Introduction - eXist: A NoSQL Database and Application Development Platform - page 1

CHAPTER 1
Introduction
What Is eXist?
As it turns out, this is quite a difficult question to answer. The problem lies in the
wide audience that eXist serves. eXist is many things to many people, and thus there
is no single succinct answer.
eXist is an open source piece of software written in Java that is freely available in both
source code and binary form. eXist has always been made available under the Lesser
GNU Public License (LGPL), version 2.1. While eXist makes use of many other open
source libraries itself, all of these are compatible with the LGPL, and eXist eschews
the GPL license in favor of freedom of choice for its users.
eXist was conceived as a native XML database. As a database, its unit of atomicity is
the document, so we could very easily brand it a NoSQL document database . How‐
ever, to do so would be to do an injustice to the software, and worse, to all of those
who have contributed to making eXist much more than just a NoSQL database over
the years.
Unlike most NoSQL databases, which each have their own proprietary database
query language, eXist makes use of a standardized query language developed by the
W3C: XML Query Language (XQuery). With a standard query language, you have
the ability to write code that can be used not just on eXist, but on any platform or
processor that supports XQuery. Some of the benefits of XQuery are that it is:
Synergistic
XQuery was carefully designed and evolved over a six-year period by an open
working group with many contributors, meaning that many real industry use
cases were considered during its construction. XQuery has been influenced by