Abstract:
A system for, and method of, constructing an Object Linking and Embedding (OLE) for Process Control (OPC) compliant data server from a device-specific noncompliant user application and a real-time process control system employing the system or the method. In one embodiment, the system includes: (1) a generic OPC compliant interface object and (2) a template associated with the generic OPC compliant interface object. The template is modifiable and combinable with a device-specific interface portion to yield the device-specific noncompliant user application. The device-specific noncompliant user application is dynamically linkable with and aggregates to the generic OPC compliant interface object to yield the OPC compliant data server.

Description:
COPYRIGHT NOTICE 
     A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyrights whatsoever. 
     REFERENCE TO COMPUTER PROGRAM LISTING APPENDIX 
     A computer program listing appendix containing computer program listings of a template and associated documentation in a file named “ProgramListing.txt” having a file size of 59 KB and created on Jun. 13, 2003 from a Previously submitted microfiche is submitted with this application and is incorporated herein by reference. 
     TECHNICAL FIELD OF THE INVENTION 
     The present invention is directed, in general, to real-time process control systems and, more specifically, to a system and method for constructing an Object Linking and Embedding (OLE) for Process Control (OPC) compliant data server from a noncompliant user application and a real-time process control system employing the system or method. 
     BACKGROUND OF THE INVENTION 
     Real-time process control systems were first implemented within a single computer system. As the need to monitor and control more physical devices increased, the complexity and size of the process control systems also increased. Shortly thereafter, single computer real-time process control systems were unable to process all the information within a timely manner as required by the real-time process control environments. 
     To correct this processing problem, real-time process control systems evolved into multiple computer systems that were connected to each other with proprietary communication interfaces. The multiple computer systems processed data locally and then communicated the information to the other computer systems over the proprietary communication interfaces. Since, the computer systems did not use a standard communication interface nor a standard protocol between each of the computer systems, modifications and additions to the systems were difficult, if not impossible. 
     This inter-computer incompatibility problem was resolved when the computer industry developed standardized networks and network protocols. Two of the industry standards were Ethernet and Transmission Control Protocol/Internet Protocol (“TCP/IP”) used on  10  base  2  coaxial cable. Ethernet and TCP/IP allowed various computer systems the ability to communicate to each other without using proprietary communication interfaces. 
     The next evolution in real-time process control systems was object oriented distributed processing. In object oriented distributed processing, requesting programs (“clients”) would call resource programs (“objects”) to process a request. In this design, the clients and objects may be located on different computers on the network or are on the same computer. To facilitate a standardized way for clients to locate and communicate with objects, Microsoft Corporation developed the Component Object Model (“COM”) protocol. The COM protocol, incorporated into software libraries called “COM libraries,” defines a standardized interface for locating and communicating to objects over the network without requiring the clients to know the location of the desired objects. 
     The process control industry incorporated the COM standard and Object Linking and Embedding (“OLE”) in its real-time process control standard, calling the resulting standard OLE for Process Control (“OPC”). The OPC standard defined the interfaces for distributed real-time process control object processing. 
     For companies to sell real-time process control systems, the real-time process control systems had to be COM and OPC compliant. This required the developers of the systems to have learned the intricacies of the COM and the OPC standards. Next, the programmers had to write detailed software programs that implemented the COM standards. Then, the programmers had to write detailed software programs that implemented the OPC standards which incorporated the COM standards. Finally, the programmers had to repeat this process for each type of distributed object processing that was performed within the real-time process control system. 
     When the programmers found an incorrect implementation of the COM and the OPC standards, the programmers had to correct each software program that was affected. This whole process incurred a great amount of time and expense. What is needed in the art is a way to rapidly develop COM/OPC compliant software for real-time process control systems. 
     SUMMARY OF THE INVENTION 
     To address the above-discussed deficiencies of the prior art, the present invention provides a system for, and method of, constructing an OPC compliant data server from a device-specific noncompliant user application and a real-time process control system employing the system or the method. In one embodiment, the system includes: (1) a generic OPC compliant interface object and (2) a template associated with the generic OPC compliant interface object. The template is modifiable and combinable with a device-specific interface portion to yield the device-specific noncompliant user application. The device-specific noncompliant user application is dynamically linkable with and aggregates with the generic OPC compliant interface object to yield the OPC compliant data server. 
     The present invention therefore introduces the broad concept of dividing an OPC compliant data server into two distinct portions: a first portion that is generic and OPC compliant and a second portion that is specific to an underlying device or process control system and does not need to be entirely OPC compliant. A user wishing to create an OPC compliant data server is merely required to customize a template to yield the second portion. During run-time, the first and second portions are dynamically linked. The second portion aggregates the first, allowing the noncompliant second portion to inherit at least some of the attributes of the compliant first portion. 
     In one embodiment of the present invention, the system further includes a class factory that creates multiple related instances of objects. In a related embodiment, the class factory creates objects and manages global resources with respect to the objects. Those skilled in the pertinent art are familiar with class factories and their use in other object-oriented environments. The present invention can employ class factories to instantiate the objects needed to enable a particular server. 
     In one embodiment of the present invention, the system further includes a cache memory associated with the generic OPC compliant interface object. The generic OPC compliant interface object retrieves items from the cache memory in response to requests from multiple OPC clients. In a related embodiment, the generic OPC compliant interface object retrieves information from a device through the device-specific noncompliant user application and stores the information in the cache memory. 
     In one embodiment of the present invention, the class factory is capable of self-registration. However, the present invention need not be capable of self-registration. 
     In one embodiment of the present invention, the generic OPC compliant interface object is Component Object Module (COM) compliant. Those skilled in the pertinent art will perceive, however, that the present invention may be employed to advantage in object-oriented environments that are not COM-compliant. 
     The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 illustrates a block diagram of a real-time process control system that forms one environment within which the present invention can operate; 
     FIG. 2 illustrates a block diagram of a real-time process control software architecture; 
     FIG. 3 illustrates a block diagram of the overall process of creating an OPC compliant data server according to the principles of the present invention; and 
     FIG. 4 illustrates a block diagram of an OPC compliant data server of FIG. 3 constructed according to the principles of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring initially to FIG. 1, illustrated is a block diagram of a real-time process control system, generally designated  100 , that forms one environment within which the present invention can operate. The real-time process control system  100  comprises a network  110  that interconnects a server  102 , an operator interface  104  and a field unit  106 . In the illustrated embodiment of the present invention, the real-time process control system  100  may comprise any number of servers  102 , operator interfaces  104  and field units  106 . 
     The network  110  comprises an industry standard network and industry standard network protocols. In the illustrated embodiment, the industry standard network is “ 10  base T,” employing twisted pair cables. Other embodiments of the present invention use other networks comprising “ 10  base  2 ” employing coaxial cables, fiber optic cables or a combination of the two. Wireless communications may also be used for all or part of the network communications. The industry standard network protocols, in one embodiment of the present invention, are ETHERNET® and Transmission Control Protocol/Internet Protocol (“TCP/IP”). 
     The server  102  comprises software programs that monitor, process information, and control the physical devices within the real-time process control system  100 . The software programs comprise a requesting program “client,” and a resource program “object” and other miscellaneous programs. The client program sends requests to object programs to perform specific functions. The object programs receive requests and perform the appropriate functions based upon the type of requests sent. The client programs and object programs communicate over the network  110  or internally within the server  102 . 
     The operator interface  104  comprises a computer and a display. The operator interface  104  displays information concerning the current state of the system  100 . The operator interface  104  also accepts operator input to perform functions such as controlling a physical device or requesting other information to be displayed on the operator interface&#39;s  104  display. The operator interface  104  may comprise both client programs and object programs. The operator interface  104  communicates to other programs over the network  110 . 
     The field unit  106  comprises object programs that perform tasks related to the physical devices that make up the real-time process control system  100 . In one embodiment of the present invention, the field unit&#39;s object programs collect status information, process data and control the physical devices. In other embodiments, the field unit  106  may perform more or less functions than described above. The field unit  106  responds to client&#39;s requests over the network  110 . 
     Turning now to FIG. 2, illustrated is a block diagram of a real-time process control software architecture, generally designated  200 . The real-time process control software architecture  200  comprises an operator display software  202 , a data processor software  204 , an alarm processor software  206 , a trend processor software  208 , a scan processor software  220 , a historical processor software  222 , a report processor software  224 , a field unit software  230 , a database software  240  and the network  110  of FIG.  1 . In the illustrated embodiment of the present invention, the real-time process control software architecture  200  may comprise a plurality of the above software types. 
     The operator display software  202  displays the real-time process control system  100  information on a display or a plurality of displays. The operator display software  202  also processes the operator requests and communicates to other real-time process control software over the network  110 . 
     The data processor software  204  processes the data collected and the data generated from the real-time process control system  100 . The data processor software  204  stores and retrieves data to the database software  240  and communicates to other real-time process control software over the network  110 . 
     The alarm processor software  206  performs alarm processing on the data collected. The alarm processor software  206  notifies the operator display software  202  and the report processor software  224  of any alarm conditions or non-alarm conditions that exist in the real-time process control system  100 . The alarm processor software  206  also stores and retrieves information from the database software  240  over the network  110 . 
     The trend processor software  208  performs trending functions for the real-time process control system  100 . The trend processor software will collect operator selected data, generate the desired trend information and distribute the trend data to the operator display software  202  and the database software  240  over the network  110 . 
     The scan processor software  220  collects data from a plurality of field units  230  and converts the data into the appropriate form usable by the real-time process control system  100 . The scan processor software  220  distributes, over the network  110 , the collected data to the other software processors so the software processors can perform their associated functions. The scan processor software  220  also stores and retrieves information from the database software  240 . 
     The field unit  230  collects the specific data from the physical devices attached to the field unit  230 . The physical devices are not shown since there are a multitude of physical devices that can be monitored by a real-time process control system. The field unit  230  sends the physical device data to the scan processor software  220 . The field unit  230  also processes control requests. 
     The historical processor software  222  collects and processes historical information about the real-time process control system  100 . The historical processor software  222  also performs archival functions and stores information to the database software  240 . 
     The report processor software  224  generates the reports for the real-time process control system  100 . The report processor software  224  sends the generated reports to the operator display software  202 , the historical processor software  222 , the database software  240  and to printing devices if attached to the system  100 . 
     The database software  240  processes all request for retrieval and storage of information for the real-time process control system  100 . In other embodiments of the present invention, the system  100  comprises a plurality of database software units contained on a plurality of computers. 
     Those skilled in the art should know that other embodiments of the present invention may include a plurality of processing software described above. Also, other embodiments of the present invention may include more or less processing software types and contain more or less functional capabilities than described above. 
     Turning now to FIG. 3, illustrated is a block diagram of the overall process of creating an OPC compliant data server according to the principles of the present invention, generally designated  300 . The user of the present invention starts with a template  310  and a device specific interface  320 . The template  310  is a collection of source code for data server software routines such as the ones disclosed in the computer program listing appendix submitted with this application and are incorporated herein by reference. The user then modifies the template  310  to meet the user&#39;s specific real-time process control requirements. 
     The device specific interface  320  is the user&#39;s software program that interfaces with the user&#39;s specific device or devices. The user combines the template  310  and the device specific interface  320  to produce a device specific noncompliant user application  330 . 
     The device specific noncompliant user application  330  performs the user&#39;s required functions, but is not OPC compliant. In the illustrated embodiment of the present invention, the invention also comprises a server base dynamically linked library (“server base DLL”)  335 . The server base DLL  335  comprises software routines, when implemented with the device specific noncompliant user application, allows the device specific noncompliant user application  330  to perform data server functions. The advantage of using the server base DLL  335 , is that the user saves time by not programing the data server functions. 
     The present invention also comprises a set of software programs that implement the OPC/COM interface standards in the form of a generic OPC compliant interface object  340 . Since the generic OPC compliant interface object  340  is also COM compliant, the generic OPC compliant interface object  340  is capable of self-registration. 
     In the illustrated embodiment of the present invention, there is aggregation between the device specific noncompliant user application  340  and the generic OPC compliant interface object  340 . Aggregation is a method, under the COM standard, to implement object inheritance associated with object oriented distributed processing. In aggregation, an outer object passes the inner component&#39;s interface pointer directly to the client program instead of reimplementing all the functions of the interface and then forwarding the call to the inner component. In the present invention, the interface of the device specific noncompliant user application  330  aggregates to the generic OPC compliant interface object  340 . 
     Background information concerning COM aggregation is discussed in Inside COM by Dale Rogerson, Microsoft Press 1997 and in Essential COM by Don Box, Addison-Wesley 1998. The foregoing publications are incorporated herein by reference. 
     Next, the user links the base server DLL  335  and the generic OPC compliant interface object  340  with the device specific noncompliant user application  330  to produce the final OPC compliant data server  350 . The OPC compliant data server  350  is the data server for a specific device. The above process is repeated for each device in the real-time process control system  100  requiring an OPC compliant data server. 
     In the illustrated embodiment of the present invention, the generic OPC compliant interface object  340  is a set of dynamically linkable libraries (“DLLs”). When the user links the DLLs, the DLLs are not incorporated into the OPC compliant data server  350  executable software. The OPC compliant data server  350  executable software contains operating system calls that will load the DLLs when needed. 
     The advantage of using DLLs for the OPC/COM compliant interface software and the server base software is that when new updates to the OPC/COM compliant interface software or the server base software are distributed, the user does not have to recompile all the software they have written. The user merely loads the new DLLs on the machine where the OPC compliant data server  350  is located and reinitialize the software program. Thus, the present invention saves the user a tremendous amount of time and effort by not requiring the user to recompile the user&#39;s software programs each time a correction or enhancement is made to the OPC/COM compliant interface software. 
     Those skilled in the art should note that the present invention is not restricted to the use of a generic OPC compliant interface object in the form of DLLs. The use of a generic OPC compliant interface object may be implemented on different types of operating systems that may or may not use DLLs. Also, those skilled in the art should realize that the procedure described above is an overview of the use of the present invention and the present invention is not limited to the procedure described above. 
     Turning now to FIG. 4, illustrated is a block diagram of an OPC compliant data server of FIG. 3 constructed according to the principles of the present invention. The OPC compliant data server  350  comprises one or more instances of a device specific server  410 , a cache memory  420  and a class factory  430 . Each instance of the device specific server  410  comprises the device specific noncompliant user application  330  and the generic OPC compliant interface object  340 . See FIG. 3 for a description of the use and advantages of the generic OPC compliant interface object  340 . Each instance of the device specific server  410  processes client requests and communicates with the appropriate physical device. 
     The cache memory  420  comprises a cached storage area used by the OPC compliant data server  350 . In one embodiment of the present invention, a client program requests information from the OPC compliant data server  350 . The generic OPC compliant interface object  340  then retrieves the appropriate data from the device through the device specific noncompliant user application  330 , returns the data to the client and stores the data in the cache memory  420 . Upon subsequent requests from clients, the generic OPC compliant interface object retrieves the data from the cache memory  420 . The cache memory  420  increases throughput and performance of the OPC compliant data server  350 . 
     In another embodiment of the present invention, for each client information request, the generic OPC compliant interface object  340  retrieves the appropriate data from the cache memory  420  and returns the data to the client. Upon a predetermined interval, the generic OPC compliant interface object  340  retrieves the appropriate data from the device through the device specific noncompliant user application  330  and updates the data in the cache memory  420 . 
     The class factory  430 , which is part of the server base DLL  335 , creates and manages the device specific server  410  instances and performs class registration under the COM standard. The class factory also manages the other resources associated with each instance of the device specific server  410 . 
     Those skilled in the art should note that the OPC compliant data server may contain more or less features than described above. Also, the OPC compliant data server is not limited to Class registration under the COM standard and may be implemented on different operating systems. 
     Although the present invention has been described in detail, those skilled in the art should understand that they can make various changes, substitutions and alterations herein without departing from the spirit and scope of the invention in its broadest form.