Abstract:
Disclosed are apparatus and methods for controlling execution of a target software component within an isolated execution unit. In general terms, an intermediary software component is introduced within the isolated execution unit. This intermediary component program can initialize the isolated execution unit, and then start a target software component within the isolated execution unit. The intermediary component also establishes communication back to the parent (e.g., using an inter isolation communication). The intermediary component communicates with the target software component using the target component&#39;s unchanged API and mediates the communication back to the parent using the established inter isolation communication.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The invention relates generally to software applications and, more particularly, to methods and apparatus for controlling execution of a software component that resides within an isolated execution unit.  
           [0002]    In many software applications, there is a need for isolated execution units. An isolated execution unit generally does not share its states with other software modules which are not a part of the isolated execution unit. Conventionally, a software module that does not reside within an isolated execution unit cannot communicate with other software modules that do reside in the isolated execution unit. For example, an isolated execution unit does not share memory with another software module that does not reside within the isolated execution unit. Since isolated execution units do not share states, a particular isolated execution unit is protected from an erroneous behavior running in another isolated execution unit. Examples of isolated execution units include a “process” in a Unix operating system or a Logical Virtual Machine on a Java platform.  
           [0003]    Each isolated execution unit may also create one or more internal software components. For example, a isolated execution unit may take the form of a browser application that spawns a software component in the form of an applet. Several different software component models have been proposed, including Java applet, Java Xlet and Java servlet. Those software component models typically have unique APIs (Application Programming Interfaces) that are different from each other.  
           [0004]    There are some cases where it is better to locate and execute these software components in different isolated execution units than the one that creates them in order to isolate erroneous behavior. For example, a web browser spawns an isolated execution unit; it instantiates a new applet in it; then the web browser starts the execution of the applet. However, there are several difficulties to practicing this scheme. FIG. 1 is a diagrammatic representation of a typical isolated execution unit setup. As shown, a isolated execution unit  102  includes an internal software component  104 . The isolated execution unit has API  108 , and the software component  104  has API  110  that may differ from the isolated execution unit&#39;s API  108 . A parent program  106  communicates with the isolated execution unit  102  through the API  108  of the isolated execution unit  102 . However, the parent program  106  cannot communicate with the software component  104  since the software component&#39;s API  110  is not accessible by the parent program  106 . That is, the software component&#39;s API  110  is “isolated” from the parent program  106 .  
           [0005]    Since the parent program  106  cannot communicate with the software component, the parent program  106  cannot access API  110  of the software component  104 . The parent program may need to access the API  110  to control the software component for any number of reasons. In one example, the isolated execution unit  102  represents a web browser and the software component  104  is an applet. If the applet  104  misbehaves, it is desirable to shut down the applet. However, in this setup the applet can only be terminated by shutting down the entire browser  102 . That is, the browser  102  is needlessly shut down. Of course, shutting down the browser is typically very undesirable. In another example, the parent program cannot initialize the state of the isolated execution unit before execution of the software component to a desired state. For example, this initialization may include assigning initial values to execution environment variables.  
           [0006]    A conventional technique for solving this problem is to provide multiple APIs within the isolated execution unit for each kind of software component within the isolated execution unit. FIG. 2 is a diagrammatic representation of a communication mechanism, where an isolated execution unit  202  has been modified to expose an internal component&#39;s API. As shown, the isolated execution unit  202  includes API  208  for software component  204 . A parent program  206  may then communicate with software component  204  through the exposed API  208 .  
           [0007]    This approach has several associated disadvantages. Since an API must be created for each software component, a significant number of API&#39;s may have to be created. Additionally, modification of an isolated execution unit is not desirable. One reason is that modification of the isolated execution unit can be rather complex and time consuming. Also, modification of the isolated execution unit for each software component cancels out the advantages of using software components in the first place, e.g., the ability to simply use software components “as is” without modification.  
           [0008]    Accordingly, there is a need for improved mechanisms for controlling or monitoring execution of a software component that is associated with an isolated execution unit.  
         SUMMARY OF THE INVENTION  
         [0009]    Broadly speaking, the present invention fills these needs by providing apparatus and methods for controlling or monitoring execution of a target software component within an isolated execution unit. In general terms, an intermediary software component is introduced within the isolated execution unit. In order to communicate back to the parent program, an inter isolation communication mechanism may be used. In that case, the intermediary software component may be designed or modified to perform initialization of such a communication mechanism and use the communication mechanism to communicate with the parent. This intermediary component program can initialize the isolated execution unit, and then start a target software component within the isolated execution unit. That is, the intermediary component establishes a communication path back to the parent (e.g., using an inter isolation communication). The intermediary component may then communicate with the target software component using the target component&#39;s unchanged API and mediates the communication back to the parent using the established communication path.  
           [0010]    In one embodiment, a method for controlling or monitoring a target software component of an isolated execution unit is disclosed. An intermediary software component is introduced within an isolated execution unit. An identifier of a target software component is indicated to the intermediary software component. The target software component having the indicated identifier is initiated within the isolated execution unit. A communication path is established between the intermediary software component and an external program that is outside of the isolated execution unit whereby the external program can control or monitor the target software component via the established communication path.  
           [0011]    In a further implementation, the identifier of the target software component is provided by the external program. Preferably, the established communication path uses an inter isolation communication protocol. For example, the inter isolation communication protocol is a remote method invocation technique. Additionally, the communication path is established by the intermediary software component. In one implementation, the isolated execution unit is initialized by the intermediary software component. In a further implementation, one or more parameters for initializing the isolated execution unit may be indicated by the external program to the intermediary software component. The initialization of the isolated execution unit is based on the indicated one or more parameters.  
           [0012]    In a further aspect, an execution control parameter is indicated to the intermediary software component and the indicated execution control parameter is invoked on the target software component using an application programming interface (API) of the target software component. Additionally, the execution control parameter is a request that has a first format of an inter isolation communication protocol. The intermediary software component translates the first format into a second format that is acceptable by the API of the target software component.  
           [0013]    In another implementation, the intermediary software component receives a result from the target component in response to the invoked execution control parameter and sends the result to the external program. The result has a first format that is acceptable by the API of the target software component. The intermediary software component translates the first format into a second format that is an inter isolation communication protocol before sending the result to the external program.  
           [0014]    In another aspect, the invention pertains to a computer implemented system operable to control or monitor a target software component of an isolated execution unit. The computer system includes an isolated execution unit, an intermediary software component within the isolated execution unit, and an external program that is outside of the isolated execution unit. The external program is configured to indicate an identifier of a target software component to the intermediary software component. The intermediary software component is configured to start the target software component having the indicated identifier within the isolated execution unit and establish a communication path between the intermediary software component and the external program whereby the external program can control the target software component via the established communication path. The components of the computer implemented system are further adapted to provide one or more of the above described methods. In another embodiment, the invention pertains to a computer readable medium having instructions for controlling or monitoring a target software component of an isolated execution unit. The computer readable medium includes computer code for performing the above described methods.  
           [0015]    Advantages of the present invention will become apparent upon reading the following detailed descriptions and studying the various figures of the drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The invention, together with further advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings.  
         [0017]    [0017]FIG. 1 is a diagrammatic representation of a typical isolated execution unit setup.  
         [0018]    [0018]FIG. 2 is a diagrammatic representation of a communication mechanism, where an isolated execution unit has been modified to expose an internal component&#39;s API.  
         [0019]    [0019]FIG. 3 is a diagrammatic representation of a communication mechanism for controlling execution of a target software component of an isolated execution unit in accordance with one embodiment of the present invention.  
         [0020]    [0020]FIG. 4 is a flowchart illustrating a procedure for communicating with a target component of an isolated execution unit in accordance with one embodiment of the present invention.  
         [0021]    [0021]FIG. 5 is a flowchart illustrating the operation of FIG. 4 of communicating between the parent program and the target component in accordance with one embodiment of the present invention.  
         [0022]    [0022]FIG. 6 is a diagrammatic representation of a general-purpose computer system suitable for implementing the present invention.  
         [0023]    [0023]FIG. 7 is a diagrammatic representation of a virtual machine which is supported by computer system of FIG. 6, and is suitable for implementing the present invention.  
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0024]    Reference will now be made in detail to specific embodiments of the invention. While the invention will be described in conjunction with specific embodiments, it will be understood that it is not intended to limit the invention to the described embodiments. On the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present invention.  
         [0025]    [0025]FIG. 3 is a diagrammatic representation of a communication mechanism  300  for controlling execution of a target software component of an isolated execution unit in accordance with one embodiment of the present invention. In general terms, an external program  302  sets up an intermediary component  306  within an isolated execution unit  304  (e.g., the intermediary component becomes a part of the isolated execution unit). In the illustrated embodiment, the external program is a parent program of the isolated execution unit. However, the execution unit may have been created by another external program or parent program. The intermediary component  306  then sets up a communication path  314  to the external program  302 . The external program  302  may then make a request through path  314  to the intermediary component  306 . The intermediary component  306  then translates the request and sends it to a target component  308  through communication path  316  and the target component&#39;s API  318 . Results in response to the request may also be sent from the target component  308 , translated by the intermediary component  306 , and sent to the external program  302  through communication path  316 . In sum, the intermediary component  306  communicates with the external program via the established path  314  and communicates with the target component  308  through the target&#39;s own API  318 .  
         [0026]    [0026]FIG. 4 is a flowchart illustrating a procedure  400  for communicating with a target component of an isolated execution unit in accordance with one embodiment of the present invention. Of course, the procedure of FIG. 4 may be applied to multiple components within a same or different isolated execution unit. Initially, an external program may create a new isolated execution unit in operation  402 . Alternatively, the isolated execution unit may already have been created by another external program. The external program then starts an intermediary component within the new isolated execution unit that is given a target components name and one or more desired state(s) for the isolated execution unit and/or target component in operation  404 .  
         [0027]    The intermediary component then starts execution in operation  406 . The intermediary component then initializes the isolated execution unit into the one or more desired state(s) supplied by the external program in operation  408 . The intermediary component also starts the name target component in operation  410 . The target component may also be initialized into one more desired states previously supplied by the external program. The states may include any configurable state. For example, a particular variable may be set, which may include setting the current working directory, the maximum number of file descriptors that the isolated execution unit can use, a name of input data file, etc.  
         [0028]    Additionally, the intermediary component establishes a communication path to the external program in operation  412 . The external program may then communicate with the intermediary component via the established communication path so as to communicate with the target component in operation  414 . This communication may be in any suitable form for controlling or monitoring execution of the target component. For example, the external program may make a method request to the target component via the established communication path.  
         [0029]    [0029]FIG. 5 is a flowchart illustrating the operation  414  of FIG. 4 of communicating between the external program and the target component in accordance with one embodiment of the present invention. The illustrated operation  414  of FIG. 5 merely represents an example communication sequence between an external program and a target component of an isolated execution unit. Of course, there are numerous forms that such a communication could take. In the illustrated embodiment, the external program initiates a control parameter or request to be sent to the target component in operation  502 . The request is in a form for communicating through the established communication path. Preferably, the communication path uses an inter isolation communication protocol. In a specific implementation, the inter isolation communication protocol is a remote method invocation (RMI) technique. By way of examples, the request may take the form of a command for controlling execution of the target component (e.g., a method request) or a request for information from the target component to monitor execution of the target component. Other examples include requests to change the presentation of the GUI (graphical user interface), to perform calculation of data, send and receive information to and from server machines, etc.  
         [0030]    The external program then sends the request to the intermediary component via the established communication path in operation  504 . The intermediary component then receives the request in operation  506 . The intermediary component then invokes the request on the target component via the target component API in operation  508 . In other words, the request from the external program is translated into a request that is acceptable to the API of the target component. In one implementation, an intermediary component is created for each target component within the isolated execution unit and each intermediary component contains translation mechanisms for its particular target component&#39;s API type. For example, a first intermediary component is set up for communicating with a first target having an applet type API, and a second intermediary component is set up for communicating with a second target having an Xlet type API. Alternatively, the intermediary component may include translation mechanisms for each type of target component. For example, a single intermediary component includes translation mechanisms for an applet type API and an Xlet type API.  
         [0031]    The intermediary component then receives the results of the request from the target component in response to the request in operation  510 . The results may be in any suitable form. By way of examples, the results may include information requested by the external program or a response to a request to control the target component&#39;s execution. For instance, the result may indicate whether the request was completed or request additional information from the external program that is required for the target component to perform the request from the external program. Of course, the request from the external program may not require any results from the target component. The intermediary component then sends the results of the request to the external program via the established communication path in operation  512 . That is, the results may be translated from a format suitable for the target component&#39;s API (e.g. applet API) into a format suitable for the established communication path (e.g., RMI).  
         [0032]    [0032]FIG. 6 illustrates a typical, general-purpose computer system suitable for implementing the present invention. The computer system  1030  includes any number of processors  1032  (also referred to as central processing units, or CPUs) that are coupled to memory devices including primary storage devices  1034  (typically a read only memory, or ROM) and primary storage devices  1036  (typically a random access memory, or RAM). The computer system may take any suitable form. For example, the computer system may be integrated with a navigational system or television set top box.  
         [0033]    Computer system  1030  or, more specifically, CPUs  1032 , may be arranged to support a virtual machine, as will be appreciated by those skilled in the art. One example of a virtual machine that is supported on computer system  1030  will be described below with reference to FIG. 7. As is well known in the art, ROM acts to transfer data and instructions uni-directionally to the CPUs  1032 , while RAM is used typically to transfer data and instructions in a bi-directional manner. CPUs  1032  may generally include any number of processors. Both primary storage devices  1034 ,  1036  may include any suitable computer-readable media. A secondary storage medium  1038 , which is typically a mass memory device, is also coupled bi-directionally to CPUs  1032  and provides additional data storage capacity. The mass memory device  1038  is a computer-readable medium that may be used to store programs including computer code, data, and the like. Typically, mass memory device  1038  is a storage medium such as a hard disk or a tape which generally slower than primary storage devices  1034 ,  1036 . Mass memory storage device  938  may take the form of a magnetic or paper tape reader or some other well-known device. It will be appreciated that the information retained within the mass memory device  1038 , may, in appropriate cases, be incorporated in standard fashion as part of RAM  1036  as virtual memory. A specific primary storage device  1034  such as a CD-ROM may also pass data uni-directionally to the CPUs  1032 .  
         [0034]    CPUs  1032  are also coupled to one or more input/output devices  1040  that may include, but are not limited to, devices such as video monitors, track balls, mice, keyboards, microphones, touch-sensitive displays, transducer card readers, magnetic or paper tape readers, tablets, styluses, voice or handwriting recognizers, or other well-known input devices such as, of course, other computers. Finally, CPUs  1032  optionally may be coupled to a computer or telecommunications network, e.g., an Internet network or an intranet network, using a network connection as shown generally at  1012 . With such a network connection, it is contemplated that the CPUs  1032  might receive information from the network, or might output information to the network in the course of performing the above-described mechanisms for managing target components. Such information, which is often represented as a sequence of instructions to be executed using CPUs  1032 , may be received from and outputted to the network, for example, in the form of a computer data signal embodied in a carrier wave. The above-described devices and materials will be familiar to those of skill in the computer hardware and software arts.  
         [0035]    As previously mentioned, a virtual machine may execute on computer system  1030 . FIG. 7 is a diagrammatic representation of a virtual machine which is supported by computer system  1030  of FIG. 6, and is suitable for implementing the present invention. When a computer program, e.g., a computer program written in the Java™ programming language, is executed, source code  1110  is provided to a compiler  1120  within compile-time environment  1105 . Compiler  1120  translates source code  1110  into byte codes  1130 . In general, source code  1110  is translated into byte codes  1130  at the time source code  1110  is created by a software developer.  
         [0036]    Byte codes  1130  may generally be reproduced, downloaded, or otherwise distributed through a network, e.g., network  1012  of FIG. 6, or stored on a storage device such as primary storage  1034  of FIG. 6. In the described embodiment, byte codes  1130  are platform independent. That is, byte codes  1130  may be executed on substantially any computer system that is running on a suitable virtual machine  1140 .  
         [0037]    Byte codes  1130  are provided to a runtime environment  1135  which includes virtual machine  1140 . Runtime environment  1135  may generally be executed using a processor or processors such as CPUs  1032  of FIG. 6. Virtual machine  1140  includes a compiler  1142 , an interpreter  1144 , and a runtime system  1146 . Byte codes  1130  may be provided either to compiler  1142  or interpreter  1144 .  
         [0038]    When byte codes  1130  are provided to compiler  1142 , methods contained in byte codes  1130  are compiled into machine instructions. In one embodiment, compiler  1142  is a just-in-time compile which delays the compilation of methods contained in byte codes  1130  until the methods are about to be executed. When byte codes  1130  are provided to interpreter  1144 , byte codes  1130  are read into interpreter  1144  one byte code at a time. Interpreter  1144  then performs the operation defined by each byte code as each byte code is read into interpreter  1144 . That is, interpreter  1144  “interprets” byte codes  1130 , as will be appreciated by those skilled in the art. In general, interpreter  1144  processes byte codes  1130  and performs operations associated with byte codes  1130  substantially continuously.  
         [0039]    When a method is invoked by another method, or is invoked from runtime environment  1135 , if the method is interpreted, runtime system  1146  may obtain the method from runtime environment  1135  in the form of a sequence of byte codes  1130 , which may be directly executed by interpreter  1144 . If, on the other hand, the method which is invoked is a compiled method which has not been compiled, runtime system  1146  also obtains the method from runtime environment  1135  in the form of a sequence of byte codes  1130 , then may go on to activate compiler  1142 . Compiler  1142  then generates machine instructions from byte codes  1130 , and the resulting machine-language instructions may be executed directly by CPUs  1032 . In general, the machine-language instructions are discarded when virtual machine  1140  terminates. The operation of virtual machines or, more particularly, Java™ virtual machines, is described in more detail in The Java™ Virtual Machine Specification by Tim Lindholm and Frank Yellin (ISBN 0-201-63452-X) which is incorporated herein by reference.  
         [0040]    Although only a few embodiments of the present invention have been described, it should be understood that the present invention may be embodied in many other specific forms without departing from the spirit or the scope of the present invention. By way of example, the operations involved with managing target components may be reordered. Steps may also be removed or added without departing from the spirit or the scope of the present invention.  
         [0041]    Although the techniques for managing target components in accordance with the present invention are particularly suitable for implementation with respect to a Java™ based environment, the techniques may generally be applied in any suitable object-based environment. In particular, the techniques are suitable for use in platform-independent object-based environments. It should be appreciated that the methods may also be implemented in some distributed object-oriented systems. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.