Abstract:
The present invention relates to electronic books that are accessed over a computer network, such as the Internet. One embodiment of the invention relates to a shared electronic book, i.e. a book in which multiple users each have the right to access the book but only one of the users is allowed to actually access the book at a given point in time. Another embodiment of the invention relates to the detection of potentially fraudulent access of an electronic book. Yet a further embodiment of the invention is concerned with preventing electronic copying of an electronic book when the book is provided to users over an intranet that is not under the direct control of the provider of the electronic book.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    The present application is a divisional application of U.S. patent application Ser. No. 09/006,815. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to electronic books that are transmitted over a network, such as the Internet, to a user&#39;s personal computer or work station.  
         BACKGROUND OF THE INVENTION  
         [0003]    Presently, an individual with a personal computer can access web sites on the Internet of book stores. At such a web site, a user can search for a particular book or type of book, view a selection of books that meet the user&#39;s search criteria, and order a copy of one or more books that are identified in the searching process, which are then sent to the user&#39;s address. This type of system works well for consumer oriented books. However, this system does not work well for books that are frequently updated. Examples of frequently updated books include the reference books that are used in the legal, banking and insurance industries. These books are periodically updated to reflect changes in the laws that govern these industries. For these types of books, web sites have evolved that allow a customer to take out a subscription on a book of interest. The customer can then access the most recent edition of this book from the web site and view selected pages of the book on their personal computer or workstation. Books that are accessed in this fashion are typically referred to as “electronic” books.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention is directed to a problem that was identified with respect to the current systems that allow customers to subscribe to “electronic” books. The problem involved the need for several individuals in an organization to have access to a particular electronic book. Under the prior subscription system, this need required the organization to purchase a separate subscription for each individual that required access to the particular book. As a consequence, each individual with a subscription was able to access their own individual copy of the book at any time.  
           [0005]    The present invention recognizes that in many situations not all of the individuals in an organization need to have unlimited access to the book, i.e. be able to access the book at any time, and addresses these situations by providing several individuals with the right to access an electronic book but limiting the actual access of the book to one individual at a time. In other words, the invention provides an electronic book that can be shared by a number of users.  
           [0006]    The present invention addresses a number of problems associated with providing shared access to an electronic book. In providing shared access to an electronic book over the Internet or an intranet, it was recognized that there is no provision for determining when an individual&#39;s exclusive access to or use of an electronic book has terminated or should be considered to have terminated. Without the ability to determine if termination has occurred or to effect termination, the book cannot be provided to other users that have a right to access the book. Further, while it is possible to provide a mechanism that permits the user to explicitly release the book so that the book can be used by others, such a mechanism is unreliable because it depends on the user to execute the release. The present invention address this problem by making use of a “cookie”, i.e. a temporary identifier that is assigned to a user when the user accesses a web site and is used in communications between the user and the web server. The “cookie” is part of the WorldWideWeb/Internet protocol and was included in the protocol to provide a web server with the ability to keep track of the “state” of communications between the web server and all of the users that are accessing the web server. In essence, the “cookie” is a unique, temporary identifier that is assigned to each user that is accessing a web server. In contrast to the “state” tracking use of the “cookie”, the present invention makes use of the “cookie” mechanism to terminate a user&#39;s exclusive use of a book, thereby permitting other users to access the book. To elaborate, upon accessing the web server on which the shared electronic book is located, a user is assigned a “cookie” for use in subsequent communications with the web server. The user is then able to request access to a shared electronic book. If the shared electronic book is available, the user is granted exclusive access to the book for a predetermined period of time. Each request that the user transmits to the web server with respect to the book during this predetermined period of time is accompanied by the “cookie” assigned to the user. If the web server does not see the “cookie” assigned to the user accompanying a request with respect the book to which the user has been granted exclusive access within the predetermined period of time or some portion thereof, the user&#39;s exclusive access to the shared electronic book is terminated upon expiration of the predetermined period of time. At this point, the book is again available to all users that have a right to access the book.  
           [0007]    To facilitate termination of a particular user&#39;s exclusive access to a shared electronic book when the user only needs to refer to the book quickly and for a brief period of time, and thereby make the book available to the other users, one embodiment of the invention involves releasing the book from a particular user upon expiration of the predetermined period of time if the “cookie” and associated request relating to the book are not received within a portion of the predetermined period of time that commences after the predetermined period of time starts. For example, a particular user is granted exclusive access to a shared book for 30 minutes and the noted portion of the  30  minute period is defined to be the last 15 minutes of the 30 minute period. If a “cookie” relating to the book is not seen in the last 15 minutes of the 30 minute period, the user&#39;s access to the book is terminated upon expiration of the 30 minute period, even if a “cookie” was seen in the first 15 minutes of the 30 minute period. This assures that when a user that has been granted exclusive access to a book only needs to access the book quickly and for a short period of time, other users are not foreclosed from obtaining access to the shared book for an extended period of time.  
           [0008]    In another embodiment, a user is able to renew or extend the period of time during which they have exclusive access to a shared electronic book. Again, the user is granted exclusive access to a shared electronic book for a predetermined period of time. If a “cookie” and associated request relating to the book are seen during the predetermined period of time, the user is granted a further period of exclusive access to the book. For example, if the user is initially granted a 30 minute period of exclusive access to a book and a “cookie” with an associated request relating to the book is seen by the web server during this 30 minute period, the user is granted a further period of exclusive access to the book.  
           [0009]    A further embodiment addresses the concerns of (1) providing a user that has been granted exclusive access to a shared electronic book with the ability to renew or extend the period during which they have exclusive access to the book and (2) not foreclosing other users from having access to a shared electronic book when a user that has been granted exclusive access to a book only needs to refer to the book quickly and for a short period of time. This embodiment of the invention only renews or extends a user&#39;s exclusive access to a shared book if a “cookie” and associated request relating to the book are received during a portion of the predetermined period of time that commences after the predetermined period of time commences. To continue with the prior example, if a “cookie” and associated request relating to the book are seen in the last 15 minutes of the 30 minute period, the period of exclusive access is extended for a further period of time. If, on the other hand, “cookie” and associated request relating to the book are not seen in the last 15 minutes of the 30 minute period, the book is released. This release occurs even if a “cookie” and associated request relating to the book are seen in the first 15 minutes of the 30 minute period.  
           [0010]    To address the possibility of a user being able to continually renew their exclusive access to a shared book so that the ability of the other users to access the book is undesirably inhibited, another embodiment reduces the length of the renewal periods as the number of renewals increases. In an alternative embodiment, the number of “cookies” and associated requests that must be seen during the period when a user has exclusive access to a share book in order to obtain a renewal is increased as the number of renewals increases. In a further embodiment, users are pre-assigned a priority code. If a user requests a book and is denied access because another user with a lower priority has exclusive access, the user with the lower priority will not be granted a renewal, and at the point that the book again becomes available, the user with the higher priority is granted exclusive access to the book for a period of time. In yet a further embodiment, if a user has been granted exclusive access to a book and some predetermined number of other users have requested access to the book and been denied access during the user&#39;s exclusive access period, the user will not be granted a renewal. When the user&#39;s exclusive access period expires and the book will then become available to the other users.  
           [0011]    Another problem that is related to providing shared access to an electronic book and the type of access in a which a user can access their own copy of a particular electronic book at any time is the misappropriation or unauthorized sharing an authorized user&#39;s password and the subsequent use of the password to obtain unauthorized access to an electronic book. The present invention addresses this problem in the Internet/intranet situation by making use of the “cookie” to identify situations in which it is likely that one or more individuals are fraudulently obtaining access to a particular electronic book. It should be appreciated that at the point in the process during which “cookies” are issued it is difficult to distinguish the situation in which an authorized user is alternately accessing an electronic book from two different computers and the situation in which two different users, at least one of which is an unauthorized user, are accessing the electronic book. Consequently, if two individuals at two different personal computers or work stations are using an authorized user&#39;s password to access an electronic book, each user will be issued a unique “cookie”. For example, the first user at the first personal computer will be issued “cookie01” and the second user at the second personal computer will be issued “cookie02”. As previously noted, a “cookie” accompanies each communication from a user to the web server. The present invention looks for a pattern in the timing of the two unique “cookies” or, stated differently, at the timing of the communications coming from the first and second personal computers to identify situations in which it is likely that at two different individuals are using a single authorized user&#39;s password to access an electronic book  
           [0012]    In one embodiment, it is assumed that two communications containing a particular “cookie” define the endpoints of a period of time during which a first individual is accessing one or more electronic books. If the periods of time associated with the two unique cookies that have been issued to what appears to be a single authorized user overlap, then this is considered to be indicative of the situation where an unauthorized user is obtaining access to a particular electronic book. For example, if (1) “cookie01” is first received at time “t1” and later received at time “t2”; (2) “cookie02” is first received at time “t3” and later received at time “t4”; (3) time “t3” occurs between times “t1” and “t2”; and (4) time “t4” is later than time “t2”, then there is an overlap that is indicative of fraud. In certain situations, however, such an overlap can still be associated with the situation in which a single authorized user is alternately using two different computers to access one or more books. To address this situation, a further constraint is used that the overlap happen over a relatively short period of time during which it is unlikely that a single authorized user is alternatingly using two different computers. To continue with the example, if the difference between times “t2” and “t3” is less than a predetermined period of time and there is an overlap, fraud is presumed.  
           [0013]    In another embodiment, the time at which the two different “cookies” are received is combined with information related to the distance between personal computers with fixed locations to identify a situation in which fraud is likely to be occurring. To elaborate, this embodiment is based upon the assumption that fraud is likely to be occurring when the difference in times of the two unique “cookies” that define the endpoints of the overlap is less than the time it would reasonably take for the authorized user to travel between the locations of the two computers. To continue with the prior example, if the difference between times “t2” and “t3” is less than the time it would reasonably take for an individual to travel between the fixed locations of the first and second personal computers, then it is likely that an unauthorized individual is accessing the electronic book.  
           [0014]    Another problem that is addressed by the present invention involves the situation in which an organization has purchased two or more separate subscriptions to the same electronic book for individuals within the organization and the book is available to the users over an intranet rather than the Internet. An intranet is essentially a localized version of the Internet in which an organization has a web server, a number of personal computers that each has a web browser, and a network for conducting communications between the web server and the personal computers. In the intranet situation, the electronic book is located on the organization&#39;s web server and therefore out of the direct control of the provider of the book. In this case, it is necessary to make it difficult for the electronic book to be electronically copied.  
           [0015]    The present invention addresses this problem by encrypting the electronic book and only decrypting the pages or portions of the electronic book for as long as it takes to service all of the requests for access to pages or portions of the book. Once all of the requests have been serviced, the pages of portions of the electronic book that have decrypted are then re-encrypted. With this protection scheme, unauthorized electronic copying of the electronic book becomes difficult and if possible, likely to be quite expensive. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a block diagram of a web server, a plurality of personal computers or work stations that each has a web browser, and the Internet/internet for conveying communications between each of the plurality of personal computers and the web browser;  
         [0017]    [0017]FIG. 2A shows the display, as seen on a subscriber&#39;s monitor, of the subscriber&#39;s personal “bookshelf” and the subscriber&#39;s shared “bookshelf”;  
         [0018]    [0018]FIG. 2B shows the display, as seen on a subscriber&#39;s monitor, of two pages of one of the books from the subscriber&#39;s shared bookshelf;  
         [0019]    [0019]FIG. 3 is a flowchart of the decision process performed in the electronic bookshelf web server to assure that a shared electronic book that is reserved for a particular user will become available to other users that have the right to access the shared book under certain circumstances and to assure that a user can extend their period of exclusive use of the shared electronic book under certain circumstances;  
         [0020]    [0020]FIG. 4 illustrates an overlap in the pattern in which two “cookies” are being used that is indicative of someone obtaining fraudulent access to the electronic books.  
         [0021]    [0021]FIG. 5 is a flowchart of the events that occur in identifying unauthorized access to the electronic bookshelf by an unauthorized individual who has obtained the username and password of an authorized user; and  
         [0022]    [0022]FIGS. 6A and 6B are flowcharts illustrating the steps used to deter copying of an electronic book that is provided to subscribers over an intranet. 
     
    
     DETAILED DESCRIPTION  
       [0023]    [0023]FIG. 1 generally illustrates a computer network system for providing electronic books to a plurality of subscriber&#39;s computers or computer terminals, which is hereinafter referred to as system  10 . The system  10  includes an electronic book web server  12 , a plurality of subscriber computers or computer terminals  14 , and an Internet system  16  for conveying communications between the server  12  and each of the subscriber computers  14 . The electronic book web server  12  includes or has access to the electronic books that are provided to the subscriber computers  14  via the Internet. In addition, the server  12  has software for managing the communications with the subscriber computers  14 . The subscriber computers  14  can be personal computers, work stations, web televisions or any other type of machine that is capable of communicating with the server  12 . Generally, the subscriber computers  14  each include a web browser, a monitor and some kind of input device, like a keyboard or mouse. In addition, the subscriber computers  14  are each equipped with software for use in viewing the electronic books provided by the server  12 . The Internet systems  16  includes a server I/O interface  18  for facilitating communications from the subscriber computers  14  to the server  12  and from the server  12  to the subscriber computers  14 . Likewise, a subscriber I/O interface  20  conveys communications from the server  12  to the subscriber computers  14  and from the subscriber computers  14  to the server  12 . Generally, the function of the server I/O interface  18  and/or the subscriber I/O interface  20  is provided by an internet server provider (ISP). The Internet system  16  operates on a number of different levels. The level presently being used to communicate electronic book related information is the World Wide Web (www).  
         [0024]    The World Wide Web operates according to a predetermined protocol. Part of this protocol is what is termed a “cookie.” A cookie is a unique identifier that is assigned to a computer when the computer initially accesses a web server. The cookie permits the web server to keep track of the state of communications between the server and the computer in subsequent communications.  
         [0025]    [0025]FIG. 2A illustrates a library display  24  that is typically seen on the monitor of a subscriber computer  14  after a subscriber obtains access to the server  12 . The display  24  includes a personal library portion  26  that shows all of the electronic books that the subscriber can access at any time, i.e. does not share with another subscriber. Also part of the display  24  is a shared library portion  28  that illustrates all of the electronic books that the subscriber shares with other subscribers, i.e. has the right to access but cannot access at the same time as another subscriber is accessing the book.  
         [0026]    [0026]FIG. 2B illustrates an electronic book display  32  that is typically seen on the monitor of the subscriber computer  14  after the subscriber has selected a book for viewing from either the personal library portion  26  or the shared library portion  28  of the library display  24 . The book display includes apage display  34  that shows one or more pages of the selected book.  
         [0027]    With reference to FIG. 3, the operation of the web server  12  is discussed with respect to the situation in which several subscribers share a particular electronic book. In particular, the communications between the server  12  and subscriber computer  14  that relate to (1) termination of a subscriber&#39;s exclusive access to an electronic book so that the other subscribers that have the right to access the book have an opportunity to do so; and (2) the ability of a subscriber to renew or continue their exclusive access to a book. Initially, the subscriber must obtain access to the server  12 . This is accomplished by using the Internet system  16  to transmit a username and password from a subscriber computer  14  to the server  12 . If the username and password are valid, the server  12  assigns a “cookie” (unique id) to the subscriber and transmits the cookie to the subscriber computer  14  via the internet system  16 . Subsequently, the subscriber uses the subscriber computer  14  to communicates a request, which includes the cookie, to the server  12  for access to a particular shared book. If the book is available, i.e. not presently allocated to another subscriber, the server  12  conveys a message to the subscriber computer  14  via the Internet system  16  that the subscriber has been granted exclusive access to the book. Subsequently, the subscriber user the subscriber computer  14  to submit requests to the server  12  that particular pages of the selected book be sent to the subscriber computer  14 .  
         [0028]    The subsequent requests, which each include the cookie assigned to the subscriber computer  14 , are analyzed by the server  12  for determining whether or not to terminate the subscriber&#39;s exclusive access to the book and for determining whether or not to extend the period of the subscriber&#39;s exclusive access. To elaborate, when the server  12  initially grants the subscriber exclusive access to the book, the subscriber is only granted a predetermined period of exclusive access. For example, the server  12  may grant the subscriber a  30  minute period of exclusive access to the selected book. If the server  12  does not receive a request with the noted cookie from the user within this predetermined period of time, the server  12  revokes the subscribers exclusive access to the book, thereby making the book available to other subscribers.  
         [0029]    To facilitate termination of a particular subscriber&#39;s exclusive access to a book when the subscriber only needs to access the book for quick and brief period of time, the subsequent requests transmitted from the subscriber computer  14  to the server  12  via the Internet system  16  are further analyzed. Specifically, if the server  12  does not receive a subsequent request from the subscriber computer  14  within the later portion of the period of time during which the subscriber has exclusive access to the book, the server  12  terminates the subscriber&#39;s exclusive access to the book upon expiration of the predetermined period.  
         [0030]    In many cases, the subscriber needs to make use of the selected book for more than the predetermined period of time. In such situations, it is desirable to provide a mechanism for the subscriber to extend the period during which they have exclusive access to the book. As shown in FIG. 3, if the server  12  receives a subsequent request from the subscriber within the predetermined time that the subscriber has been granted exclusive access, the subscriber&#39;s period of exclusive access is extended. To accommodate the need to terminate the subscriber&#39;s exclusive privilege when the subscriber only needs to view the book for a quick and brief period of time and the need to extend the period of exclusive access to the book, the server  12  operates so as to only extend the period of exclusive access if a subsequent request from the subscriber is received within the later portion of the predetermined period of exclusive access.  
         [0031]    To address the possibility that a subscriber is obtaining an inordinate number of extensions to their period of exclusive access, the conditions under which the server  12  grants extensions are modified. For example, the server  12  can require that more requests be received and/or the reduce the period of time when one or more requests must be received to obtain an extension. Alternatively, the server  12  can reduce the period of an extension as the number of extensions increases. A further alternative is to pre-assign users a priority code. The server  12  then uses this priority to determine whether or not to renew a user&#39;s exclusive access to a book Specifically, the server  12  will not renew a lower priority user&#39;s exclusive access if a higher priority user has requested exclusive access to the book during the lower priority user&#39;s period of exclusive access to the book. Another method that the server  12  can utilize to address this problem is to deny renewal of a user&#39;s exclusive access to a book if a predetermined number of other users have requested access to the book during the user&#39;s period of exclusive access.  
         [0032]    While the server  12  has been described as monitoring the period that a subscriber has exclusive access period to a book or portion thereof, another embodiment of the system  10  downloads both the book or a portion of the book and the viewing software to the subscriber computer  14 . In this embodiment, the viewing software monitors the period or periods of exclusive access to the book that are accorded to the subscriber as previously described. Specifically, the viewing software disallows viewing of the book or portion of the book that has been downloaded onto the subscriber computer  14  if the subscriber explicitly terminates exclusive access to the book or the period of exclusive access has expired. In the situation in which the subscriber explicity terminates exclusive access, the viewing software establishes a communication link with the server  12  via the Internet  16  and then informs the server  12  that the subscriber has terminated their exclusive access to the book. Expiration of the period of exclusive access is monitored by both the server  12  and the viewing software. The server  12 , upon detecting expiration of the exclusive access period, makes the book available to other subscribers. The viewing software, upon detecting expiration of the exclusive access period, prevents the subscriber from viewing the downloaded book or portion thereof.  
         [0033]    The conditions under which a subscriber&#39;s exclusive access is renewed are the same as described hereinabove. However, the manner in which renewal occurs involves the viewing software establishing a communication between the subscriber computer  14  to the server  12  via the Internet  16  and then communicating with the server  12  concerning renewal of the subscriber&#39;s exclusive access to the book. For example, the server  12  may have determined that a higher priority user is waiting to access the book and inform the subscriber computer  14  that the renewal is being denied. In this case, the viewing software operates to disallow viewing of the relevant book just as if the subscribers period of exclusive access had expired.  
         [0034]    With reference to FIGS. 4 and 5, the present invention also addresses the problem of one or more persons obtaining the information, such as a password, that an authorized subscriber uses to access the server  12  and using this information to obtain unauthorized access to electronic books provided by the server  12 . The server  12  addresses this problem by again making use of the cookies received from two subscriber computers  14  where the individual or individuals associated with the subscriber computers  14  obtained access to the server  12  using a valid subscriber&#39;s access information. Specifically, the server  12  looks for a pattern in the cookies received from the two subscriber computers  14  that is indicative of fraud. With particular reference to FIGS. 4 and 5, when one or more individuals uses two different subscriber computers  14  to obtain access to the server  12 , the two subscriber computers  14  are each assigned a unique cookie for the subsequent communications. For example, one of the subscriber computers  14  could be assigned “cookie01” and the other subscriber computer  14  could be assigned “cookie02”. The server  12  looks for a pattern in these two unique cookies that is indicative of fraud. Specifically, the server  12  defines a session for the first subscriber computer  14  as the time between the receipt of two consecutive cookies. Likewise, a session for the second subscriber computer  14  is defined by the server  12  to be the time between two consecutive cookies. If there is an overlap in the two sessions, the server  12  presumes that someone is fraudulently accessing the server  12 . In this case, the valid subscriber is prevented from accessing the server  12  to view books. Typically, all requests for access that are associated with the suspect password are denied for a specified period of time, after which the user that is the owner of the suspect password is asked/required to change their password. To avoid locking out a valid subscriber that is using two subscriber computers  14  to access the server  12 , the period of overlap that the server  12  uses to make a determination that fraud is likely to be occurring is relatively narrow. For example, the overlap needed for the server  12  to take remedial action may be 5 minutes or less. A possible refinement to the overlap period having to be less than a predetermined period of time in order for the server  12  to conclude the one or more individuals is likely to be fraudulently accessing the server  12  is possible if the locations of the two subscriber computers  14  are fixed. In this case, fraud would be indicated if the overlap period is less than the time it would reasonably take for an individual to travel between the fixed locations of the two subscriber computers  14 .  
         [0035]    With reference to FIG. 6, the present invention also addresses the problem of unauthorized copying of the electronic books when the system is implemented in an intranet or local network environment in which the provider of the electronic book does not have direct control over the access to the electronic books. In this situation, copying is deterred by encrypting the electronic books and decrypting an electronic book or portion thereof only for the period of time during which there are pending requests for access to the book. Once there are no requests for access to the electronic book, the book or portion thereof is re-encrypted. With reference to FIG. 6A, this methodology is implemented by initializing a counter to 0 in the server  12  before any requests for access to a particular electronic book are serviced. The counter is used to keep track of requests that are potentially being simultaneously processed by multiple versions or threads of the process illustrated in FIG. 6B. It should also be appreciated that because the counter provides this tracking function, operations involving the counter, such as incrementing and decrementing the counter, are atomic, i.e. cannot be interrupted.  
         [0036]    With reference to FIG. 6B, each request for access to a particular electronic book cause a separate thread or version of the illustrated process to commence. Initially, the validity of the request is tested by assessing whether the requesting subscriber has the right to access the book. If the request is invalid, the process terminates. If, on the other hand, the request is valid, the counter is incremented and tested to determine if the counter is equal to one. When the counter is first incremented, i.e. goes from a value of 0 to a value of 1, the electronic book or relevant portion of the book are decrypted and provided to the first subscriber that submitted a request. After the decrypted electronic book or portion of the book has been provided to a first requesting subscriber, the counter is decremented. If there are other outstanding requests for access to the relevant portion of the book (i.e. if the counter is still greater than 0) after the first requesting subscriber has been serviced, the decrypted book or portion of the book is provided to the next requesting subscriber by a second active version of the illustrated process and so on in FIFO order until all the requests have been serviced. Once all the requests have been serviced (i.e. the counter has been decremented such that it is now equal to 0), the last active version of the illustrated process causes the book or relevant portion of the book to be re-encrypted, thereby making it difficult for someone to make unauthorized copies of the electronic book. To further deter copying, the book is encoded with the server&#39;s domain name, and decryption is allowed only on the server whose domain name matches the domain name encoded in the book.  
         [0037]    The foregoing description of the invention has been presented for purposes of illustration and description. Further, the description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and the skill or knowledge in the relevant art are within the scope of the present invention. For example, the inventions are applicable to the Internet, an intranet and other computer networks. Moreover, the inventions, while described with respect to electronic books, are also applicable to other types of read-only data. It should also be appreciated that steps of the various inventions can, in many instances, be performed in different sequences from those described. The preferred embodiment described hereinabove is further intended to explain the best mode known of practicing the invention and to enable others skilled in the art to utilize the invention in various embodiments and with the various modifications required by their particular applications or uses of the invention. It is intended that the appended claims be construed to include alternate embodiments to the extent permitted by the prior art.