Front End XML For ASP Developers - There's a Bonus (Page 4 of 5 )
One of the most wonderful additions to the MSXML library (starting with version 3.0) is the ServerXMLHTTP class. It allows for seamless communications over the HTTP protocol from any language that has integration with COM architecture. This includes ASP, Visual Basic, C++, etc.
Why is this so important? We could use socket connections to do the same thing, couldn't we? Well, yes and no. Because this component understands the HTTP protocol syntax, most of the protocol communication functionality is hidden from developers, thus allowing them to focus on business logic.
Very often, ServerXMLHTTP acts as part of custom protocols built between different tiers of applications. The process is best described with the following diagram:
This logic virtually eliminates the complexity of such sophisticated protocols as RPC, RMI, DCOM, or CORBA, and yet still manages to mimic most of the functional requirements of these protocols, and then some.
It has a major advantage over all other protocols. Because the server software is a standard HTTP web server, this type of communication is not tied to any specific Operating System, programming language or technology. Nor does it require any additional software or special configurations on either one of the tiers.
No Cure For All As with any other technology, XML has its disadvantages and drawbacks. XML solves some development hassle, but may create performance problems and lack of standards across organizations.
Correctly formatting data as XML increases its size ten-fold or even more, which leaves very large XML streams to be loaded into parsing components. Any significant (by database standards) number of records would take seconds to load in MSXML.
On the other hand, the freedom XML gives developers in terms of syntax often backfires. Even within same organization, the number of custom XML dictionaries (DTD's) can reach dozens, most of them dealing with very similar problems.
It is true that there are such standards as OFX (Open Financial exchange), which is a set of XML tags that can represent any financial information, but the industry is nowhere near to controlling how developers manipulate XML tags within their applications.