S08P1803 Description Information Processing Apparatus, Information Processing Method, Display Control Apparatus, Display Controlling Method, and Program Technical Field [0001] The present invention relates to an information processing apparatus, an information processing method, a display control apparatus, a display controlling method, and a program. More particularly, the invention relates to an information processing apparatus, an information processing method, a display control apparatus, a display controlling method, and a program for allowing a provider subjectively to control the manner in which to display pictures using a plurality of video streams. Background Art [0002] Multi-screen display techniques have been implemented or proposed whereby a plurality of streams derived from broadcasts, networks, or storage are multi-decoded into a plurality of pictures to be displayed on a single display. S08P1803 [0003] For example, when a plurality of pictures are displayed in a so-called PinP (Picture in Picture) format, the user can watch the picture of a program on a given channel displayed in large form on a main screen while viewing the picture of a program on another channel display in small form on a sub screen. [0004] And when the pictures of programs on two different channels are displayed side by side in the right-hand half and the left-hand half of the display, the user can simultaneously watch the pictures of the programs on the two channels. [0005] Patent Document 1 discloses techniques which, when multi-screen display is designated in a normal display state, permit quick switchover to multiple screens. Patent Document 1: Japanese Patent Laid-Open No. 2000-13712 Disclosure of Invention Technical Problem [0006] Generally, the streams to be used for ordinary S08P1803 multi-screen display are of different programs. For example, in the case of the above-mentioned PinP multi¬screen display, the stream providing the source of the picture to be display on the main screen and the stream providing the source of the picture to be displayed on the sub screen are frequently of different programs. [0007] That is, there is no function that would allow the provider to specify how to coordinate a plurality of streams for picture display, in such a manner that the same program would be displayed on the main and the sub screens as viewed from different angles, whereby the single program would be provided to the user. [0008] Also, whether multi-screen display is given in the ordinary PinP format or involves the left-hand half and the right-hand half of the screen showing pictures side by side, the manner in which the display is provided depends on the implementation of the display device and is not designated by the provider. [0009] From now on, with the popularization of displays having at least the resolution of full HD (High Definition), broadcasts or media may be prepared in such S08P1803 a manner that a single program is provided using a plurality of pictures displayed on a single display screen. In such cases, there may be demands for the provider of programs to subjectively control the manner in which to display the pictures involved. [0010] The present invention has been made in view of the above circumstances and envisages allowing the provider subjectively to control the manner in which to display pictures using a plurality of video streams. Technical Solution [0011] An information processing apparatus according to a first aspect of the present invention includes: multiplexing means for multiplexing video streams including vertical and horizontal picture size information; adding means for adding compose information to a multiplexed stream obtained through multiplexing by the multiplexing means, the compose information having first information designating a screen used for picture display, second information designating the number of windows formed on the screen, third information designating the video streams used for picture display in S08P1803 the windows, and fourth information designating the positions of the windows on the screen; and providing means for providing a display control apparatus with the multiplexed stream to which the adding means has added the compose information, the display control apparatus controlling the display of pictures on the screen. [0012] The windows may be variable in size. [0013] The adding means may add to the multiplexed stream the compose information further including information designating the number of screens used for picture display as well as the first through the fourth information about the respective screens. [0014] The adding means may add to the multiplexed stream the compose information further including information designating the timing at which to form the windows. [0015] The multiplexing means may set a display timestamp for designating the display timing at which to display simultaneously some of the pictures derived from the video streams for displaying the pictures in the respective windows. S08P1803 »^> [0016] The adding means may add to the multiplexed stream the compose information further including information designating the .size of the screen designated by the first information. [0017] An information processing method or a program according to the first aspect of the present invention includes the steps of: multiplexing video streams including vertical and horizontal picture size information; adding compose information to a multiplexed stream obtained through multiplexing, the compose information having first information designating a screen used for picture display, second information designating the number of windows formed on the screen, third information designating the video streams used for picture display in the respective windows, and fourth information designating the positions of the respective windows on the screen; and providing a display control apparatus with the multiplexed stream to which the compose information has been added, the display control apparatus controlling the display of pictures on the screen. [0018] S08P1803 fr A display control apparatus according to another aspect of the present invention acquires a multiplexed stream provided by an information processing apparatus for picture display, the multiplexed stream being obtained by multiplexing video streams including vertical and horizontal picture size information, the information processing apparatus adding to the multiplexed stream compose information including first information designating a screen used for picture display, second information designating the number of windows formed on the screen, third information designating the video streams used for picture display in the respective windows, and fourth information designating the positions of the respective windows on the screen, the display control apparatus having: separating means for separating the multiplexed stream into the video streams; analyzing means for analyzing the compose information added to the multiplexed stream so as to detect the video streams used for picture display based on the third information regarding each of the windows of which the number is designated by the second information, to detect the sizes of the windows based on the size information included in the detected video streams, and to form the windows of the detected sizes in those positions designated by the 7 S08P1803 #' fourth information which are on the screen designated by the first information; decoding means for decoding the video streams; and display controlling means for displaying in the respective windows the pictures obtained through decoding by the decoding means. [0019] The compose information may further include information designating the size of a target screen; and, if the size designated by the further-included information is different from the size of the designated screen, then the display controlling means may change the sizes of the pictures obtained through decoding by the decoding means, [0020] A display controlling method or a program according to the other aspect of the present invention includes the steps of: separating a multiplexed stream into video streams; analyzing compose information added to the multiplexed stream so as to detect the video streams used for picture display based on third information regarding each of the windows of which the number is designated by second information, to detect the sizes of the windows based on size information included in the detected video streams, and to form the windows of the detected sizes in S08P1803 those positions designated by fourth information which are on a screen designated by first information; decoding the video streams; and displaying in the respective windows the pictures obtained through decoding. [0021] According to the first aspect of the present invention, video streams including vertical and horizontal picture size information are multiplexed; compose information is added to a multiplexed stream obtained through multiplexing, the compose information including first information designating a screen used for picture display, second information designating the number of windows formed on the screen, third information designating the video streams used for picture display in the respective windows, and fourth information designating the positions of the respective windows on the screen; and a display control apparatus is provided with the multiplexed stream to which the compose information has been added, the display control apparatus controlling the display of pictures on the screen. [0022] According to the second aspect of the present invention, a multiplexed stream is separated into video streams; compose information added to the multiplexed S08P1803 §- stream is analyzed so as to detect the video streams used for picture display based on third information regarding each of the windows of which the number is designated by second information, to detect the sizes of the windows based on size information included in the detected video streams, and to form the windows of the detected sizes in those positions designated by fourth information which are on a screen designated by first information; the video streams are decoded; and the pictures obtained through decoding are displayed in the respective windows. Advantageous Effects [0023] According to the present invention the provider can subjectively control the manner in which to display pictures using a plurality of video streams. Brief Description of Drawings [0024] [Fig. 1] Fig. 1 is a view showing a typical configuration of a system providing programs and practiced as one embodiment of the present invention. [Fig. 2] 10 S08P1803 Fig. 2 is a view showing the concept of compose information. [Fig. 3] Fig. 3 is a view showing typical windows displayed on a screen based on the compose information. [Fig. 4] Fig. 4 is a view showing other typical windows displayed on the screen based on the compose information. [Fig. 5] Fig. 5 is a view showing other typical windows displayed on the screen based on the compose information. [Fig. 6] Fig. 6 is a view showing a typical window displayed on the screen based on the compose information. [Fig. 7] Fig. 7 is a view showing how pictures are typically changed. [Fig. 8] Fig. 8 is a view showing typical descriptions of the compose information. [Fig. 9] Fig. 9 is a block diagram showing a typical structure of a transmission device. [Fig. 10] 11 S08P1803 if Fig. 10 is a block diagram showing a typical structure of a reception device. [Fig. 11] Fig. 11 is a flowchart explaining the process of-the transmission device. [Fig. 12] Fig. 12 is a flowchart explaining the process of the reception device. [Fig. 13] Fig. 13 is a flowchart explaining a compose information analyzing process performed in step S13 of Fig. 12. [Fig. 14] Fig. 14 is a view showing another typical configuration of the providing system. [Fig. 15] Fig. 15 is a perspective view showing a typical layout of screens. [Fig. 16] Fig. 16 is a view showing a typical layout of screens. [Fig. 17] Fig. 17 is a block diagram showing another typical structure of the reception device. 12 S08P1803 1^1 [Fig. 18] Fig. 18 is a view showing the concept of how compose information is added. [Fig. 19] Fig. 19 is a view showing where compose information is typically inserted. [Fig. 20] Fig. 20 is a block diagram showing a typical structure of a personal computer. Explanation of Reference Symbols [0025] 1 Transmission device, 2 Reception device, 3 Screen, 11-1 through 11-n Encoders, 12 Multiplexer, 13 Compose information addition section, 14 Transmission section, 21 Reception section, 22 Demultiplexer, 23 Compose information analysis section, 24-1 through 24-n Decoders, 25 Display control section Best Mode for Carrying Out the Invention [0026] Fig. 1 is a view showing a typical configuration of a system providing programs and practiced as one embodiment of the present invention. 13 S08P1803 [0027] As shown in Fig. 1, the providing system is made up of a transmission device 1 and a reception device 2. The reception device 2 is connected with a screen 3 by means of a cable or the like. [0028] The transmission device 1 is a device set up on the side of a program provider such as a broadcasting station, [0029] The transmission device 1 separates the picture of one program taken by one camera into a predetermined number of areas per frame, and encodes the pictures of the separated areas into separate streams or encodes the pictures of one program taken by a plurality of cameras into separate streams respectively, thereby generating a plurality of video streams (PES (Packetized Elementary Stream)) for use in displaying the pictures of one program. [0030] Also, the transmission device 1 multiplexes a plurality of generated video streams into a multiplexed stream (TS (Transport Stream)) for use in displaying the pictures of one program. [0031] 14 S08P1803 ii The transmission device 1 adds four-dimensional compose map information to the multiplexed stream generated, and provides the reception device 2 with the program constituted by the multiplexed stream to which the four-dimensional compose map information has been added. Programs are provided by use of broadcast waves, over networks, or by means of recording media such as a DVD (Digital Versatile Disc) or Blu-ray (registered trademark) Disc. [0032] Four-dimensional compose map information represents the display relations between a plurality of streams sharing a given time period as a single program, the information being given to the reception device 2 by the transmission device 1 specifying how to coordinate respective video streams making up the multiplexed stream for the display of pictures. In the ensuing description, the four-dimensional compose map information may be simply referred to as the compose information where appropriate. [0033] The compose information includes, among others, information designating the video streams to be used in displaying pictures in various positions on the screen 3. 15 S08P1803 11^ 9P As will be discussed later, where a plurality of screens are set up on the side of the reception device 2, the compose information will include information about the respective screens. [0034] The reception device 2 is set up on the program receiving side such as in the household. [0035] The reception device 2 receives programs provided by the transmission device 1, and decodes each of the video streams making up a multiplexed stream. Also, the reception device 2 causes the screen 3 to display the pictures obtained by decoding the respective video streams, in accordance with the information included in the compose information. The pictures displayed on the screen 3 in accordance with the information included in the compose information are the pictures constituting a single program, so that the user can view that one program. [0036] Fig. 2 is a view showing the concept of compose information. [0037] As shown in Fig 2, the compose information is made 16 S08P1803 up of a predetermined number of compose maps arrayed chronologically for reference purposes. Each of the compose maps denotes, among others, the screens on which to display pictures and those positions on each screen in which to display the pictures. [0038] A compose map fo in Fig. 2 is the information to be referenced at a given time; a compose map fi is the information to be referenced at a time subsequent to the time at which the compose map fo is referenced; and a compose map fs is the information to be referenced at a time subsequent to the time at which compose map fi is referenced. Where a single compose map group is made up of the compose maps fo through f2 as shown in Fig. 2, following the reference made to the compose map fz for picture display, the compose maps are referenced in successively repeated fashion starting from the compose map fo for continuous picture display. The compose map group is represented by a parameter Tm. [0039] Dotted lines Li, shown three vertically and three horizontally, denote the demarcations of screens. The areas demarcated by the dotted lines Li indicate how pictures are to be displayed on each screen. If one 17 S08P1803 screen is prepared on the side of the reception device 2 as shown in Fig. 1, then only one top left area out of the 16 areas demarcated by the dotted lines Li is used. If 16 screens are prepared on the side of the reception device 2, then all areas of the compose map fo are used. The screens are represented by parameters Sn. [0040] Solid lines L2, shown seven vertically and seven ^ horizontally including those overlapping with the dotted lines Li, indicate how one screen is to be separated. In the ensuing description, the areas formed on one screen for the display of pictures may be referred to as windows where appropriate. The screen is a picture display area established physically as a device, whereas the windows are picture display areas formed on a single screen. One window displays one picture obtained by decoding one Si> video stream. Each of the windows is variable in size. [0041] Fig. 2 shows an example of compose information in which four windows are formed by bisecting respectively each of the screens vertically and horizontally. [0042] The position of each window on the screen is defined by a parameter Hp indicating the horizontal 18 S08P1803 ^y. position and by a parameter Vq indicating the vertical position relative to a predetermined position such as the top left corner of the screen. [0043] Through the use of the parameters Sn Tm, Hp and Vq, each of the windows is identified by Window_ID(Sn, Tm, Hp, Vq) . [0044] For example, the window corresponding to the top left area Aoi in Fig. 2 is identified by Window_ID(SO, TO, HO, VO), by the parameter SO indicating that this is a window formed on a first screen SO, by the parameter TO indicating that this is a window in which the picture is displayed by referencing the first of the compose maps constituting the same compose map group, by the parameter HO indicating that this is a window formed on the left-hand side when the screen SO is separated into four areas, and by the parameter VO indicating that this is a window formed on the upper side when the screen SO is separated into four areas. [0045] And the window corresponding to the area Ao4 is identified by Window_ID(SO, TO, HI, VI), by the parameter SO indicating that this is a window formed on the first 19 S08P1803 wBt jg screen SO, by the parameter TO indicating that this is a window in which the picture is displayed by referencing the first of the compose maps constituting the same compose map group, by the parameter HI indicating that this is a window formed on the right-hand side when the screen SO is separated into four areas, and by the parameter VI indicating that this is a window formed on the lower side when the screen SO is separated into four areas. [0046] Likewise, the window corresponding to the area A02 is identified by Window_ID(SO, TO, HI, VO), and the window corresponding to the area A03 is identified by Window_ID(SO, TO, HO, VI). [0047] The compose information includes PIDs of video streams indicating which video streams are to be decoded into pictures for display in the windows identified as described above. The compose information also includes information designating the screen size (screen resolution targeted by the transmission device 1) indicated by dashed lines L3 in Fig. 2. [0048] Specific descriptions of the compose information 20 S08P1803 will be discussed later. [0049] Fig. 3 is a view showing typical windows displayed on the screen 3 based on the compose information. [0050] Fig. 3 shows an example where the picture of one program taken by one camera is separated into four areas per frame and where the pictures of the respective separated areas are encoded, as the separate streams, into four video streams which in turn are multiplexed, whereby the program is provided. [0051] In this case, based on the compose information attached to the multiplexed stream, the reception device 2 forms windows Wo, Wi, W2, and W3 in the top left area, top right area, bottom left area, and bottom right area of the screen 3 respectively. [0052] In the compose information, as described above in reference to Fig. 2, the window WQ is identified by Window_ID(SO, TO, HO, VO) , the window Wi by Window_ID (SO, TO, HI, VO), the window W2 by Window_ID(SO, TO, HO, VI), and the window W3 by Window_ID(SO, TO, HI, VI). [0053] 21 S08P1803 % B The parameter Vq included in Window_ID of the window Wo is VO, and the same parameter VO is included in Window_ID of the window Wi as Window_ID included in the parameter Vq. Thus it is detected that the reception device 2 need only form two windows on the upper side of the screen 3. [0054] The windows Wo and Wi are detected to be positioned left and right, respectively, based on the values of the parameter Hp included in Window_IDs of these windows. [0055] The parameter Vq included in Window_ID of the window W2 is VI, and the same parameter VI is included in Window_ID of the window W3 besides the window W2 as Window_ID included in the parameter Vq. Thus it is detected that the reception device 2 need only form two windows on the lower side of the screen 3. [0056] The windows W2 and W3 are detected to be positioned left and right, respectively, based on the values of the parameter Hp included in Window_IDs of these windows. [0057] The information about the vertical and horizontal sizes of pictures is included in the video stream. Thus 22 S08P1803 the windows Wo through W3 are formed by allocating the areas of the same sizes as those of the pictures in the positions detected as described above. The correspondence relations between the respective windows and the video streams used for picture display in the respective windows are also represented by the compose information. [0058] In this manner, the reception device 2 forms the windows in accordance with the specifications given by the transmission device 1 based on the sizes of the windows (i.e., sizes of the pictures to be displayed in the v/indows) and on the positions of the windows. [0059] And the relations of correspondence between PID and Window_ID included in the compose information are detected by the reception device 2, with the window Wo displaying a picture Q-0 obtained by decoding the video stream identified by a relevant PID. The same applies to the windows Wi through W3; pictures Q-1 through Q-3 are displayed after being obtained by decoding the video streams identified by the respective relevant PIDs. [0060] When the pictures Q-0 through Q-3 are arranged to appear in mutually synchronized fashion, the screen 3 23 S08P1803 ■^ displays the picture of the original single program taken by one camera. [0061] When the compose information is utilized as described above, the transmission device 1 enables the reception device 2 to display on the screen 3 one big original picture based not on a single video stream but on four separate video streams. [0062] Fig. 4 is a view showing other typical windows displayed on the screen 3 based on the compose information. [0063] Fig. 4 shows an example where the pictures of a soccer match taken as those of one broadcast program by four cameras set up at four different locations are encoded into four different streams which in turn are multiplexed, whereby the program is provided. [0064] In this case, as with the case explained above by referring to Fig. 3, the reception device 2 forms windows Wo, Wi, Wa, and W3 in the top left, top right, bottom left, and bottom right areas of the screen 3, respectively, based on the compose information added to the multiplexed 24 S08P1803 & stream. [0065] In the compose information, the window Wo of Fig. 4 is also identified by Window_ID(SO, TO, HO, VO), and the window Wi is identified by Window_ID(SO, TO, HI, VO). The window W2 is identified by Window_ID(SO, TO, HO, VI), and the window W3 is identified by Window_ID(SO, TO, HI, VI) . From each parameter constituting Window_ID included in the compose information, it is detected that the reception device 2 need only bisect the screen 3 vertically and horizontally respectively into four windows. [0066] And the correspondence relations between FID and Window_ID included in the compose information are detected by the reception device 2, with the window Wo displaying a picture Q-O which is obtained by decoding the video stream identified by a relevant FID and which represents the picture of the soccer broadcast being taken from a given angle. The same applies to the windows Wi through W3; pictures Q-1 through Q-3 are displayed after being obtained by decoding the video streams identified by the respective relevant PIDs, the pictures representing those of the soccer broadcast taken from 25 ■■■ S08P1803 1^ different angles respectively. [0067] When the pictures Q-0 through Q-3 are arranged to appear in mutually synchronized fashion, the screen 3 displays the pictures of the original single program taken by the four cameras. [0068] When the compose information is utilized as described above, the transmission device 1 can respectively display a plurality of pictures of one program taken by a plurality of cameras in the relevant positions on the screen 3 of the reception device 2. [0069] Fig. 5 is a view showing other typical windows displayed on the screen 3 based on the compose information. [0070] Fig. 5 shows an example where the pictures of one program taken by six cameras are encoded respectively into six video streams which in turn are multiplexed, whereby the program is provided. [0071] In this case, based on the compose information added to the multiplexed stream, a window Wo having 26 S08P1803 ^^ approximately the same width as the horizontal width of the screen is formed in the uppermost area of the screen 3; in the second area from the top of the screen 3 are formed windows Wi through W4 each having a width equal to one of four equal parts making up the horizontal width of the screen 3; and a window W5 having approximately the same width as the horizontal width of the screen 3 is formed in the lowermost area of the screen 3. [0072] In the compose information, the window Wo is identified by Window_ID(SO, TO, HO, VO), the window Wi is identified by Window_ID(SO, TO, HO, VI), and the window W2 is identified by Window_ID(SO, TO, HI, VI) . The window W3 is identified by Window_ID(SO, TO, H2, VI), the window W4 is identified by Window_ID(SO, TO, H3, VI), and the window W5 is identified by Window_ID(SO, TO, HO, V2). [0073] The parameter Vq included in Window_ID of the window Wo is VO, and there is no other Window_ID that would include the same VO in the parameter Vq. Thus it is detected that the reception device 2 need only form one window in the uppermost area of the screen 3. [0074] The parameter Vq included in Window_ID of the 27 S08P1803 ^^^ window Wi is VI, and there are Window_IDs of the windows W2, W3, and W4 which include the same VI in the parameter Vq besides the Window Wi. Thus it is detected that the reception device 2 need only form fo.ur windows in the second area from the top of the screen 3. [0075] Also, as for the order of the windows Wi through W4, the windows Wi, W2, W3, and W4 are detected to be positioned from left to right, in that order, based on the values of the parameter Hp included in Window_IDs of the respective windows. [0076] The parameter Vq included in Window_ID of the window W5 is V2, and there is no other Window_ID that would include the same V2 in the parameter Vq. Thus it is detected that the reception device 2 need only form one window in the lowermost area of the screen 3. [0077] From the positions of the windows WQ through W5 detected as described above and from the picture size information included in each of the six video streams, it is detected that the reception device 2 need only form the respective windows as shown in Fig. 5. [0078] 28 S08P1803 %f And the correspondence relations between PID and Window_ID included in the compose information are detected by the reception device 2, with the window Wo displaying a picture Q-0 obtained by decoding the video stream identified by a relevant PID. The same applies to the windows Wi through W5; pictures Q-1 through Q-5 are displayed after being obtained by decoding the video streams identified by the respective relevant PIDs. [0079] When the pictures Q-0 through Q-5 are arranged to appear in mutually synchronized fashion, the screen 3 displays illustratively a panorama-view picture of the original single program taken by a plurality of cameras. [0080] When the compose information is utilized as described above, the transmission device 1 separates the panorama-view picture taken by a plurality of video ' cameras into six video streams to be provided, thus allowing the reception device 2 to display the original single panorama-view picture on the screen 3. [0081] Fig. 6 is a view showing a typical window displayed on the screen 3 based on the compose information. [0082] 29 S08P1803 .6 Fig. 6 shows an example in which pictures of an object are taken from left and right by two cameras set up at two different locations, the taken pictures being encoded into two video streams, as different streams respectively, which in turn are multiplexed, whereby the program is provided. [0083] In this case, based on the compose information added to the multiplexed stream, a window Wo and a window Wi are formed alternately in a chronologically staggered manner by the reception device 2 over the entire screen 3 In Fig. 6, the window Wi is indicated by broken lines because it is formed at a time different from the time at which the window Wo is formed. [0084] In the compose information, the window WQ is identified by Window_ID(SO, TO, HO, VO) and the window Wi by Window_ID(SO, Tl, HO, VO). [0085] The parameter Tm included in Window_ID of the window Wo is TO, and the parameter Tm included in Window_ID of the window Wi is Tl. Thus it is detected that the reception device 2 need only form the windows WQ and Wi at different times. 30 S08P1803 # [0086] Based on the information about the compose map group included in the compose information, it is also detected that the windows Wo and Wi need only be formed . alternately, as window Wo, window Wi, window WQ, window Wi, .... [0087] From the fact that there is no window other than the window WQ that needs to be formed at the time of TO, and from the information in the video stream about the size of the picture to be displayed in the window WQ, it is detected that the reception device 2 need only form the window Wo over the entire screen 3. [0088] Likewise, from the fact that there is no window other than the window Wi that needs to be formed at the time of Tl, and from the information in the video stream about the size of the picture to be displayed in the window Wi, it is detected that the reception device 2 need only form the window Wi over the entire screen 3, [0089] The correspondence relations between PID and Window_ID included in the compose information are detected by the reception device 2. The window Wo formed 31 S08P1803 ir at a given time displays a picture P-0 which is obtained by decoding the video stream identified by a relevant PID and which depicts the object as it is taken from left for example. [0090] And the window Wi formed at a time subsequent to the time at which the window WQ was formed displays a picture P-1 which is obtained by decoding the video stream identified by a relevant PID and which depicts the object as it is taken from right. [0091] Thus when the displays of the pictures P-0 and P-1 are switched alternately in a predetermined cycle by use of the compose information as shown in Fig. 7, the transmission device 1 enables the reception device 2 to display a 3-D picture on the screen 3 by taking advantage of the human's parallax. [0092] Fig. 8 is a view showing typical descriptions of the compose information. The numbers shown on the left-hand side of Fig. 8 together with a colon (:) each are given only for explanatory purposes and do not constitute any part of the compose information. [0093] 32 S08P1803 ir A description "Window_Linkage_flag" on line 1 indicates the presence of a plurality of windows. A description "If (Window_Link;age_Flag) on line 2 and subsequent descriptions on the lines that follow constitute the content of the compose information. [0094] A description "Number_of_Screens, S" on line 3 denotes the number S of screens targeted by the compose information. The number S is variable. In the above example, the number S is 1. [0095] A description "For{i=0; i