Patent Publication Number: US-11652652-B2

Title: Function as a service console for an online application exchange platform

Description:
BACKGROUND 
     Field 
     The present disclosure relates to online platforms for developers to offer applications for the public and keep track of domain events associated with one or more applications in a flexible manner. More specifically, the present disclosure provides function as a service (FaaS) handles in an online application exchange platform to allow developers to deploy code for added value to an application when triggered by a domain event, and keep track of the service costs. 
     Related Art 
     Current application exchange platforms have rigid architectures that preclude the tracking of added features to one or more applications, especially in terms of service costs. Typically, the usage of computational resources and access to authorized parties creates a complex track that results in revision overtime and ultimately loss revenue. When a user wants to expand access to an application service or perform outgoing calls to a third party, there is no simple way to handle subscriptions and credentials, keep track of billing items, and assess what party is responsible for what piece of the incurred cost. What is needed is a flexible way to manage an application exchange platform that provides developers, platform owners, and application end users direct access to added features, new applications, new services, and a transparent cost distribution. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The accompanying drawings, which are included to provide further understanding and are incorporated in and constitute a part of this specification, illustrate disclosed embodiments and, together with the description, serve to explain the principles of the disclosed embodiments. In the drawings: 
         FIG.  1    illustrates an example architecture suitable to provide an online application exchange platform, according to some embodiments. 
         FIG.  2    is a block diagram illustrating an example server and client from the architecture of  FIG.  1   , according to certain aspects of the disclosure. 
         FIG.  3    illustrates a group of online applications offered in an online application exchange platform, according to some embodiments. 
         FIG.  4    illustrates a dashboard for an application in an application exchange platform, according to some embodiments. 
         FIG.  5    is a flowchart illustrating steps in a method for managing a service function in an application exchange platform, according to some embodiments. 
         FIG.  6    is a flowchart illustrating steps in a method for configuring a wrapper function in a console for an online application exchange platform, according to some embodiments. 
         FIG.  7    is a block diagram illustrating an example computer system with which the client and server of  FIGS.  1  and  2   , and the methods of  FIGS.  5  and  6    can be implemented, according to some embodiments. 
     
    
    
     In the figures, elements and steps denoted by the same or similar reference numerals are associated with the same or similar elements and steps, unless indicated otherwise. 
     SUMMARY 
     In a first embodiment, a computer-implemented method includes receiving, from a developer, a service function, wherein the service function includes configuration details for an application available through an online application exchange. The computer-implemented method also includes deploying the service function in the online application exchange, identifying a first domain event requesting access to the service function from a user, and calling, with a wrapper function, the service function in the online application exchange, in response to the first domain event. The computer-implemented method also includes recording, with a wrapper function executed on top of the service function, a metric associated with the service function and a return parameter, emitting a second domain event indicative of a completion of the service function, and charging, with a billing tool, an appropriate party based on a usage metadata for the service function. 
     In a second embodiment, a system includes a memory, storing instructions and one or more processors. The one or more processors are configured to execute the instructions to cause the system to receive, from a developer, a service function, wherein the service function includes configuration details for an application available through an online application exchange. The one or more processors also execute instructions to cause the system to deploy the service function in the online application exchange, to identify a first domain event requesting access to the service function from a user, to call, with a wrapper function, the service function in the online application exchange, in response to the first domain event, and to record, with a wrapper function executed on top of the service function, a metric associated with the service function and a return parameter. The one or more processors also execute instructions to cause the system to emit a second domain event indicative of a completion of the service function, to charge, with a billing tool, an appropriate party based on a usage metadata for the service function, and to grant fine grained permissions to an end user based on the configuration details. 
     In a third embodiment, a non-transitory, computer-readable medium stores instructions which, when executed by a processor, cause a computer to perform a method, the method includes receiving, from a developer, a service function, wherein the service function includes configuration details for an application available through an online application exchange, deploying the service function in the online application exchange, and identifying a first domain event requesting access to the service function from a user. The method also includes calling, with a wrapper function, the service function in the online application exchange, in response to the first domain event, recording, with a wrapper function executed on top of the service function, a metric associated with the service function and a return parameter, and emitting a second domain event indicative of a completion of the service function. The method also includes charging, with a billing tool, an appropriate party based on a usage metadata for the service function, granting fine grained permissions to an end user based on the configuration details, and decrypting a secret key in the configuration details upon receipt of the first domain event. 
     In yet another embodiment, a system includes a means for storing instructions and a means for executing the instructions. The means for executing instructions are configured to cause the system to receive, from a developer, a service function, wherein the service function includes configuration details for an application available through an online application exchange. The means for executing instructions also causes the system to deploy the service function in the online application exchange, to identify a first domain event requesting access to the service function from a user, to call, with a wrapper function, the service function in the online application exchange, in response to the first domain event, and to record, with a wrapper function executed on top of the service function, a metric associated with the service function and a return parameter. The means for executing instructions also causes the system to emit a second domain event indicative of a completion of the service function, to charge, with a billing tool, an appropriate party based on a usage metadata for the service function, and to grant fine grained permissions to an end user based on the configuration details. 
     DETAILED DESCRIPTION OF THE FIGURES 
     In the following detailed description, numerous specific details are set forth to provide a full understanding of the present disclosure. It will be apparent, however, to one ordinarily skilled in the art, that the embodiments of the present disclosure may be practiced without some of these specific details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the disclosure. 
     Current application exchange platforms have rigid architectures that preclude the tracking of added features to one or more applications, especially in terms of service costs. Typically, the usage of computational resources and access to authorized parties creates a complex track that results in revision overtime and ultimately loss revenue for developers and platform owners. Ultimately, these deficiencies are passed down to the end users (e.g., application subscribers) in the form of cumbersome interactions and unsatisfactory performance. 
     To resolve the above technical problems arising in the field of computer networking, an application exchange platform as disclosed herein offers a user interface (UI) where a developer can select which domain event they wish to subscribe to. In some embodiments, a developer may also specify configurations such as whitelisted universal resource locations (URLs) that a function in an application may call out to. The developer may also establish fine grained permissions or roles to grant a function in the application, as well as an authorization context such as secrets, and external authorization server URLs. 
     In addition, some embodiments include an authorization server to offer a developer the ability to implement authentication of external resources to make external calls to whitelisted URLs. In another embodiment, the platform includes an interceptor to inject authorization credentials to whitelisted URLs into function calls configured by the developer. 
     To facilitate the handling of service functions in an application, an application exchange platform as disclosed herein may provide a lightweight, wrapper function. The wrapper function measures the metrics of tool usage while the application is run by an end user. Based on this metric data, once the service function completes execution, the metrics can be forwarded to a usage/billing service and charged to the appropriate party. In some embodiments, a developer may wish to absorb the cost themselves, and in some embodiments, the developer may want to transfer the fees onto the end user. The fees generated can be determined by the exchange platform, and the extra revenue could be split between the developer, the exchange platform, and the marketplace owner. This could be decided by the developer in one embodiment, in another it might be decided by the exchange platform. The detailed cost information can be propagated by the Wrapper Function when it reports the function result/usage. The Wrapper Function can also report unhandled exceptions to the dashboard for the developer. 
     System Overview 
       FIG.  1    illustrates an example architecture  10  suitable to provide an online application exchange platform  100 , according to some embodiments. Online application exchange platform  100  may include one or more servers  130 - 1  and  130 - 2  (hereinafter, collectively referred to as “servers  130 ”) coupled to a database  152 . Online application exchange platform  100  may be accessed by one or more developers using client devices  110 - 1 ,  110 - 2 , through  110 - n  (hereinafter, collectively referred to as “client devices  110 ”). The developers may create and upload applications  122 - 1 ,  122 - 2 , through  122 - n  (hereinafter, collectively referred to as “applications  122 ”) onto online application exchange platform  100  via a network  150 . 
     Servers  130  may include any device having an appropriate processor, memory, and communications capability for hosting the documents and applications associated with the device provisioning engine. The device provisioning engine may be accessible by multiple participants through various client devices  110  over the network  150 . Client devices  110  can be, for example, handsets, desktop computers (coupled with handsets, or standalone), mobile computers, tablet computers (e.g., including e-book readers), mobile devices (e.g., a smartphone or PDA), or any other devices having appropriate processor, memory, and communications capabilities for accessing the device provisioning engine on one of servers  130 . Network  150  can include, for example, any one or more of a local area network (LAN), a wide area network (WAN), the Internet, and the like. Further, network  150  can include, but is not limited to, any one or more of the following network topologies, including a bus network, a star network, a ring network, a mesh network, a star-bus network, tree or hierarchical network, and the like. 
       FIG.  2    is a block diagram  200  illustrating an example server  130  and client device  110  in the architecture  10 , according to certain aspects of the disclosure. Client device  110  and server  130  are communicatively coupled over network  150  via respective communications modules  218 - 1  and  218 - 2  (hereinafter, collectively referred to as “communications modules  218 ”). Communications modules  218  are configured to interface with network  150  to send and receive information, such as data, requests, responses, and commands to other devices on the network. Communications modules  218  can be, for example, modems or Ethernet cards. 
     Client device  110  may be any one of a desktop computer, a laptop, or a mobile computing device. Client device  110  may include a processor  212 - 1  and a memory  220 - 1 . Processor  212 - 1  is configured to execute instructions, such as instructions physically coded into processor  212 - 1 , instructions received from software in memory  220 - 1 , or a combination of both. An input device  214  and an output device  216  enable the user to interact with client device  110 . Examples of input device  214  and output device  216  may include a mouse, a keyboard, a display, a touch-interactive display, and the like. A user of client device  110  may use input device  214  to submit a document or a media file to application programming interface (API) layer  230  via a user interface of application  222 . Application  222  may enable the user of client device  110  to edit a document (text editor), to create presentation slides, or a chart including data, or perform any other computational task hosted by server  130 . 
     Server  130  includes a memory  220 - 2 , a processor  212 - 2 , and communications module  218 - 2 . Memory  220 - 2  includes a subscription management engine  232 . Subscription management engine  232  includes instructions which, when executed by processor  212 - 2 , cause server  130  to perform at least partially steps as disclosed herein. In some embodiments, subscription management engine  232  includes instructions to communicate with application  222  to add a user or a group of users, or to add a resource address that the users of application  222  may call, while running. An API layer  230  handles the communications between server  130  and application  222  in client device  110 . Subscription management engine  232  may include an event management tool  240 , billing management tool  242 , an identity management tool  244 , an application discovery tool  246 , a developer tool  248 , and a wrapper function tool  250 . 
     Wrapper function  250  is configured to measure the metrics of tool usage while application  222  is running. Based on this metric data, subscription management engine  232  generates a usage/billing service. The detailed cost information can be propagated by wrapper function  250  when it reports the function result/usage. Wrapper function  250  can also report unhandled exceptions to the dashboard for the developer. 
     Furthermore, in some embodiments, subscription management engine  232  may include instructions to retrieve and provide to one or more users at least some of the data in a database  252  associated with a given application  222 . Hereinafter, processors  212 - 1  and  212 - 2  will be collectively referred to as “processors  212 ,” and memories  220 - 1  and  220 - 2  will be collectively referred to as “memories  220 .” 
     The user may access application  222  installed in memory  220 - 1  of client device  110 . The user may access application  222  via a web browser installed in client device  110 . Execution of application  222  may be controlled by processor  212 - 1  in client device  110 . In some embodiments, application  222  is downloaded and installed by the user into client device  110 , from server  130 . 
       FIG.  3    illustrates a group of online applications  322 - 1  through  322 - 24  (hereinafter, collectively referred to as “applications  322 ”) offered in an online application exchange platform  300 , according to some embodiments. Applications  322  may include desktop-based applications such as text editors, comma delimited documents, table management applications, presentation creating applications, document editors, design applications, and the like. In some embodiments, an end user may access and run applications  322  via a web browser. In some embodiments, an end user may have a plug in for applications  322  installed in a client device, and run the application directly from the plug in. 
       FIG.  4    illustrates a dashboard  400  for an application  422  in an application exchange platform, according to some embodiments. Dashboard  400  enables developers to view functions usages and their outcome. In dashboard  400 , an application  422  is selected by a developer of the application exchange platform. Dashboard  400  illustrates graphically, to the developer, different aspects of application performance associated with a service function, FaaS  405 , such as a subscription roster  410  and an event log  415 . Subscription roster  410  may include names, addresses, and contact information for the users that have access to application  422  and the resources it uses and provides (CPU, GPU, memory allocation, and the like). Subscription roster  410  may also include authorization credentials for the users, passwords and access codes, encrypted keys, and associated scripts that users may access or activate while logging into application  422 . Event log  415  may include a list of events and times of occurrence for application  422 . In some embodiments, event log  415  may include details as to the time a user has been logged into application  422 , and any external call for resources and other services. Accordingly, the developer may have a clear indication of the costs incurred by different users while logged into application  422 . In one embodiment it is possible for a function to be triggered by one or many events. The function can be written in a way that an abstract function can handle multiple types of events. 
     Dashboard  400  may also include graphical displays such as dials  450 - 1 ,  450 - 2 , and  450 - 3  (hereinafter, collectively referred to as “dials  450 ”), or other graphical indicators for different metrics (e.g., metric A, metric B, metric C, and the like), wherein the metrics may be indicative of CPU usage, GPU usage, or memory usage of a given user, while logging into application  422 . 
     Through event log  415 , the developer may select an event, and be directed to an in browser integrated development environment (IDE), or alternatively a repository they can push to (e.g., a Git. repository) that has an auto generated method entry point to provide an event object. The developer can call internal GraphQL or REST application programming interfaces, emit their own events, or run any code they wish. In some embodiments, dashboard  400  may provide a software development kit (SDK)  420  for easier integration of FaaS  405  into application  422 . Dashboard  400  may enable a developer to retry failed events, or cancel long running events that they would like to terminate. 
     In some embodiments, FaaS  405  may be configured to return parameters or an object with fields (e.g., dials  450  for metrics A, B, or C), as a result of an event or action. The values in dials  450  can represent the resulting status of the function, for example, an HTTP return code or pre-defined states of the function, such as SUCCEEDED, FAILED, and PENDING. 
       FIG.  5    is a flowchart illustrating steps in a method  500  for managing a service function in an application exchange platform, according to some embodiments. Method  500  may be performed at least partially by any one of the network servers hosting a subscription management engine (e.g., subscription management engine  232 ), while communicating with any one of a plurality of client devices (e.g., servers  130  and clients  110 ). To perform at least some of the steps in method  500 , the subscription management engine may access an event management tool, a billing management tool, an identity management tool, an application discovery tool, a developer tool, and a wrapper function as disclosed herein (e.g., event management tool  240 , billing management tool  242 , identity management tool  244 , application discovery tool  246 , developer tool  248 , and wrapper function  250 ). At least some of the steps in method  500  may be performed by a computer having a processor executing commands stored in a memory of the computer (e.g., processors  212  and memories  220 ). For example, at least some of the commands may be included in an application installed in a client device accessible by a user, and hosted via an API layer in the network server (e.g., application  222 , API layer  230 ). Further, steps as disclosed in method  500  may include retrieving, editing, and/or storing files in a database that is part of, or is communicably coupled to, the computer (e.g., database  252 ). Methods consistent with the present disclosure may include at least some, but not all, of the steps illustrated in method  500 , performed in a different sequence. Furthermore, methods consistent with the present disclosure may include at least two or more steps as in method  500  performed overlapping in time, or almost simultaneously. 
     Step  502  includes receiving, from a developer, a service function, wherein the service function includes configuration details for an application available through an online application exchange. In some embodiments, the configuration details include a whitelist and an external authentication network address, and step  502  includes granting fine grained permissions to end users based on the configuration details. In some embodiments, the configuration details include a secret key, and step  502  includes decrypting the secret key upon receipt of the first domain event. 
     Step  504  includes deploying the service function in the online application exchange. In some embodiments, the first domain event is a subscription request to an application from a user, and step  504  includes requesting user credentials to validate a user account for the application. 
     Step  506  includes identifying a first domain event requesting access to the service function from a user. 
     Step  508  includes calling, with a wrapper function, the service function in the online application exchange, in response to the first domain event. 
     Step  510  includes recording, with a wrapper function executed on top of the service function, a metric associated with the service function and a return parameter. In some embodiments, step  510  includes reporting, to the developer, the metric associated with the service function. In some embodiments, step  510  includes recording a return parameter provided by the service function. In some embodiments, step  510  includes generating a value for the metric as a nonlinear combination of a CPU usage, a number of threads used by the service function, and a memory usage. In some embodiments, the return parameter includes one of a “success,” “fail,” or “pending” event, and step  510  includes resubmitting a request for the service function when the return parameter is failed. 
     Step  512  includes emitting a second domain event indicative of a completion of the service function. 
     Step  514  includes charging, with a billing tool, an appropriate party based on a usage metadata for the service function. In some embodiments, step  514  includes determining a cost that has a non-linear dependence with a computational time usage to execute the service function. In some embodiments, step  514  includes updating a function dashboard in a developer console when the second domain event is emitted. In some embodiments, step  514  includes recording the domain event indicative of a completion of the service function in a database. In some embodiments, step  514  includes charging either of an end user of the application or a platform owner, based on a selection by the developer. 
       FIG.  6    is a flowchart illustrating steps in a method  600  for configuring a wrapper function, according to some embodiments. Method  600  may be performed at least partially by any one of the network servers hosting a subscription management engine (e.g., subscription management engine  232 ), while communicating with any one of a plurality of client devices (e.g., servers  130  and clients  110 ). To perform at least some of the steps in method  600 , the subscription management engine may access an event management tool, a billing management tool, an identity management tool, an application discovery tool, a developer tool, and a wrapper function as disclosed herein (e.g., event management tool  240 , billing management tool  242 , identity management tool  244 , application discovery tool  246 , developer tool  248 , and wrapper function  250 ). At least some of the steps in method  600  may be performed by a computer having a processor executing commands stored in a memory of the computer (e.g., processors  212  and memories  220 ). For example, at least some of the commands may be included in an application installed in a client device accessible by a user, and hosted via an API layer in the network server (e.g., application  222 , API layer  230 ). Further, steps as disclosed in method  600  may include retrieving, editing, and/or storing files in a database that is part of, or is communicably coupled to, the computer (e.g., database  252 ). Methods consistent with the present disclosure may include at least some, but not all, of the steps illustrated in method  600 , performed in a different sequence. Furthermore, methods consistent with the present disclosure may include at least two or more steps as in method  600  performed overlapping in time, or almost simultaneously. 
     Step  602  includes receiving, from a service function executed by an application, a value for the usage of a computational resource when the service function has completed a task. 
     Step  604  includes generating a metric indicator with the value for the usage of the computational resource. 
     Step  606  includes determining a cost incurred by a third party based on the metric indicator. 
     Step  608  includes preparing and distributing an invoice for the cost incurred by the third party to a designated party. 
     Hardware Overview 
       FIG.  7    is a block diagram illustrating an example computer system  700  with which the client devices  110  and servers  130  of  FIGS.  1  and  2   , and methods  500  and  600  can be implemented, according to some embodiments. In certain aspects, computer system  700  may be implemented using hardware or a combination of software and hardware, either in a dedicated server, or integrated into another entity, or distributed across multiple entities. 
     Computer system  700  (e.g., client device  110  and server  130 ) includes a bus  708  or other communication mechanism for communicating information, and a processor  702  (e.g., processors  212 ) coupled with bus  708  for processing information. By way of example, the computer system  700  may be implemented with one or more processors  702 . Processor  702  may be a general-purpose microprocessor, a microcontroller, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a Programmable Logic Device (PLD), a controller, a state machine, gated logic, discrete hardware components, or any other suitable entity that can perform calculations or other manipulations of information. 
     Computer system  700  can include, in addition to hardware, a code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them stored in an included memory  704  (e.g., memories  220 ), such as a Random Access Memory (RAM), a flash memory, a Read-Only Memory (ROM), a Programmable Read-Only Memory (PROM), an Erasable PROM (EPROM), registers, a hard disk, a removable disk, a CD-ROM, a DVD, or any other suitable storage device, coupled to bus  708  for storing information and instructions to be executed by processor  702 . The processor  702  and the memory  704  can be supplemented by, or incorporated in, a special purpose logic circuitry. 
     The instructions may be stored in the memory  704  and implemented in one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer-readable medium for execution by, or to control the operation of, the computer system  700 , and according to any method well known to those skilled in the art, including, but not limited to, computer languages such as data-oriented languages (e.g., SQL, dBase), system languages (e.g., C, Objective-C, C++, Assembly), architectural languages (e.g., Java, .NET), and application languages (e.g., PHP, Ruby, Perl, Python). Instructions may also be implemented in computer languages such as array languages, aspect-oriented languages, assembly languages, authoring languages, command line interface languages, compiled languages, concurrent languages, curly-bracket languages, dataflow languages, data-structured languages, declarative languages, esoteric languages, extension languages, fourth-generation languages, functional languages, interactive mode languages, interpreted languages, iterative languages, list-based languages, little languages, logic-based languages, machine languages, macro languages, metaprogramming languages, multiparadigm languages, numerical analysis, non-English-based languages, object-oriented class-based languages, object-oriented prototype-based languages, off-side rule languages, procedural languages, reflective languages, rule-based languages, scripting languages, stack-based languages, synchronous languages, syntax handling languages, visual languages, wirth languages, and xml-based languages. Memory  704  may also be used for storing temporary variable or other intermediate information during execution of instructions to be executed by processor  702 . 
     A computer program as discussed herein does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, subprograms, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network. The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. 
     Computer system  700  further includes a data storage device  706  such as a magnetic disk or optical disk, coupled to bus  708  for storing information and instructions. Computer system  700  may be coupled via input/output module  710  to various devices. Input/output module  710  can be any input/output module. Exemplary input/output modules  710  include data ports such as USB ports. The input/output module  710  is configured to connect to a communications module  712 . Exemplary communications modules  712  (e.g., communications modules  218 ) include networking interface cards, such as Ethernet cards and modems. In certain aspects, input/output module  710  is configured to connect to a plurality of devices, such as an input device  714  (e.g., input device  214 ) and/or an output device  716  (e.g., output device  216 ). Exemplary input devices  714  include a keyboard and a pointing device, e.g., a mouse or a trackball, by which a user can provide input to the computer system  700 . Other kinds of input devices  714  can be used to provide for interaction with a user as well, such as a tactile input device, visual input device, audio input device, or brain-computer interface device. 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, tactile, or brain wave input. Exemplary output devices  716  include display devices, such as an LCD (liquid crystal display) monitor, for displaying information to the user. 
     According to one aspect of the present disclosure, the client device  110  and server  130  can be implemented using a computer system  700  in response to processor  702  executing one or more sequences of one or more instructions contained in memory  704 . Such instructions may be read into memory  704  from another machine-readable medium, such as data storage device  706 . Execution of the sequences of instructions contained in main memory  704  causes processor  702  to perform the process steps described herein. One or more processors in a multi-processing arrangement may also be employed to execute the sequences of instructions contained in memory  704 . In alternative aspects, hard-wired circuitry may be used in place of or in combination with software instructions to implement various aspects of the present disclosure. Thus, aspects of the present disclosure are not limited to any specific combination of hardware circuitry and software. 
     Various aspects of the subject matter described in this specification 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 subject matter described in this specification, or any combination of one or more 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. The communication network (e.g., network  150 ) can include, for example, any one or more of a LAN, a WAN, the Internet, and the like. Further, the communication network can include, but is not limited to, for example, any one or more of the following network topologies, including a bus network, a star network, a ring network, a mesh network, a star-bus network, tree or hierarchical network, or the like. The communications modules can be, for example, modems or Ethernet cards. 
     Computer system  700  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 with each other. Computer system  700  can be, for example, and without limitation, a desktop computer, laptop computer, or tablet computer. Computer system  700  can also be embedded in another device, for example, and without limitation, a mobile telephone, a PDA, a mobile audio player, a Global Positioning System (GPS) receiver, a video game console, and/or a television set top box. 
     The term “machine-readable storage medium” or “computer-readable medium” as used herein refers to any medium or media that participates in providing instructions to processor  702  for execution. Such a medium may take many forms, including, but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as data storage device  706 . Volatile media include dynamic memory, such as memory  704 . Transmission media include coaxial cables, copper wire, and fiber optics, including the wires that include bus  708 . Common forms of machine-readable media include, for example, floppy disk, flexible disk, hard disk, magnetic tape, any other magnetic medium, CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, an EPROM, a FLASH EPROM, any other memory chip or cartridge, or any other medium from which a computer can read. The machine-readable storage medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter effecting a machine-readable propagated signal, or a combination of one or more of them. 
     As used herein, the phrase “at least one of” preceding a series of items, with the terms “and” or “or” to separate any of the items, modifies the list as a whole, rather than each member of the list (i.e., each item). The phrase “at least one of” does not require selection of at least one item; rather, the phrase allows a meaning that includes at least one of any one of the items, and/or at least one of any combination of the items, and/or at least one of each of the items. By way of example, the phrases “at least one of A, B, and C” or “at least one of A, B, or C” each refer to only A, only B, or only C; any combination of A, B, and C; and/or at least one of each of A, B, and C. 
     To the extent that the term “include,” “have,” or the like is used in the description or the claims, such term is intended to be inclusive in a manner similar to the term “comprise” as “comprise” is interpreted when employed as a transitional word in a claim. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. 
     A reference to an element in the singular is not intended to mean “one and only one” unless specifically stated, but rather “one or more.” All structural and functional equivalents to the elements of the various configurations described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and intended to be encompassed by the subject technology. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the above description. 
     While this specification contains many specifics, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of particular implementations of the subject matter. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
     The subject matter of this specification has been described in terms of particular aspects, but other aspects can be implemented and are within the scope of the following claims. For example, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. The actions recited in the claims can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the aspects described above should not be understood as requiring such separation in all aspects, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Other variations are within the scope of the following claims.