently uses the help menus. 
     Thus, the portable document downloading process  140  anticipates that the user will utilize the help menus, and the portable document downloading process  140  begins to download those first document structures  135 -N associated with the help menus (for the first document  130 ) prior to the user requesting those help menus. 
     In step  226 , the portable document downloading process  140  identifies a security policy associated with the first document structure  135 -N. The security policy prevents a downloading of the first document structure  135 -N prior to a download request from the user. The portable document downloading process  140  allows for a configurable cache. As part of the speculative downloading of documents and document structures, the portable document downloading process  140  pre-fetches documents and document structures. Some security policies prevent documents and document structures from being pre-fetched, and stored in a cache. Thus, the portable document downloading process  140  has the capability to identify a security policy and selectively configure the cache in accordance with the security policy, such that documents and/or document structures are not pre-fetched. 
       FIG. 8  is an embodiment of the steps performed by the portable document downloading process  140  when it prioritizes a download of at least one first document structure  135 -N, and at least one second document structure  155 -N, based on the current interaction associated with the first document  130 . 
     In step  227 , the portable document downloading process  140  prioritizes a download of at least one first document structure  135 -N and at least one second document structure  155 -N based on the current interaction associated with the first document  130 . If both the first document  130  and the second document  150  are opened on the client  120 , the portable document downloading process  140  prioritizes requests for document structures associated with either document, based on the document with which a user is currently interacting. 
     In step  228 , the portable document downloading process  140  identifies at least one first document structure  135 -N associated with the current interaction associated with the first document  130 . The portable document downloading process  140  identifies that the user is currently interacting with, for example, the first document  130 . The portable document downloading process  140  identifies a plurality of first document structures  135 -N associated with the first document  130 . 
     In step  229 , the portable document downloading process  140  downloads at least one first document structure  135 - 1  prior to at least one other first document structure  135 - 2  not associated with the current interaction associated with the first document  130 . Among the plurality of first document structures  135 -N, not all of them will be associated with the current interaction with the first document  130 . For example, the help menus are a first document structure  135 - 3  associated with the first document  130 . However, until the user accesses the help menus, there does not exist a current interaction with that particular first document structure  135 - 3 . The portable document downloading process  140  identifies which first document structures  135 -N from the plurality of first document structures  135 -N are needed to satisfy any requests from the user. 
     In step  230 , the portable document downloading process  140  downloads at least one first document structure  135 - 1  prior to at least one second document structure  155 - 1 . Based on the current interaction with the first document  130  by the user, the portable document downloading process  140  prioritizes the downloads and downloads the first document structures  135 -N prior to downloading any second document structures  155 -N. In other words, the user may have the first document  130  and the second document  150  opened on the client  120 . Both the first document  130  and the second document  150  have associated first document structures  135 -N and second document structures  155 -N, respectively. The portable document downloading process  140  identifies that the user is interacting with the first document structures  135 -N associated with the first document  130 , and not the second document structures  155 -N associated with the second document  150 . Thus, the portable document downloading process  140  downloads the first document structure  135 - 1  prior to downloading the second document structure  155 - 1 . 
     During the prioritizing of the download of at least one first document structure  135 -N, in step  231 , the portable document downloading process  140  differentiates between: 
     i) receiving a request from a user to retrieve at least one first document structure  135 - 1 . 
     ii) anticipating receipt of a request for at least one first document structure  135 - 1 . 
       FIG. 9  is an embodiment of the steps performed by the portable document downloading process  140  when it prioritizes a download of at least one first document structure  135 - 1 , and at least one second document structure  155 - 1 , based on the current interaction associated with the first document  130 . 
     In step  232 , the portable document downloading process  140  prioritizes a download of at least one first document structure  135 - 1 , and at least one second document structure  155 - 1 , based on the current interaction associated with the first document  130 . The current interaction of the user with the first document  130  gives any downloads of first document structures  135 -N priority over the downloading of any second document structures  155 -N. Should the current interaction of the user shift from the first document  130  to the second document  150 , the downloading of the second document structures  155 -N would take priority over the downloading of the first document structures  135 -N. 
     In step  233 , the portable document downloading process  140  determines that a download involving at least one first document structure  135 - 1  is occurring. In an example embodiment, the download is a result of a request from the user. In another example embodiment, the download is a result of the portable document downloading process  140  speculatively downloading (i.e., pre-fetching) the first document structures  135 - 1  in anticipation of a request from the user. 
     In step  234 , the portable document downloading process  140  determines that a download involving at least one second document structure  155 - 1  is occurring at the same time the download involving at least one first document structure  135 - 1  is occurring. 
     In step  235 , the portable document downloading process  140  suspends the download involving the at least one second document structure  155 - 1  such that the first document structure  135 - 1  (which has been determined by the portable document downloading process  140  to have a higher priority than the second document structure  155 - 1 ) can download more quickly. 
     In step  236 , the portable document downloading process  140  detects the downloading of at least one first document structure  135 - 1  has completed. 
     In step  237 , the portable document downloading process  140  resumes the downloading of at least one second document structure  155 - 1 . The portable document downloading process  140  selectively pauses downloads to allow those first document structures  135 -N that are currently needed, to complete. Once those downloads have completed, the portable document downloading process  140  resumes the download of any downloads that were paused. 
     While computer systems and methods have been particularly shown and described above with references to configurations thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope disclosed herein. Accordingly, the information disclosed herein is not intended to be limited by the example configurations provided above.