United States Patent (19)
`Lazarus et al.
`
`54 INTELLIGENTELECTRONIC PROGRAM
`GUIDE MEMORY MANAGEMENT SYSTEM
`AND METHOD
`76 Inventors: David Beryl Lazarus, 7852 Spring
`Ave., Elkins Park, Pa. 19027; Michael
`Dean Ellis, 1300 Kingwood Pl,
`Boulder, Colo. 80304
`
`56
`
`(21) Appl. No.: 476,451
`22 Filed:
`Jun. 7, 1995
`(51
`Int. Cl. .............. H04N 5/50; H04N 7/10
`(52) U.S. Cl. ............................. 348/7; 348/906; 348/569;
`348/460
`58 Field of Search ............................ 348/906, 7,564,
`348/569, 12, 13, 6,460; H04N 5/50, 7/10
`References Cited
`U.S. PATENT DOCUMENTS
`4,706,121 11/1987 Young ..................................... 358/.42
`4,751,578 6/1988 Reiter et al. ...
`... 348/906
`5,038,211
`8/1991 Hallenbeck .....
`... 348/460
`5,465,113 11/1995 Gilboy .......
`... 348/906
`5,532,754 7/1996 Young ........
`... 348/906
`5,559,548 9/1996 Davis et al. ...
`... 348/6
`B1 4,706,121 12/1993 Young .....................
`... 358/.42
`FOREIGN PATENT DOCUMENTS
`WO00670 1/1991 WIPO.
`WO14284 6/1994 WIPO.
`WO29811 12/1994 WIPO :
`
`US005652613A
`Patent Number:
`11
`45 Date of Patent:
`
`5,652,613
`Jul. 29, 1997
`
`OTHER PUBLICATIONS
`
`Cherricks, S. et al., “An Individually Addressable TV
`ReceiverWith Interactive Channel Guide Display, VCR, and
`Cable Box Control", IEEE Transactions on Consumer Elec
`tronics. vol. 40, No. 3, Aug. 1994, pp. 317–328.
`
`Primary Examiner Victor R. Kostak
`Attorney, Agent, or Firm-Weil, Gotshal & Manges LLP
`57
`ABSTRACT
`A television electronic program guide intelligent memory
`management system and method automatically deletes the
`least valuable stored program information at that moment as
`free memory space is needed by the system. In advance of
`a program schedule update, the system executes a two-level
`memory “housekeeping” operation in which the system first
`scans the memory to identify obsolete schedule information.
`If, after this sweep, there is insufficient memory available for
`the next update, the system performs a second-level memory
`"triage" operation wherein schedule information is auto
`matically prioritized in accordance with pre-defined rules for
`assessing the current value of the information to each viewer
`based on program air time, channel and other variables
`relating to program utility. The system then deletes schedule
`information in ascending order of value, starting with the
`least valuable information, and continues until enough space
`is available in memory to store the schedule update.
`
`14 Claims, 2 Drawing Sheets
`
`NTIALIZE
`HOUSEKEEPNG
`ROUTINE
`
`110
`
`FIND+DELETE L-120
`ExPRED
`RECORS
`
`MEMORY TRAGE” 140
`
`
`
`
`
`
`
`
`
`
`
`SUFFCENT
`FREE MEMORY
`
`NITIALIZE
`TRAGE
`
`coMPUTE
`SHOWING
`WALUES
`
`
`
`COMPUTE
`OA
`PROGRAM
`
`
`
`
`
`END
`HOUSEKEEPNG
`ROUNE
`
`WALUABLE
`INFO
`
`-1-
`
`Amazon v. Audio Pod
`US Patent 9,954,922
`Amazon EX-1077
`
`

`

`U.S. Patent
`
`Jul. 29, 1997
`
`Sheet 1 of 2
`
`5,652,613
`
`NITALIZE
`HOUSEKEEPNG
`ROUTINE
`
`-110
`
`
`
`
`
`FIND+DELETE L-120
`EXPRED
`RECORDS
`
`MEMORY "TRAGE” 140
`
`
`
`
`
`SUFFICIENT
`FREE MEMORY
`
`
`
`NTALIZE
`TRAGE
`
`COMPUTE
`SHOWING
`VALUES
`
`PROGRAM
`
`DELETE
`LEAST
`VALUABLE
`INFO
`
`
`
`
`
`
`
`SUFFCENT
`FREE MEMORY
`
`
`
`
`
`
`
`END
`HOUSEKEEPING
`ROUTINE
`
`FG.1
`
`-2-
`
`

`

`U.S. Patent
`
`Jul. 29, 1997
`
`Sheet 2 of 2
`
`5,652,613
`
`VARIABLE NAME
`time period
`time period
`time period
`channel value
`channel value
`channel value
`channel value
`hours away
`hours away
`hours away
`hours away
`
`|
`
`|
`
`|
`
`
`
`
`
`
`
`
`
`
`
`
`
`VALUE
`2
`3
`2
`2
`4
`16
`8
`4
`1
`
`FG.2
`
`||
`
`MEANING
`12AM-6AM
`6AM-7PMOPM2AM
`PM-10PM
`||
`normal
`favorite
`purchased
`purchased favorite
`0-6 hours
`||
`6-12 hours
`12-18 hours
`> 24 hours
`
`
`
`
`
`-3-
`
`

`

`1
`INTELLIGENT ELECTRONIC PROGRAM
`GUIDE MEMORY MANAGEMENT SYSTEM
`AND METHOD
`
`5,652,613
`
`2
`Accordingly, there is a need for an intelligent EPG
`memory management system which takes into account the
`differing utility of the various types of program information
`stored in the EPG so as to maximize the value of the EPG
`to the viewer. One proposed solution to this need is dis
`cussed in U.S. Pat. No. 5,038,211 to Hallenbeck (hereinafter,
`“Hallenbeck”). In the EPG system of Hallenbeck, schedule
`information is transmitted to the viewer in three separate
`transmissions, the first of which is used by a user-configured
`information pre-filter in the EPG to determine whether the
`information in the subsequent transmissions should be
`stored or discarded.
`This selective reception approach to EPG memory man
`agement has at least two drawbacks, however. First, the
`transmission of schedule information must be carried out
`using special protocols, which introduces complexity on the
`service provider's side of the EPG. A second drawbackis the
`pre-filter's inability to ascribe intermediate values of utility
`to program schedule information. By making an initial
`binary determination as to utility (valuable-store; not
`valuable-reject), the EPG of Hallenbeck may prevent
`potentially useful information from reaching the viewer.
`Moreover, the pre-filtering scheme of Hallenbeck does not
`take into account the fact that the value of program infor
`mation will in general vary over time, making a priori
`determinations about the future utility of information inap
`propriate in certain situations. In other words, to the extent
`the EPG of Hallenbeck makes a projection as to the future
`value of program information sent to the viewer when it is
`received, its pre-filtering scheme is likely to be overinclu
`sive as to the information rejected.
`It is therefore one object of the present invention to
`provide an EPG memory management system that does not
`require special transmission protocols. It is a further object
`of the present invention to implement an EPG which initially
`stores the schedule information for the viewer's service area
`and which then permits the program information to assume
`a continuous range of values according to its present utility
`so that the least valuable information stored in memory can
`be identified and deleted on a real-time basis as free memory
`space is needed by the system.
`BRIEF SUMMARY OF INVENTION
`These and other objects are accomplished in accordance
`with the presentinvention by a memory management system
`and method in which program schedule information is sent
`to viewers in a single transmission. The program schedule
`for the corresponding time period is initially stored in the
`EPG memory and is thus available for the viewer's perusal.
`In advance of the next schedule update, the system of the
`present invention executes a two-level memory "housekeep
`ing” operation to make room in memory for the information
`in the update. First, the system performs a high-level scan of
`the memory to identify obsolete schedule information
`(expired programming). If, after this Sweep, there is insuf
`ficient memory available for the next update, the system
`performs a second-level memory "triage” operation wherein
`schedule information is prioritized in accordance with pre
`defined rules for assessing the current value of the informa
`tion to each viewer. The system then deletes schedule
`information in ascending order of value, starting with the
`least valuable information, and continues until enough space
`is available in memory to store the schedule update.
`BRIEF EDESCRIPTION OF THE DRAWNGS
`FIG. 1 is an overview of the memory management opera
`tions implemented by the present invention; and
`
`FIELD OF INVENTION
`The present invention relates to a memory management
`system and method, and, in particular, to an intelligent
`system and method for allocating the finite memory
`resources of a television electronic program guide ("EPG")
`according to the current utility of the program schedule
`information stored in the EPG's memory.
`BACKGROUND OF INVENTION
`There are known EPG systems which provide television
`viewers with on-screen program schedule information in a
`convenient format. In so-called interactive EPGs, the opera
`tion of the EPG is under user control so that the user may
`browse schedule information in any order, select programs
`from on-screen menus for current or future viewing, order
`pay-per-view programming and perform other useful opera
`tions on demand. An example of an advanced EPG system
`is described in co-pending application serial no. 08/119367
`by Bennington, et al., entitled "Electronic Television Pro
`gram Guide Schedule System and Method” (hereinafter,
`"Bennington et at."), incorporated herein by reference.
`Most EPGs operate in the following basic manner: pro
`gram schedule information, and sometimes applications
`and/or systems software, is transmitted to equipment located
`on the viewer's premises (usually a "set-top box”) by way of
`broadcast, cable, direct satellite or some other suitable form
`of transmission. The set-top box contains memory so that the
`program schedule information can be retained for later
`viewing. The program schedule information stored in the
`set-top box is periodically updated (e.g., on a continuous,
`daily, weekly, bi-weekly basis). A programmed microcon
`troller in the set-top box cooperates with the viewer's
`television set to display the stored program schedule infor
`mation and to implement other functions of the EPG in
`response to user-generated signals. The functions available
`will depend on the sophistication of the particular EPG.
`In all such EPGs in which schedule information is stored
`in memory in customer premises equipment, memory stor
`age capacity is a major concern. The size of the memory will
`govern the volume of programming information available
`for the viewer's inspection at any one time and thus directly
`effect the perceived value of the EPG to viewers. Cost and
`physical size considerations place practical limits on the
`storage capacity of the set-top box. Therefore, there must be
`some mechanism for managing this finite resource so as to
`maximize the perceived value of the EPG to the user.
`In this regard, simply deleting program information as it
`becomes outdated to make room for the new program
`schedule information for every available channel in the
`viewer's service area, as in some EPGs proposed, is less than
`optimal in terms of maximizing value to the viewer. The
`most valuable programming information to a given viewer
`will not, in general, correspond to the complete schedule for
`all available channels for the time period covered by the
`information. For instance, schedule information for a pre
`mium channel that the viewer doesn't subscribe to will be of
`lesser interest to the viewer than, say, the schedule infor
`mation for the "major" channels (e.g., ABC, CBS, NBC,
`CNN). If the EPG permits the viewer to load one or more
`“favorite channels” into the EPG, the viewer will obviously
`be more interested in the schedules for those channels than
`others.
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`

`

`25
`
`3
`FIG. 2 is a table of variables and corresponding numerical
`values used to quantify the current value of the schedule
`information held in the EPG's memory.
`DETAILED DESCRIPTION OF APREFERRED
`EMBODIMENT
`The system and method of the present invention may be
`implemented on any suitable EPG platform having storage
`means for storing program schedule information, pro
`grammed processor means for executing a memory man
`10
`agement software program in accordance with the inven
`tion's various memory management functions, and a clock
`for keeping track of the current date and time. The program
`of the present invention may be stored in a separate storage
`means or in a separate portion of the same storage means
`used for the schedule information. The coding of a program
`to carry out the procedures of the present invention will be
`readily apparent to the ordinarily-skilled programmer.
`A suitable platform for implementing the present inven
`tion is the EPG of Bennington, et al., mentioned above.
`Referring to FIG. 1 of Bennington, et al., the program of the
`present invention is loaded into and stored in non-volatile
`memory EEPROM 20. Schedule information in this plat
`form is stored in a database constructed in DRAM 18. As
`explained in Bennington, et al., no special transmission
`protocols are required to send and receive program schedule
`information. Thus, program schedule information for the
`viewer's service area for the corresponding time period may
`be sent to the viewer's set-top box in a single data stream
`transmission and loaded into the database. The specific data
`items held in the schedule database will be discussed below
`in connection with the memory management routines that
`they support. The construction and organization of the
`program schedule database are routine tasks, as the
`ordinarily-skilled artisan will appreciate. Microcontroller 16
`provides a suitable processor means for executing the pro
`gram of the present invention, and the clock 19 keeps track
`of the current time and date (for comparing against schedule
`records). Other suitable hardware configurations will occur
`to those skilled in the art to which the present invention
`pertains. The present invention is not directed to the par
`ticular details of the reception and display means of the
`EPG, and, to avoid obscuring the present invention, the
`operation of such elements will not be discussed here.
`It is useful to begin with an overview of the invention,
`presenting FIG. 1 in a flowchart format. The primary func
`tion of the present invention is to create free space in the
`memory used for schedule information storage. This is
`accomplished by what will be referred to as a database
`"housekeeping" routine 100. The housekeeping routine may
`50
`be invoked as often as necessary to free up space in the
`memory. In some preferred embodiments of the invention,
`the housekeeping function is performed at least in advance
`of every program schedule information update. The house
`keeping routine may be invoked more or less frequently
`depending on the EPG's particular requirements. For
`example, in some preferred embodiments of the present
`invention, a complete new schedule is sent to subscribers on
`a daily, weekly, or some other periodic basis, with no data
`sent in between complete schedule updates. In these
`embodiments, the housekeeping routine need only be run in
`advance of the next schedule. In other preferred
`embodiments, the system does not wait until a complete new
`schedule is ready to be transmitted before updating the EPG.
`Rather, incremental updates to the program schedule are
`continuously sent to subscribers. In this "cyclical” mode of
`operation, when all of the data in a schedule has been sent,
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`transmission of schedule data updates immediately begins.
`Each subsequent transmission includes updates to schedule
`information already stored in the EPG as well as new data
`for the end of the covered time period. Any schedule data
`that has expired since the last transmission is not sent.
`Because new records are constantly received by the EPG,
`the housekeeping routine must be invoked more frequently
`that in embodiments in which complete new program sched
`ules are sent on a daily or other periodic basis.
`Once the housekeeping routine is initialized 110, the
`system begins a search of the schedule database for expired
`records. To do this, the find and delete subroutine 120 scans
`each program record to identify program records whose time
`and date data indicate that the record is expired. All such
`records are tagged and deleted from the program schedule
`database. Next, the system determines whether sufficient
`memory space is available to store the incoming schedule
`information. In this subroutine 130, the system compares the
`available memory space with a predetermined memory
`utilization value, above which the system deems the avail
`able free memory space insufficient. If there is insufficient
`free space memory available, the system then invokes the
`triage subroutine 140 wherein, as explained more fully
`below, information contained in unexpired program records
`is prioritized and deleted according to its current value to the
`viewer. The triage routine 140 stops after enough informa
`tion has been deleted to accommodate the new schedule
`information to be stored. At this point, the housekeeping
`routine terminates 150, ready to be invoked again as needed.
`The detailed steps involved in each of the subroutines just
`discussed will now be explained. In this illustrative embodi
`ment of the present invention, a program schedule record
`includes a calendar date, program start time and duration
`field for each scheduled showing of the program. For
`program showings which start on one day and end on
`another, the calendar date field is set to the date on which
`the program ends. Where the calendar date field for a
`showing is greater than the current date, the find and delete
`routine 120 retains the data associated with the showing, as
`the record corresponds to future programming. Where the
`calendar date field is less than the current date, the program
`record corresponds to expired programming and the data
`associated with the showing is therefore deleted. If the
`calendar date is equal to the current date, the system adds
`the program start time and duration fields together and
`compares the sum to the current time. Data for each showing
`are then deleted or retained depending on the outcome of the
`comparison. The find and delete routine 120 proceeds in this
`manner until the entire program schedule database has been
`scanned and purged of expired records. Where all of the
`showings of a particular program are expired, the system
`deletes the entire record corresponding to that program
`(which, as will be discussed later, contains other information
`about the program). If the EPG system permits time
`sensitive messages to be stored, these too can be deleted in
`the manner just described. In general, any information stored
`in the EPG that may become obsolete by virtue of the
`passage of time can be scanned and deleted in accordance
`with the present invention.
`After the system makes the first pass through the program
`schedule database, it next determines whether sufficient
`memory space has been freed-up to accommodate the
`incoming data. The comparison routine 130 does this by
`retrieving a previously stored memory utilization parameter
`that can be set to any value according to the particular
`system requirement. In a preferred embodiment, the utiliza
`tion parameter is chosen to be at least as large as the space
`
`-5-
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`

`

`S
`in memory occupied by the maximum amount of informa
`tion that can be sent in a program schedule update. In this
`way, the EPG can receive a complete program schedule for
`the corresponding time period. The memory utilization
`parameter may, of course, be set to any arbitrary value based
`on the requirements of the particular EPG system. Where,
`for instance, the EPG accepts smaller amounts of data (i.e.,
`Smaller than an entire program schedule), the memory
`utilization parameter could be set to a lower value than
`where the EPG must accommodate a full program schedule
`in an update. In the preferred embodiment described above
`in which incremental updates are continuously sent to
`subscribers, the system would set the memory utilization
`parameter according to the number of hours of new program
`schedule data it wishes to support in the next schedule
`update. If the system determines that there is sufficient free
`memory, then the housekeeping routine 100 terminates. If,
`on the other hand, the deletion of expired records fails to free
`up enough memory space as determined by the predeter
`mined utilization parameter, then the triage routine 140 must
`be invoked.
`The triage routine 140 of the present invention performs
`an information prioritization function, quantifying the cur
`rent value of the information associated with each program
`record so that the least valuable information can be tagged
`25
`and deleted on a real-time basis. The program schedule
`records in this illustrative embodiment of the present inven
`tion include, in addition to data identifying the program
`name, the program air time(s) and channel(s) carrying the
`program, data corresponding to a program's full title ("Long
`Title”) and a summary description of the program's content
`("Information Record”), both of which need only be stored
`once for a given program. Other informational records may
`also be stored as part of the program records. For purposes
`of illustration, however, only the Long Title and Information
`Record will be considered. It should be understood that any
`type of data associated with a program in the schedule can
`be evaluated and prioritized in accordance with the present
`invention.
`The Long Title and Information Records associated with
`each program, while helpful, are not necessary to identify a
`program and its corresponding air times and, moreover, tend
`to occupy a good deal of the system's memory. The object
`of the triage routine in this exemplary embodiment is
`therefore to identify the least valuable Long Title and
`45
`Information Records in the database so that this data may be
`deleted. In this way, space is made available in memory
`while at the same time retaining the core schedule informa
`tion (program short title, air time(s) and channel(s)) for each
`program in the schedule. Of course, it will be immediately
`recognized that any type of information stored in the EPG's
`memory may be valued in accordance with the techniques of
`the present invention.
`After the triage routine is initialized 141, the system first
`visits each scheduled showing of a program and assigns a
`value to each of three program variables associated with the
`showing. The variable names and their corresponding values
`are displayed in the table at FIG. 2. As shown in this table,
`the higher values are assigned to time periods, channels and
`air times more likely to interest the viewer. As can also be
`seen in the table of FIG. 2, the EPG of the preferred
`embodiment permits the viewer to designate favorite chan
`nels and keeps a record of these channels along with the
`premium channels that the viewer has purchased. The "nor
`mal” channels are those not designated purchased or
`favorite, and, accordingly, have lower values attached to
`them. The list of variables shown in FIG. 2 is illustrative
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`only, and it will be readily understood that other variables
`may be used to quantify the current usefulness of program
`information, the number of such variables limited only by
`the capacity of the particular EPG system to which the
`present invention is applied. Likewise, the specific values
`chosen for each the variable ranges in the preferred embodi
`ment are exemplary only, and may be in general be varied
`according to local demographics or other parameters.
`The system next computes a value for each showing of a
`program 142 according to the following equation:
`schedule record value-channel-value"time period'hours
`away
`(1)
`Other variables may be multiplicatively added to the
`above equation (1), such as a "selected program” variable
`equal to a high value (e.g., 8) when the viewer has set a
`reminder to watch that program or has purchased that
`specific program, and equal to unity for all other programs.
`A "scope" variable corresponding to the value of a data tag
`attached the program record and indicative of the degree to
`which the program is "local” in nature may also be included
`in equation (1). Higher scope values would be assigned to
`data with a more local orientation, reflecting its higher level
`of interest to the viewer. Once the schedule record value
`for every showing of a program has been computed, the
`system adds all of the schedule record values for a given
`program together to arrive at a total value for that program's
`data ("total program value") 143. This unique aspect of
`the presentinvention allows the EPG to ascribe a continuous
`range of values of utility to program information, thereby
`transforming an otherwise subjective judgment ("what is the
`“value' of a program?") into an objective one, suited to
`automatic execution. Alternatively, the system could be
`programmed to use the highest schedule record value for
`a program as that program's value. This embodiment might
`be useful in instances where it is determined that viewers are
`more interested in programs with very high individual
`schedule record values (e.g., a program with its last
`scheduled showing in two hours) than in programs with
`lower individual schedule record values but high aggre
`gated program values.
`After the total program value for every program stored
`in memory has been computed, the system is ready to make
`a determination as to the least valuable Long Title and
`Information Records in memory. In one embodiment, the
`least valuable Information Record and Long Title are simply
`those associated with the program having the lowest total
`program value as computed above. In that case, the system
`would tag the corresponding Long Title and Information
`Record and delete their data from memory 144. Deletion of
`data would proceed in this manner, beginning with the next
`least valuable program, until enough free space has been
`created (determined in routine 145, as in the find and delete
`routine 120, by the pre-defined memory utilization
`parameter). Alternatively, the system could be configured to
`weight the Information Record and Long Title data differ
`ently. In this embodiment of the present invention, Record
`Values would be computed for each of the two types of data
`in accordance with the equation:
`(2)
`Record Value=total-program value"record type,
`where record type is a unique value assigned by the system
`to the type of data (Information Record or Long Title)
`associated with the program. Deletion of data would then be
`carded out starting with the lowest Record Value data,
`whether that be an Information Record or Long Title, and
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`5,652,613
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`continuing until sufficient free space in memory is available.
`In this embodiment, equation (1) and equation (2) could be
`combined into a single equation for ease of execution.
`Whichever embodiment is being used, the least valuable
`data is deleted until compliance with the pre-determined 5
`utilization parameter is achieved in step 145. In instances
`where two program records have identical values, the system
`deletes the largest record as measured in total number of
`bytes.
`Thus, it can be seen that the present invention allows the
`EPG to manage its memory resources in a more flexible and
`efficient manner in comparison to prior art systems. No
`special transmission protocols are required. And, rather than
`fixing a binary value to program data and rejecting it on that
`basis before it is stored, the present invention stores the
`program data in a given schedule update as it is received and
`permits the value of the data to vary over a continuous range
`of values during its residency in memory. The viewer gains
`the two-fold benefit of having all potentially valuable pro
`gram information available at the outset, while at the same
`20
`time having the least valuable information stored in the EPG
`identified and deleted on a real-time basis as memory space
`is needed.
`It will be appreciated that although the present invention
`has been described by reference to particular embodiments,
`many other embodiments may be implemented without
`departing from the spirit and scope of the invention as set
`forth in the following claims.
`What is claimed is:
`1. In a television electronic program guide (EPG) system,
`including means for receiving program schedule informa
`tion including program names, scheduled air times and
`channels, means for storing the program schedule
`information, means for executing an EPG program and
`display means for displaying schedule information
`on-screen, a memory management system comprising:
`a) means for storing the program schedule information
`associated with programs to be shown in a correspond
`ing time period;
`b) means for automatically deleting expired program
`schedule information from the storage means to create
`free space to accommodate storage of new program
`schedule information; and
`c) means for automatically deleting, as needed to create
`additional free space in the storage means for storage of
`new program schedule information, unexpired program
`45
`schedule information according to its current utility to
`a viewer.
`2. A memory management system according to claim 1
`further comprising means for specifying the amount of free
`space in storage means needed.
`3. A memory management system according to claim 2
`further comprising means for comparing actual free space in
`the storage means with the needed amount.
`4. The memory management system according to claim 3
`wherein the means for deleting expired program schedule
`information is activated when the comparison means indi
`cates actual free space in the storage means is less than the
`needed amount and deactivated when the comparison means
`indicates free space in the storage means is greater than or
`equal to the amount needed.
`5. The memory management system according to claim 4
`60
`wherein the means for deleting unexpired program schedule
`information is activated when the storage means contains no
`expired program schedule information and the comparison
`means indicates actual free space in the storage means is still
`less than the amount needed and deactivated when the
`comparison means indicates free space in the storage means
`is greater than or equal to the amount needed.
`
`35
`
`8
`6. The memory management system according to claim 5
`wherein the means for deleting unexpired program schedule
`information includes means for assigning a utility value to
`each program for which corresponding program schedule
`information is stored in the storage means and means for
`deleting program schedule information in decreasing order
`of utility of the program corresponding to such information.
`7. The memory management system according to claim 6
`wherein the means for assigning utility values to programs
`includes means for computing a value for each scheduled
`showing of a program according to utility criteria including
`channel, showing time and hours away, and means for
`aggregating such values to compute a total value for each
`program.
`8. In a television electronic program guide (EPG) system,
`including means for receiving program schedule informa
`tion including program names, scheduled air times and
`channels, means for storing the program schedule
`information, means for executing an EPG program and
`display means for displaying schedule information
`on-screen, a method for managing EPG memory comprising
`the steps of:
`a) storing the program schedule information associated
`with programs to be shown in a corresponding time
`period;
`b) automatically deleting expired program schedule infor
`mation from the storage means to create free space to
`accommodate storage of new program schedule infor
`mation; and
`c) automatically deleting, as needed to create additional
`free space in the storage means for storage of new
`program schedule information, unexpired program
`schedule information according to its current utility to
`a viewer.
`9. The memory management method according to claim 8
`further comprising the step of specifying the amount of free
`space in the storage means needed.
`10. The memory management method according to claim
`9 further comprising the step of comparing actual free space
`in the storage means with the needed amount.
`11. The memory management method according to claim
`10 wherein the step of deleting expired program schedule
`information is carried out when the comparison step indi
`cates actual free management in the storage means is less
`than the needed amount and concluded when the comparison
`means indicates free space in the storage means is greater
`than or equal to the amount needed.
`12. The memory management method according to claim
`11 wherein the step of deleting unexpired program schedule
`information is carried out if the comparison step indicates
`actual free space in the storage means is less than the amount
`needed and there is no expired program schedule informa
`tion in the storage means and concluded when the compari
`son means indicates free space in the storage means