Abstract:
A hierarchical set of records has multiple hierarchical levels and depths. Each of the records has a tag that is unique within the hierarchical set of records. A method for retrieving a record includes identifying one of the records in the hierarchical set and modifying the tag, thereby producing a key. The hierarchical set of records is indexed only once. A record is selected and retrieved based on the indexing which applies the key to the hierarchical set of the records.

Description:
BACKGROUND 
     The present invention relates generally to data management, and particularly to managing data stored hierarchically. 
     Hierarchical data sets are useful and popular. Such data sets are generally composed of multiple records. In a hierarchical set of records, a record can have multiple “children,” which are related to the record and exist at a lower level of the hierarchy. Such a record is referred to as the “parent” record of the children records. The children of a record may have children, and so on, limited only by the size of the database. Within a set of children of a single record, it is often useful to order the children, such that there is a first child, a second child, and so on. 
     To date the utility of these hierarchical data sets has been limited by the efficiency of the tools available for managing the data. Conventional methods of storing hierarchical data in a database involve multiple expensive calls to update and/or query the database. For example, in order to select the second grandchild of a record, three queries are necessary. The first query selects the child of the record. The second query selects the first child of the child. The third query selects the second child of the child. 
     SUMMARY 
     In general, in one aspect, the invention features a method, apparatus, and computer-readable media for retrieving records in a hierarchical set of the records having a plurality of hierarchical levels and a plurality of hierarchical depths, each of the records having a tag that is unique within the hierarchical set of the records. It comprises identifying one of the records in the hierarchical set of the records; modifying the tag, thereby producing a key; indexing the hierarchical set of the records only once, thereby selecting one or more of the records within the hierarchical set of the records, wherein indexing the hierarchical set of the records only once comprises applying the key to the hierarchical set of the records; and retrieving the selected records. 
     Particular implementations can include one or more of the following features. Applying comprises selecting those of the records in the hierarchical set of the records having a tag that matches the key. Identifying one of the records comprises receiving a selection of the one of the records from a user; and receiving a command from the user; and wherein modifying the tag is based on the command from the user. Each of the records has one or more fields, and implementations can comprise displaying a field of each of the retrieved records on a display, wherein the position of each of the fields on the display represents the hierarchical depth and hierarchical level of the corresponding one of the retrieved records. Each tag is a number having a plurality of digits; the position of each of the digits represents one of the hierarchical depths; the value of each of the digits represents one of the hierarchical levels; and modifying the tag comprises selecting at least one of the digits according to the command from the user; and changing the value of the selected digits according to the command from the user. Each tag is a number having a plurality of digits; the position of each of the digits represents one of the hierarchical depths; the value of each of the digits represents one of the hierarchical levels; the command from the user requests retrieving the children of the identified record; and modifying the tag comprises selecting the digit corresponding to the hierarchical depth of the identified record; and setting the value of each digit corresponding to a hierarchical depth below the hierarchical depth corresponding to the selected digit to a wildcard value. Each tag is a number having a plurality of digits; the position of each of the digits represents one of the hierarchical depths; the value of each of the digits represents one of the hierarchical levels; the command from the user requests retrieving the parent of the identified record; and modifying the tag comprises selecting the digit corresponding to the hierarchical depth of the identified record; and setting the value of the selected digit to a null value. Each of the records represents one of a message and a folder. 
     In general, in one aspect, the invention features a method, apparatus, and computer-readable media for adding a new record to a hierarchical set of records having a plurality of hierarchical levels and a plurality of hierarchical depths, each of the records in the hierarchical set of records having a tag that is unique within the hierarchical set of records. It comprises identifying one of the records in the hierarchical set of records as the parent of the new record; modifying the tag, thereby producing a key; adding the key to the new record; and indexing the hierarchical set of records only once, thereby adding the new record to the hierarchical set of records, wherein indexing the hierarchical set of records only once comprises applying the key to the hierarchical set of records. 
     Particular implementations can include one or more of the following features. Identifying one of the records comprises receiving a selection of the one of the records from a user. Each tag is a number having a plurality of digits; the position of each of the digits represents one of the hierarchical depths; the value of each of the digits represents one of the hierarchical levels; the identified record represents a message; identifying one of the records further comprises receiving a command from the user that requests replying to the message; and modifying the tag comprises selecting the digit corresponding to the hierarchical depth immediately below the hierarchical depth of the identified record; and incrementing the value of the selected digit. Applying comprises selecting those of the records in the hierarchical set of the records having a tag that matches the key. Each tag includes a plurality of digits; the position of each of the digits represents one of the hierarchical depths; and the value of each of the digits represents one of the hierarchical levels. 
     In general, in one aspect, the invention features a method, apparatus, and computer-readable media for selecting records in a hierarchical set of the records having a plurality of hierarchical levels and a plurality of hierarchical depths, each of the records having a tag that is unique within the hierarchical set of the records. It comprises identifying one of the records in the hierarchical set of the records; modifying the tag; and indexing the hierarchical set of the records only once, thereby selecting one or more of the records within the hierarchical set of the records, wherein indexing the hierarchical set of the records only once comprises applying the modified tag to the hierarchical set of the record. 
     Particular implementations can include one or more of the following features. Each tag includes a plurality of digits; the position of each of the digits represents one of the hierarchical depths; and the value of each of the digits represents one of the hierarchical levels. Applying comprises selecting those of the records in the hierarchical set of the records having a tag that matches the key. 
     Advantages that can be seen in implementations of the invention include one or more of the following. Implementations of the present invention permit manipulation of a database representing an indented threaded discussion with only a single access of the database. For examples, messages can be added, deleted, and retrieved through a single database access such as a query or call. 
     The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  shows a display of an indented threaded discussion. 
         FIG. 2  is a flowchart of a process for retrieving the parent of a message in an indented threaded discussion according to one implementation. 
         FIG. 3  is a flowchart of a process for retrieving the children of a message in an indented threaded discussion according to one implementation. 
         FIG. 4  is a flowchart of a process for adding a message to an indented threaded discussion according to one implementation. 
       The leading digit(s) of each reference numeral used in this specification indicates the number of the drawing in which the reference numeral first appears. 
     
    
    
     DETAILED DESCRIPTION 
     One common type of hierarchical data is an indented threaded discussion. Originally found only in Internet newsgroups, indented threaded discussions have found increasing popularity as a way to manage and display a discussion among multiple participants. Indented threaded discussion management tools are now found in consumer products such as electronic mail software programs. 
       FIG. 1  shows a display of an indented threaded discussion. An indented threaded discussion begins when a user posts a message  102  in a forum available to multiple users, where the posted message is not a reply to another message. Such a message is referred to herein as the “origin” message of the discussion. Any origin message constitutes the “head” of a thread. Thus message  102  is both the origin message of a discussion and the head of a thread. All replies to a message are part of the thread. Of course, a forum can have multiple discussions. 
     When a user posts a reply to a message, the reply is generally displayed underneath the message, and indented once. Any message having replies to it is the head of a thread. Thus a discussion can have many threads. The head of thread is indented once relative to the message to which it replies. 
     Message  104  is a reply to message  102 . Therefore, reply  104  is displayed underneath message  102 , and indented once, as shown in  FIG. 1 . A reply  106  to the reply  104  is indented once further. A reply  108  to the reply  106  to the reply  104  is indented once further still. 
     When a user posts another reply  110  to origin message  102 , it is shown indented only once, and is shown beneath message  104  and its children  106  and  108 . A subsequent reply  112  to origin message  102  is also shown indented once, and is shown beneath message  110 . A reply  114  to message  112  is shown indented twice and beneath message  112 . 
     A display such as the display of  FIG. 1  allows a user to rapidly understand the structure of the discussion hierarchy and the place each message has in the hierarchy. The place a message has in the hierarchy can be described in terms of two dimensions of the hierarchy: level and depth. The depth of a message is the number of threads that contain the message. For example, referring to  FIG. 1 , the depth of message  108  is three because it is contained by the threads headed by messages  106 ,  104  and  102 . The depth of an origin message such as message  102  is zero. 
     The level of a message at a particular depth represents the number of messages at that particular depth that precede that message. For example, referring to  FIG. 1 , the level of message  112  is three because it has a depth of one and is preceded by messages  110  and  104 , both also at a depth of one. The order of precedence within each hierarchical depth can be determined by any number of factors or combinations thereof. In a threaded discussion group, the chronological order of the messages, as determined by the time and date of the posting of each message, is most commonly used. When the records in the hierarchical data set represent containers such as folders, the alphabetical order of the names of the folders can be used. In addition, the user of the display may select any field in the records, and thereby cause the contents of that field to determine the order of precedence. The level of an origin message such as message  102  is zero. 
     Referring again to  FIG. 1 , messages at a single hierarchical level, such as messages  104 ,  110 , and  112 , are shown in chronological order, while the children of a message (that is, replies to the message, replies to those replies, and so on) are shown beneath the message and above the next message at the same hierarchical level. The messages displayed to the user are generally stored in some sort of database such as a table. Each row of the table represents a message. Each message has multiple fields such as subject, author, text, date of posting, and so on. Each column represents one of the fields. 
     Conventional tools for managing such indented threaded discussions are notoriously inefficient. Normally either multiple rows of the table must be updated upon the creation of a new message or multiple queries have to be performed to display an indented thread. The number of rows needing updates could be as large as the number of messages in the thread. 
     Implementations of the present invention associate a tag with each record in a hierarchical set of records, such that the tag is unique within the hierarchical set of records. The tag is generally one of the fields of the records. Table 1 depicts a portion of a database table representing the discussion of  FIG. 1  according to one implementation. 
     
       
         
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Tag 
                 Depth 
                 Level 
                 Subject 
               
               
                   
               
             
             
               
                 0000 
                 0 
                 0 
                 Bike Rides in the Bay Area 
               
               
                 1000 
                 1 
                 1 
                 Old La Honda 
               
               
                 1100 
                 2 
                 1 
                 re: Old La Honda 
               
               
                 1110 
                 3 
                 1 
                 re: re: Old La Honda 
               
               
                 2000 
                 1 
                 2 
                 Page Mill Road 
               
               
                 3000 
                 1 
                 3 
                 The Bears Loop 
               
               
                 3100 
                 2 
                 1 
                 re: The Bears Loop 
               
               
                   
               
             
          
         
       
     
     Each tag is a number having a plurality of digits, one for each of the depths of the hierarchy. The hierarchy of Table 1 has four depths; thus each tag has four digits. In one implementation, the digits are arranged so that the most significant digit represents the first depth of the hierarchy (that is, the depth of the origin message), the next most significant digit represents the second depth of the hierarchy, and so on. Other implementations employ other arrangements of the digits. 
     The value of each digit represents a level in the hierarchy. Assume the hierarchy of Table 1 has four levels. Then each digit can have a values ranging from zero to three. A value of zero indicates that the message does not exist at that depth in the hierarchy. Of course, other ranges of levels and depths can be supported, as will be apparent to one skilled in the relevant art after reading this description. One implementation supports 16 levels and 16 depths. In that implementation, the tag is a 16-digit hexadecimal number represented by a “big int,” a signed 64-bit number having values ranging from −2 63  to 2 63 . 
     Each tag uniquely identifies the position of its record in the hierarchy. For example, the tag “3100” shows that the record is the first child of the third child of the origin message. 
     One advantage of the disclosed tag is that the tag of a record may be determined quickly and easily, without indexing the database, by modifying the tag of a related record. 
       FIG. 2  is a flowchart of a process  200  for retrieving the parent of a message in an indented threaded discussion according to one implementation. Process  200  receives a command from a user (step  202 ). The command identifies message  108  and requests retrieving the parent of message  108 . Process  200  modifies the tag of message  108  to produce a key. To do this, process  200  first selects the digit corresponding to the hierarchical depth of message  108  (step  204 ). Referring to Table 1, message  108  has a depth of three. Therefore, process  200  selects the third most significant digit of the tag of message  108 . The depth of each message need not be stored in the table, but can be determined in real time, with knowledge of the hierarchical depth represented by each digit. Where tags have digits arranged according to increasing depths in the hierarchy, such as the tags of Table 1, one can select the digit corresponding to the hierarchical depth of a message by simply select the least significant non-zero digit. 
     Process  200  then sets the value of the selected digit to a null value (step  206 ). In the tags of Table 1, the null value is zero. Of course, other values can be selected as the null value. The resulting key is “1100”, which is the tag of message  106 , the parent of message  108 . Process  200  then indexes the database only once by applying the key to the database (step  208 ), thereby selecting the record for message  106 . Process  200  then retrieves message  106  (step  210 ) and displays message  106  to the user (step  212 ). 
       FIG. 3  is a flowchart of a process  300  for retrieving the children of a message in an indented threaded discussion according to one implementation. Process  300  receives a command from a user (step  302 ). The command identifies message  104  and requests retrieving all of the messages in the thread for which message  104  is the head. These messages include the children of message  104 , the children of the children of message  104 , and so on. 
     Process  300  modifies the tag of message  104  to produce a key. To do this, process  300  first selects the digit corresponding to the hierarchical depth of message  104  (step  304 ). Referring to Table 1, message  104  has a depth of one. Therefore, process  300  selects the most significant digit of the tag of message  104 . Process  300  then sets the value of each digit corresponding to a hierarchical depth below the hierarchical depth of the selected digit to a wildcard value (step  308 ). The resulting key is “1XXX”, where “X” represents a wildcard value that can match any value. 
     In one implementation, applying a key to the database selects all records in the database having tags that match the key. Process  300  indexes the database only once by applying the key to the database (step  310 ), thereby selecting the records for the messages in the thread headed by message  104 . Referring to Table 1, the key “1XXX” matches the tags for records corresponding to messages  106  and  108 . Process  300  then retrieves messages  106  and  108  (step  312 ) and displays messages  106  and  108  to the user (step  314 ). 
     Process  300  can also be used to delete a message. When a message is deleted, so are all of its children. Process  300  selects a message and all of its children. The records corresponding to the selected messages are then deleted. 
       FIG. 4  is a flowchart of a process  400  for adding a message to an indented threaded discussion according to one implementation. Process  400  receives a command from a user (step  402 ). The command identifies message  114  and requests replying to message  114 . Process  400  modifies the tag of message  114  to produce a key. To do this, process  400  first selects the digit corresponding to the hierarchical depth immediately below the hierarchical depth of message  114  (step  404 ). Referring to Table 1, message  114  has a depth of two. Therefore, process  400  selects the third most significant digit of the tag of message  104 . Process  400  then increments the value of selected digit (step  406 ). The resulting key is “3110”. Process  400  then indexes the database only once by adding a record to the database having the key as its tag (step  408 ). The record corresponds to the new message. 
     The invention can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Apparatus of the invention can be implemented in a computer program product tangibly embodied in a machine-readable storage device for execution by a programmable processor; and method steps of the invention can be performed by a programmable processor executing a program of instructions to perform functions of the invention by operating on input data and generating output. The invention can be implemented advantageously in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. Each computer program can be implemented in a high-level procedural or object-oriented programming language, or in assembly or machine language if desired; and in any case, the language can be a compiled or interpreted language. Suitable processors include, by way of example, both general and special purpose microprocessors. Generally, a processor will receive instructions and data from a read-only memory and/or a random access memory. Generally, a computer will include one or more mass storage devices for storing data files; such devices include magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks. Any of the foregoing can be supplemented by, or incorporated in, ASICs (application-specific integrated circuits). 
     A number of implementations of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other implementations are within the scope of the following claims.