Abstract:
An event notification channel is provided in a computer controlled object oriented programming system having at least one event supplier object and a plurality of event consumer objects which may be run continuously without interruption and without loss of event notification to any consumer object irrespective of whether any of the consumer objects are off line for filter modification or any other maintenance purpose. The channel transmits events from supplier objects to a plurality of filter objects, each respectively associated with one of the plurality of consumer objects for passing only selected events to the associated consumer object. The system includes a plurality of proxy consumer objects, each associated with one of said consumer objects and between said filter object and said supplier object, whereby said proxy consumer object may receive supplier transmitted events on behalf of its associated consumer object. Thus, where the actual consumer object is off line for filter modification, the proxy will remain in the system and receive the transmitted events.

Description:
TECHNICAL FIELD 
   The present invention relates to user-interactive object oriented programming systems and particularly to event notification transmission between event supplier objects and event consumer objects in such object oriented programming systems. 
   BACKGROUND OF RELATED ART 
   The 1990&#39;s decade has been marked by a technological revolution driven by the convergence of the data processing industry with the consumer electronics industry. The effect has in turn driven technologies which have been known and available but relatively quiescent over the years. Two of these technologies are the Internet related distribution and object oriented programming systems. The computer and communications industries have extensively participated in the development and continual upgrading of object oriented programming systems, such as the Java system. For details and background with respect to object oriented programming systems, such as the Java programming system, C++ and others, reference may be made to some typical texts:  Just Java,  2nd Edition, Peter van der Linden, Sun Microsystems, 1997 ; Thinking in Java , Bruce Eckel, Prentice Hall PTR, 1998; and  Objects, Components and Frameworks with UML , Desmond F. D&#39;Sousa et al., Addison-Wesley, 1998. The convergence of the electronic entertainment and consumer industries with data processing has exponentially accelerated the demand for wide ranging communications distribution channels and the World Wide Web (Web) or Internet, which had quietly existed for over a generation as a loose academic and government data distribution facility, reached “critical mass” and commenced a period of phenomenal expansion, which has not as yet abated. 
   With the expanded accessibility of hundreds of thousands of programmers, information distributors and users to each other, not to mention to potential users of such programs via the expanded Internet client base, an obvious need became apparent: cooperative program systems in a distributed programming environment. Object oriented programming offered the solution. With its potentially interchangeable objects or units within which both data attributes and functions were stored in a predefined uniform framework, as well as the predefined object interfaces with each other, object oriented programming systems have found acceptance as the programming system for the Internet. In all areas of data processing and communications, as well as the electronic entertainment and consumer industries having anything to do with the Internet, there has been a substantial movement to object oriented programming systems. 
   Object oriented programming systems are event driven, i.e. the event is an outgoing notification from a given component to all other registered or interested components in the programming system. In other words, there are registered observer or consumer objects in a system which have registered an interest in selected states or attribute values of subject or supplier objects. Such changes in state or attribute values cause the supplier object to broadcast a notification of this change, which constitutes an event to all registered observers or consumers. In such systems, the supplier objects may be designed or developed without any reference as to how the consumer objects operate and new consumers or observers may be added without regard to the suppliers. The notification message may contain more information or less information, i.e. events about the nature of the changes in the supplier and the observer or consumer may take place, i.e. filter out whatever details or events that it is interested in. A general recitation about the handling of events notification between producers or suppliers and consumers may be found in the above-referenced  Just Java  text at pp. 198-205. As mentioned above, the consumer objects generally use filtering objects respectively associated with the consumer objects to parse or filter out from the broadcast events transmitted from the supplier objects, those events selected by the particular consumer objects. Filter objects are described in the above text,  Just Java  at pp. 292-301. 
   While such event notification processes have been quite effective in the distribution of event data from a plurality of suppliers to pluralities of consumers, problems are encountered when it is desired to modify or replace the filter objects associated with particular consumers of event data or otherwise take the consumer objects “off line” during continuous runs of the event notification and distribution systems, which, because of the extensive numbers of suppliers and consumers, often seems to be continuously running. Accordingly, any interruption of the event notification system for any change is not practical. 
   SUMMARY OF THE PRESENT INVENTION 
   The present invention provides for an event notification channel for an object oriented programming system with a plurality of supplier objects and a plurality of event consumer objects which may be run continuously without interruption and without loss of event notification to any consumer object irrespective of whether any of the consumer objects are off line for filter modification or any other maintenance purpose. The event notification channel comprises means for transmitting events from supplier objects to a plurality of filter objects, each respectively associated with one of said plurality of consumer objects for passing only selected transmitted events to said one consumer object. The system includes a plurality of proxy consumer objects, each associated with one of said consumer objects and between said filter object and said supplier object, whereby said proxy consumer object may receive supplier transmitted events on behalf of its associated consumer object. Thus, when the actual consumer object is off line for filter modification, the proxy will remain in the system and receive the transmitted events. The notification channel will, preferably, further include means for distributing the events received by the proxy consumer objects respectively to the filter objects associated with said consumer objects. In order to cover the times when consumer objects may be off line as described above, the notification channel further includes means for delaying said distribution of events received by a proxy consumer object until the filter object for the consumer object associated with said proxy consumer object becomes operational. Each of the proxy consumer objects, preferably, includes a proxy input object for receiving said supplier transmitted events, and a proxy output object for holding said received events until the filter object for the consumer object associated with said proxy consumer object becomes operational. As previously mentioned, the present invention may be effectively implemented on networks such as the Web or Internet. In such a case, the notification channel object may be included in a network distribution server. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be better understood and its numerous objects and advantages will become more apparent to those skilled in the art by reference to the following drawings, in conjunction with the accompanying specification, in which: 
       FIG. 1  is a block diagram of a generalized local network on which the present invention may be implemented; 
       FIG. 2  is a block diagram of a generalized data processing system including a central processing unit (CPU) which may be used to provide either the computer display terminal from which the supplier object transmits events to the notification channel or the computer display terminal on which the consumer object receives events from the notification channel; 
       FIG. 3  is a block diagram of a generalized wide area network (WAN), such as the Internet, on which the present invention may be implemented; 
       FIG. 4  is a block diagram of a generalized object oriented notification channel in accordance with the present invention; 
       FIG. 5  is a diagrammatic illustration of part of a display screen showing an initial dialog box which may be used to make modifications in either supplier objects or consumer objects without interrupting the running of the events notification channel; 
       FIG. 6  is the display screen of  FIG. 5  at a next stage in making modification of supplier or consumer objects; 
       FIG. 7  is the display screen of  FIG. 6  at a next stage in making modification of supplier or consumer objects; and 
       FIG. 8  is the display screen of  FIG. 7  at a later stage of making such object modifications. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   With reference to  FIG. 1  there is shown a representative diagram of a local network which may be used in the simplest illustrative hardware to implement the present invention. Interactive display computer terminal  43  contains the object oriented software providing the supplier objects which provide the events transmitted via connector  46  to server computer  44  which will contain the event notification channel object in accordance with the present invention to be subsequently described in detail. The events processed through the events notification channel object in server  44  are, in turn, transmitted over connector  47  to the receiving interactive display computer terminal  45  which contains the event consumer object which has registered interest in the received events. It is understood that there may be a plurality of such transmitting terminal  43  respectively containing event supplier objects, as well as a plurality of receiving terminals  45  respectively containing event consumer objects. Also, pluralities of supplier objects and consumer objects may include, respectively, a computer display transmitting terminal and receiving terminal  45 . 
     FIG. 2  shows a typical computer display terminal which may function as either transmitting terminal  43  or receiving terminal  45 . A CPU  10 , such as a PC microprocessors or workstations, e.g. RISC System/6000™ (RS/6000) (RISC System/6000 is a trademark of International Business Machines Corporation) series available from International Business Machines Corporation (IBM), is provided and interconnected to various other components by system bus  12 . An operating system  41  runs on CPU  10 , provides control and is used to coordinate the function of the various components of FIG.  1 . Operating system  41  may be one of the commercially available operating systems such as the AIX 6000™ operating system or OS/2™ operating system available from IBM (AIX 6000 and OS/2 are trademarks of IBM); Microsoft&#39;s Windows 95™ or Windows NT™, as well as UNIX and AIX operating systems. Application programs  40 , controlled by the system, are moved into and out of the main random access memory (RAM)  14 . These programs include the objects manipulated in the object oriented programs of the present invention, e.g. the event supplier objects and their associated filter objects, as well as the event consumer objects and their associated filter objects. A read only memory (ROM)  16  is connected to CPU  10  via bus  12  and includes the basic input/output system (BIOS) that controls the basic computer functions. RAM  14 , I/O adapter  18  and communications adapter  34  are also interconnected to system bus  12 . I/O adapter  18  may be a small computer system interface (SCSI) adapter that communicates with the disk storage device  20 . Communications adapter  34  interconnects bus  12  with an outside network, enabling the data processing system to communicate with other such systems over a local area network (LAN) or WAN, which includes, of course, the Web or Internet. I/O devices are also connected to system bus  12  via user interface adapter  22  and display adapter  36 . Keyboard  24  and mouse  26  are all interconnected to bus  12  through user interface adapter  22 . Display adapter  36  includes a frame buffer  39 , which is a storage device that holds a representation of each pixel on the display screen  38 . Images may be stored in frame buffer  39  for display on monitor  38  through various components, such as a digital to analog converter (not shown) and the like. By using the aforementioned I/O devices, a user is capable of inputting information to the system through the keyboard  24  or mouse  26  and receiving output information from the system via display  38 . 
   Now with respect to  FIG. 3 , there will be described a network application of the present invention. A computer display terminal may function as either the event transmitting terminal containing the supplier objects or the event receiving terminal containing the consumer objects. For purposes of this illustration, its function will be the receiving terminal. A generalized diagram of a portion of a network such as the Internet is shown. The receiving computer controlled display terminal  58  will be used to support the consumer objects, which will be receiving their filtered events as will hereinafter be described in greater detail. Reference may be made to the text,  Mastering the Internet , G. H. Cady et al., published by Sybex Inc., Alameda, Calif., 1996, pp. 136-147, for typical connections between local display terminals to the Internet via network servers, any of which may be used to implement and support the event notification channel portion of this invention. The system embodiment of  FIG. 3  is one of these known as a host-dial connection. Such host-dial connections have been in use for over 30 years through network access servers  53  which are linked  51  to the Internet  50 . The servers  53  provide network services to the client&#39;s display terminal, such as receiving terminal  58 . The network server  53  is accessed by the terminal  58  through a normal dial-up telephone linkage via modem  54 , telephone line  55  and modem  52 . Data, including events, is downloaded to receiving terminal  58  through controlling server  58  via the telephone line linkages from server  53  which may have accessed them from the internet  50 . It will be understood that in the same manner, the computer controlled display terminal may also function as an event transmitting terminal containing supplier objects. In either situation, the event notification channel of the present invention may conveniently be embodied in the network server  53 . 
   With respect to  FIG. 4 , the event notification channel of the present invention will now be described. Push supplier objects  1  ( 71 ) and  2  ( 72 ) and their respective associated filter objects  86  and  87  are in the transmitting display terminals, while push consumer objects  1  ( 73 ) and  2  ( 74 ) and their respective associated filter objects  84  and  85  are in receiving display terminals. The flow of the events to the consumer objects  73  and  74  is through the event notification channel object  61 . This channel may be implemented as part of any standard object request broker service, such as COBRA (Common Object Request Broker Architecture), an industry standard. For additional details on object request broker architectures, please refer to the text,  Object Technology in Application Development , Daniel Tkach et al., Addison-Wesley Publishing, 1996, pp. 147-151. Consumer objects may register or unregister their interest in events, which are prespecified occurrences in an object which are of interest to one or more of the consumer objects. The supplier objects provide the events. Thus, supplier objects  71  and  72  provide the events transmitted via event notification channel object  61  to consumer objects  73  and  74 . Channel object  61  uses standard COBRA requests in transmitting requests. The events which the supplier objects send out are respectively controlled through supplier filter objects  86  and  87 , while the events which the consumer objects will selectively receive are controlled through consumer filter objects  84  and  85 . The filter objects will encapsulate the constraints which will determine the events to be passed to the respective consumer object associated with the filter object. In a filter object, each encapsulated constraint has two structural components: a sequence of data structures, each of which indicates an event type made up of a domain and a type name; and, the properties of an event, expressed in constraint grammar. Some of the general principals involved in the creation of filter objects using Java programming may be found in the above-referenced  Just Java  text at pp. 92-95. 
   Now, within the event notification channel, there will be described the functions of the proxy consumer objects. 
   Each proxy consumer object includes two subobjects: the first proxy consumer object which is associated with push consumer object  1  ( 73 ) is made up of consumer proxy output object  1  ( 77 ) and consumer proxy input object  1  ( 75 ); while the second proxy consumer object which is associated with push consumer object  2  ( 74 ) is made up of consumer proxy output object  2  ( 78 ) and consumer proxy input object  2  ( 76 ). These objects permit the modification of the consumer objects without interrupting the continuous running of the notification channel. It should be noted that the proxy consumer objects are tracked and, to some extent, controlled by a supplier administrator object  63  which tracks proxy input object list  64  and consumer administrator object  62  which tracks proxy output object list  65 . Consumer proxy input object  75  represents a run time interface which is the equivalent of the interface of consumer object  73  as filtered by filter  84 , but at removed location interfacing with supplier object  71 . Likewise, consumer proxy input object  76  represents a run time interface which is the equivalent of the interface of consumer object  74  as filtered by filter  85 , but at removed location interfacing with supplier object  72 . Similarly, consumer proxy output object  77  represents an interface which is the equivalent of the interface of supplier object  71  as filtered by filter  86 , but at removed location interfacing with consumer object  73 . Likewise, consumer proxy output object  78  represents an interface which is the equivalent of the interface of supplier object  72  as filtered by filter  87 , but at removed location interfacing with consumer object  74 . 
   The creation of proxy objects is well known in object oriented programming. One of the proxy functions is to represent object functions at locations remote from the original objects. Reference may be made to the above-mentioned D&#39;Sousa et al. text with respect to proxies. 
   In accordance with this invention, if one of the consumer objects, e.g. consumer object  73 , were to have its selected events modified, and, thus, object  73  and its filter were taken off line, the notification channel shown in  FIG. 4  would continue its regular uninterrupted operation. The removal of the consumer object  73  and filter object  84  would be transparent to supplier object  71  and filter object  86  as they would continue to see the same filtered consumer object interface as provided by consumer proxy input object  75  which would receive the events intended for consumer object  73 . These events would be passed through master event list  81  from which they would reach message queue  82 . Then, when the modified push consumer object  73  and filter object  84  were put back on line, sweep thread- 1 ,  79  would move the events from queue  82  through proxy consumer output object  77  to the modified filtered consumer object  73 . It will be understood that consumer proxy input object  76 , message queue  83 , consumer proxy output object  78  and sweeper thread- 2 ,  80  would perform the same functions if consumer object  74  and its associated filter  85  were to be taken off line for modification. 
   In this connection, it should also be noted that there is an additional benefit with respect to the need to remove a supplier object, e.g. supplier object  71  and its filter  86  for modification. This would be transparent to consumer object  73  and filter object  84  as they would continue to see the same filtered supplier object interface as provided by consumer proxy output object  77 , which still provides events. 
   Now, with respect to  FIGS. 5 through 8 , which are interactive dialog screen portions which would be represented, for example, on an event consumer&#39;s terminal such as display terminal  45  in  FIG. 1  or display terminal  58  in  FIG. 2 , there will be described a simple example of an interface sequence for the modification of the filtered events selected for a consumer object. In the dialog screen of  FIG. 5 , the user selects the channel in which his event consumer object to be modified is located: Channel  2 . This brings up the dialog box screen of  FIG. 6  from which the user selects “push-con”, the push consumer object, in turn resulting in the dialog screen of  FIG. 7  from which the user selects “push C-2” which represents push consumer object  2 , and brings up menu  90  from which the user selects, for example, to show exiting filters. This results in the dialog of  FIG. 8  from which the user selects filter  2  for modification from menu  91 . This results in a filter object  2  being removed from the line, or running process, which continues to run while the selected filter object is modified as previously described. 
   One of the preferred implementations of the present invention is as a routine in an operating system made up of programming steps or instructions resident in RAM  14 ,  FIG. 2 , during computer operations. Until required by the computer system, the program instructions may be stored in another readable medium, e.g. in disk drive  20 , or in a removable memory, such as an optical disk for use in a CD-ROM computer input or in a floppy disk for use in a floppy disk drive computer input. Further, the program instructions may be stored in the memory of another computer prior to use in the system of the present invention and transmitted over a LAN or a WAN, such as the Internet, when required by the user of the present invention. One skilled in the art should appreciate that the processes controlling the present invention are capable of being distributed in the form of computer readable media of a variety of forms. 
   Although certain preferred embodiments have been shown and described, it will be understood that many changes and modifications may be made therein without departing from the scope and intent of the appended claims.