Native XML databases - Making Sense of NoSQL - page 100

The key difference between HTML and XML is that the semantics (or meaning) of
each HTML element has been predefined by W3C standards. In the sales order exam-
ple, the meaning of each sales order element is determined by the individual organi-
zation. Even though there may be an XML standard for sales orders, each organization
can decide to create data element names specific to their organization and store those
element names, and their definition, in a data dictionary.
Anyone who's familiar with XML recognizes it as a mature standard with an ecosys-
tem of tools to support it. There are tools to extract subtrees from XML documents
( XPath ), tools to query XML documents ( XQuery ), tools to validate XML documents
( XML Schema and Schematron), and tools to transform XML documents from one
format to another.
RDBMS vendors like Oracle, Microsoft, and IBM have included XML management
features in their products. Their approach is to add an XML column type to the
RDBMS . Once added, XML documents are stored in the column in the same way a
binary large object ( BLOB ) is stored. Though this strategy meets the needs of many use
cases, it lacks portability since object-relational mapping tools don't generate the cor-
rect SQL to select XML elements within BLOB s.
The main disadvantage of XML , and a limitation of native XML systems, is that XML
is a standard that attempts to solve many different types of problems with a single for-
mat. Without adequate tools and training, development staff may become frustrated
with XML 's complexity and continue to use simpler formats such as JSON or CSV . With-
out good GUI tools, developers are forced to view raw XML files that can be more ver-
bose than the corresponding JSON representation.
Despite this issue, many developers find that native XML databases offer a simpler
way of solving problems. Their rich query language and XML standards help to lower
overall costs. It should also be noted that native XML databases don't store literal XML .
They store a compact version in a compressed format. XML files are only used to put
data into and retrieve data from the database.
Now that you have an understanding of what native XML databases are and the
kinds of problems they solve, let's explore how native XML databases are used to build
applications that can add, transform, search, and update XML documents.

5.2 Building applications with a native XML database

Native XML databases and their associated tools are key to increasing developer pro-
ductivity. Using simple query languages allows programmers and nonprogrammers to
simply create and customize reports. The combination of standards, mature query
languages, robust tools, and document orientation makes the application develop-
ment process faster. You'll find it difficult to convince native XML users to move to
another platform once they've created applications with these systems.
Getting started with a native XML database can be simpler than you think. If you
understand the concept of dragging files and folders, you're well on your way to creat-
ing your first native XML database. As you browse through the next section, you'll see
how simple it can be to get started.