Architecture - eXist: A NoSQL Database and Application Development Platform - page 72

Figure 4-5 should be interpreted as depicting that only the REST
Server and SOAP Server services of eXist are directly manipulata‐
ble by the XQuery URL Rewrite facility (see “URL Mapping Using
URL Rewriting” on page 194 ). However, it also shows that RESTXQ
can be coupled with the XForms Filter; while this is indeed the case
and may be desirable, it is not enabled by default in eXist (but may
be configured easily).
Storage Architecture
So far we have mostly been looking at the high-level architecture of eXist depending
on the type of application you wish to build with it. You should at least have a cur‐
sory understanding of how eXist structures its resources into collections from read‐
ing Chapter 3 . We will now look much more closely at the storage architecture of
eXist, as you may be wondering, “What happens when I actually store a document
into eXist?”
XML Document Storage and Indexing
When given an XML document, eXist first takes the document and parses it (while
validating it if requested), and then extracts all of the information from the document
and stores it while also indexing the document's key features (see Figure 4-6 ).
eXist does not store your XML documents as a series of XML files
on disk, as this is not an efficient storage format for database oper‐
ations.
eXist stores an XML document by taking the information making
up the document and separating it into distinct parts that are then
stored in a series of optimized binary files on disk. This process is
transparent to users; they can always ask eXist for the XML docu‐
ment they originally stored, and the complete document will be
reconstituted and presented to them as it was.
The indexes that eXist builds from your XML documents during storage enable you
to later perform fast and efficient queries against the documents in the database. The
structural index employed by eXist is fixed, but additional indexes are configurable
by the users depending on their query requirements; see “Configuring Indexes” on
page 275 for index configuration details.