a/d trends - Thin Clients: The Lazy Developer's Client/Server Model
For years, the marketing promises of the "thin client" model of client/server computing sounded more like snake oil than a real, proven cure. Suddenly, that snake oil is looking more like Viagra. What happened?
Originally, thin client was lovingly referred to as "screen scraping." The idea behind screen scraping was that applications that once required character terminals could suddenly run with graphical user interfaces without requiring as much as one line of changed code.
As the world went, "Ho-hum," the AS/400 world rabidly embraced this technology, which takes a 5250 data stream and interprets it as a bitmap on the PC. The bitmap becomes a regular window in Win 3.11, Win 95, NT or OS/2.
The drawback of this technology was that nobody could be fooled into confusing the application with a Windows GUI application. The interface still looked and felt like a "green screen."
I refer to the next level as re-facing.
Once again, without changes to the good old RPG/CL/DDS code, re-facing technology actually provided a graphical facade to the 5250 screens. Instead of punching "2" and then "enter" on the command line, a user could point to the desired option and click the mouse. (Behind the scenes, the re-facing tool played a sleight-of-hand and produced the 5250 data stream equal to "2", "enter"). This technology worked quite well for PC clients. IBM used this technology, known as Graphical Access, for OS/400 operating system commands.
The weakness here was that the tools used had to generate different versions for different clients. Furthermore, users of the tools quickly realized that the product only worked on a basis of "you can't use what you don't already have." Pressure came back on developers to change the applications.
Next came network computing, making screen scraping even more exciting, since dependencies on the client were eliminated. With technologies like 5250 -to -HTML gateway, the existing AS/400 application (unchanged for the past 10 years), could become fully Web-enabled and accessible through any browser. Many vendors followed with tools for doing this. New types of client hardware became available. Customers could suddenly choose to use IBM network Stations, that came with 5250 emulation capabilities, or use their browser and Java capabilities.
The recent Terminal Server Edition announcement from Microsoft is the icing on the thin client cake and is generating interest throughout the entire IT world. Terminal Server Edition brings multi-user function to NT 4.0, allowing any type of PC with Win 3.11, Win 95 or NT to access it. Microsoft used to call this "Hydra."
In addition, Citrix Systems Inc. now supports an additional product called MetaFrame. This supports the ICA interface for other devices, like Mac, DOS, Unix and others. Instead of requiring DOS-based PCs, the user now can run on any PC or NC, so long as it is attached to an NT server with Terminal Server Edition and MetaFrame.
Why is this technology so exciting? Simply because it solves so many customer problems so elegantly.
Customer problems generally originate when their users become dependent on a mixture of client applications. There are some DOS, some Win 3.11, some Win 95, some NT, some OS/2, some Mac and some Unix. What client operating system do you run if you need to connect all of these? How could these diverse operating systems ever be integrated?
Along came technology from Citrix, which evolved to a multi-user NT. The solution came right from the IBM mainframe textbook -- have a single, central computer timeshare its cycles to deliver a variety of applications to attached "terminals." This "thin client" only requires the bitmaps of the screen and the tracking of mouse movements.
It gets a little complicated. This interface originally was X.11, but Citrix evolved it to what is called ICA. After Microsoft got into the picture, they developed a variant called T-share.
Recent IBM Network Stations now also provide full support for ICA. And what does this mean for the AS/400?
Well, remember how difficult it is to convince users that are dependent on Office 97 to switch to Network Stations? Remember how hard it is to wean users off DOS applications and old PCs in order to prepare them for newer e-business or client/server technologies? How can all these systems be converged onto a single desktop, and then provide room to grow with new technologies such as Java or ActiveX?
A 200 MHz IPCS running NT 4.0 with Terminal Server Edition and or MetaFrame is all it takes. And it leaves the rest of the AS/400 alone to do the 64-bit things it likes to do.
In the end, this "new development" is a bit like those clothes you leave in the back of the closet -- you know if you wait long enough, they'll come back into fashion.
In the case of the brave new world of the thin client, I maintain you'll be able to spot the difference!
--Mark Buchner is president and founder of Astech Solutions Inc. (Aurora, Ontario), which applies technology to the practical needs of the AS/400 market. firstname.lastname@example.org.