ELEMENTS OF AN XML SCHEMA REPOSITORY

Developing XML for use in internal applications can be useful for
standardizing the data flowing from one system to another. The real 
power of
XML, however, starts to show when XML is used to share information 
between
organizations. One problem with sharing XML documents is validating the
content and sharing the schema that defines the content model. Using a
repository can provide a centralized resource for publishing and 
retrieving
XML schemas.

WHY YOU WANT TO CENTRALIZE

If your organization is using XML heavily, you'll want to centralize
your XML schemas. Of course, "schemas" includes XML Schemas, document 
type
definitions (DTDs), and any other information that is related to 
managing
your XML infrastructure. When your schemas are not centralized, it can
become difficult to find out where the schema is located when it comes 
time
to validate an XML document.

Centralizing schema information provides several benefits. One key
benefit is manageability. When your schemas and other information are
dispersed, you'll have difficulty knowing where a particular schema 
resides.
While this can impact your ability to find the schema, imagine what an
application will do. Keeping the information in one place also allows 
you to
share it with other organizations easier. That way, they won't have to
search for the information either.

WHAT THE REPOSITORY IS AND DOES

An XML schema repository is basically a storage medium that understands
how to store and retrieve your XML schemas and other resources such as
XML documents and documentation about the schemas. The repository 
provides
all of the necessary information for creating systems that will 
interact
with your XML definitions. It also provides a mechanism for adding new
content and updating existing content. Keep in mind that your XML 
schemas
will change.

The repository offers several key features. Obviously, it allows you to
access the XML schemas and other information. It usually does this by
using a standard mechanism such as a Web interface. It should also 
allow
users to search for specific XML information using keywords or 
applications.
Not every repository user will be human; sometimes applications and
programs will access the repository. This means that the search and 
retrieval
functions should be well defined so that an application can easily
interface with the repository.

REPOSITORY SOLUTIONS

There are many approaches to implementing an XML repository solution.
The following are simply some concepts that may apply when you decide 
to
create and use an XML schema repository. These are included to help you
understand some of the options that are available.

FILE SYSTEM-DRIVEN FTP SITE
One of the simplest solutions for creating an XML schema repository is
to install an FTP server and create a file system-based repository. 
This
basically means using the FTP protocol's existing functionality for
uploading and downloading content. It also means creating a file system
hierarchy that represents the structure and organization of your 
content. Some
of the benefits of this approach include ease of setup and the simple 
and
standard FTP interface.

DATABASE-DRIVEN WEB SITE
Of course, FTP sites are not always the easiest sites to browse. For
example, setting up default index pages doesn't work. Also, you may 
want to
better control access and storage of your information. To accomplish
this, you might create a database-driven Web site. This means setting 
up a
Web server and a database server and creating the appropriate Web
application for handling, uploading, and downloading of content. You 
can use
various methods for handling security and access to the information, 
including
hooking into an existing LDAP authentication infrastructure. This
solution also allows you to categorize your documents in multiple ways 
as well
as provide search functionality.

OUTSOURCING
If you choose not to take on the task of setting up a repository at 
all,
outsourcing may be a good option. This means finding a good partner 
that
can provide the services you and your trading partners need to handle
your (and possibly your trading partners') XML data. You may reap more
benefits with this approach if you or your trading partners are using
standard XML vocabularies. There are various online repositories such 
as
Microsoft's BizTalk.org and Oasis' XML.org that currently provide 
schema hosting
for companies.
http://click.online.com/Click?q=1f-rvwqI58DvyIYvAW1x11DH2bqC8sR 
http://click.online.com/Click?q=34-pJpSIcdc2934QU53_w-syi4E-7uR 

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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