Patent Publication Number: US-8984537-B2

Title: Maintaining data states upon forced exit

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of and claims priority to U.S. patent application Ser. No. 12/840,216 (U.S. Pat. No. 8,429,674 B 2), filed on Jul. 20, 2010, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to database application programs on a mobile device. 
     BACKGROUND 
     A mobile device, such as a smart phone or a tablet device, can execute various application programs that access one or more data stores. The application programs can include, for example, a database reporting program that is configured to display a formatted view of data stored in the one or more data stores, or a database editing program that is configured to update the data in the one or more data stores. The data stores can be hosted on server computers that are located remotely from the mobile device. For the application programs to access the data stores, the mobile device can utilize one or more connections to the data stores through a communications network. 
     A mobile device can include various features that can force an application program to terminate. For example, a mobile device can include a “home” button that, when pressed, causes a display screen to switch immediately from displaying content of the application program to displaying a system screen or to displaying an output of a second application program. After the switch, the application program can exit. The mobile device can switch display content without providing a prompt for a user to save data currently being viewed or edited, or states of the data. If the application program is a database reporting program or database editing program that is currently connected to a data store, the current connection can be terminated, and states of the connection lost. 
     SUMMARY 
     Methods, program products, and systems of maintaining data states upon forced exit are disclosed. In one aspect, an application program executing on the mobile device can maintain a connection to a remote data store and retrieve and cache data from the data store. When the mobile device receives an event that forces the application program to terminate, the mobile device can provide a time window in which the mobile device can perform various state-preservation actions. During the time window, the mobile device can store data states, including states of the connection and states of the cached data. When the application program is re-launched, the mobile device can use the stored data states to restore a connection and a displayed view. 
     In some implementations, a mobile device can receive an event to terminate one or more connections connecting the mobile device to one or more data stores. The event can correspond to a time window in which the mobile device can perform one or more actions to preserve data states. Within the time window, the mobile device can store states of at least one of the one or more connections on a storage device. The mobile device can terminate the one or more connections before, during, and after storing the states. 
     These and other implementations can be utilized to achieve one or more of the following advantages. Maintaining data states upon forced exit can be utilized to provide a sense of consistency to the user. States of a currently open connection of an application program can be maintained even when the application program is forced to terminate. A user&#39;s current viewing states can also be maintained. When the application program re-launches, the mobile device can automatically display content that a user was viewing when the forced exit of an application program occurred, with data connection restored. 
     The techniques of maintaining data states upon forced exit can be utilized to reduce network traffic. Cached data and states of the cached data are stored on a mobile device upon forced exit of an application program that accesses data in remote data stores. Upon re-launching of the application program, only “dirty” data are retrieved from the remote data stores to the mobile device. Accordingly, a complete data download that may include data that are not dirty can be avoided, thus reducing network traffic. 
     The details of one or more implementations of techniques of maintaining data states upon forced exit of an application program are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of maintaining data states upon forced exit of an application program will become apparent from the description, the drawings, and the claims 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates exemplary techniques of maintaining data states upon a forced exit of an application program. 
         FIG. 2  illustrates exemplary techniques of maintaining data states upon a loss of connection to a data store. 
         FIG. 3  illustrates a timeline of events that occur in maintaining data states upon a forced exit of an application program. 
         FIGS. 4A and 4B  illustrate exemplary user interfaces of maintaining data states upon a forced exit of an application program. 
         FIGS. 5A and 5B  are flowcharts illustrating exemplary processes of maintaining data states upon a forced exit and restoring the data states. 
         FIG. 6  is a flowchart illustrating an exemplary process of maintaining data states upon a forced exit of an application program. 
         FIG. 7  is a block diagram illustrating an exemplary device architecture of a mobile device implementing the features and operations of maintaining data states upon a forced exit of an application program. 
         FIG. 8  is a block diagram of an exemplary network operating environment for mobile devices implementing features and operations of maintaining data states upon a forced exit of an application program. 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     Overview of Maintaining Data States upon Forced Exit 
       FIG. 1  illustrates exemplary techniques of maintaining data states upon a forced exit of an application program. For convenience, the techniques will be described in reference to mobile device  100  in various stages A, B, and C of maintaining data states. 
     At exemplary stage A, an exemplary application program currently executing on mobile device  100  can be forced to exit. The exemplary application program can be a database reporting program. The database reporting program can be configured to display data of a data store. For example, the database reporting program can display employee names under column heading “Emp” and revenue under column heading “Rev” associated with each employee name on display screen  104 . The employee names and revenues can be stored as data fields or data records in data store  106  or data store  110  or both. 
     The database reporting program can access data in data store  106  and data store  110 . Mobile device  100  can connect to data store  106  and data store  110  through communications network  120 . The connection can be maintained on an as-needed basis, or while the database reporting program executes on mobile device  100 . 
     While the database reporting program is connected to data store  106  and data store  110 , an event can occur that forces the database reporting program to exit. In a forced exit, the database reporting program can lose control of display screen  104  immediately. The event can force the application program to terminate without providing a user interface that allows a user to save the current states of the connection and view. 
     The event can occur when particular data are being viewed in particular display settings. For example, the event can occur when a user is viewing data relating to employees Adam, Betty, and Carl. The event can be triggered by an input through control element  102 . Control element  102  can have multiple functions. In some implementations, control element  102  can be a home button that, when pushed, forces an exit of an application program currently executing on mobile device  100 . In some implementations, control element  102  can be a switch that, when activated for a specified period of time, turns on or off mobile device  100 . Control element  102  is shown to be positioned at a lower middle front section of mobile device  100  for illustrative purposes. In various implementations, control element  102  can be positioned in any part of mobile device  100  (e.g., top, bottom, side, or back). 
     Upon receiving the event, mobile device  100  can provide a time window (e.g., a number of seconds) to the application program for cleaning up (e.g., release control of computing resources). The application program can utilize the time window as a grace period to save current data states. The time window can be provided by an operating system of mobile device. The time window can be defined by a length of time between the occurrence of the event and an actual time that the operating system revokes all resources provided to the application program (e.g., memory and CPU cycle), or any time period specified by user or system parameters. The actual termination time can be a time when the operating system revokes all resources provided to the application program (e.g., memory and CPU cycle), or any time period specified by user or system parameters. The actual termination time can be a time when the operating system shuts down, or a time when the operating system enters a “power save” or “sleep” mode. 
     During the time window, mobile device  100  can store one or more data states. The data states can include states of the connections between mobile device  100  and data stores  106  and  110 . The states of the connections can include, for example, identifiers (e.g., host names) of data stores  106  and  110  and other connection parameters (e.g., port numbers, database identifiers, user names, and passwords) of the connection. 
     In some implementations, the data states can include data or references to cached data, including data currently being displayed on display screen  104 . Cached data can include data retrieved from data stores  106  and  110  to mobile device  100  for current use (e.g., current display). For example, the data states can include references indicating that data relating to employees Adam, Betty, and Carl are being displayed. The data states can include metadata of the data being displayed, including, for example, a number of times that the data have been modified by various users. The data states can include display settings of the data that are currently being displayed on display screen  104 . Mobile device  100  can terminate the connections before, during, or after the data states are stored. The application program can exit at the end of the time window. 
     At exemplary stage B, mobile device  100  can receive a request to restore the terminated connections and states of cached data. The request can result from, for example, a touch input to re-launch the application program received from display screen  104  upon a user touching icon  108  that is associated with the application program. In response to the request, mobile device  100  can reactivate the database reporting application program by providing various computing resources to the database reporting application program. The database reporting application program can retrieve the saved data states. Upon retrieving the saved states, the database reporting application program can examine the stored data states, restore the connections according to the stored data states, and update cached data when necessary. For example, the database reporting application program can identify one or more remote data stores to connect to, based on host names in the stored states, and connect to the data stores using connection parameters. 
     At exemplary stage C, upon restoring the connections, mobile device  100  can further restore a view of display screen  104  as when the event occurred. Some of the data can be retrieved from a cache on mobile device. Some of the data can be retrieved from data stores  106  and  110 . Mobile device  100  can determine which portions of the data are to be retrieved from the cache and which from data stores  106  and  110  based on information indicating whether the data have been updated when the application program is not active. For example, based on the stored data states, mobile device  100  can determine that data relating to Carl has changed. Mobile device  100  can retrieve data related to Adam and Betty from cached data, and retrieve data related to Carl from data stores  106  and  110 . Mobile device  100  can display the data using display setting stored in the data states. 
       FIG. 2  illustrates exemplary techniques of maintaining data states upon a loss of connection to a data store. The techniques will be described in reference to mobile device  200 , which, like mobile device  100 , can be an exemplary mobile device configured to implement the features and operations of maintaining data states upon a forced exit. For convenience, the techniques will be described in reference to mobile device  100  in various stages D, E, and F of maintaining data states. 
     Mobile device  200  can connect to data store  206  and data store  210  through communications network  220 . Communications network  220  can include a wireless communications network. Mobile device  200  can be a mobile device that connects to communications network  220  wirelessly. To connect to communications network  220  wirelessly, mobile device  200  can utilize various wireless communication technologies. For example, mobile device  200  can connect to communications network  220  using Wi-Fi™ technologies or cellular communication technologies. 
     Mobile device  200  can communicate with data stores  206  and  210  by sending and receiving wireless signals. Strength of the wireless signals can vary. The variance can be due to various factors. For example, a change of distance between mobile device  200  and a wireless access point or a cellular tower of communications network  220  can cause the signal strength to change. Mobile device  200  can maintain a connection to communications network  220  and connections to data stores  206  and  210  if the signal strength satisfies a threshold. 
     For illustrative purposes, signal strength bars  222 ,  224 , and  226  are used to indicate strength of wireless signals received by mobile device  200  at various stages. Signal strength bars  222 ,  224 , and  226  can be graphic user interface (GUI) elements that can be displayed on a display screen of mobile device  200 . Lengths of signal strength bars  222 ,  224 , and  226  can indicate strengths of the wireless signal. A longer signal strength bar can indicate stronger wireless signal. If the signal strength fails to satisfy the threshold, a length of a signal strength bar can be zero. 
     For illustrative purposes, at exemplary stage D, mobile device  200  can be wirelessly connected to data stores  206  and  210 . The signal strength is sufficiently strong such that data communications between mobile device  200  and data stores  206  and  210  can occur smoothly. The strong wireless signal is indicated by signal strength bar  222 . 
     At exemplary stage E, the wireless signals can weaken sufficiently such that the wireless signals fail to satisfy the threshold for maintaining a connection. For example, at exemplary stage E, mobile device  200  can move away from a wireless access point or a cellular tower, move into a place where metal objects interfere with the wireless signal (e.g., an elevator car), or move into a place difficult for wireless signals to reach (e.g., a basement of a building). As a result, signal strength bar  224  can have a length of zero. 
     In some implementations, mobile device  200  can proceed to save data states when the signal strength fails to satisfy the threshold signal strength. Mobile device  200  can identify states of the connections and states of cached data after the actual connections to data stores  206  and  210  are lost. Mobile device  200  can store the data states on a storage device, and provide a user interface indicating that connections have been lost. 
     In some implementations, mobile device  200  can estimate a time when the strength of the wireless signal will fail to satisfy the threshold signal strength for maintaining a connection. If a failure is imminent, (e.g., when the estimated time falls below a threshold value), mobile device  200  can determine that data states are to be saved, and proceed to collect and save the states. Estimating the time when the strength of the wireless signal will fail to satisfy the threshold signal strength can include measuring a rate of change (e.g., rate of decrease) in signal strength. Additionally or alternatively, a location-aware mobile device can estimate the time based on a current location of the mobile device, a known location of a wireless access point or cellular tower, and a speed of movement of the mobile device. The time when the strength of the wireless signal will fail to satisfy the threshold signal strength can be estimated based on an estimate of time the mobile device moves out of a communication range of the wireless access point or cellular tower. 
     The data states can be stored in an encrypted data structure  228   a . Encrypted data structure  228   a  can include a file, a local or remote database record, an entry in a system log, or any other data structure. Data structure  228   a  can be encrypted in various ways, including encrypted using an encryption key that is generated based on a hardware profile of mobile device  200 , to prevent data structure  228   a  from being copied to another device and used to make unauthorized connections to data stores  206  and  210 . 
     Encrypted data structure  228   a  can include states of connection  230  and states of cached data  232   a.  States of connection  230  can include, for example, identifiers (e.g., host names, domain names, or IP addresses) of data stores  206  and  210 , the connection parameters, and order of the connections. The order of the connections can be determined by one or more dependencies of the data stores. For example, a particular application program can require that mobile device  200  connect to data store  206  before connecting to data store  210 . The order of the connections can be stored accordingly. 
     Encrypted data structure  228   a  can include states of cached data  232   a . States of cached data  232   a  can include states of data cached on mobile device  200  when a forced exit event or a loss of connection event occurs. When an application program displays data retrieved from data stores  206  and  210 , some data can be retrieved from data stores  206  and  210  and stored on a storage device (cache) local to mobile device  200 . Thus, if a user browses through data stored in the cache, mobile device  200  need not send multiple requests to data stores  206  and  210 . The cached data can be associated with metadata describing the states of the cached data. The metadata can include, for example, indicators on whether the cached data are shared data that can be updated by multiple users. If the cached data are shared data, the metadata can include an indicator indicating a number of times the data have been updated, time of each update, and an identifier of each user making the update. When the connections are restored, the states of cached data  232   a  can be used to determine what data in the cache need to be updated. 
     In some implementations, the states of cached data  232   a  can include one or more references to the data records or data fields being displayed on a display screen when the forced exit or loss of connection occurred. The states of cached data  232   a  can include whether a data record or data field is “dirty” (e.g., has been edited on mobile device  200 ). 
     The states of cached data  232   a  can include display settings of the data records or data fields when a forced exit event or a loss of connection event occurs. The display settings can include zoom factors (e.g., zoomed 125%), cursor positions, cursor shapes, and window layouts and relative positions. 
     At exemplary stage F, mobile device  200  can automatically re-establish the connections to data store  206  and data store  210  when the wireless signal becomes sufficiently strong again, as indicated by signal strength bar  226 . Upon detecting that connection can be established, mobile device  200  can retrieve the saved date states, including states of connections  230  and states of cached data  232   a  from encrypted data structure  228   a.  Using the states of connections  230 , mobile device  200  can re-establish the connections to data stores  206  and  210 . 
     Upon re-establishing the connections, mobile device  200  can retrieve from data store  206  and  210  metadata that correspond to the cached data. The metadata can include information on whether data previous downloaded to and cached on mobile device  200  have been changed. Mobile device can compare the metadata retrieved from data store  206  and  210  and metadata retrieved from encrypted data structure  228   a  to determine if the cached data need to be updated. For example, if a modification count on a data record or data field as recorded in metadata retrieved from data store  206  and  210  differs from a modification count on the data record or data field as recorded in metadata retrieved from encrypted data structure  228   a,  mobile device  200  can determine that further editing by another user on the data record or data field has occurred after the data record or data field was cached. Mobile device  200  can refresh this data record or data field in the cache by downloading the data. Mobile device  200  can additionally or alternatively update the states of the cached data  232   a  into states of the cached data  232   b.  States of the cached data  232   b  can be stored in updated encrypted data structure  228   b.  In some implementations, states of the cached data  232   b  can be updated in real time. For example, a modification count on a data record or data field, as stored in states of the cached data  232   b,  can be updated when another user updates the data record or data field on data store  206  or data store  210 . 
     Mobile device  200  can additionally or alternatively determine if a conflict exists based on states of cached data  232   a.  A conflict can exist when, for example, a shared data record or data field is edited on mobile device  200  and marked as dirty, and the modification count from the data stores  106  and  110  and modification count as recorded in cached data  232   a  do not match one another. The conflict can occur when connections to the data stores  206  and  210  are lost before the edit by user of mobile device  200  is committed, and other users edited the same shared data record or data field when the connection was lost. When a conflict exists, mobile device  200  can provide a user interface and prompt the user to resolve the conflict. 
     Mobile device  200  can present data on a display device in the same manner as the data were displayed at time when the forced exit occurred or when connections to the data stores were lost. Presenting the data in the same manner as the data were displayed can include presenting the data using the display settings at time when the connection to the data stores are lost, as saved in encrypted data structure  228   a.  The display settings can include zoom factor, cursor position, cursor type, etc. 
     Exemplary Time Line of Maintaining Data States upon Forced Exit 
       FIG. 3  illustrates an exemplary timeline of events that occur in maintaining data states upon a forced exit. Various event stages  310 ,  312 ,  314 ,  316 , and  318  of mobile device  300 , data store  302 , and connection between mobile device  300  and data store  302  are shown along the exemplary time line. 
     At time t 0 , mobile device  300  can be connected to data store  302 . The connection can be facilitated through a communications network. An application program on mobile device  300  can access data stored on data store  302 . At least a portion of the accessed data can be stored locally on mobile device  300  in a data cache. 
     At time t 1 , mobile device  300  receives an event to terminate the connection between mobile device  300  and data store  302 . The event can include, for example, a forced exit of the application program, a power off of mobile device  300 , a low battery event that indicates mobile device  300  will be shut down automatically due to low battery reserve, a weakening or loss of wireless communications signal, and unplugging of a wired networking connector (e.g., a network cable) from mobile device  300 . 
     The event can correspond to a time window (e.g., a time window between t 1  and t 2 ). The time window can be defined by an operating system of mobile device  300 , configured by user, or determined by other factors. These factors can include, for example, estimated time until wireless signals will fail to satisfy a threshold, or estimated time until the battery will fail to supply sufficient voltage or current to mobile device  300 . Within the time window, an application program can perform actions to store data states in an encrypted data structure. 
     In the time window, the connection can have various states, as represented by the dashed arrow between mobile device  300  and data store  302  as shown in event stage  312 . In some implementations, the connection can be terminated at time t 1 . In some implementations, the connection can be terminated at time t 2 , or any time between t 1  and t 2 . The time window may not be sufficiently wide to allow all data states to be identified, retrieved, or stored. Mobile device  300  can attempt to store a maximum number of data states during the time window. 
     At time t 3 , the application program can be re-launched. The connection between mobile device  300  and data store  302  can be restored. Restoring the connection can include retrieving connection states stored upon the forced exit. For example, mobile device  300  can identify an IP address associated with data store  302  and attempt to connect to that IP address. In some implementation, restoring the connection can include tiered attempts if a first attempt fails. For example, if an attempt to connect to a data store represented by a particular IP address fails, mobile device  300  can attempt to connect to the data storing using a hostname (e.g., “janes-server”), which can be a label that is assigned to a device of a communications network and is used to identify the device. The hostname can be a domain name (e.g., “janes-server.mycompany.com”) recognizable by a domain name system (DNS). Restoring the connection can additionally include attempting to connect to data store  302  using the stored parameters including port number, database name, user name, and password. 
     In some implementations, restoring the connection can include attempting to restore a spooled connection using a connection identifier. Mobile device  300  can store a connection identifier of a connection to data store  302  as part of the connection states. The connection identifier can be a string or numeric value provided by data store  302  that uniquely identifies a connection stored in a connection pool, which can be a cache of database connections maintained so that the connections can be reused when future requests to the database are requested. Mobile device  300  can attempt to restore the connection using the stored connection identifier. 
     At time t 4 , mobile device  300  can restore a display according to display settings at time t 1 . Restoring the display can include providing for display data that were displayed at time t 1  using the settings at time t 1 . Cached data can be updated if updates on data store  302  exist. One or more conflict resolution prompts can be displayed if an uncommitted local edit and an update on data store  302  exists. The cursor position can be restored. 
     Exemplary User Interface of Maintaining Data States upon Forced Exit 
       FIGS. 4A and 4B  illustrate exemplary user interfaces of maintaining data states upon a forced exit of an application program. The exemplary user interfaces are described in reference to mobile device  400 . 
       FIG. 4A  illustrates mobile device  400  executing a database application program that displays a user interface on display screen  402 . The user interface can include interactive content based on data retrieved from a data store. The data retrieved from the data store can be cached on mobile device  400 . The interactive content can be displayed in multiple windows, e.g., window  404   a  and window  406 . Window  404   a  can be displayed on top, substantially covering window  406 . Display screen  402  can be a touch-sensitive display screen that is configured to receive touch inputs. For example, a touch on an uncovered portion of window  406  can bring window  406  to the top. 
     Data displayed in window  404   a  can include exemplary data records and data fields on employees and revenue associated with the employees, e.g., “Adam  100 ,” “Betty  200 ,” and “Carl  300 .” The data records can be shared data records that can be updated by multiple users. A user using mobile device  400  can update name and/or revenue values for Betty and Carl. After the update, the user moves a cursor  412   a  to data record “Adam  100 .” An event can occur that forces the application program to exit. For example, the event can be an input received from control element  408 , which can be a home button. Upon receiving the event, the application program can surrender display screen  402 , e.g., by giving control of display screen  402  to an operating system. The application program can store, in a time window, the data states, including states of the connections and states of cached data on a storage device. 
       FIG. 4B  illustrates mobile device  400  that displays a user interface on display screen  402  when restoring a connection based on saved data states. Mobile device  400  can receive a request to restore the connection. For example, mobile device  400  can receive a request to re-launch the application program. Upon receiving the request, mobile device  400  can retrieve the stored data states. Using the state of connection in the stored data states, mobile device  400  can reestablish a connection to a data store. Using states of cached data in the retrieved data states, mobile device  400  can identify data cached on mobile device  400 . The cached data can include, for example, data records “Adam  100 ,” “Betty  200 ,” and “Carl  300 .” Accordingly, mobile device can retrieve metadata of the cached data records from the data store. 
     Mobile device  400  can compare metadata retrieved from the data store with metadata stored in the data states and determine whether a conflict exists. For example, mobile device  400  can determine that data records “Betty  200 ” and “Carl  300 ” may have been updated on mobile device  400  as well as in the data store. Upon the determination, mobile device  400  can provide for display user interface  410 , which can include, for example, a pop-up window that prompts the user to select whether to update the data using the current data from the server. The data records that may be updated can be provided for display in highlight. 
     Mobile device  400  can display the data records using display settings in the retrieved data states. For example, mobile device  400  can display window  404   b  and  406  according to the same relative position between window  404   a  and  406 . Layout, zoom factor, and cursor position at time the event occurred can be reproduced. For example, cursor  412   b  can be provided for display at the same location in window  404   b  as cursor  412   a  in window  404   a  and in the same shape. 
     Exemplary Processes of Maintaining Data States upon Forced Exit 
       FIGS. 5A and 5B  are flowcharts illustrating exemplary processes of maintaining data states upon a forced exit and restoring the data states. For convenience, the exemplary processes will be described in reference to a mobile device that implements the processes. The mobile device can be a mobile device such as mobile device  100 ,  200 ,  300 , or  400  as described above in  FIGS. 1-4 . 
       FIG. 5A  is a flowchart illustrating an exemplary process  500  of storing the data states. The mobile device can receive ( 502 ) a notification that one or more connections to data stores will terminate or has terminated. The notification can be a notification associated with an event that forces an application program that manages the one or more connections to exit (e.g., to surrender control of computing resources to the operating system). Alternatively or additionally, the notification can be a notification associated with a loss of connection. The notification can be received when data from the data store retrieved through the one or more connections are displayed on a display screen of the mobile device. 
     The mobile device can capture ( 504 ) data states upon receiving the notification. Capturing the data states can include storing various states of the connections, cached data, and display settings on a non-volatile storage device. Capturing the data states can occur in parallel, or in a sequential manner. For example, in some implementations, data states related to multiple connections can be stored sequentially, one connection at a time. 
     The mobile device can determine ( 506 ) whether a time window for cleaning up has closed. The time window can be associated with the event that forces an application program to exit. If the time window is closed, the application program terminates. If the time window has not closed yet, the mobile device can determine ( 508 ) whether all data states are captures. For example, the mobile device can examine a data structure registering all data store connections, and determine whether states of all connections and data associated with the connections have been preserved. Upon determining that states of all connections and data associated with the connections have been preserved, the application program can terminate. Otherwise, the mobile device continues to capture data states for a subsequent connection. 
       FIG. 5B  is a flowchart illustrating an exemplary process  540  of restoring connection using stored the data states. A mobile device can receive ( 542 ) a request to restore a connection between the mobile device and a data store. The request can include, for example, a request to launch an application program that was forced to exit. 
     The mobile device can determine ( 546 ) whether stored connection states exist. Determining whether the stored data states exits can include, for example, identifying an encrypted data structure, and determining that the encrypted data structure includes states of the connection. 
     Upon determining that the stored states of connection exist, the mobile device can open ( 548 ) one or more connections using the stored connection states. Opening the connection using the stored connection states can include retrieving an identifier of a data store to which the mobile device can connect, and retrieving the connection parameters related to the data store from the stored connection states. The mobile device can open the connection to the data store identified by the identifier using the connection parameters. Upon determining that the stored data states do not exist, the mobile device can open ( 550 ) a new connection, if the new connection is requested by the application program. 
     The mobile device can determine ( 552 ) if shared data to be provided for display have been modified by other users since the application program was forced to exit. Determining if the shared data have been modified can include identifying first metadata of the shared data in locally stored states of cached data, retrieving second metadata of the shared data from the data store, and comparing the first metadata and second metadata. If the shared data were modified, the mobile device can retrieve ( 554 ) the updated data from the data store. If conflict exists, the mobile device can resolve the conflict automatically or provide a user interface for resolving the conflict. 
     If shared data were not modified, the mobile device can provide ( 556 ) data for display using stored data states. Providing data for display using the stored data states can include providing the data for display using display settings stored in the data states. 
       FIG. 6  is a flowchart illustrating exemplary process  600  of maintaining data states upon a forced exit. For convenience, the exemplary process  600  will be described in reference to a mobile device that implements exemplary process  600 . The mobile device can be a mobile device such as mobile device  100 ,  200 ,  300 , or  400  as described above in  FIGS. 1-4 . 
     The mobile device can receive ( 602 ) an event to terminate one or more connections connecting the mobile device to one or more data stores. The event can correspond to a time window in which the mobile device can perform one or more actions to terminate the one or more connections. The event can include a notification of a forced exit of an application program or a loss or imminent loss of the one or more connections. The application program can be an application program that utilizes or manages the one or more connections. 
     In some implementations, the mobile device can determine the time window by inquiring, to an operating system of the mobile device, a time window corresponding to the forced exit of the application program. The time window can be a grace period provided by the operating system to all application programs for cleaning up, or a time window specific to the application program. 
     In some implementations, the data store can be connected to the mobile device through a wireless communications network. In such cases, the event to terminate one or more connections can include an indication that a loss of connection to the wireless communication has occurred or is imminent. In some implementations, the indication can include a weakening of a wireless signal of the wireless communications network indicating that a signal strength of the wireless signal will fail to satisfy a threshold. In some implementations, the indication can include an indication that the mobile device has moved or will move out of a communication range of the wireless communications network based on a projected motion path of the mobile device and a current geographic location of the mobile device. 
     In some implementations, the mobile device can determine the time window, including determining a projected time until connection to the wireless communications network is lost and determining the time window based on the projected time. 
     Within the time window, the mobile device can store ( 604 ) data states on a storage device. The data states can include states of at least one of the one or more connections. Storing the data states within the time window can include storing states of a maximum number of connections as limited by the time window. In some implementations, storing the data states can include storing states of cached data. The cached data can include a data record that is configured to be modifiable by multiple users. Storing the state of a data record can include storing an indicator indicating a number of times the data record has been updated. Storing the data states can include storing display settings for displaying data upon occurrence of the event. The display settings can include, for example, a windows setting, a zoom setting, or a position of a cursor being displayed when the event occurs. 
     The mobile device can terminate ( 606 ) the one or more connections. Terminating the one or more connections can occur before, during, or after the mobile device stores the data states. 
     Optionally, the mobile device can receive ( 608 ) a request to restore the one or more connections. The request can include, for example, an input for re-launching an application program that utilizes or manages the connections that has been forced to exit. 
     Upon receiving the request to restore the one or more connections, the mobile device can retrieve ( 610 ) the stored data states. Retrieving the stored data states can include reading an encrypted data structure using a decryption key that is generated based on a hardware profile of the mobile device. 
     The mobile device can restore ( 612 ) the one or more connections according to the retrieved states. Restoring the one or more connections can include determining that a shared data record or data field in the one or more data stores changed after the one or more connections are terminated. Upon the determining, the mobile device can refresh cached data to reflect the changed data record or data field. If a data record or field is changed both on the mobile device and in the data store, a conflict can occur. If a conflict occurs, the mobile device can provide for display a user interface for resolving the conflict. Restoring the one or more connections can optionally include applying display settings stored in the retrieved data states to displayed data, including, for example, a cursor position. 
     Exemplary Mobile Device Architecture 
       FIG. 7  is a block diagram of an exemplary architecture  700  for a mobile device implementing the features and operations of maintaining data states upon a forced exit of an application program. A mobile device (e.g., mobile device  100 ) can be, for example, a handheld computer, a personal digital assistant, a cellular telephone, an electronic tablet, a network appliance, a camera, a smart phone, an enhanced general packet radio service (EGPRS) mobile phone, a network base station, a media player, a navigation device, an email device, a game console, or a combination of any two or more of these data processing devices or other data processing devices. 
     Mobile device  100  can include memory interface  702 , one or more data processors, image processors and/or processors  704 , and peripherals interface  706 . Memory interface  702 , one or more processors  704 , and/or peripherals interface  706  can be separate components or can be integrated in one or more integrated circuits. Processors  704  can include application processors (APs) and baseband processors (BPs). The various components in mobile device  100 , for example, can be coupled by one or more communication buses or signal lines. 
     Sensors, devices, and subsystems can be coupled to peripherals interface  706  to facilitate multiple functionalities. For example, motion sensor  710 , light sensor  712 , and proximity sensor  714  can be coupled to peripherals interface  706  to facilitate orientation, lighting, and proximity functions of the mobile device. Location processor  715  (e.g., GPS receiver) can be connected to peripherals interface  706  to provide geopositioning. Electronic magnetometer  716  (e.g., an integrated circuit chip) can also be connected to peripherals interface  706  to provide data that can be used to determine the direction of magnetic North. Thus, electronic magnetometer  716  can be used as an electronic compass. Accelerometer  717  can also be connected to peripherals interface  706  to provide data that can be used to determine change of speed and direction of movement of mobile device  100 . 
     Camera subsystem  720  and an optical sensor  722 , e.g., a charged coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) optical sensor, can be utilized to facilitate camera functions, such as recording photographs and video clips. 
     Communication functions can be facilitated through one or more wireless communication subsystems  724 , which can include radio frequency receivers and transmitters and/or optical (e.g., infrared) receivers and transmitters. The specific design and implementation of the communication subsystem  724  can depend on the communications network(s) over which a mobile device is intended to operate. For example, a mobile device can include communication subsystems  724  designed to operate over a GSM network, a GPRS network, an EDGE network, a Wi-Fi or WiMax network, and a Bluetooth network. In particular, the wireless communication subsystems  724  can include hosting protocols such that the mobile device can be configured as a base station for other wireless devices. 
     Audio subsystem  726  can be coupled to a speaker  728  and a microphone  730  to facilitate voice-enabled functions, such as voice recognition, voice replication, digital recording, and telephony functions. 
     I/O subsystem  740  can include touch screen controller  742  and/or other input controller(s)  744 . Touch-screen controller  742  can be coupled to a touch screen  746  or pad. Touch screen  746  and touch screen controller  742  can, for example, detect contact and movement or break thereof using any of a plurality of touch sensitivity technologies, including but not limited to capacitive, resistive, infrared, and surface acoustic wave technologies, as well as other proximity sensor arrays or other elements for determining one or more points of contact with touch screen  746 . 
     Other input controller(s)  744  can be coupled to other input/control devices  748 , such as one or more buttons, rocker switches, thumb-wheel, infrared port, USB port, and/or a pointer device such as a stylus. The one or more buttons (not shown) can include an up/down button for volume control of speaker  728  and/or microphone  730 . 
     In one implementation, a pressing of the button for a first duration may disengage a lock of the touch screen  746 ; and a pressing of the button for a second duration that is longer than the first duration may turn power to mobile device  100  on or off. The user may be able to customize a functionality of one or more of the buttons. The touch screen  746  can, for example, also be used to implement virtual or soft buttons and/or a keyboard. 
     In some implementations, mobile device  100  can present recorded audio and/or video files, such as MP3, AAC, and MPEG files. In some implementations, mobile device  100  can include the functionality of an MP3 player, such as an iPod™. Mobile device  100  may, therefore, include a pin connector that is compatible with the iPod. Other input/output and control devices can also be used. 
     Memory interface  702  can be coupled to memory  750 . Memory  750  can include high-speed random access memory and/or non-volatile memory, such as one or more magnetic disk storage devices, one or more optical storage devices, and/or flash memory (e.g., NAND, NOR). Memory  750  can store operating system  752 , such as Darwin, RTXC, LINUX, UNIX, OS X, WINDOWS, or an embedded operating system such as VxWorks. Operating system  752  may include instructions for handling basic system services and for performing hardware dependent tasks. In some implementations, operating system  752  can include a kernel (e.g., UNIX kernel). 
     Memory  750  may also store communication instructions  754  to facilitate communicating with one or more additional devices, one or more computers and/or one or more servers. Memory  750  may include graphical user interface instructions  756  to facilitate graphic user interface processing; sensor processing instructions  758  to facilitate sensor-related processing and functions; phone instructions  760  to facilitate phone-related processes and functions; electronic messaging instructions  762  to facilitate electronic-messaging related processes and functions; web browsing instructions  764  to facilitate web browsing-related processes and functions; media processing instructions  766  to facilitate media processing-related processes and functions; GPS/Navigation instructions  768  to facilitate GPS and navigation-related processes and instructions; camera instructions  770  to facilitate camera-related processes and functions; magnetometer data  772  and calibration instructions  774  to facilitate magnetometer calibration. The memory  750  may also store other software instructions (not shown), such as security instructions, web video instructions to facilitate web video-related processes and functions, and/or web shopping instructions to facilitate web shopping-related processes and functions. In some implementations, the media processing instructions  766  are divided into audio processing instructions and video processing instructions to facilitate audio processing-related processes and functions and video processing-related processes and functions, respectively. An activation record and International Mobile Equipment Identity (IMEI) or similar hardware identifier can also be stored in memory  750 . Memory  750  can include data states instructions  776  that can be used to maintain data states of one or more data connections or data records upon a forced exit of an application program utilizing the data connections. 
     Each of the above identified instructions and applications can correspond to a set of instructions for performing one or more functions described above. These instructions need not be implemented as separate software programs, procedures, or modules. Memory  750  can include additional instructions or fewer instructions. Furthermore, various functions of the mobile device may be implemented in hardware and/or in software, including in one or more signal processing and/or application specific integrated circuits. 
     Exemplary Operating Environment 
       FIG. 8  is a block diagram of an exemplary network operating environment  800  for mobile devices implementing the features and operations of maintaining data states upon a forced exit of an application program. Mobile devices  802   a  and  802   b  can be mobile device such as mobile device  100  of  FIG. 1 . Mobile devices  802   a  and  802   b  can, for example, communicate over one or more wired and/or wireless networks  810  in data communication. For example, a wireless network  812 , e.g., a cellular network, can communicate with a wide area network (WAN)  814 , such as the Internet, by use of a gateway  816 . Likewise, an access device  818 , such as an 802.11g wireless access device, can provide communication access to the wide area network  814 . 
     In some implementations, both voice and data communications can be established over wireless network  812  and the access device  818 . For example, mobile device  802   a  can place and receive phone calls (e.g., using voice over Internet Protocol (VoIP) protocols), send and receive e-mail messages (e.g., using Post Office Protocol 3 (POP3)), and retrieve electronic documents and/or streams, such as web pages, photographs, and videos, over wireless network  812 , gateway  816 , and wide area network  814  (e.g., using Transmission Control Protocol/Internet Protocol (TCP/IP) or User Datagram Protocol (UDP)). Likewise, in some implementations, the mobile device  802   b  can place and receive phone calls, send and receive e-mail messages, and retrieve electronic documents over the access device  818  and the wide area network  814 . In some implementations, mobile device  802   a  or  802   b  can be physically connected to the access device  818  using one or more cables and the access device  818  can be a personal computer. In this configuration, mobile device  802   a  or  802   b  can be referred to as a “tethered” device. 
     Mobile devices  802   a  and  802   b  can also establish communications by other means. For example, wireless device  802   a  can communicate with other wireless devices, e.g., other mobile devices  802   a  or  802   b,  cell phones, etc., over the wireless network  812 . Likewise, mobile devices  802   a  and  802   b  can establish peer-to-peer communications  820 , e.g., a personal area network, by use of one or more communication subsystems, such as the Bluetooth™ communication devices. Other communication protocols and topologies can also be implemented. 
     The mobile device  802   a  or  802   b  can, for example, communicate with one or more services  830  and  840  over the one or more wired and/or wireless networks. For example, one or more location services  830  can determine one or more location identifiers of wireless access gateways (cell towers or wireless access points) and latitude and longitude coordinates associated with the location identifiers, and provide the one or more location identifiers to mobile devices  802   a  and  802   b  for determining current locations mobile devices  802   a  and  802   b  using the location identifiers. One or more data store services  840  can provide data services including shared data services. The data store services  840  can include service of providing metadata of shared data records, including a number of times shared data records are updated, by which users, and at what time. 
     Mobile device  802   a  or  802   b  can also access other data and content over the one or more wired and/or wireless networks. For example, content publishers, such as news sites, Really Simple Syndication (RSS) feeds, web sites, blogs, social networking sites, developer networks, etc., can be accessed by mobile device  802   a  or  802   b.  Such access can be provided by invocation of a web browsing function or application (e.g., a browser) in response to a user touching, for example, a Web object. 
     A number of implementations of the invention have been described. Nevertheless, it will be understood that various modifications can be made without departing from the spirit and scope of the invention. Accordingly, other implementations are within the scope of the following claims.