XML FAQs
When developing XML solutions, several questions are asked repeatedly. 
Sometimes the answers are obvious, and other times they are more 
complex. Below are a few of the most frequently asked questions related 
to XML, as well as a few answers.

WHAT'S THE EASIEST WAY TO VIEW XML FILES?
One of the simplest ways to view XML documents is to use Microsoft's 
Internet Explorer Web browser. All releases of Internet Explorer from 
version 5 and up contain built-in technology for reading and parsing 
XML documents. By viewing an XML document in Internet Explorer, you can 
navigate the hierarchical document tree to view different parts of the 
document.

HOW CAN I ACCESS XML DOCUMENTS FROM WITHIN MY JAVA APPLICATIONS?
The most common method of accessing XML documents from Java 
applications is to use Sun Microsystems' Java API for XML (JAXP for 
short). JAXP provides all of the necessary functionality for parsing 
XML documents using both Document Object Model (DOM) and Simple API for 
XML (SAX).

WHAT'S THE DIFFERENCE BETWEEN A DTD AND A SCHEMA?
A Document Type Definition (DTD) is functionally similar to an XML 
Schema. The major difference is in the exact functionality that each 
provides. XML Schemas were developed to overcome some of the 
functionality that was lacking in DTDs, such as stronger type checking. 
The other difference is that DTDs use their own language to define a 
document type; Schemas use XML to define the elements of an XML 
document.

ARE DTDs OR SCHEMAS REQUIRED TO PROCESS XML DOCUMENTS?
The answer to this question depends on your application and 
circumstances. You can create and parse XML documents easily enough 
without a DTD or Schema; however, you have no validation that the 
element names are correct. By specifying a DTD or Schema, you gain the 
ability to not only verify that elements are named correctly but that 
other business rules can be met, such as correct data types.

WE RECEIVE XML DATA FROM A CUSTOMER IN A CERTAIN FORMAT, BUT OUR 
APPLICATION REQUIRES SOMETHING DIFFERENT. HOW CAN WE SOLVE THIS?
The best and easiest solution is to use eXtensible Stylesheet Language 
Transformation (XSLT). This technology allows you to create a template 
that defines how incoming XML data should be converted into a different 
format.

SINCE XML DATA IS BASICALLY TEXT, HOW CAN I PROTECT XML DOCUMENTS 
TRANSMITTED ON THE INTERNET?
There are two ways to protect XML data on the Internet. The first (and 
most mature) is to use VPN technology to create secure network links 
between the computers transmitting data. The second is to use some form 
of encryption. You can either encrypt the XML document using a variety 
of tools such as PGP, or you can take advantage of the XML 
specifications for signing and digitally encrypting your documents.

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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