Introduction - eXist: A NoSQL Database and Application Development Platform - page 4

documents. Another key advantage of XML over JSON is that you can adopt
namespaces to cleanly model different business domains.
Schemaless
RDBMSs and even several NoSQL databases require you to define your data
schema before you can start storing your data. eXist is entirely flexible, and
allows you to store your documents without specifying any schema whatsoever.
It is ideal for business problems that have high-variability data and also helps
developers rapidly prototype and evolve applications. However, schemaless
should not be confused with providing validation of documents . Should you wish,
you can also define a schema in eXist and have eXist enforce that only docu‐
ments meeting your schema requirements are stored or updated.
Portable queries
RDBMSs typically use a standardized SQL query language; however, in practice,
apart from the most basic queries it can be hard to run the same SQL queries
across different RDBMS database products. Likewise, most NoSQL systems have
their own proprietary query languages, which are entirely product-specific. eXist
takes a very different approach and provides XQuery and XSLT, which are W3C
standardized query and transformation languages, meaning that with very little
effort you can execute your eXist queries on any other product that provides an
XQuery and/or XSLT processor.
Structured search
Like many database systems, eXist allows you to define different indexes for your
searches. However, combined with the ability to search based on the document
structure, this makes eXist search results more precise than those of almost any
other database when dealing with structured documents such as TEI, DocBook,
and DITA. eXist will consistently have better search metrics (precision and
recall) than search systems that ignore document structure. If findability is high
on your list of desired attributes, then eXist is a great choice.
Forms
Oracle provides Oracle forms for use with its RDBMS. We are not aware of any
NoSQL databases that provide form support for constructing end-user interfaces
that can feed directly into the database. eXist supports XForms (another W3C
standard), which allows you to easily capture user input into XML documents in
the database. Some organizations find that eXist is ideal not just for managing
data collection with forms, but also for entire backend workflows around the
content publishing process.
Application development
Like some RDBMSs and NoSQL databases, eXist is embeddable into your own
applications. However, when you are using eXist as a server, it really becomes an
application platform and offers more than almost any other database system.