as shown in fig1 a , a word processing document 162 can be reviewed by one or more reviewers 160 and can be edited by one or more editors 170 . the reviewers 160 can make comments 164 about the document 162 and assign the comments 166 to the editors 170 . a reviewer or editor can be a human or alternatively , can be a machine programmed to perform a reviewing or editing function . different comments can be assigned and sent to different editors . for example , in fig1 a , comment 1 is assigned and sent to editor 1 and comment 2 is assigned and sent to editor 2 . as shown in fig1 b , the editors 170 can make changes 172 to the document as a result of the comments received from the reviewers 160 . the changes 172 can be sent back to the reviewers 160 for their review . as shown in fig1 a and 1b respectively , comments can be sent independently 168 of other comments and changes can be sent independently 174 of other changes . comments and changes can be sent as soon as they are completed , so that the recipients can begin reviewing the comments and changes while further comments and changes are still being completed . in this manner , the review and editing process is expedited . as shown in fig1 c , changes 172 can be classified 180 according to the comments 164 . for example , in fig1 c , change 1 is classified under comment 1 to represent that change 1 was made as a result of comment 1 . similarly , change 2 is classified under comment 2 . this makes it easier for reviewers to check that all their comments were addressed by the changes . as shown in fig1 d , in one implementation , a system 100 includes client computers 101 used for reviewing and editing documents . in general , a client computer refers to a general - purpose computer that is capable of accessing a user interface ( e . g ., a desktop personal computer , a workstation , or a laptop computer running an application program ), or a more special - purpose computer ( e . g ., a device specifically programmed to operate as a client of a particular application program ). in the illustrated example , an author 102 creates a document . the author 102 submits the created document for review by one or more reviewers 104 . the reviewers 104 read the document and associate one or more comments with the document in a review mode . in general , a comment relates to a reviewer &# 39 ; s suggestions and ideas relating to the document . a comment can contain proposed changes relating to the document . in this specification , a comment may also be referred to as an issue . the two terms are used interchangeably . in an edit mode , one or more editors 105 reviews the issues generated by the reviewers 104 and makes changes to the document as a result of the issues generated by the reviewers . the author 102 may be an editor 105 . again in a review mode , a reviewer 104 may , in turn , view the changes made by the editor 105 . in fig1 d , users engage in a collaborative review process relating to the document by accessing a collaborative review system 108 using the client computers 101 . a collaborative review system 108 refers to any computer system which can be used to enable one or more users , such as , for example , editors and / or reviewers to engage in an electronically interactive review and editing process of a document . the collaborative review system 108 can run locally on each of the client computers 101 or can run remotely and accessed using a network 109 . the network 109 can be one of a variety of established networks , such as , for example , the internet , a public switched telephone network ( pstn ), the world wide web ( www ), a wide - area network (“ wan ”), a local - area network (“ lan ”), or a wireless network . the collaborative review system 108 provides access to a document record 112 for the document . the document record 112 includes the document as well as the issues associated with the document . in the illustrated example , the document record 112 is stored on a server 114 . the document record 112 includes the version of the document initially created by the document author , referred to as a source document 116 . in one implementation , the source document 116 can be represented in more than one format . for example , it can be represented in the source format as well as in another format , for example , in pdf format . additionally , issues generated by the reviewers 104 , in a review mode , are stored in an issue record 122 and are accessible to the editors 105 , in an edit mode . the one or more reviewers 104 , using client computers 101 to access the collaborative review application 108 , can access the document record 112 for review and addition of issues to the issue record 122 . the system 100 is implemented such that a reviewer 104 in a review mode of the system 100 can generate an issue and submit the issue to the issue record 122 , enabling the editor 105 to access the submitted issue in the document record 112 . the reviewer 104 can continue to review the document and generate additional issues in the review mode while the editor 105 accesses the submitted issue . there is no need for the editor 105 to wait for the reviewer 104 to review the entire electronic document before the editor 105 can view issues generated by the reviewer 104 . the issue record 122 contains issues 124 associated with the document . fig1 b shows an implementation of the issue 124 and its data structure components associated with electronic document review . the issue 124 includes a user identifier 126 uniquely identifying a user who generated the issue 124 . for example , the user identifier 106 can identify a reviewer 104 . the issue 124 also includes a discussion thread 128 for a user to enter written comments , such as for example , suggestions for the document . a time stamp 130 indicating the time the issue 124 is submitted to the issue record 122 is included . the issue 124 also includes location information 132 that associates the issue 124 with a particular location in the document . this location can be user - selected , and can vary in granularity depending on what the user selects . the granularity can range from a single character to the whole document . additionally , the issue 124 includes a difference record 134 indicating all changes made to the document by the editors 105 as a result of the issue 124 . for example , when an editor 106 accesses an issue , all changes made to the document by the editor while the issue is accessed are stored in a difference record 134 for the issue . in one implementation , the document is comprised of a set of atomic elements , such as , for example , a sequence of characters . the difference record 134 contains a description of operations that transform one sequence of characters into another . the operations can include : inserting a character after a given character position , deleting a character at a given position , and / or replacing one character with another ( this can be described as delete followed by insert ). there are infinitely many sequences of these three operations that convert one version of the document into another . the process of generating the difference record will be described in more detail below with reference to fig3 . when in edit mode , the editor 105 “ opens ” one issue at a time for review , the editor 105 can make changes to the document based on the issue , and the editor 105 “ closes ” the addressed issue once the changes are made . changes made by the editor 105 accessing an issue between the opening and closing of the issue are stored as part of the issue &# 39 ; s difference record 134 . upon closing an issue , the issue is automatically submitted to the document record 112 . the end of edit mode is indicated by the closing of the issue 124 , i . e . submission of the issue to the document record 112 . an issue submitted to the document record 112 is available for access by a reviewer or editor . the difference record 134 of a submitted issue can be presented to a reviewer or editor to show the changes made to the document as a result of the issue . for example , referring to fig1 a , a reviewer 104 can access a submitted issue n to view changes made by the editor 105 to the document as a result of the issue n . the reviewer 104 can then generate an additional issue a relating to a version of the document associated with the initial issue n . in the system 100 , the issues in the issue record 122 are organized in a tree structure 150 . each issue in the tree structure 150 contains information associating the issue with its parent issue . in the illustrated example , issue n is the parent issue of issue a . in other implementations , the issues in the issue record 122 can be organized as a list . additionally , referring to fig1 e , the issue 124 has a status 152 indicating , for example , if the issue is “ open / to edit ,” “ open / to review ,” or “ closed .” each issue can be automatically categorized as “ old ” or “ new / changed ” for each reviewer and editor in the collaborative review application 108 . when an issue is created or changed , it is considered “ new / changed ” for every user other than the originator of the changes . when an editor 105 closes the issue , it is considered “ old ” for the editor 105 . when a reviewer 104 views the document difference record 134 for an issue , it becomes “ old ” for the reviewer 104 . however , using the collaborative review application 108 , the reviewer 104 and the editor 105 can mark an old issue back to “ new / changed ” if it requires their future attention . in addition to viewing changes as a result of one or more issues , using the system 100 document editors and reviewers are able to synchronize to the latest version of the document . for example , selecting a “ get latest changes ” button in the collaborative review application 108 can display the latest version of the document to users . fig2 is a flow chart of a process 200 illustrating the creation of an issue associated with electronic document review . the process 200 can be implemented by a system similar to the system 100 illustrated in fig1 a . a system implementing the process 200 can be implemented such that multiple editors can have access to the document record 112 . the process 200 illustrates associating a document editor 105 with an issue 124 . when a reviewer 104 creates an issue , the reviewer 104 can assign the issue to one or more editors 105 . for example , the reviewer 104 can select editors from a list of editors . the editors 105 can search / sort issues assigned only to them . an editor can also reassign an issue to another editor . sections of documents can be pre - assigned to editors . an issue made in a given section can by default be assigned to the editor responsible for that section . in the process 200 , a document record associated with a document for review is accessed by a reviewer ( 210 ). the process 200 waits for the reviewer to generate an issue ( 215 ). when an issue is generated ( 217 ), the issue is associated with an editor ( 220 ). the issue is submitted to the document record ( 230 ). the submitted issues in the document record are sorted by editor ( 240 ). the editor associated with an issue is allowed to access the issue ( 250 ). optionally , the assigned editor can reassign the issue to another editor ( 260 ). modifications made to the document based on the issue are received ( 270 ). a difference record 134 for the issue 124 is generated based on the received modifications ( 280 ). the document record 112 is updated ( 290 ). fig3 is a flow chart illustrating a process 300 for associating changes made to a document with an issue 124 . the process 300 can be implemented by a system similar to the system 100 illustrated in fig1 a . the process 300 begins with receipt of a “ current issue ” selection from a user ( 310 ). when an editor desires to make changes to a document based on issues , one issue at a time is designated as the “ current issue ” and all changes associated with that issue are recorded in the issues difference record . when an editor first activates an issue , i . e . selects an issue as the current issue , the initial state of the document is recorded ( 320 ). this can be accomplished by storing a snapshot of the document in the document record 112 . changes made to the document by the editor are received ( 330 ). when an indication is received that the editor is done making changes associated with the current issue ( 335 ), the changed state of the document is compared with the recorded initial state ( 340 ). this comparison can be performed using conventional document comparison tools . one such tool is the windiff tool , which is part of visual studio 6 , available from microsoft corporation of redmond , wash . the output of this comparison is stored in the difference record 134 ( 350 ). the difference record 134 is associated with the issue ( 360 ). the issue is submitted to the issue record 122 for the document ( 370 ), and the document record is updated ( 380 ). an application for implementing a document review process can be designed such that each reviewer and / or editor has his / her own workspace . the workspaces will contain information common to the document record 112 . using their own workspace editors and reviewers can generate and / or review issues associated with a document . each workspace may be hosted , for example , on the client computers 101 illustrated in fig1 . each reviewer and editor can also have information that is specific to his or her workspace ( and different for other reviewers and editors ). for example , a flag for each issue indicating whether or not the reviewer or editor has addressed an issue is specific to each workspace . fig4 illustrates an interface 400 displayed to an editor in a document review process . the interface 400 can be an interface of the workspace described earlier . additionally , the interface 400 can be an interface in an application similar to the collaborative review application 108 illustrated in fig1 a . the editor first activates an issue to be viewed in an edit mode . in the interface 400 , an active issue is indicated by an open circle 402 . when an issue is activated , an initial snapshot of the document is taken , as described earlier . the editor can then make changes to the document , while in the edit mode . the editor can optionally review the document changes from the initial snapshot by selecting a “ show differences ” portion 404 of the interface 400 . the editor can then submit the changes by selecting a “ submit changes ” portion 406 of the interface 400 . submission classifies the issue as “ old ” for the editor and as a result the issue can be disabled or hidden on the interface 400 . fig5 illustrates an interface 500 displayed to a reviewer in a document review process . the interface 500 can be an interface of the workspace described earlier . additionally , the interface 500 can be an interface in an application similar to the collaborative review application 108 illustrated in fig1 a . each reviewer reads the issues and can create sub - issues . the initial status of the issue is designated as “ open / to correct ”. issues are submitted one at a time and editors can have immediate access to them , by pressing a “ get latest changes ” button 502 . a “ new / changed issues ” folder 504 in the interface 500 includes a dynamic list 506 of all the issues the editor has not yet accessed . the dynamic list 506 can be implemented such that a reviewer can filter the list as the reviewer desires . for example the reviewer may want to display all issues that are currently “ open / to review and show them grouped into “ new / changed ” vs . “ reviewed .” the reviewer can open each issue one at a time , review the issue difference record , and if satisfied , the reviewer can set the issue &# 39 ; s status to “ closed .” if further changes are necessary , the reviewer can add comments to a discussion thread associated with an issue and submit the issue by changing the status to “ open / to correct .” the reviewer can also select multiple issues and preview their common document difference record at once . in the interface 500 , when one or more issues are selected , a “ show differences ” button 508 becomes enabled . clicking the button 508 can display a union or a composite of the difference records for the selected issues . after the difference records for one or more issues are reviewed , the issue ( s ) automatically move to a “ reviewed issues ” folder 510 . the reviewer can drag issues back to the “ new / changed issues ” folder 504 if the reviewer wants to get back to them later . pressing the “ get latest changes ” button 502 gets the latest copy of the document , and can move any newly editor - addressed issues back to the “ new / changed issues ” folder 504 . a useful issue reviewing process for a reviewer can be to first review how each issue proposed by the reviewer has been addressed , and then to select all remaining issues in the “ new / changed issues ” folder 504 and review them at once , to see what else has changed due to addressing issues proposed by other reviewers , or due to new additions to the document . displaying differences between two versions of a document can be accomplished in multiple ways . in an example involving text - only documents , a single view can show removed text as crossed out and new text as highlighted . if the combined difference records of two or more issues are to be shown , and a portion of the document is changed by both issues , the chronologically last issue can take priority . in a highly advanced system , when previewing the document differences associated with an issue , portions of the changes that have been later on changed again ( e . g . as a result of fixing subsequent issues ) can be highlighted ; users can even be enabled to jump to those issues . in some cases , the changes for the selected issue or issues may depend on changes for other issues . for example , suppose that as a result of a first issue , the word “ location ” was changed to “ position ”. then as a result of a second issue , the word “ position ” was further changed to “ place ”. in this example , the second change is dependent on the first change . in such cases , the document difference record shows not only the changes for the selected issue or issues , but also the changes upon which the former - mentioned changes depend . however , the former - mentioned changes are distinguishable from the other changes . for example , they can be presented in a different color from the other changes . the invention and all of the functional operations described in this specification can be implemented in digital electronic circuitry , or in computer hardware , firmware , software , or in combinations of them . the invention can be implemented as a computer program product , i . e ., a computer program tangibly embodied in an information carrier , e . g ., in a machine - readable storage device , for execution by , or to control the operation of , data processing apparatus , e . g ., a programmable processor , a computer , or multiple computers . a computer program can be written in any form of programming language , including compiled or interpreted languages , and it can be deployed in any form , including as a stand - alone program or as a module , component , subroutine , or other unit suitable for use in a computing environment . a computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network . method steps of the invention can be performed by one or more programmable processors executing a computer program to perform functions of the invention by operating on input data and generating output . method steps can also be performed by , and apparatus of the invention can be implemented as , special purpose logic circuitry , e . g ., an fpga ( field programmable gate array ) or an asic ( application - specific integrated circuit ). processors suitable for the execution of a computer program include , by way of example , both general and special purpose microprocessors , and any one or more processors of any kind of digital computer . generally , a processor will receive instructions and data from a read - only memory or a random access memory or both . the essential elements of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data . generally , a computer will also include , or be operatively coupled to receive data from or transfer data to , or both , one or more mass storage devices for storing data , e . g ., magnetic , magneto - optical disks , or optical disks . information carriers suitable for embodying computer program instructions and data include all forms of non - volatile memory , including by way of example semiconductor memory devices , e . g ., eprom , eeprom , and flash memory devices ; magnetic disks , e . g ., internal hard disks or removable disks ; magneto - optical disks ; and cd - rom and dvd - rom disks . the processor and the memory can be supplemented by , or incorporated in special purpose logic circuitry . to provide for interaction with a user , the invention can be implemented on a computer having a display device , e . g ., a crt ( cathode ray tube ) or lcd ( liquid crystal display ) monitor , for displaying information to the user and a keyboard and a pointing device , e . g ., a mouse or a trackball , by which the user can provide input to the computer . other kinds of devices can be used to provide for interaction with a user as well ; for example , feedback provided to the user can be any form of sensory feedback , e . g ., visual feedback , auditory feedback , or tactile feedback ; and input from the user can be received in any form , including acoustic , speech , or tactile input . the invention can be implemented in a computing system that includes a back - end component , e . g ., as a data server , or that includes a middleware component , e . g ., an application server , or that includes a front - end component , e . g ., a client computer having a graphical user interface or a web browser through which a user can interact with an implementation of the invention , or any combination of such back - end , middleware , or front - end components . the components of the system can be interconnected by any form or medium of digital data communication , e . g ., a communication network . examples of communication networks include a local area network (“ lan ”) and a wide area network (“ wan ”), e . g ., the internet . the computing system can include clients and servers . a client and server are generally remote from each other and typically interact through a communication network . the relationship of client and server arises by virtue of computer programs running on the respective computers and having a client - server relationship to each other . alternatively , the computing system can include computers that have a peer - to - peer relationship to each other . the invention has been described in terms of particular implementations . other implementations are within the scope of the following claims . for example , the steps of the invention can be performed in a different order and still achieve desirable results .