While technology is advancing in leaps and bounds, is it actually keeping up with the needs of its end-users?
Yesterday, solutions were developed within the confines of proprietary development languages, approaches and databases. But these can no longer cope with the rapidly changing needs of the real world. There will probably never be a silver bullet for this but rather an evolutionary path that will increasingly provide end-users the functionality they need without resorting to complex programming. XML is just such an evolution and has been put to the test in Wonderware's SuiteVoyager portal platform.
The Internet is reshaping this world. Your choice of computing platform may eventually become a non-issue. The key issue will be that which defines what the Internet is all about - communications or, more specifically, conversation. To converse on the Internet you have to speak a language that everyone understands. Today, the language of the web is hypertext markup language (HTML), which is supported by the hypertext transfer protocol (HTTP) and its secure version, HTTPS. HTML was great for static web pages - the stuff you used to read before the onslaught of flashing neon artwork launched an epidemic of migraine headaches among Internet surfers far and wide. To produce all this flash, web designers have been using Java, ActiveX and other proprietary technologies that need browser plug-ins, such as Macromedia Flash.
While these technologies are great for this type of application, they have limitations when it comes to extending the scope of web functionality - especially if you are thinking about enhancing the usefulness of, say, your human-machine interface (HMI) or control software by adding some programmability.
Enter XML, the eXtensible markup language, which is a subset of HTML. Just like today's tools that generate HTML on the fly, tools are quickly becoming available that can be used to generate XML on the fly to be delivered to end users' web browsers. What is great about XML is that we can use it to do some of the things we now do with traditional object-oriented programming techniques. In terms of communications, we have arrived at the third level in Windows technologies. First, there was dynamic data exchange (and its network equivalent, NetDDE). This moved data primarily among Windows applications, but was not very object oriented. Next, Microsoft's component object model (COM) and its network equivalent, Distributed COM (DCOM), set the stage for sharing object-based communications; this became the foundation for OLE for process control (OPC).
What might object-based data be? How about a pressure reading from a smart pressure transmitter, or a compensated flow reading from a smart Coriolis flowmeter? The trouble is that this object model is Microsoft proprietary. To work on other platforms, much of the OLE engine has to be exported and recompiled for use on those platforms. And, of course, other platforms such as Mac and Unix have their own object models. So without some conversion software from a third party or without re-porting and recompiling object engines, you would not be able to move this object-oriented data from one platform to another. There are many that believe XML represents the third level of object-based communications and will have a dramatic impact on the evolution of all software. In fact, some believe that XML might be the transcendent communications solution for all computing platforms.
But what is XML? It is a text-based extensible mark-up language that adds structure and type to information and allows the information to be stored anywhere on the Internet. This allows data from multiple sources to be aggregated into a single unit of information. Each piece of information has application-specific type and an XML-specific structure in human readable text. XML is a universal data exchange format, which is like a contract by which applications can interact with one another. Because XML allows for self-describing information, it facilitates the development of powerful distributed applications.
XML also has the ability to address several layers of data between users' hardware and their applications (Figure 1). While the hardware deals with sectors and bit streams, operating systems, and files/packets, and the application deals with classes and objects, XML can handle entities and documents, elements and attributes, structural items, and types and instances. An XML-based web server can handle client-side editing, the building of SQL queries, the downloading of forms, and the conversion of data objects to HTML.
Other new technologies that can be used with XML include the vector mark-up language (VML), XSL, and the simple object access protocol (SOAP). eXtensible style sheet language (XSL) provides many different views of the same XML data; thus, it can deliver the right view to the right person-operator, engineer, executive and so on. Extensible style sheets allow the developer to separate content from display and to provide the look-and-feel that the user wants. In Wonderware's SuiteVoyager, a built-in style sheet processor acquires data from XML and XSL-based documents and converts the data to fit the end user's viewing device - whether that be a portable digital assistant, laptop, paging device, or a desktop computer (Figure 2).
Wonderware views XML as a roadmap to the future, which is why its SuiteVoyager portal platform makes heavy use of XML as the fundamental communications system. XML is included with the data handlers and will be incorporated in almost every part of SuiteVoyager, including history, alarms, graphics applications, legacy reports, Avantis Reports, business data, configuration and licence manager and, of course, its web-based clients - whatever shape or form they assume. XML brings both industrial data and business information to users, and is believed by many to be a more neutral and open tool than Java or ActiveX. With XML, no compiling is required, and the code is easily extensible.
XML provides connectivity and application interaction at design time and run time and is capable of context interpretation and shared evolution (migration). In other words, XML can resolve many open system issues and takes us one step closer to a new level of 'networkability' that will eventually lead to truly ubiquitous computing.
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