XML INFRASTRUCTURE

There are many components to a technology solution. When designing a
database application, for example, there is the database software, the
application software, the hardware that runs the application, and more. 
The
same is true for XML; there are many components to an XML solution. 
Let's 
examine some of the infrastructure surrounding XML technology.

DEVELOPMENT

One of the key ingredients in creating an XML solution is the
development environment. This includes elements such as development 
tools,
operating systems, and other platform considerations. When implementing 
an XML
solution, each of these components plays a key role.

The platform may include the operating system and the underlying
hardware, but it might also include application servers and middleware. 
These
components are important because they may introduce constraints on your 
XML
implementation or they might provide proprietary technology related to
XML. The platform may also include design tools, such as Computer Aided
Software Engineering (CASE), that help facilitate XML development.

The development environment is also important. Considerations include
the obvious issue of programming language, as well as more specialized
tools such as XML design tools. In addition to design tools that are 
part of
a middleware or CASE solution, there are other XML tools that focus
explicitly on creating XML document type definitions (DTDs), schemas, 
and
documents.

PERSISTENCE AND STORAGE

Beyond developing your XML documents, you have to deal with managing
them. This includes both persisting XML data from within an application 
as
well as storing XML documents outside of the application. Persistence 
is
important because your XML data (or object) can't remain in memory all 
of
the time. Most applications have a limited amount of memory they can 
use
to store information. When an XML document is being used by an
application, it's often stored in some type of persistence mechanism. 
This
mechanism keeps track of the current state (or information) of each XML 
document
that's in memory. When a document needs to be accessed and it's state
modified, the document may be pulled out of persistent storage, 
updated, and
put back into persistent storage.

Beyond persistence from within the application, you'll also have to 
deal
with storing XML documents over longer periods of time. This means that
once an application is finished using a particular document, it's
important to keep the document stored for later retrieval. There are 
many
approaches to the storage of XML documents, including relational 
databases,
object databases, and indexed XML files. Each of these approaches has
different merits. The method you choose should reflect how you plan to 
use the
XML documents long term. Archiving XML documents for interactive
searching in a real-time application might require a different approach 
than
simply archiving the documents.

TRANSPORT

Many organizations are using XML not just to describe data for
applications in their organization but also to describe data they share 
with other
organizations. Globally, companies are using XML to help solve
business-to-business integration (B2Bi) issues. How your organization 
moves data
to and from other organizations is an important part of your overall 
XML
infrastructure. The transport you use can affect your options for
security, network access, and overall availability.

There are many ways to share your XML data. These can include 
delivering
direct access to your application via an Application Programming
Interface (API) as well as direct access to your storage platform, such 
as an
Oracle database. These approaches allow an external application to 
directly
access your documents programmatically.

Other approaches include delivering your documents using a traditional
network transfer protocol such as File Transfer Protocol (FTP) and
Hypertext Transfer Protocol (HTTP). These solutions allow a user to 
make use of
standard tools like FTP clients and Web browsers to retrieve the XML
documents.

SUMMARY

Developing an infrastructure around your XML documents will help your
XML initiatives be more successful. Defining a working development
environment may define your XML constraints and capabilities. Your 
long-term
objectives can determine your storage strategy. Finally, your 
integration
solution may be affected by your transport mechanisms.

Brian Schaffner is a senior consultant for DMR Consulting, a Fujitsu
company. He provides architecture, design, and development support for 
DMR's
Telcom360 group.

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