A fundamental issue facing the publishing and information industries as they consider electronic publishing is how to prevent the unauthorized and unaccounted distribution or usage of electronically published materials.  Electronically published materials are typically distributed in a digital form and recreated on a computer based system having the capability to recreate the materials.  Audio and video recordings, software, books and multimedia works are all being electronically published.  Companies in these industries receive royalties for each accounted for delivery of the materials, e.g. the sale of an audio CD at a retail outlet.  Any unaccounted distribution of a work results in an unpaid royalty (e.g. copying the audio recording CD to another digital medium.) 
The ease in which electronically published works can be “perfectly” reproduced and distributed is a major concern.  The transmission of digital works over networks is commonplace.  One such widely used network is the Internet.  The Internet is a widespread network facility by which computer users in many universities, corporations and government entities communicate and trade ideas and information.  Computer bulletin boards found on the Internet and commercial networks such as CompuServ and Prodigy allow for the posting and retrieving of digital information.  Information services such as Dialog and LEXIS/NEXIS provide databases of current information on a wide variety of topics.  Another factor which will exacerbate the situation is the development and expansion of the National Information Infrastructure (the NII).  It is anticipated that, as the NII grows, the transmission of digital works over networks will increase many times over.  It would be desirable to utilize the NII for distribution of digital works without the fear of widespread unauthorized copying. 
The most straightforward way to curb unaccounted distribution is to prevent unauthorized copying and transmission.  For existing materials that are distributed in digital form, various safeguards are used.  In the case of software, copy protection schemes which limit the number of copies that can be made or which corrupt the output when copying is detected have been employed.  Another scheme causes software to become disabled after a predetermined period of time has lapsed.  A technique used for workstation based software is to require that a special hardware device must be present on the workstation in order for the software to run, e.g., see U.S. Pat.  No.  4,932,054 entitled “Method and Apparatus for Protecting Computer Software Utilizing Coded Filter Network in Conjunction with an Active Coded Hardware Device.”  Such devices are provided with the software and are commonly referred to as dongles. 
Yet another scheme is to distribute software, but which requires a “key” to enable it's use.  This is employed in distribution schemes where “demos” of the software are provided on a medium along with the entire product.  The demos can be freely used, but in order to use the actual product, the key must be purchased.  These scheme do not hinder copying of the software once the key is initially purchased. 
A system for ensuring that licenses are in place for using licensed products is described in PCT Publication WO 93/01550 to Griswold entitled “License Management System and Method.”  The licensed product may be any electronically published work but is most effective for use with works that are used for extended periods of time such as software programs.  Griswold requires that the licensed product contain software to invoke a license check monitor at predetermined time intervals.  The license check monitor generates request datagrams which identify the licensee.  The request datagrams are sent to a license control system over an appropriate communication facility.  The license control system then checks the datagram to determine if the datagram is from a valid licensee.  The license control system then sends a reply datagram to the license check monitor indicating denial or approval of usage.  The license control system will deny usage in the event that request datagrams go unanswered after a predetermined period of time (which may indicate an unauthorized attempt to use the licensed product).  In this system, usage is managed at a central location by the response datagrams.  So for example if license fees have not been paid, access to the licensed product is terminated. 
It is argued by Griswold that the described system is advantageous because it can be implemented entirely in software.  However, the system described by Griswold has limitations.  An important limitation is that during the use of the licensed product, the user must always be coupled to an appropriate communication facility in order to send and receive datagrams.  This creates a dependency on the communication facility.  So if the communication facility is not available, the licensed product cannot be used.  Moreover, some party must absorb the cost of communicating with the license server. 
A system for controlling the distribution of digitally encoded books is embodied in a system available from VPR Systems, LTD.  of St. Louis, Mo. The VPR system is self-contained and is comprised of: (1) point of sale kiosks for storing and downloading of books, (2) personal storage mediums (cartridges) to which the books are downloaded, and (3) readers for viewing the book.  In a purchase transaction, a purchaser will purchase a voucher card representing the desired book.  The voucher will contain sufficient information to identify the book purchased and perhaps some demographic information relating to the sales transaction.  To download the book, the voucher and the cartridge are inserted into the kiosk. 
The VPR system may also be used as a library.  In such an embodiment, the kiosk manages the number of “copies” that may be checked out at one time.  Further, the copy of the book is erased from the users cartridge after a certain check-out time has expired.  However, individuals cannot loan books because the cartridges may only be used with the owners reader. 
The foregoing distribution and protection schemes operate in part by preventing subsequent distribution of the work.  While this certainly prevents unauthorized distributions, it does so by sacrificing the potential for subsequent revenue bearing uses.  For example, it may be desirable to allow the lending of a purchased work to permit exposure of the work to potential buyers.  Another example would be to permit the creation of a derivative work for a fee.  Yet another example would be to permit copying the work for a fee (essentially purchasing it).  Thus, it would be desirable to provide flexibility in how the owner of a digital work may allow it to be distributed. 
While flexibility in distribution is a concern, the owners of a work want to make sure they are paid for such distributions.  In U.S. Pat.  No.  4,977,594 to Shear, entitled “Database Usage Metering and Protection System and Method,” a system for metering and billing for usage of information distributed on a CD-ROM is described.  The system requires the addition of a billing module to the computer system.  The billing module may operate in a number of different ways.  First, it may periodically communicate billing data to a central billing facility, whereupon the user may be billed.  Second, billing may occur by disconnecting the billing module and the user sending it to a central billing facility where the data is read and a user bill generated. 
U.S. Pat.  No.  5,247,575, Sprague et al.,  entitled “Information Distribution System”, describes an information distribution system which provides and charges only for user selected information.  A plurality of encrypted information packages (IPs) are provided at the user site, via high and/or low density storage media and/or by broadcast transmission.  Some of the IPs may be of no interest to the user.  The IPs of interest are selected by the user and are decrypted and stored locally.  The IPs may be printed, displayed or even copied to other storage medias.  The charges for the selected IP's are accumulated within a user apparatus and periodically reported by telephone to a central accounting facility.  The central accounting facility also issues keys to decrypt the IPs.  The keys are changed periodically.  If the central accounting facility has not issued a new key for a particular user station, the station is unable to retrieve information from the system when the key is changed. 
A system available from Wave Systems Corp. of Princeton, N.Y., provides for metering of software usage on a personal computer.  The system is installed onto a computer and collects information on what software is in use, encrypts it and then transmits the information to a transaction center.  From the transaction center, a bill is generated and sent to the user.  The transaction center also maintains customer accounts so that licensing fees may be forwarded directly to the software providers.  Software operating under this system must be modified so that usage can be accounted. 
Known techniques for billing do not provide for billing of copies made of the work.  For example, if data is copied from the CD-ROM described in Shear, any subsequent use of the copy of the information cannot be metered or billed.  In other words, the means for billing runs with the media rather than the underlying work.  It would be desirable to have a distribution system where the means for billing is always transported with the work.