Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. 119(e) to U.S. Provisional Patent Application Ser. No. 61/898,507, filed Nov. 1, 2013 and U.S. Provisional Patent Application Ser. No. 61/985,034, filed Apr. 28, 2014, the teachings of which are incorporated herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The present principles relate to providing recommendations based on user behavior. More particularly, the present principles relates to using binary user feedback to determine information about specific users who share an account. 
       BACKGROUND ART 
       [0003]    On-line commerce providers provide personalized recommendations for items by collecting user ratings about items ordered previously. Such items can constitute virtually any variety of goods or services, but only audio-visual content, and specifically movies, are considered herein for the sake of simplicity. Typically, multiple individuals within a single household (family members, roommates, etc.) may share a common account associated with delivery of movies for both viewing and rating. Content Providers who deliver movies on-line reluctantly deploy multiple accounts because users typically perceive log-in screens as a nuisance and a barrier to ordering and rating movies. This is especially true on devices lacking a keyboard, such as televisions or gaming platforms, where the entry of a password can prove difficult and time-consuming. Account sharing persists even when content providers offer the option of registering secondary accounts, as the latter typically have access to a subset of the services enjoyed by the primary account holder. Finally, such users may regard sharing as a partial (if unconscious) privacy protection mechanism, as users might not want to release the household composition and demographics. 
         [0004]    The use of a single account by multiple individuals poses a challenge to providing accurate personalized recommendations. Informally, the recommendations provided to a “composite” account holder often result from ratings of two or more dissimilar users and may not match the interests of any single user. Moreover, recommendation methods relying on low-rank assumptions (such as matrix factorization) can fail when relying on data derived from a composite of individual users. Such a failure can arise because “mixing” entries from different rows of a low-rank matrix results in a matrix that need not be low-rank. Beyond personalized recommendations, the ability to differentiate among individual users has value as it can aid in determining the household&#39;s demographics. Such information can be subsequently monetized through, e.g., targeted advertising. 
         [0005]    Past recommendation techniques have focused on identifying the users of an account from the users&#39; ratings. However, such existing techniques cannot provide a solution to this problem where the feedback is binary (e.g., −1 if a movie is not watched; +1 if it is), instead relying on the users to select from a range of values. One existing approach makes use of the principal Hessian directions (pHd) method. The pHd approach uses dimensionality reduction and data visualization by generalizing principal component analysis to the regression (discriminative) setting. Unfortunately, the pHd approach fails in general for the mixture models of interest in the present case. 
       BRIEF SUMMARY OF THE PRESENT PRINCIPLES 
       [0006]    In accordance with first preferred embodiment of the present principles, a method for providing recommendations of items based on user behavior commences by first tracking user which items offered to users were purchased. This behavior for each is stored in a user profile. The span of the user profiles is determined from which recommendations for items can be made. 
         [0007]    According to another aspect of the present principles, a method for finding the space spanned by user profiles commences by estimating a mean and covariance for a set of labeled items associated with a user profile; identifying a vector that belongs to a convex cone spanned by the user profiles based on the estimated mean and covariance, the labels and items; mirroring the labels in a negative space defined by the identified vector; computing a weighted covariance matrix based on the mirrored labels; and computing eigenvalues and eigenvectors of the weighted covariance matrix, wherein a first set of eigenvalues share a value and wherein a remainder of the eigenvalues correspond to eigenvectors that span the profile. 
         [0008]    According to another aspect of the present principles, a system for finding the space spanned by user profiles includes a storage device configured to store a set of labeled items associated with a user profile; and a processor configured to estimate a mean and covariance for the set of labeled items, to identify a vector that belongs to a convex cone spanned by the user profiles based on the estimated mean and covariance, the labels and items, to mirror the labels in a negative space defined by the identified vector, to compute a weighted covariance matrix based on the mirrored labels, and to compute eigenvalues and eigenvectors of the weighted covariance matrix, wherein a first set of eigenvalues share a value and wherein a remainder of the eigenvalues correspond to eigenvectors that span the profile. 
         [0009]    These and other aspects, features and advantages of the present principles will become apparent from the following detailed description of exemplary embodiments, which is to be read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present principles may be better understood in accordance with the following exemplary figures, in which: 
           [0011]      FIG. 1  is a diagram of a streaming network that delivers personalized content in accordance with the present principles; 
           [0012]      FIG. 2  is a diagram of a system that delivers personalized content in accordance with the present principles; 
           [0013]      FIG. 3  is a diagram of a touch screen interface in accordance with the present principles; 
           [0014]      FIG. 4  is a diagram of gestural controls in accordance with the present principles; and 
           [0015]      FIG. 5  is a block/flow diagram of a method for finding a number of users associated with a profile and their span in accordance with the present principles. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The present principles are directed to determining the span of the user profiles of a single account based on binary feedback. Embodiments of the present invention identify composite accounts within, e.g., a movie delivery system, and furthermore identify the individuals sharing such an account to learn accurate profiles of different users&#39; behaviors. 
         [0017]    The present description illustrates the present principles. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the present principles and are included within its spirit and scope. 
         [0018]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the present principles and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. 
         [0019]    Moreover, all statements herein reciting principles, aspects, and embodiments of the present principles, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. 
         [0020]    Thus, for example, it will be appreciated by those skilled in the art that the block diagrams presented herein represent conceptual views of illustrative circuitry embodying the present principles. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudocode, and the like represent various processes which may be substantially represented in computer readable media and so executed by a computer or processor, whether or not such computer or processor is explicitly shown. 
         [0021]    The functions of the various elements shown in the figures may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term “processor” or “controller” should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (“DSP”) hardware, read-only memory (“ROM”) for storing software, random access memory (“RAM”), and non-volatile storage. 
         [0022]    Other hardware, conventional and/or custom, may also be included. Similarly, any switches shown in the figures are conceptual only. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the implementer as more specifically understood from the context. 
         [0023]    In the claims hereof, any element expressed as a means for performing a specified function is intended to encompass any way of performing that function including, for example, a) a combination of circuit elements that performs that function or b) software in any form, including, therefore, firmware, microcode or the like, combined with appropriate circuitry for executing that software to perform the function. The present principles as defined by such claims reside in the fact that the functionalities provided by the various recited means are combined and brought together in the manner which the claims call for. It is thus regarded that any means that can provide those functionalities are equivalent to those shown herein. 
         [0024]    Reference in the specification to “one embodiment” or “an embodiment” of the present principles, as well as other variations thereof, means that a particular feature, structure, characteristic, and so forth described in connection with the embodiment is included in at least one embodiment of the present principles. Thus, the appearances of the phrase “in one embodiment” or “in an embodiment”, as well any other variations, appearing in various places throughout the specification are not necessarily all referring to the same embodiment. 
         [0025]    Referring now to  FIG. 1 , a block diagram is shown of a system  100  for delivering content to a home or end user in connection with determining user information and profiles. The content originates from a content source  102 , such as a movie studio or production house. The content may be supplied in at least one of two forms. One form may be a broadcast form of content. The broadcast content is provided to the broadcast affiliate manager  104 , which is typically a national broadcast service. The broadcast affiliate manager may collect and store the content, and may schedule delivery of the content over a deliver network, shown as a first delivery network  106 . The first delivery network  106  may include satellite link transmissions from a national center to one or more regional or local centers. The first delivery network  106  may also include local content delivery using local delivery systems such as over-the-air broadcast, satellite broadcast, or cable broadcast. The locally delivered content is provided to a receiving device  108  in a user&#39;s home, where the content will subsequently be searched by the user. It is to be appreciated that the receiving device  108  can take many forms and may be embodied as a set top box/digital video recorder (DVR), a gateway, a modem, etc. Further, the receiving device  108  may act as entry point, or gateway, for a home network system that includes additional devices configured as either client or peer devices in the home network. 
         [0026]    A second form of content is referred to as special content. Special content may include content delivered as premium viewing, pay-per-view, or other content not otherwise provided to the broadcast affiliate manager such as, e.g., movies, video games or other video elements. In many cases, the special content may be content requested by the user. The special content may be delivered to a content manager  110 . The content manager  110  may be a service provider, such as an Internet website, affiliated, for instance, with a content provider, broadcast service, or delivery network service. The content manager  110  may also incorporate Internet content into the delivery system. The content manager  110  may deliver the content to the user&#39;s receiving device  108  over a separate delivery network, second delivery network  112 . The second delivery network  112  may include high-speed broadband Internet type communications systems. It is important to note that the content from the broadcast affiliate manager  104  may also be delivered using all or parts of the second delivery network  112  and content from the content manager  110  may be delivered using all or parts of the first delivery network  106 . In addition, the user may also obtain content directly from the Internet via the second delivery network  112  without necessarily having the content managed by the content manager  110 . 
         [0027]    Several adaptations for utilizing the separately delivered content may be possible. In one possible approach, the special content is provided as an augmentation to the broadcast content, providing alternative displays, purchase and merchandising options, enhancement material, etc. In another embodiment, the special content may completely replace some programming content provided as broadcast content. Finally, the special content may be completely separate from the broadcast content, and may simply be a media alternative that the user may choose to utilize. For instance, the special content may be a library of movies that are not yet available as broadcast content. 
         [0028]    The receiving device  108  may receive different types of content from one or both of the delivery networks. The receiving device  108  processes the content, and provides a separation of the content based on user preferences and commands. The receiving device  108  may also include a storage device, such as a hard drive or optical disk drive, for recording and playing back audio and video content. Further details of the operation of the receiving device  108  and features associated with playing back stored content will be described below in relation to  FIG. 2 . The processed content is provided to a display device  114 . The display device  114  may be a conventional 2-D type display or may alternatively be an advanced 3-D display. 
         [0029]    The receiving device  108  may also be interfaced to a second screen such as a touch screen control device  116 . The touch screen control device  116  may be adapted to provide user control for the receiving device  108  and/or the display device  114 . The touch screen device  116  may also be capable of displaying video content. The video content may be graphics entries, such as user interface entries, or may be a portion of the video content that is delivered to the display device  114  The touch screen control device  116  may interface to receiving device  108  using any well-known signal transmission system, such as infra-red (IR) or radio frequency (RF) communications and may include standard protocols such as infra-red data association (IRDA) standard, Wi-Fi, Bluetooth and the like, or any other proprietary protocols. 
         [0030]    In the example of  FIG. 1 , the system  100  also includes a back end server  118  and a usage database  120 . The back end server  118  includes a personalization engine that analyzes the usage habits of a user and makes recommendations based on those usage habits. The usage database  120  is where the usage habits for a user are stored. In some cases, the usage database  120  may be part of the back end server  118 . In the present example, the back end server  118  (as well as the usage database  120 ) is connected to the system the system  100  and accessed through the second delivery network  112 . 
         [0031]    Referring now to  FIG. 2 , a block diagram of an embodiment of a receiving device  200  is shown. Receiving device  200  may operate similar to the receiving device described in  FIG. 1  and may be included as part of a gateway device, modem, set-top box, or other similar communications device. The device  200  shown may also be incorporated into other systems including an audio device or a display device. In either case, several components necessary for complete operation of the system are not shown in the interest of conciseness, as they are well known to those skilled in the art. In the device  200  shown in  FIG. 2 , the content is received by an input signal receiver  202 . The input signal receiver  202  may be one of several known receiver circuits used for receiving, demodulation, and decoding signals provided over one of the several possible networks including over the air, cable, satellite, Ethernet, fiber and phone line networks. The desired input signal may be selected and retrieved by the input signal receiver  202  based on user input provided through a control interface or touch panel interface  222 . Touch panel interface  222  may include an interface for a touch screen device. Touch panel interface  222  may also be adapted to interface to a cellular phone, a tablet, a mouse, a high end remote or the like. 
         [0032]    The decoded output signal is provided to an input stream processor  204 . The input stream processor  204  performs the final signal selection and processing, and includes separation of video content from audio content for the content stream. The audio content is provided to an audio processor  206  for conversion from the received format, such as compressed digital signal, to an analog waveform signal. The analog waveform signal is provided to an audio interface  208  and further to the display device or audio amplifier. Alternatively, the audio interface  208  may provide a digital signal to an audio output device or display device using a High-Definition Multimedia Interface (HDMI) cable or alternate audio interface such as via a Sony/Philips Digital Interconnect Format (SPDIF). The audio interface may also include amplifiers for driving one more sets of speakers. The audio processor  206  also performs any necessary conversion for the storage of the audio signals. 
         [0033]    The video output from the input stream processor  204  is provided to a video processor  210 . The video signal may be one of several formats. The video processor  210  provides, as necessary, a conversion of the video content based on the input signal format. The video processor  210  also performs any necessary conversion for the storage of the video signals. 
         [0034]    A storage device  212  stores audio and video content received at the input. The storage device  212  allows later retrieval and playback of the content under the control of a controller  214  and also based on commands, e.g., navigation instructions such as fast-forward (FF) and rewind (Rew), received from a user interface  216  and/or touch panel interface  222 . The storage device  212  may be a hard disk drive, one or more large capacity integrated electronic memories, such as static RAM (SRAM), or dynamic RAM (DRAM), or may be an interchangeable optical disk storage system such as a compact disk (CD) drive or digital video disk (DVD) drive. 
         [0035]    The converted video signal, from the video processor  210 , originating either from the input or from the storage device  212 , is provided to the display interface  218 . The display interface  218  further provides the display signal to a display device of the type described above. The display interface  218  may be an analog signal interface such as red-green-blue (RGB) or may be a digital interface such as HDMI. It is to be appreciated that the display interface  218  can generate the various screens for presenting the search results in a three dimensional gird as will be described in more detail below. 
         [0036]    The controller  214  is interconnected via a bus to several of the components of the device  200 , including the input stream processor  202 , audio processor  206 , video processor  210 , storage device  212 , and a user interface  216 . The controller  214  manages the conversion process for converting the input stream signal into a signal for storage on the storage device or for display. The controller  214  also manages the retrieval and playback of stored content. Furthermore, as will be described below, the controller  214  performs searching of content and the creation and adjusting of the gird display representing the content, either stored or to be delivered via the delivery networks, described above. 
         [0037]    The controller  214  is further coupled to control memory  220  (e.g., volatile or non-volatile memory, including RAM, SRAM, DRAM, ROM, programmable ROM (PROM), flash memory, electronically programmable ROM (EPROM), electronically erasable programmable ROM (EEPROM), etc.) for storing information and instruction code for controller  214 . Control memory  220  may store instructions for controller  214 . Control memory may also store a database of elements, such as graphic elements containing content. The database may be stored as a pattern of graphic elements. Alternatively, the memory may store the graphic elements in identified or grouped memory locations and use an access or location table to identify the memory locations for the various portions of information related to the graphic elements. Further, the implementation of the control memory  220  may include several possible embodiments, such as a single memory device or, alternatively, more than one memory circuit communicatively connected or coupled together to form a shared or common memory. Still further, the memory may be included with other circuitry, such as portions of bus communications circuitry, in a larger circuit. 
         [0038]    Referring now to  FIG. 3 , the user interface process of the present disclosure employs an input device that can be used to express functions, such as fast forward, rewind, etc. To allow for this, a tablet or touch panel device  300  (which is the same as the touch screen device  116  shown in  FIG. 1 ) may be interfaced via the user interface  216  and/or touch panel interface  222  of the receiving device  200 . The touch panel device  300  allows operation of the receiving device or set top box based on hand movements, or gestures, and actions translated through the panel into commands for the set top box or other control device. In one embodiment, the touch panel  300  may simply serve as a navigational tool to navigate the grid display. In other embodiments, the touch panel  300  will additionally serve as the display device allowing the user to interact directly with the navigation through the grid display of content. The touch panel device may be included as part of a remote control device containing more conventional control functions such as activator buttons. The touch panel  300  can also include at least one camera element. As described in further detail below, content displayed on the touch panel device  300  may be zapped or thrown to the main screen (e.g., display device  114  shown in  FIG. 1 ). 
         [0039]    Referring now to  FIG. 4 , the use of a gesture sensing controller or touch screen, such as that shown above, provides for a number of types of user interaction. The inputs from the controller are used to define gestures and the gestures, in turn, define specific contextual commands. The configuration of the sensors may permit defining movement of a user&#39;s fingers on a touch screen or may even permit defining the movement of the controller itself in either one dimension or two dimensions. Two-dimensional motion, such as a diagonal, and a combination of yaw, pitch and roll can be used to define any 4-dimensional motion, such as a swing. A number of gestures are illustrated in  FIG. 4 . Gestures are interpreted in context and are identified by defined movements made by the user. 
         [0040]    Bumping  420  is defined by a two-stroke drawing indicating pointing in one direction, either up, down, left or right. The bumping gesture is associated with specific commands in context. For example, in a Time Shifting mode, a left-bump gesture  420  indicates rewinding, and a right-bump gesture indicates fast-forwarding. In other contexts, a bump gesture  420  is interpreted to increment a particular value in the direction designated by the bump. Checking  440  is defined as in drawing a checkmark. It is similar to a downward bump gesture  420 . Checking is identified in context to designate a reminder, user tag or to select an item or element. Circling  440  is defined as drawing a circle in either direction. It is possible that both directions could be distinguished. However, to avoid confusion, a circle is identified as a single command regardless of direction. Dragging  450  is defined as an angular movement of the controller (a change in pitch and/or yaw) while pressing a button (virtual or physical) on the tablet  300  (i.e., a “trigger drag”). The dragging gesture  450  may be used for navigation, speed, distance, time-shifting, rewinding, and forwarding. Dragging  450  can be used to move a cursor, a virtual cursor, or a change of state, such as highlighting outlining or selecting on the display. Dragging  450  can be in any direction and is generally used to navigate in two dimensions. However, in certain interfaces, it is preferred to modify the response to the dragging command. For example, in some interfaces, operation in one dimension or direction is favored with respect to other dimensions or directions depending upon the position of the virtual cursor or the direction of movement. Nodding  460  is defined by two fast trigger-drag up-and-down vertical movements. Nodding  460  is used to indicate “Yes” or “Accept.” X-ing  470  is defined as in drawing the letter “X.” X-ing  470  is used for “Delete” or “Block” commands. Wagging  480  is defined by two trigger-drag fast back-and-forth horizontal movements. The wagging gesture  480  is used to indicate “No” or “Cancel.” 
         [0041]    Depending on the complexity of the sensor system, only simple one-dimensional motions or gestures may be allowed. For instance, a simple right or left movement on the sensor as shown here may produce a fast forward or rewind function. In addition, multiple sensors could be included and placed at different locations on the touch screen. For instance, a horizontal sensor for left right movement may be placed in one spot and used for volume u/down, while a vertical sensor for up down movement may be place in a different spot and used for channel up/down. In this way, specific gesture mappings may be used. As discussed in further detail below, a two finger swipe gesture may be utilized to initiate the throwing or moving of content from the tablet  300  to the main screen or display device  114 . 
         [0042]    Referring now to  FIG. 5 , a method is shown that may be implemented by, e.g., a content distribution service, an online market service, etc. (e.g., content manager  110  or the broadcast affiliate manager  104 ) to ascertain information about multiple users associated with a single account using binary feedback information. 
         [0043]    Block  502  receives a set of binary labels as an input. These labels are provided by one or more users sharing an account and are associated with a set of items. For example, the items in question may be movies, and the labels can indicate whether the account has viewed these movies or not. Alternatively, the items could be products advertised to the account and the labels may indicate whether the account purchased the products or not. The label for an item i is denoted herein as y i . 
         [0044]    Block  504  receives a set of item descriptors, one of each of labeled item. These descriptors could be, e.g., vectors describing the genre or actors participating in a movie or other features of the product advertised. This feature descriptor may be represented as a vector of real-valued numbers of dimension d (where d is the number of features). The descriptor of item i will be shown herein as x i . 
         [0045]    Using this information, block  506  estimates the mean and covariance of the underlying features x i . To do this, block  506  constructs estimates of the feature mean and covariance over the features and labels. A standard Gaussian version of the features may then be constructed as {circumflex over (Σ)} −1/2 (X i −{circumflex over (μ)}), where {circumflex over (Σ)} is the covariance and {circumflex over (μ)} is the feature mean. 
         [0046]    Using the calculated estimates, block  508  identifies a vector r that belongs to a convex code spanned by the vectors profiling each user. The vector may be calculated as 
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         [0000]    where n is the number of labels, and this vector lies in the interior of the convex cone spanned by the parameter profiles. The vector r may then be used to perform a mirroring operation, where all labels lying in the negative half space determined by r are flipped, for example by changing +1 to −1 and −1 to +1 in block  510 . The flipped labels are denoted herein by Z i . 
         [0047]    Block  512  computes a weighted covariance matrix Q over all x i , where each point&#39;s contribution is weighed by the mirrored labels. The matrix Q is determined as 
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         [0000]    The spectrum of Q has a specific structure that reveals the span of the users. In particular, Q converges to a matrix that contains an eigenvalue with multiplicity n-k, where n is the number of labels and k is a number of remaining eigenvalues. 
         [0048]    Block  514  calculates eigenvectors and eigenvalues of the matrix Q. Most eigenvalues of Q will be equal to each other (i.e., a number of eigenvalues having multiplicity n-k), but a small number of eigenvalues will differ. The standout eigenvalues are calculated by finding the median value of all the eigenvalues and identifying the k values furthest from the median. The number of eigenvalues that “stand out” in this respect is interpreted as being a number of users associated with the account. The eigenvectors corresponding to the stand-out eigenvalues yield the span of the user profiles. Block  516  rotates the eigenvectors by multiplying by to obtain the span and outputs these quantities. The resulting span is a set of vectors that are in the subspace defined by all linear combinations of the vectors. 
         [0049]    The span output by block  516  can be used for several tasks. For example, the span may be used to predict a label for an item given a new feature vector (in other words, predicting whether a user would watch this movie). The span may also be used for clustering, allowing the content provider to identify which user associated with an account generated a particular label. Any algorithm that does either clustering or prediction will run with improved accuracy if one first projects the features to the span defined by profiles. Using such information allows the content provider to make a recommendation using well known techniques. For example, if a user choose a movie with a certain actor, the content provider could recommend other movies with that actor. 
         [0050]    These and other features and advantages of the present principles may be readily ascertained by one of ordinary skill in the pertinent art based on the teachings herein. It is to be understood that the teachings of the present principles may be implemented in various forms of hardware, software, firmware, special purpose processors, or combinations thereof. 
         [0051]    Most preferably, the teachings of the present principles are implemented as a combination of hardware and software. Moreover, the software may be implemented as an application program tangibly embodied on a program storage unit. The application program may be uploaded to, and executed by, a machine comprising any suitable architecture. Preferably, the machine is implemented on a computer platform having hardware such as one or more central processing units (“CPU”), a random access memory (“RAM”), and input/output (“I/O”) interfaces. The computer platform may also include an operating system and microinstruction code. The various processes and functions described herein may be either part of the microinstruction code or part of the application program, or any combination thereof, which may be executed by a CPU. In addition, various other peripheral units may be connected to the computer platform such as an additional data storage unit and a printing unit. 
         [0052]    It is to be further understood that, because some of the constituent system components and methods depicted in the accompanying drawings are preferably implemented in software, the actual connections between the system components or the process function blocks may differ depending upon the manner in which the present principles are programmed. Given the teachings herein, one of ordinary skill in the pertinent art will be able to contemplate these and similar implementations or configurations of the present principles. 
         [0053]    Although the illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the present principles is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the scope or spirit of the present principles. All such changes and modifications are intended to be included within the scope of the present principles as set forth in the appended claims.

Technology Category: g