Re: xml to green screen application -- MIDRANGE-L

----- Original Message -----
From: "Brad Stone" <brad@bvstools.com>

> Are you referring to displaying XML as a green screen
> display file, as opposed to using it for HTML on a web page?

No. I realize this is a little unusual.  And frankly I don't know
everything it is being used for.

I am going to take the long way around on this and explain a
little about XML.

XML is used to send structured messages (often database-like)
across the internet by enclosing text in tags that look like HTML.

So for a particular database entry you might have:

<customerrecord>
<name>Brad Jensen</name>
<address>9810 E 42nd Street</address>
<city>Tulsa</city>
</cusomerrecord>

part of the power of XML is that you can make up your own tags.
You can have an XML transmission that contains, for example, the
equivalent of a master record and many transaction records. The
receiving end gets an object that looks like this

customerrecord.name="Brad Jensen"
customerrecord.address="9810 E 42nd Street"

etc. The receiving end can respond with more XML to the original
sender.

You can just make up tags on the fly, or you can include a
Document Type Definition as part of the XML. This says what the
tags are supposed to look like, and lets you syntax check the
tags.

You can put all sorts of object in XML, including pictures, audio,
etc. (I guess they MIME encode it, I haven't gotten that far
actually using it yet.)

Now, why would you want something that could translate between XML
and a green screen application?

One reason would be to have a very rapid and flexible method for
integrating web pages with your (God Bless Them) legacy
applications. ODBC and OLE DB are fine, but there is more to an
application than reading and writing data records. If you try to
reproduce your business logic that is in your current applications
with CGI programs, you have the double whammy of debugging both
CGI problems (which can be nontrivial) and keeping your logic
correct. If the application program changes and evolves, your CGI
version also has to change exactly the same way.

Suppose you want to look up an item using an item number. You
create a web page that inputs the item number field, you wrap it
in XML and send it to the XML-to-greenscreen converter. It does a
good old fashioned item lookup using your regular software. The
response that is returned to the screen gets wrapped in XML and
returned to the web application, which displays it as a web page.
The web page won't look anything like a green screen application.
You may not be the information directly, you may just be doing a
price lookup or quantity on hand for an ordering system.

If it is done with some intelligence, then the greenXML server can
logon as multiple screens to handle many conversations at once, it
might email confirmations, page the operator when needed, keep a
log file, generate status web pages, or do anything else you can
do from a PC.

You use a generalized XML application to do this, because it is a
lot simpler and more robust than screen scraping, and much more
scalable. And now you have a generalized solution, instead of a
hard coded single solution. And you can do it without modifying
canned software, or meddling with the database, or even knowing
the internals at all.

I realize my initial posting was far from clear. I hope this
helps.

And please don't take my simplified XML explanation as gospel.
It's meant to be a broad outline.

Brad Jensen