Clarification of tcp/ip socket communication w/data buffers 1

[swebbie]

Hi all,

I'm trying to understand how a Progress-based application interacts with an Access-based application. My consultant explains that they would interface the transactions as XML data buffers (based on DTD files).
Is anyone familiar with this, and if so, could you please provide some explanation, or direct me to documentation?

Thanks so much,

Sunny

 

[bcastner]

I suspect the consultant was saying "go away."

A DTD or Document Type Definition is used to define the allowable syntax used in your documents. By placing a DTD into your document you can validate or check your markup against an established standard. XHTML 1.0 has three flavors of DTD: Transitional, Strict and Frameset.

For a reasonably clear explanation from W3C:

http://www.w3.org/XML/1998/06/xmlspec-report.htm

The answer to your question is unfortunately a little complicated, (and has little to do with TCP-IP).

But as only recently (and to be officially released next month) Access had any official support of XML, what is occuring is that an ODBC connection is made to Access, a SQL query processed, the return information parsed to conform with what Promise requires.

You will allocate buffers to store the results of the Access query; and likely buffers while they are processed into useful form for Promise.

During which you are using Winsock services to open a connection and buffer packets received until they can be processed. Well below that level is TCP-IP that generally does not care if you allocated buffers or not. It is only concerned if you need to request a send of a packet.

I am not criticizing your consultant, and I shortened a lot with the explanation above. There are a whole lot of buffers in RAM, disk, and likely both that are used to make a remote connection to a database, and convert the results into usable form for another database. XML and DTD are ways to force compliance between the two disparate databases so that the end results are meaningful reports. The forcing of XML schemas is relatively new stuff to help make this possible. But the TCP-IP side of the transaction is treated essentially as a "black box" that should not matter to the Promise programmer, or to the Access database being queried.

Hope that helps.
Bill

 

[swebbie]

Bill,

Thanks so much for the help and clarification. No harps about the consultant remark - Historically he's given me garbage answers. Thanks for helping me sort through them.

 

[bcastner]

Promise programmers are like this. They are sheer Gold, and while the underlying database language is very rich it is decidedly not easy.

If you are in a position to manage such beasts, the watchword should be to treat them like artists; but verify. Sort of like how Ronald Reagan treated disarmament negotiations with Gorbachov.

Best.