Abstract:
A look-up function and query capability of aspects associated with aspect objects is enabled in a client device. A web client application, such as a web browser, executes in the client device. The aspects are associated with functions of real world objects such as pumps, motors, mixing units, compressors, conveyors, transformers or switchgears. The client device does not need to be pre-loaded with any specific software relating to a control system other than the web browser.

Description:
TECHNICAL FIELD 
     The present invention is concerned with control systems where real world objects are represented as Aspect Objects. The method and the system according to the invention are particularly suitable for use in industrial plants of industries such as a chemical, pharmaceutical, food, metal, mines, building material, pulp and paper. Other industries and utilities where the invention is particularly useful are automotive, consumer products, power generation, power distribution, waste water handling, oil refineries, pipelines and offshore platforms. 
     BACKGROUND ART 
     WO00102953, hereby incorporated by reference, entitled “Method of integrating an application in a computerized system” describes a method to represent real world objects (referred to as real world entities in WO00102953) in a computerized system in a systematic way, in which different types of information about the real world object may be obtained, linked to the real world object, processed, displayed and acted on. In WO00102953 a real world object is represented by a certain kind of software object called a composite object. Each application integrated in the computerized system defines interfaces that are independent of the implementation of the application itself. These interfaces may be used by other applications, implementing other aspects or groups of aspects of a composite object (hereinafter in this description a composite object is referred to as an Aspect Object), such that the applications can co-operate to provide a functionality for the representation of a real world object that is the sum of all aspects. A problem with the method disclosed in WO00102953 is that it does not disclose how to resolve access to an Aspect of an Aspect Object based on Internet technology. 
     U.S. Pat. No. 6,170,007 describes how a web server in a device provides access to the user interface functions for the device through a device web page. A network interface in the device enables access to the web page by a web browser such that a user of the web browser accesses the user interface functions for the device through the web page. A remaining problem is how to get access from a web browser to different functions of a real world object represented as an Aspect Object, such as a CAD-drawing or maintenance record of the device, where the functionality resides in a number of unrelated applications. 
     U.S. Pat. No. 6,400,997 describes an apparatus and a method for factory automation and tracking with focus on a factory automation apparatus, which includes a plurality of portable tablets and an automation server in a wireless communication. 
     There are a number of enabling technologies, which enable remote access across a network. Examples of such technologies are RPC (Remote Procedure Calls), DCOM (Distributed COM) and CORBA (Common Object Request Broker Architecture). Another example of a technology enabling remote access to objects by use of Internet technologies is called Web Services. 
     WO 0077653A1 describes a method and apparatus for providing network services. The description relates how HTTP (Hypertext Transfer Protocol) may be used, including the HTTP methods GET and POST to provide input data for a web service. The description also includes such functions as one called a Web Service Provider and one called a Web Services Directory. The latter function provides information about which web services are available and where they may be found. A remaining problem is to enable access to an Aspect of an Aspect Object from a World Wide Web presentation means, which Aspect represents a function or facet of a real world object connected to a control system, such as a industrial control system. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to enable a web client application to access a function of a real world object represented as an Aspect Object in a Control System. 
     This object is achieved by a method to enable access to a function of a real world object represented as an Aspect Object in a Control System, the method comprising calling a Control System from a web client application in a client device, downloading from the Control System a representation of the Aspect Object and Aspects associated with the Aspect Object, downloading from the Control System a representation of an Aspect Category and an Aspect Type, and downloading a representation of an Aspect System Object to the client device wherein a function of the real world object is enabled for access. Compared to the prior art this enables a user of the client device to easily access functions of a large number of real world objects represented as Aspect Objects from the client device which does not need to be pre-installed with software referring to Aspect Objects, Aspects, Aspect Types or Aspect System Objects of the Control System. 
     It should be appreciated that since the query for a reference to an interface of the Aspect System Object and an associated table look-up is performed in the client device, instead of in the Control System, the Control System is more efficiently used, which provides for increased reliable control of the real world objects. 
     Another object of the invention is to provide a computer program that causes a computer or processor to carry out one or more steps of the above described method. 
     Yet another object of the invention is to provide a computer readable medium having a program recorded thereon, where the program is capable of making a computer perform any of the steps in the above described method. 
     Another object of the invention is to provide a control system for access of a function of a real world object associated as an Aspect of an Aspect Object, the Control System comprising means for handling a call from a client device external to the Control System, means for downloading to the client device a first software component comprising a representation of the Aspect Object and an Aspect associated with the Aspect Object, means for downloading to the client device a second software component, which second software component comprises a representation of an Aspect Category and an Aspect Type and means for downloading an Aspect System Object to the client device wherein a function of the real world object is enabled for access. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described in more detail in connection with the enclosed schematic drawings. 
         FIG. 1  shows an overview of a method according to the prior art. 
         FIG. 2  shows a more detailed overview of the table look-up of a method according to the prior art. 
         FIG. 3  shows an overview of a method according to the invention, a web server and a user of an Internet client application who intends to access a function of a real world object. 
         FIG. 4  shows an example of two software components, which, according to the invention, are downloaded to the web client application. 
         FIG. 5  shows schematically a system based on the invention, where the name look-up of an Aspect is performed in the same computer or computing client device as where the web client application is executing. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In order to appreciate the invention it is beneficial to study some specific prior art. WO00102953 describes a method for integration of many and various types of applications in a computerized system, based on a concept where real world objects are represented as Composite Objects. Examples of a real world objects are a valve, a transmitter, an actuator or a sensor. An example of a more complex real world object is a mixing unit, a motor, a compressor, a reactor, a boiler, a conveyor, a switchgear unit or an industrial robot. Yet another example of a real world object is a product, a raw material or a production batch. A Composite Object is in this application referred to as an Aspect Object. Different functions or facets of a real world object, such as its physical location, the current stage in a process, a control function, an operator interaction, a simulation model, some documentation about the real world object are described as different Aspects of the Aspect Object. Each Aspect Object is a container for one or more Aspects. An Aspect Object is not an object in the traditional meaning of object-oriented systems, but rather a container of references to such traditional objects, which implement the different Aspects.  FIG. 1  shows a schematic overview of how according to the prior art a client application  1  in a computerized system  10  gets access to a function associated with an Aspect of an Aspect Object  3  representing a real world object  11 . The client application  1  queries an Aspect Object  3  for a reference to an interface that provides the function. The client application queries the Aspect Object  3  by invoking a method of a known interface  2  of the Aspect Object  3 . A typical name of such of a method of such an interface  2  is QueryAspectInterface. In the system according to the prior art a reference to an interface of an Aspect System Object  8  is found by means of a Table look-up  4 , the reference is returned to the client  9 . An Aspect System Object  8  is, for example, a COM object that provides access to at least part of the functionality of an Aspect. According to the prior art objects are, for example, identified by class identifiers (CLSID) and interfaces are, for example, identified by interface identifiers (IID). An Aspect System Object is initialized with a reference (i.e. a pointer) to an Aspect. The Aspect System Object  12  may contain several references of interfaces, which enable access to traditional objects and software applications. 
       FIG. 2  shows the mechanism of the table look-up  4 , according to the prior art, in more detail. According to the prior art the mechanism for finding a reference to an interface of an Aspect System Object  8  involves that a client application  1  queries an Aspect Object  3  for a reference to an interface.  FIG. 2  shows that the Aspect Object  3  examines its Aspects, including Aspect 2   22  through the Aspect Category  23 . An Aspect Category  23  identifies the Aspect Type  24 , which describes a piece of a software application, which is integrated in the computerized system. Such a piece of a software application may for instance implement methods associated with functions of a real world object  11 . Examples of such functions are open, close, start, move, mix or heat. Examples of more complex functions are “disconnect phase fault” or “adapt to second type of car body”. Access to functions through interfaces of Aspect System Objects according to the prior art involves instantiation of Aspect System Objects, Composite Objects, the Aspect Category, and the Aspect Type, implemented, for example, as COM objects. Such instantiations are made in clients and servers of an Aspect based computerized system  10 , such as a Control System. A drawback with prior art is that it requires software, such as for example dll&#39;s (dynamic link libraries) to be preinstalled in the client devices hosting the client application  1 . 
       FIG. 3  shows an overview of a method according to the present invention. The method enables access to an Aspect of an Aspect Object from a web client application, such as a web browser, which executes in a client device, without requiring that the client device  32  is pre-installed with any software other than the web client application  31 . A web client application is any software application that is intended for general use on an Intranet or Internet  30 , hence a web browser is an example of a web client application. An instance of the Aspect Object  38  resides in a control system  10 , which comprises at least one Aspect System  39 . The Aspect Object  38  may have been instantiated in the Control System before the method is applied. The Control System  10  typically comprises a plurality of Aspect Systems. An Aspect System  39  makes it possible to create and associate Aspects to Aspect Objects  38  in the Control System  10 . When a new function is added to the Control System  10 , software is typically supplied as an Aspect System  39  to the Control System  10 . 
       FIG. 3  shows an overview of a method according to the invention. A web client application  32 , which executes in a client device  31 , calls a control system  10  and requests for a representation of an Aspect Object. The Control System comprises at least one Aspect System  39 . As an example of how a call can be initiated, a user  31   b  of the web client application may initiate the call. For instance a process operator may request to access a certain Aspect of an Aspect Object. The call is performed across the Internet or an intranet  30 . The call may be divided into a plurality of messages. A first software component  34  is downloaded via the Internet or the intranet  30  to the client device  32 . The first software component  34  comprises a representation of the Aspect Object  38  and at its Aspects  39 . After the download of the first software component  34  to the client device  32 , the Aspect Object  38  represented in the first software component is initialized by the web client application  31 . It may also be said that the web client application incarnates the Aspect Object  52 . A second software component  36  is also downloaded to the client device  32 , which second software component  36  comprises a representation of an Aspect Category  43  and an Aspect Type  44 . The information in the first and second software components is used to request a representation of an Aspect System Object that corresponds to the Aspect which is requested by the web client application  31 . The control system  10  supports a download of the representation of the Aspect System Object  39   b . The downloaded Aspect System Object  51  is initialized in the client device  32 . 
       FIG. 4  shows a more detailed representation of the first software component  34  and the second software component  36 .  FIG. 4  shows that after downloading the first  34  and the second  36  software component to the client device, the client device comprise software capable of performing a table look-up to find a reference to the Aspect System Object that implements the function. The table look-up is initiated by the web client application  31 , which calls a method of an interface of the Aspect Object  38 . An example of name the method of the interface is QueryAspectInterface. In one embodiment an interface type is passed as a parameter to the Aspect Object  38 . The interface type is denoted as a .NET interface type (.NET is a Trademark of Microsoft Inc.). This in contrast to a table look-up according to the prior art, which typically involved an interface type denoted as a COM interface identifier (IID). It should be noted that compared with  FIG. 2 ,  FIG. 4  shows that the first and second components are downloaded to the client device, and may exist anywhere on any client device in an intranet or the Internet. This in contrast to the prior art as indicated by  FIG. 2 , where an Aspect Object and Aspect Type reside within the Control System. In one embodiment of the invention the first software component  34  is downloaded before the second software component  36 . In another embodiment the second software component  36  is downloaded before the first software component  34 . The software component may also be divided into several packages or messages. As an example the representation of the Aspect Object of the first software component may be sent in a package other than one or several Aspects  42 . 
       FIG. 5  shows schematically a system based on the invention. The system enables a web client application  31  to use a table look-up  53  local to the client device  32 , which is a more efficient approach when it comes to using resources of the Control System  10  compared to a system according to the prior art. A user of the web client application  31  may, through a user interface of the client device  32 , query an Aspect of the Aspect Object  52  by a reference of an interface of the Aspect System Object  51 . A reference of an interface of the Aspect System Object  39  is received  54  by the web client application  31 . The Aspect System Object  51  handles the calls to a corresponding Aspect System  39  in the Control System  10 , which implements the function. The Aspect System Object  51  previously initialized in the client device  32  provides access to the functions implemented by the Aspect System  39  in the Control System  10 . Communication between the Aspect System Object  51  and the Aspect System  39  is, for example, implemented as web services defined in Hyperscript Markup Language (HTML).