METHOD FOR DESCRIBING THE HUMAN INTERFACE FEATURES AND FUNCTIONALITY OF AV/C-BASED DEVICES

Abstract: A method and system for providing a user interface for a networked target device using panel subunit descriptor information maintained by the target device. The present invention utilizes a panel subunit to allow any compliant device (e.g., a target device) to describe the appearance of its physical (and logical) controls and displays to another device (e.g., an intelligent controller) and allows the controller to trigger actions on the target as if a user had physically manipulated the controls on the target device directly. The panel subunit uses objects defined with several standard types of controls and displays (e.g., push buttons, sliders, dials, LCD screens, etc.) that are commonly found on consumer electronic devices. The control types have well defined behaviors (e.g., buttons are pushed, dials are moved, values are input, etc.). In addition, the panel subunit defines a set of commands which are to be applied to any of these controls when selected by the user. The commands are defined to be sufficiently generic so that they apply to most types of controls. The panel subunit also defines generic user interaction commands (or user events) which can be applied to the controls (e.g., press, press and hold, release, input value, etc.) by a user. The purpose of these user events is to encapsulate the typical user manipulated action for the controls and to let the target device decide the manner in which to interpret the user actions on its own. A status descriptor keeps the intelligent controller informed of the status of the target device being manipulated.

Description: METHOD FOR DESCRIBING THE HUMAN INTERFACE FEATURES AND FUNCTIONALITY OF AV/C-BASED DEVICES BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to the field of consumer electronic devices. More specifically, the present invention relates to methods and systems for providing user interfaces for networked electronic devices including remote devices. RELATED ART The typical home entertainment system today consists of a variety of different consumer electronic devices which present and record audio/visual media in different ways. In the field of media devices, there is a spectrum of features for products of a given class (VCRs, video camera, etc.). Most of the features are represented by physical controls or elements on a control panel on the device which can be manipulated by a human user. Recently, a class of consumer electronic media devices has been introduced that can be networked together using a standard communication protocol layer (e.g., IEEE 1394 communication standard). The IEEE 1394 standard is an international standard for implementing an inexpensive high-speed serial bus architecture which supports both asynchronous and isochronous format data transfers. The IEEE 1394 standard provides a high-speed serial bus for interconnecting digital devices thereby providing universal input/output connection. The IEEE 1394 standard defines a digital interface for applications thereby eliminating the need for an application to covert digital data to an analog form before it is transmitted across the bus. Correspondingly, a receiving application will receive digital data from the bus, not analog data and will therefore not be required to convert analog data to digital form. The IEEE 1394 is ideal for consumer electronics communication in part because devices can be added to or removed from the serial bus while the bus is for transmitting data between the then existing devices. Each device on the bus is a "node" and contains its own address space. The provision of the IEEE 1394 serial communication bus for networking consumer electronic devices has introduced a powerful new platform on which device functionality and inter-operability can be built. For instance, in such a system, complex operations involving media transfers, media recordings and media presentation can be performed that involve two or more devices acting in concert. However, interaction between these devices can be complex, error prone and laborious if it is required that each device be directly touched in order to properly configure the desired operation. The problems associated with properly configuring the media operation can be exacerbated if one or more of the devices are remotely located and/or need constant attention and or adjustment. What is needed is an effective mechanism for interfacing with networked consumer electronic devices to facilitate media operations between two or more devices. In addition, it is often desired to provide remote control access to the features performed by a consumer electronic device so that these devices can be accessed from a central location within a home or office. However, not all consumer electronic devices are able to provide a sophisticated display system for remote interaction, e.g., some devices offer only a small liquid crystal display (LCD) or a small collection of light emitting diodes (LEDs) as display devices. What is needed is a mechanism for interfacing remotely with devices that provides a sophisticated level of user interaction for many devices. Also, in many consumer electronic systems, each device can have its own remote control unit. In systems having even a modest amount of devices, the user discovers that three or more different and bulky remote control devices are required to perform media operations. What is needed is a mechanism for interfacing with electronic devices that reduces the problems of having different remote control units for different devices. What is needed further is a mechanism for interfacing with electronic devices that is flexible and can adapt to new devices and device types within the consumer electronics market. SUMMARY OF THE INVENTION Accordingly, the present invention provides an effective mechanism for interfacing with networked consumer electronic devices to facilitate media operations between two or more devices. The present invention also provides a mechanism for interfacing remotely with devices and that provides a sophisticated level of user interaction for many devices that themselves may have limited display capability. The present invention also provides a mechanism for interfacing with electronic devices that operates using a central remote control station and a central display for instructing different electronic devices and for receiving status information regarding the different electronic devices. The present invention provides an interface mechanism for interfacing with electronic devices that is additionally flexible and can adapt to new devices and device types within the consumer electronics market. These and other advantages of the present invention not specifically mentioned above will become clear within discussions of the present invention presented herein. A method and system are described herein for providing a user interface for a networked electronic device using panel subunit descriptor information maintained by a target device. The present invention utilizes a panel subunit to allow any compliant device (e.g., a target device) to describe the physical appearance of its controls and displays (e.g., elements) to another device (e.g., an intelligent controller) and allows the intelligent controller to trigger actions on the target device as if a user had physically manipulated the controls on the target device directly. The present invention operates within a network of consumer electronic devices, e.g., television (TV), set-top-box, video cassette recorder (VCR), compact disk (CD) device, personal computer system (PC), etc., that are coupled together using a standard communication protocol layer, e.g., the IEEE 1394 serial communication standard. An intelligent controller (e.g., a TV or set-top-box or both) monitors the network to discover the units coupled thereto and is programmed to locate panel subunits that are defined for a target device. The target device may be remotely located. In general, the panel subunit then provides the intelligent controller with information for rendering a depiction of the controls and displays of the target device and this depiction can be interacted with by a user for remotely triggering actions by the target device. The panel subunit is defined such that command interpretations and image alterations are controlled by the target device thereby reducing the responsibility of the intelligent controller in managing the user interface with generic user events. This approach allows increased flexibility to expand the user interface and adjust to future control types and display information protocols. The panel subunit uses control objects stored in an object descriptor list to define the physical controls of the target device. The control objects are defined with several standard types of controls and displays (e.g., push buttons, sliders, dials, LCD screens, etc.) that are commonly found on consumer electronic devices. The control types have well defined behaviors (e.g., buttons are pushed, dials are moved, values are input, etc.). In addition, the panel subunit defines a set of commands which are to be applied to any of these controls when selected by the user. The commands are defined to be sufficiently generic so that they apply to most types of controls. The panel subunit also defines generic user interaction commands (or user events) which can be applied to the controls (e.g., press, press and hold, release, input value, etc.) by a user. The purpose of these generic user events is to encapsulate the typical user manipulated action for the controls and to let the target device decide the manner in which to interpret the user actions on its own thereby relieving the intelligent controller of these responsibilities. A status descriptor of the panel subunit keeps the intelligent controller informed of the status of the target device being manipulated. The status descriptor data structure is dynamic and is maintained up to date by the panel subunit. The intelligent controller examines the status descriptor to update its graphical display to indicate the target device status to the user. A panel status notification command allows the intelligent controller to post a notification request to the target device to indicate when any changes in the state of the target device result in a change in the status descriptor. Related controls of a target device can be grouped together into local groups which the panel subunit allows to be displayed or processed together in special ways. More specifically, in a network of consumer electronic products, embodiments of the present invention include a method of controlling a target device comprising the steps of: a) in a computer readable memory unit of the target device, defining an identifier descriptor data structure defining a hierarchy for elements of a physical control panel of the target device by pointing to descriptor list data structures; b) in the computer readable memory unit of the target device, defining at least one descriptor list data structure containing a plurality of control objects wherein each control object defines a physical appearance and a value state for an element of the physical control panel of the target device; c) in the computer readable memory unit of the target device, defining and updating a status descriptor data structure representing current states for the control objects; and d) generating a user interface for controlling the target device by accessing the data structures of the target device and communicating generic user events to the target device for interpretation by the target device, the step d) performed by an intelligent controller coupled to the network. Embodiments include the above and further comprising the steps of: e) the target device receiving a generic user event and interpreting the generic user event to determine a functionality to implement; f) the target device implementing the functionality; and g) the target device updating the status descriptor data structure to reflect any changes resulting from step f) and wherein the step d) comprises the steps of: d1 ) accessing the plurality of control objects by accessing the identifier descriptor data structure and the descriptor list data structure; d2) displaying graphic images of the elements of the physical control panel onto a display of the intelligent controller; d3) receiving input from a user interacting with the graphic images; d4) translating the input into generic user events; and d5) communicating the generic user events to the target device to simulate user interaction with the elements of the physical control panel. Embodiments also include the above with a step g) where the target device notifies the intelligent controller when the status descriptor has changed so that the controller does not need to maintain polling. Embodiments also include a networked system implemented in accordance with the above. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates an exemplary networked system of electronic devices including a video camera, a video cassette recorder, a computer, a set-top-box, a television and a compact disk changer. Figure 2 illustrates components of an intelligent controller in accordance with the present invention. Figure 3A is a perspective view of a target device having panel display elements and panel control elements. Figure 3B is a perspective view of the target device of Figure 3A having a front panel in the flipped-open state to expose more control and display elements. Figure 4 illustrates a logical block diagram of the subunits located within a target device (a VCR) including the panel subunit of the present invention. Figure 5 illustrates descriptor information of a panel subunit in accordance with the present invention including a subunit identifier descriptor, panel lists and object lists of control objects. Figure 6 illustrates the contents of the general list information structure including a group identification structure in accordance with the panel subunit of the present invention. Figure 7A and Figure 7B illustrate exemplary control object descriptors in accordance with the panel subunit of the present invention. Figure 8 illustrates a panel subunit status descriptor data structure in accordance with the present invention. Figure 9 is a flow diagram of steps performed by an intelligent controller in " accordance with the present invention for generating a user interface. Figure 10 illustrates an exemplary user interface displayed by the present invention based on a panel subunit and representing an on-screen keyboard. Figure 11 illustrates exemplary panel subunit descriptor information for generating the on-screen keyboard example of Figure 10 in accordance with the present invention. Figure 12 illustrates exemplary steps and communications between an intelligent controller and a remote target device in accordance with the panel subunit of the present invention. DETAILED DESCRIPTION OF THE INVENTION In the following detailed description of the present invention, a panel subunit for remotely interfacing with a target device via an intelligent controller within a network of consumer electronic devices, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one skilled in the art that the present invention may be practiced without these specific details or with equivalents thereof. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention. The present invention is drawn to a panel subunit that allows any compliant device (e.g., "target device") to describe its physical appearance including controls and displays, etc., to an outside intelligent controller device. The target device can be remote to the intelligent controller. The intelligent controller then generates a user interface for the target device including: 1 ) interactive controls; and 2) user display information pertinent to the target device. The panel subunit allows the intelligent controller to trigger actions on the target device as if a user had physically manipulated the controls of the target device. The intelligent controller and the target device are connected to the same communication network (e.g., using the IEEE 1394 serial standard). The present invention can also be used in one embodiment to promote high levels of inter-operability between any of the devices which support the well known AV/C command and control protocol. Generally, the present invention allows an intelligent controller to communicate with the panel subunit of the target device and inquire about the various types of controls which it has, e.g., buttons, sliders, etc. The intelligent controller then generates, on its display, a human interface based on these control object descriptions, and when the user manipulates this human interface, the controller sends special user events to the target device. The information that is capable of being displayed by the intelligent controller can be made scaleable by the target device so that the human interface displayed can adapt to the particular display capabilities of the intelligent controller device. The intelligent controller monitors the target device to maintain the most current status presented to the user. Thus, the intelligent controller does not need to have advance knowledge of any specific features in the target device or how they are used or invoked because this functionality is the responsibility of the target device. All issues such as state transitions and inter-control dependencies are handled automatically the by target device independently of the intelligent controller responsibility. The present invention removes all requirements for items such as state transition tables and their execution environment, because it takes advantage of the functionality that is already built into a media device and used to handle the physical buttons as they are manipulated by the user. For instance, when the intelligent controller asks the target to "simulate the press of button 5," the intelligent controller does not need to have any knowledge at all about what is happening within the target device upon being notified of the user action. The state transition logic for what happens when "button 5" is pressed is all contained within the target device. This is advantageous because it enhances the inter-operability between the intelligent controller and the target device while at the same time greatly reduces the responsibilities of each. In addition to describing physical controls and appearances, the present invention can be used to describe logical controls and appearances of elements of a logical control panel. For instance, a logical control panel can be used to control a "black box" not having any physical controls but having only a 1394 connector with the black box being located in a closet or other remote location. In this case, the black box is manipulated with on screen controls via its panel subunit thereby having no physical control panel itself. NETWORK ENVIRONMENT OF THE PRESENT INVENTION Figure 1 illustrates an exemplary network system 5 that can support the embodiments of the panel subunit of the present invention. Exemplary system 5 includes consumer electronic devices (including computer systems) as nodes but could be extended equally well to cover other electronic devices. System 5 includes a video camera 10, a video cassette recorder (VCR) 12, a computer system 14, a set-top-box (STB) 13, a television set (TV) 11 and a compact disk (CD) changer 20 connected together with the network by IEEE 1394-1995 (IEEE 1394) cables 15, 16, 18 and 19. It is appreciated that the panel subunit embodiments of the present invention are equally well suited for application with any bus structure and the IEEE 1394 bus structure is shown and described herein as an example bus architecture only. The STB 13 can be coupled to receive media from a cable TV system. The IEEE 1394 cable 16 couples the video camera 10 to the VCR 12 allowing the video camera 10 to send data, commands and parameters to the VCR 12 for recording (or to any other device of the network 5). The IEEE 1394 cable 18 couples the VCR 12 to the computer system 14 allowing the VCR 12 to send data, commands and parameters to the computer system 14 for display (or to any other device of the network 5). The IEEE 1394 cable 15 couples the STB 13 to the computer system 14. The STB 13 is also coupled to the TV 11 by the cable 17. The CD changer 20 is coupled to the computer system 14 by the IEEE 1394 cable 19. The configuration 5 illustrated in Figure 1 is exemplary only and it should be apparent that an audio/video network in accordance with the present invention could include many different combinations of components. The devices within an IEEE 1394 network 5 are autonomous devices, meaning that in an IEEE 1394 network, in which a computer is one of the devices, there is no true master-slave relationship between the computer system 14 and the other devices. In fact, as described below in an exemplary embodiment of the panel subunit of the present invention, the intelligent controller is the STB 13. In many IEEE 1394 network configurations, a computer system 14 may not be present. Even in such configurations, the devices within the network are fully capable of interacting with each other on a peer-to-peer basis. It should be recognized that data, commands and parameters can be sent between all of the devices within the IEEE 1394 network 5. The IEEE 1394 serial bus used by system 5 of Figure 1 is a high-speed bus architecture for interconnecting digital devices thereby providing a universal input/output connection. The IEEE 1394 standard defines a digital interface for the applications thereby eliminating the need for an application to covert digital data to analog data before it is transmitted across the bus. Correspondingly, a receiving application receives digital data from the bus, not analog data, and therefore is not required to covert analog data to digital data. The cable required by the IEEE 1394 standard is very thin in size compared to other bulkier cables used to connect such devices. Devices can be added and removed from an IEEE 1394 bus while the bus is active. If a device is so added or removed, the bus automatically reconfigures itself for transmitting data between the then existing nodes. A node is considered a logical entity having a unique address on the bus structure. Each node provides an identification ROM, a standardized set of control registers and its own address space. The IEEE 1394 communication standard within system 5 of Figure 1 supports isochronous data transfers of digital encoded information. Isochronous data transfers are real-time transfers which take place such that the time intervals between significant instances have the same duration at both the transmitting and receiving applications. Each packet of data transferred isochronously is transferred " in its own time period. An example of an application for the transfer of data isochronously is from a VCR 12 to TV 11 of Figure 1. The VCR 12 records images and sounds and saves the data in discrete packets. The VCR 12 then transfers each packet, representing the images and sounds recorded over a limited time period, during that time period, for display by the TV 11. The IEEE 1394 standard bus architecture provides multiple channels for isochronous data transfers between applications. Specifically, a six bit channel number is broadcast with the data to ensure reception by the appropriate application. This allows multiple applications to simultaneously transmit isochronous data across the bus structure. Asynchronous transfers are traditional data transfer operations which take place as soon as possible and transfer an amount of data from a source to a destination. INTELLIGENT CONTROLLER User interface aspects of the panel subunit of the present invention are implemented within an intelligent controller device. The intelligent controller can be any device coupled within a networked system (e.g., system 5 of Figure 1 ) designated by the user and having certain basic input functionality and basic display capability. In one embodiment of the present invention, the STB 13 and the TV 11 act as the intelligent controller. In other embodiments, the computer system 14 can act as the intelligent controller or the TV 11 can act alone as an intelligent controller. Any device having "display" and input capability can act as the intelligent controller, e.g., a personal digital assistant (PDA), a hand-held electronic device, a cell phone, etc.). Within the context of the present invention, the intelligent controller is the device that provides a user interface for controlling events on another, remote, target device within the network 5. To this extent, the intelligent controller communicates with a display device and an information input device. The display and input capabilities of the intelligent controller device define the type of user interface that the intelligent controller can provide to a user and the panel subunit of the present invention allows the definition of scaleable user interface capabilities. Figure 2 illustrates the components of the intelligent controller, and in this example it is the STB 13. STB 13 includes an address/data bus 100 for communicating information, a central processor 101 coupled with the bus 100 for processing information and instructions, a volatile memory 102 (e.g., random access memory RAM) coupled with the bus 100 for storing information and instructions for the central processor 101 and a non-volatile memory 103 (e.g., read only memory ROM) coupled with the bus 100 for storing static information and instructions for the processor 101. STB 13 can also optionally include a data storage device 104 ("disk subsystem") such as a magnetic or optical disk and disk drive coupled with the bus 100 for storing information and instructions. In one embodiment, the display device 105 can be part of the intelligent controller. As shown in Figure 2, the display device (e.g.,. TV 11 ) is external to the STB 13. When incorporated into the intelligent controller, the display device 105 can be a display screen (e.g., flat panel or CRT, etc.) or it can be a liquid crystal display (LCD) panel or other suitable display device for the display of alphanumeric and/or graphic information. The intelligent controller 13 also interfaces with or includes one or more user input devices. In one embodiment, the input device can be an alphanumeric input device 106 including alphanumeric and function keys coupled to the bus 100 for communicating information and command selections to the central processor 101. Alternatively, or in addition, the intelligent controller 13 can interface with or include a cursor control or cursor directing device 107 coupled to the bus for communicating user input information and command selections to the central processor 101. The cursor directing device 107 can be implemented using a number of well known devices such as a mouse, a track ball, a track pad, an electronic pad and stylus, an optical tracking device, a touch screen etc. In addition, the user input device can also be a remote control device, e.g., a universal remote control device having a number of buttons, dials, etc., with an infra-red signal communication capability. STB 13 can also include a signal generating device 108 coupled to the bus 100 for interfacing with other networked devices over the IEEE 1394 bus. The target device of the present invention can also include one or more components as described with respect to Figure 2. Particularly, the target device in accordance with the present invention includes computer readable memory units which can include one or more ROM and/or RAM units for storing panel subunit information of the present invention which are described below. PANEL SUBUNIT OF THE PRESENT INVENTION The present invention defines a subunit type called a "panel" subunit. The panel subunit is defined for a target device and outlines characteristics for generating a user interface on an intelligent controller device (e.g., STB 13) of a network system 5. The panel subunits can be defined for multiple target devices and therefore many panel subunits can be included within a network system 5. For a particular target device, its panel subunit can be stored as a data structure within computer readable memory units of the particular target device. Figure 3A illustrates a perspective view of the VCR 12 of Figure 1 as an exemplary target device. Although, generally, any electronic device can have its own panel subunit and thereby be a "target device," the following discussion illustrates an exemplary case where the VCR 12 is the target device. VCR 12 contains a video tape slot 212 for insertion and removal of video tape media. The VCR 12 also contains one or more liquid crystal displays (LCDs) 214. Figure 3B illustrates the VCR 12 with a control panel 220 flipped-down exposing certain controls and further displays (e.g., "elements"). The control panel 220 contains another LCD display 240 and includes a scrubber control 230 or "dial." The control panel 220 also contains certain tape transport controls 250_(including play, pause, stop, rewind, fast-forward, buttons etc.). When the control panel 220 is flipped down, it exposes tuner preset buttons 225. In the present invention, devices can have more than one logical control panel. In this configuration, the VCR 12 has " two logical subpanels. The first subpanel includes the controls and display of the flip-down control panel 220 and the second subpanel includes the tape slot 212 and the tuner preset buttons 225. Another subpanel could define the LCD panel 214. Figure 4 illustrates a logical block diagram of some of the subunits that can be associated with VCR 12 in accordance with the present invention. Within the well known AV/C protocol, subunits are logical, not physical, groupings of functionality that can be individually addressed and controlled within a device. For example, a VCR device 12 can have two subunits, one subunit 312 for the actual VCR tape transport mechanism, and. another subunit 320 for the tuning functionality. The panel subunit 314 of the present invention adds a novel logical subunit that can be associated with the VCR device 12. As described further below, the panel subunit 314 of the present invention is realized, in one embodiment, as one or more data structures stored in computer readable memory units of the target device e.g., the VCR unit 12. It is possible for a panel subunit for a first device (e.g., of limited memory capacity) to exist on a second device (having more memory), whereby the second device acts as a proxy for the first device's panel subunit. The panel subunit 314 is a collection of data structures called "descriptors" that describe the physical controls on the target device (e.g., the control panel). In operation, the intelligent controller (e.g., STB 13) accesses the panel subunit 314 of the target device, and based thereon, implements a user interface for using the target device (e.g., the VCR 12). The user interface involves the display (e.g., TV 11 ) and user input devices associated with the intelligent controller, as described with respect to Figure 2. The specification for the panel subunit 314 defines several standard types of controls and displays that are commonly found on consumer electronic devices, such as push buttons, sliders, dials, LCD screens, etc. As an example, the descriptions within the panel subuttons, dial and LCD screens of Figure 3A and Figure 3B. The control types defined by the panel subunit 314 have well defined behaviors. For instance, buttons are pushed and released and typically have two ~ values, sliders may have several discrete values or a continuous range of values. Further, some standard control types may be combined within the descriptors to form hybrid or custom controls. One example of this is a dial with a push button in the middle or a button with an LED in the middle. Such composite control mechanisms are supported by the panel subunit of the present invention. Finally, vendor specific custom controls may also be defined. In addition to standard control types, the panel subunit 314 of the present invention also defines a set of commands which may be applied to any of these controls. The commands are defined to be sufficiently generic so that they apply to most types of controls. For example, issuing the command SET CONTROL VALUE (control 1 , 6) by the intelligent controller may cause a volume slider to be set to the value 6, representing a change in volume. Likewise, the same command type with different operands can be issued as SET CONTROL VALUE (control 5, "please enter the track name"), and it would cause that text to show upon the LCD display of a MiniDisc recorder 20, prompting the user to enter a name for a track on the disc. Further, within the panel subunit, some commands can be specific to certain kinds of controls. The panel subunit 314 also defines "user interaction commands" or user events which can be applied to the controls of the user interface. The purpose of these generic user events is to encapsulate the typical user manipulation actions for controls, and to let the target device interpret what it means when these user events occur thereby freeing the intelligent controller of this responsibility. For example, many CD players 20 have multiple semantic meanings for the fast forward button on thent state of the device. Consider the following: TABLE I Current Device Setting Action Result Device Is Not Playing FF Button Pressed Advance to the Next Track and Hold Device Is Playing FF Button Pressed Advance to the Next Track and Continue Playing from that Point Device Is Playing FF Button Pressed Play in "Fast Forward" Mode and Held Down As shown above, the actions taken by the target device vary based on its current state and what the user does with the physical controls. The panel subunit of the present invention defines several user action commands such as "PUSH," "PRESS AND HOLD," and "RELEASE" that are triggered by user interaction with the displayed user interface. In accordance with the present invention, the intelligent controller of the present invention has no notion of what the target device will do in response to the commands that are issued to it. All concerns regarding the state transition as shown in the Table I are handled inside of the target device. It is appreciated that the target device already needs to have this logic in place in order to process the user interaction on its physical control panel. The panel subunit of the present invention is viewed as another mechanism by which to access these logical entry points. It is important that the intelligent controller always keep the user informed regarding the status of the target device being controlled. In one embodiment, it is possible that the intelligent controller and the user are sitting in one room of a house or business office and the target device is located in another room or office. Because the intelligent controller has no pre-defined knowledge of how to interpret the user interaction elements, it needs to have a mechanism of keeping its display updated with the most current status of the target device. It does this by making use of the status reporting mechanism that has been defined for the AC/C protocol, in one embodiment, using a status descriptor data structure and a panel status notification command in accordance with the present invention. The status descriptor data structure is a dynamic data structure that is always kept up-to-date by the panel subunit 314 of the present invention. The intelligent controller can examine this structure at any time so that it can update its graphical display to indicate the target device status to the user. The panel status notification command of the present invention allows the intelligent controller to post a notification request to the target device. When any change in the state of the device results in a change to the status descriptor data structure, then the target device sends a notification to the intelligent controller. The intelligent controller then updates its graphical display as appropriate in response to the status information. The AV/C protocol allows a device (also called a unit herein) to contain any number of subunits of the same type. Therefore, a device can have more than one panel subunit of the present invention. For instance, one panel subunit can be defined for the front panel of Figure 3B and another panel subunit can be defined for the flip-down panel 220. Other panel subunits can be defined for the side and back panels, if any. Alternatively, a single panel subunit can be defined to encompass several controls as shown in Figure 5. In this approach, a single panel subunit can contain any number of control lists which are hierarchically ordered. Each control list of the present invention represents a control panel of the target device. All of these lists are accessed via the single panel subunit 314. Part of the panel subunit data structures includes geometry information describing the layout image and orientation of panels and controls so that they can be represented to the user in a manner similar to their physical appearance on the target device or in a manner "suggested" by the target device. As standard controls can be combined into hybrid controls, this geometry information can also be defined to indicate the presence of panel hierarchies, such as panels hidden behind a front flip-down face 220 (Figure 3B). This is commonly found in many VCR devices where some basic controls are on the face of the VCR device and the more advanced controls and features are hidden behind the flip-down front panel 220. PANEL DESCRIPTORS OF THE PANEL SUBUNIT Figure 5 illustrates data descriptor information maintained by computer readable memory units of a target device, e.g., VCR 12. It is appreciated that the data descriptor data structures found in Figures 5-8 and 11 are all maintained and realized within computer readable memory units of the target device in accordance with the present invention. The panel subunit 314 (Figure 4) includes a panel subunit identifier descriptor data structure 340. The identifier descriptor list 340 indicates identifiers for each of the main panel lists supported by the panel subunit 314. Each of these panel lists can contain a control object which has a child list, indicating a panel hierarchy. For instance, primary identifier list 340 relates to the front panel for the target device and includes an identifier (e.g., pointer) 342 which points to a secondary identifier structure 350 which itself includes two sub-panel descriptions (e.g., one for the face of the VCR 12 and one for the flip-down panel 220). The primary identifier 340 also includes an identifier (e.g., pointer) 344 for another secondary identifier list 390 describing a rear panel for the target device. In this manner, the main identifier and the secondary identifier structures of the panel subunit 314 can define hierarchical relationships between the descriptor list information and thereby between the panels and sub-panels themselves. The secondary identifier descriptor list 350 of Figure 5 is a descriptor list including a general list information field 352 and one object control descriptor 354 for describing the LCD display 214 (Figure 3A). A descriptor list within the present invention can include object control descriptors, general information, and pointers to child descriptor lists. Therefore, a control object within a descriptor list can point to another descriptor list indicating a parent-child relationship between the control object and the indicated descriptor list. Descriptor list 350 includes a pointer 356 indicating a child descriptor list 356a used to describe "sub-paneM" which is a portion of the controls of the front panel for VCR 12 in this example. Further, descriptor list 350 includes a pointer 358 indicating a child descriptor list 358a used to describe "sub-panel2" which is another portion of the controls of the front panel for VCR 12. In this example, the descriptor list 356a for sub-paneM defines the controls on the face of VCR 12, e.g., buttons 225 for the tuner subunit 320. The descriptor list 358a for sub-panel2 defines the controls on the flip-down control 220 of VCR 12, e.g., buttons 250, display 240, and dial 230. As with any descriptor list data structure, descriptor lists 356a and 358a each contain a respective general list information field 360 and field 380 and also contain respective lists of control objects. In accordance with the present invention, a list which contains control objects for a panel is used to describe the control panel itself, as well as to hold the collection of objects. Generally, information that describes the collection (the panel description) would contain the following: (1 ) panel identifier (e.g., front, back, left side, etc.); (2) panel layout geometry (e.g., size of panel, orientation of controls, definition of groups, etc.); (3) group descriptions for each group of controls where the following can be defined, group label, group bounding box/position within the panel, and other group related information; and (4) a name for the panel subunit. An example is shown in Figure 6. Figure 6 illustrates the information included within the general list information data structure 380 of the secondary descriptor list 358a for the front sub-paneM of the target device. Secondary descriptor list 358a contains general list information 380 and a collection of n objects 382 to 386. Exemplary data structure 380 includes fields 410-420. Field 410 indicates the hierarchical position or identifier for the descriptor list 358a in which the field is included. For instance, field 410 indicates which physical panel the information represented, e.g., whether this descriptor list 358a represents a front, side, rear, etc., control panel. In this example, descriptor list 358a is a "front" panel. Field 412 defines the opening or access options used to obtain access to the control panel for which descriptor list 358a is defined, e.g., flip- down, flip-up, flip-out, left, right, direct access, etc. In this case, control panel 220 (Figure 3B) has "flip-down" style access. Field 414 defines the general size and shape of the control panel for which descriptor list 358a is defined (e.g., rectangle, circular, oblong, triangle, polygon, etc.). In this case, control panel 220 is rectangular in shape. Fields 416-420 of Figure 6 are used to define groups within the control panel for which descriptor list 358a is defined. Groups can be used to separate certain control features that are similar or control a similar function or feature. For instance, buttons that each relate to the control of the tape mechanism for a VCR 12 can be assigned into one group while buttons that control the channel selection or the volume selection of the VCR 12 can be assigned in a separate group. Groups have special functions within the present invention, e.g., they can be displayed spatially together on the display of the intelligent controller, and can have other defined attributes in common. Field 416 indicates the number of groups defined for descriptor list data structure 358a and fields 418-420 represent the group description information for a number of exemplary groups. Figure 6 illustrates fields 430-438 which represent an exemplary group description that is contained in field 420 for an exemplary group (n-1 ). Information field 430 includes the number of control objects that are defined for this group. Field 432 includes a group identification number or string that is unique for this group and used to identify the group by control objects. Each control object that is to be included in the defined group includes the identifier 432 in its object description (described below). Field 436 indicates the spatial boundary box in which this group is included for the control panel. This information indicates where this group exists with respect to other defined groups in the user interface layout and is used for rendering the image of the control panel on the display of the intelligent controller. Field 438 is a group label that can be used to provide access to and represent the control objects of this group for cases where the display unit of the intelligent controller is not sophisticated enough to provide images or further information. Field 438 typically contains a string or other text label that can be used, in one embodiment, as a tab index in a tabbed-panel presentation of information. In a tabbed-panel presentation, all the defined tabs for all groups are displayed along the side of the display and groups are selected for presentation by selecting one tab or another. Figure 7A illustrates the data of a control object 382 in accordance with the panel subunit of the present invention. Exemplary control object 382 is included within descriptor list data structure 358a. In one embodiment, the panel subunit of the present invention presents its information to controllers via the AV/C object and object list data structures. These data structures are generic containers whose contents are specialized based on the owner of the structure. A panel subunit of the present invention contains a list of its controls (e.g., list descriptor 358a), with each control being represented by a control object in the list. Within the present invention control objects can be defined to represent user input devices (e.g., buttons, sliders, toggle switches, etc.) and can also be defined to represent information displays (e.g., LCD panels, dials, etc.). Figure 7A illustrates the information of a control object 382 representing the LCD panel 214 of Figure 3A. Field 440 describes the type of control object being defined. In this case it is "LCD Panel" type. Other control types for displaying information include "Display," "Dial," "CRT Display," "LED" and "Alpha/Numeric Display." Other control types for information input devices include "Button," "Slider," "Rotator," "Toggle Switch" and "Rocker Switch." Field 442 includes a graphical image of the control object. This image information is typically raster data (e.g., bit mapped) and may include color and other attribute data. In this particular instance, the control image 442a is in the shape and character of the outline of an LCD display to represent LCD panel 214. Field 442 could also contain a collection of images used for performing animation in a predefined sequence of presentation. Field 444 represents the dimensions of the image 442A and in one embodiment is represented in screen coordinates (x, y). To generalize these coordinates for application with many screen dimensions, the (x, y) values can be represented in relative terms with respect to the left corner, e.g., the (0, 0) coordinate position, of the display screen. Field 446 of Figure 7A represents the group identification or name with which this control object 382 is associated. Controls can be clustered into groups based on layout information defined by the panel subunit of the present invention. This field 446 is optional as an object does not necessarily need to be associated with any group at all. If a group is associated with this control object 382, then field 448 represents the relative position 448a within the group boundary 448b in which this control object 382 belongs. This information can be expressed in coordinate values. Field 450 represents the allowable or valid value ranges that can be taken by this control object in response to a user event. This field 450 can also include a data type indicator (e.g., 16-bit representing integer, floating point, etc.) In the case of a display object, field 450 represents the character or icon sets that can be displayed within the control object. In the case of a user input control object, field 450 indicates the range of possible values that can be set by this control object. If the control object was a slider, then a range of values is appropriate. If the control object is a button or toggle switch, then possibly only two states (e.g., 0 or 1) are valid for the control object. Field 452 of Figure 7A is optional and represents the equivalent AV/C command that occurs when the control object 382 is activated. This AV/C command can be communicated by the intelligent controller over the network within system 5 when the control object 382 is invoked. Field 452 is optional because the target device has the capacity to interpret changes in the control object as communicated to it by the intelligent controller without the need for a communicated AV/C command. The panel subunit 314 represents the VCR 12 in this example. The manipulation of those controls may cause a state change in other subunits within the target device. The values of field 454 represents which subunit (subunit type and ID) can be effected by this control object. Field 454 is likewise an optional field that indicates the identification of the target device associated with the control object. Again, this information is optionally included within the control object 382 but is maintained by the intelligent controller by virtue of which target object contained the panel subunit in the first instance. Field 456 is an identifier or name string that can be associated with the control object. In instances where the display device of the intelligent controller is not sophisticated, field 456 can be used to at least provide a basic textual description of the control object which is presented for user interface functionality. Field 458 contains a help string that can be displayed o controller if a help feature is employed by the user. The help string describes what the control object does. This can be extended to provide a help string for each state of the control object. The help string can identify the control object and give tips on how to use the control object, its purpose and expected functionality and value range. Figure 7B illustrates information associated with an exemplary control object 384 for one of the push buttons of buttons 250 of the flip-down panel 220 of Figure 3B. In this example, the "Play" button is being represented for VCR 12. Field 460 defines the control object as a "button" control type. Field 462 can contain multiple images or "icons" that can be used for displaying the control object. The icons can, for instance, represent different states of the control object, e.g., such as a button which is highlighted differently whether it is pressed or released. Field 462, in this case, contains a number of icons that represent the image of the button in different states (e.g., pressed or released). Image 462a represents the image for the button pressed and image 462b represents the image of the button for the button released. Field 464 represents the screen dimensions of the images of field 462 and field 466 represents a group identification, if any, for control object 384. In this case, all of the buttons 250 (Figure 3B) are clustered together into a single group because they control the tape mechanism for VCR 12, e.g., Group Identification = "Tape Mechanism," where this group would have to have been previously defined in a data structure of Figure 6. Field 468 represents the relative position 468a of the control object 384 within the group boundary 468b. In this case, the control object 384 represents the third button from the left within the collection of buttons 250. Field 470 represents the possible range of values can be represented by the button, e.g., in this case 0 to 1 , and the value is an integer. If the control object was a slider, then a possible range of values (e.g., 0 to 10) could be represented with the values being integer or floating point type. Optional field 472 represents the equivalent AV/C command for "Play" and can be communicated by the intelligent controller when control object 384 is pushed. When a user event such as PRESS is issued, it may result in the same action as if a standard AV/C command, such as the VCR subunit PLAY command, had balent AV/C command. Optional field 474 represents the network identification for the target device (in this case, the VCR subunit). Field 476 is an identifier or name string that can be associated with the control object, e.g., "Play." In instances where the display device of the intelligent controller is not sophisticated, field 476 can be used to at least provide a textual description of the control object which is presented for user interface functionality. Field 478 contains a help string that can be displayed on the display of the intelligent controller if a help feature is employed by the user, e.g., "Press Play to Start Watching A Tape in the VCR." The help string could also describe why the control object is in a particular state, e.g., "The Play Button is Disabled Because There is No Tape in the VCR." It is appreciated that the control objects of Figure 7A and Figure 7B are exemplary only and that other similar control object descriptions can be used to realize a user interface for all user inputs and user displays of the VCR 12 for all control panels. It is further appreciated that each other control object of Figure 5 can analogously be defined in accordance with the present invention. Figure 8 illustrates a panel subunit status descriptor 500. The panel subunit 314 of the present invention also includes a panel subunit status descriptor 500 data structure. The status descriptor 500 is a data structure maintained in computer readable memory units of the target device and represents the current state of all control objects defined for a particular panel subunit in accordance with the present invention. The information maintained in the status descriptor 500 is dynamic, and is kept up-to-date by the panel subunit 314 of the present invention. Within the status descriptor 500, a separate control status field is maintained for each defined control object. When changes occur to the status descriptor 500, a notification can be forwarded to any intelligent controller that previously indicated that it was to be notified of any changes. The overall status descriptor 500 contains two main areas, one area 510 contains general status information for the panel subunit and a separate area 512 is defined for each of the control list hierarchies. Within each of these control list areas are status information for each control. Status information includes the current state of the control object (e.g., the button is currently pressed) and the current value of the control object (e.g., the LCD panel is currently displaying the text "Enter Track Name."). In operation, an intelligent controller can request notification for individual control lists or for the general area of the panel status descriptor 500. When the status of one of these areas changes, the intelligent controller is notified. If status for an area changes for which an intelligent controller had not requested notification, the intelligent controller is not notified. This operation allows the various controllers and target devices to optimize the use of the system network bandwidth by not sending out unnecessary messages. Status descriptor 500 of Figure 8 is shown as an example and includes a primary status list 505 which includes a general information field 510 for panel subunit 314 and pointers 512 and 514 to other major status lists. Pointer 512 points to status list 535 for representing the status of the front panel. Status list 535 includes a status field for each control object defined for the front panel. Pointer 514 points to the status list 516 for an exemplary left side panel. Field 518 of status list 535 indicates general status information for any control objects defined with respect to the front panel including whether or not the panel is open, closed, etc. Field 520 represents the current state/value of control object 0 defined for the front panel. Likewise, field 522 represents the current state/value of control object 1 defined for the front panel. Field 526 is a pointer to the control list 530 indicating the states/values for the control objects defined with respect to the sub-paneM of the front panel. These control objects are defined with respect to descriptor list 356a (Figure 5). Within status list 530, a separate control status field is defined for each control object. Field 528 of control list 535 is a pointer to the control list 532 indicating the states/values for the control objects defined with respect to the sub-panel2 of the front panel. These control objects are defined with respect to descriptor list 358a (Figure 5). Within status list 532, a separate control status field is defined for each control object. Figure 9 is a flow diagram illustrating steps of a process 700 implemented in accordance with the panel subunit of the present invention. Process 700 is realized as program code stored within computer readable memory units of an intelligent controller and a target device of network 5. At step 710, the intelligent controller device, e.g., STB 13 and TV 11 (used as the display unit), locates electronic devices coupled to system 5. This process utilizes well known IEEE 1394 communication protocol mechanisms. At step 712, the intelligent controller reads the computer readable memory units of a target device coupled to the network 5 and discovers that this target device has a panel subunit data structure 314 defined therein. At step 714, the intelligent controller device downloads the descriptor information and the current status descriptor table for the target device and displays a user interface on the display screen of the intelligent controller based on the downloaded information. If the intelligent controller device has limited memory resources, then the panel subunit information can be downloaded and processed in portions. At step 714, the control objects of the panel subunit describe the look, shape, grouping and location for each user input element and each information display element for the user interface. Should the intelligent controller be limited in display capability, then text strings are displayed for the groups and/or for the control objects and these text strings can be displayed in a hierarchical format (e.g., using a tabbed-panel display). At step 716 of Figure 9, the intelligent controller allows the user to interact with the user interface including accepting predefined or generic user events from the user. Each control object contains an object type and each object type defines a user action that can take place with respect to the control object. For instance, buttons are "PUSHED" or "PUSHED AND HELD" or "RELEASED" and sliders and rotators can be moved to "SET A VALUE." Toggle switches can be moved between two positions, e.g., "MOVED RIGHT" or "MOVED LEFT" or "MOVED UP" or "MOVED DOWN." Other user events include setting a text value, e.g., SET TEXT VALUE, or setting a numeric value, SET VALUE, etc. These user events are defined by the control objects themselves and the intelligent controller does not interpret the meanings of these events for any target device. At step 716, irrespective of the type of user input device, e.g., keyboard, mouse and mouse button, remote control unit, pen and stylus, light pointer, joystick, etc., the intelligent controller translates the interaction between these user input devices and the user into a generic user event core recognized by the panel subunit 314 of the present invention. For instance, a button control object can be "PRESSED" and then "RELEASED" by selecting it with a mouse or selecting it with a keyboard or with a remote control button push. In either case, the user event is "PRESSED" or "RELEASED" with respect to the control object. At step 718 of Figure 9, any user events detected by the intelligent controller are forwarded over the network 5 to the target device. The target device then interprets the user event and takes the appropriate action based on its programming. The programming used by the target device at step 718 is the same programming that is already present in the target device for responding to the input devices physically located on the target device. In this case, any target device having physical controls located thereon already is programmed with the required actions to take upon these controls being directly pushed by a user. The present invention takes advantage of this pre-existing functionality within each target device. A received user event may trigger a change in one or more of the states of the control objects defined within the panel subunit of the present invention. Upon a change in state, the status descriptor 500 of the panel subunit changes thereby notifying the intelligent controller of a state change. At step 720, the intelligent controller downloads the status descriptor to determine which control object changed states. Next, the intelligent controller updates the displayed user interface to reflect the change. For instance, if the button state changed from released to pressed, then the intelligent controller may display a new image for the button state being pushed. Alternatively, if the state of the VCR tape mechanism changes from standby to play, an image within LCD panel 214 might become animated showing the tape playing, etc. At step 722, the generic user events cause the target device to implement a certain action, e.g., play, pause, etc. It is appreciated that step 722 can occur before step 720. At step 724, processing returns to step 716 to check for a next user action. In operation, the intelligent controller is not burdened with keeping state tables or by interpreting the meaning of the user events. These interpretations are performed by the target device thereby providing the panel subunit with a large amount of flexibility for adapting to new standards and control types. Furthermore, by providing a range of possible display representations, the present invention provides a flexible user interface for intelligent controllers having robust display capabilities and also for those controllers having unsophisticated displays. The panel subunit of the present invention defines generic user input events, core data structures which define a limited set of user actions or events and display elements and a basic communication protocol is used. Figures 10-12 illustrate another example of the present invention. Figure 10 illustrates a simulated or "virtual" keyboard 540 that can be generated for a target device using the panel subunit of the present invention. The virtual keyboard 540 can be used to control a "black box" device that itself has no physical keys or LEDs and whose control panel is purely virtual. In this case, the black box has no physical equivalent keyboard and relies on the intelligent controller for access to its functionality. In one example, the target device can be a subpanel for an intelligent television which has embedded software that requires user input, e.g., for web surfing or similar tasks. The virtual keyboard 540 includes groups of controls where each control defines a key or an LED. Each element is represented by its own control object. The virtual keyboard 540 of Figure 10 includes several groups (e.g., main keys, function keys, keypad keys, etc.) with various dimensions and layouts. A first group 542 includes only the ESC key while the function keys, F1-F(n), are grouped into group 544. The standard alpha keys, the tab, caps lock, shift, control, etc., keys are grouped into group 546. The numeric keys and operator keys are grouped into group 548. Also included are a numlock LED 554, a caps lock LED 556 and a scroll lock LED 558. A power on key 560 is shown along with a special button 550 having an LED 552 therein. An LED 552 embedded in the key 550 can be modeled as an LED which can be turned on or off with the appropriate panel subunit command. Thus, a key with an LED is modeled as a hybrid control object. Group 565 includes LEDs 554, 556, 558, 552 and buttons 560 and 550. Figure 11 illustrates the control object descriptor information within the panel subunit needed to realize the hybrid button 550 as an example in accordance with the present invention. Fields 572-578 define a control object. Field 572 indicates that the control object is a "HYBRID" type. Field 574 indicates that two control object definitions are included in this hybrid. Field 576 is a pointer to control object 610 (controlO) while field 578 points to control object 640 (controH ). With respect to controlO control object 610, field 612 indicates that the object is a "button" type and field 614 indicates the button image 614a. Field 616 indicates the button dimensions (x, y) and field 618 indicates a group identifier for group 565. Field 620 indicates the relative position of button 550 within the boundary of group 565. Field 622 indicates the range of values for the button 550 (e.g., 0 and 1 ). Field 624 represents the optional AV/C command, if any, corresponding to the states of button 550. Field 626 is the optional target device identification. Field 628 is the string "Special" for displays that may have only text display capability. The help string, if any, is in field 630. With respect to control 1 control object 640, field 642 of Figure 11 indicates that the object is an "LED" type and field 644 indicates the images for the different states of the LED, e.g., green for the ON state and black for the OFF state. Field 646 indicates the LED image dimensions (x, y) and field 648 indicates a group identifier for group 565. Field 650 indicates the relative position of LED 552 within the boundary of group 565. Field 652 indicates the range of values for the button 550 (e.g., ON and OFF). Field 544 represents the optional AV/C command, if any, corresponding to the states of LED 552. Field 656 is the optional target device identification. Field 658 is the string for LED 552 for displays that may have only text display capability. The help string, if any, is in field 660 Using the examples of Figure 11 , the control objects for the remainder of Figure 10 can be realized. Figure 12 illustrates steps performed by the intelligetween, for interacting with the virtual keyboard 540 of Figure 10. At step 805, the intelligent controller sends a request 807 to the target device for a notification upon any changes of the status descriptor for the virtual keyboard 540. At step 830, the target device accepts the request 807 and generates an interim signal 832 to the intelligent controller acknowledging the request 807. At step 810, the user interfaces with the virtual keyboard 540 such that the user event "PRESS" is indicated on the caps lock key of group 546. The user event "PRESS" caps lock is then transmitted 812 from the intelligent controller to step 835 of the target device. At step 835, the target device takes any action required by this user event according to its own preset programming. The status descriptor changes and this causes a status response (e.g., to the PRESS command) to be generated by the target device. At step 835, the target device forwards a new status 837 of the caps lock key to the intelligent controller indicating that the caps lock key is now pressed. Only after receiving the new status information 837 does the intelligent controller change the image of the caps lock button on the display to indicate that it is now pressed. As a side effect of the action taken by the target device, at step 840, the state of the caps lock LED 556 changes from OFF to ON. The status descriptor changes and this causes a status update message to be generated by the target device. This change in status is reported by message 822 to the intelligent controller in response to a change in the status descriptor. The intelligent controller, in response to message 822, reads the status descriptor 845 of the target device to determine which control object changed status. At 827, it is determined and returned that the status of the LED 556 changed from OFF to ON. Only in response to receiving the new status information does the intelligent controller, at step 825, then update the image for the LEe the new status of ON. It is appreciated that a direct interaction with the physical controls of the target device at step 840 can also cause a state change in the status descriptor which would then cause a notification of a status change to be forwarded to the intelligent controller. This action would also cause a change in the user interface displayed on the intelligent controller as described above The process can be repeated. One embodiment of the present invention describes the representation of device capabilities which have some types of physical control or display, e.g., something that is user-visible and that would be manipulated by a human. However, the panel subunit of the present invention can be extended to describe how to access functionality that is "built-in" to a device but which does not have a physical external button to access it. For example, many digital set-top-boxes can contain one or more MPEG2 decoders, which contain very useful media processing functions. However, it is very unlikely that there would be an MPEG2 button on the device for the user to push. Rather, the panel subunit of the present invention can be used to define interface objects within a descriptor that represent "virtual" buttons and dials for interfacing with the MPEG2 decoder. Therefore, the capabilities of the MPEG2 decoder and the means to access its capabilities can be described using the present invention even though no physical interface elements exist on the set-top-box. In furtherance of the above, because the panel subunit 314 of the present invention defines various types of controls and their attributes, it is possible for a "black box" device to be built which has no physical controls, but relies on its panel subunit of the present invention as its only means of being controlled (e.g., the virtual keyboard 540). Such a target device might be designed for situations where the hardware can be located in a remote or hidden location and the user control center (e.g., the intelligent controller) is at a different location. In this case, the target device would not have physical controls on its surface because they would never be used directly by a person. Another embodiment of the present invention is drawn to the types of information or attributes that are provided by the functionality descriptors of the panel subunit. For example, the present invention describes various attributes for a button control including its physical appearance, size and shape, a text string describing the function, e.g., "play," possibly a help string describing how to use it, and some standard commands for manipulating that control, e.g., PUSH BUTTON or SET BUTTON VALUE TO 1. A variation of this functionality can add some other attributes that may be useful either in a general way or a vender-specific way. The preferred embodiment of the present invention, a panel subunit for remotely interfacing with a target device via an intelligent controller within a network of consumer electronic devices, is thus described. While the present invention has been described in particular embodiments, it should be appreciated that the present invention should not be construed as limited by such embodiments, but rather construed according to the below claims.

Claims: CLAIMS What is claimed is: 1. A method of controlling a target device, said method comprising the steps of: a) defining an identifier descriptor data structure in a computer readable memory unit of said target device which defines a hierarchy for elements of a control panel of said target device by pointing to descriptor list data structures; b) defining at least one descriptor list data structure containing a plurality of control objects in a computer readable memory unit of said target device wherein each control object defines a physical appearance and a value state for an element of said physical control panel of said target device; c) defining and updating a status descriptor data structure representing current states for said control objects in said computer readable memory unit of said target device; and d) generating a user interface for controlling said target device by accessing said data structures of said target device and communicating generic user events to said target device for interpretation by said target device, said step d) performed by an intelligent controller coupled to said network. 2.The method of claim 1 wherein said steps take place in a network of consumer electronic products and wherein said control panel is physical. 3. The method as described in Claim 1 or 2 further comprising the steps of: e) said target device receiving a generic user event and interpreting said generic user event to determine a functionality to implement; f) said target device implementing said functionality; and g) said target device updating said status descriptor data structure to reflect any changes resulting from step f). 4. The method as described in Claim 1 , 2 or 3 wherein said elements of said control panel include information input controls and display output units. 5. The method as described in Claim 1 , 2, or 3 wherein each control object defines a control image of an element, a size of said control image and a value range of valid states for said element. 6. The method as described in Claim 5 wherein each control object additionally defines a first text string defining a name of said element and a second text string defining help information related to said element. 7. The method as described in Claim 5 wherein each control object additionally defines a group identification wherein elements are collected into discrete groups that share a common layout area within said control panel of said target device. 8. The method as described in Claim 4 wherein said step d) comprises the steps of: d1 ) accessing said plurality of control objects by accessing said identifier descriptor data structure and said descriptor list data structure; d2) displaying graphic images of said elements of said control panel onto a display of said intelligent controller; d3) receiving input from a user interacting with said graphic images; d4) translating said input into generic user events; and d5) communicating said generic user events to said target device to simulate user interaction with said elements of said physical control panel. 9. The method as described in Claim 7 wherein said step d) further comprises the steps of: d6) accessing said status descriptor data structure upon notification of a change in state of said target device; and d7) updating said graphic images of said elements of said physical control panel based on said change in state. 10. The method as described in Claim 7 wherein said intelligent controller is a set-top-box coupled to a television as said display. 11 The method of claim 9 wherein said target device is a remote target device. 12. The method as described in Claim 11 wherein said step d) further comprises the steps of: d6) accessing said status descriptor data structure upon notification of a change in state of said target device; and d7) updating said graphic images of said elements of said control panel based on said change in state. 13. The method as described in Claim 11 wherein said intelligent controller is a set-top-box coupled to a television as said display. 14. A communication network comprising: a plurality of electronic devices coupled together with a bus architecture, said devices comprising a remote target device and an intelligent controller; wherein said remote target device comprises a computer readable memory containing: an identifier descriptor data structure defining a hierarchy for elements of a control panel of said remote target device by pointing to descriptor list data structures; at least one descriptor list data structure including control objects wherein each control object defines a physical appearance and a value state for an element of said control panel of said remote target device; and a status descriptor data structure representing current states for said control objects; and wherein said intelligent controller is for accessing said data structures of said remote target device and communicating generic user events over said bus to said remote target device for interpretation by said remote target device. 15. The network as described in Claim 14 wherein said remote target device is further for receiving a generic user event and interpreting said generic user event to determine a functionality to implement; wherein said remote target device is for implementing said functionality; and wherein said remote target device is for updating said status descriptor data structure to reflect any changes resulting from said implementing said functionality. 16. The network as described in Claim 14 wherein each control object defines a control image of an element, a size of said control image and a value range of valid states for said element. 17. The network as described in Claim 15 wherein said intelligent controller is further for displaying graphic images of said elements of said control panel onto a display; wherein said intelligent controller is also for receiving input from a user interacting with said graphic images; wherein said intelligent controller is also for translating said input into generic user events; and wherein said intelligent controller is also for communicating said generic user events to said remote target device to simulate interaction of a user with said elements of said control panel. 18. The network as described in Claim 15 wherein said intelligent controller is further for accessing said status descriptor data structure upon notification of a change in state of said target device; and wherein said intelligent controller is further for updating said graphic images of said elements of said control panel based on said change. 19. The network as described in claim 15 wherein said control panel is a virtual control panel.

Inventors: KAWAMURA HARUMI, LUDTKE HAROLD AARON, SHIMA HISATO, KAWAMURA, HARUMI, LUDTKE, HAROLD, AARON, SHIMA, HISATO
Applicants: KAWAMURA HARUMI, LUDTKE HAROLD AARON, SHIMA HISATO, SONY ELECTRONICS INC, KAWAMURA, HARUMI, LUDTKE, HAROLD, AARON, SHIMA, HISATO, SONY ELECTRONICS, INC.
Application year: 1998
Main classification: H04L12
IPC codes: G06F3, H04L12, H04Q9