Advanced Topics - eXist: A NoSQL Database and Application Development Platform - page 475

XPath 2.0 Data Model (XDM) specification . If you are an experienced XQuery devel‐
oper, you're most likely already familiar with this document; if not, as an imple‐
menter of an internal module you should have at least a basic understanding of these
subjects. A very useful summary diagram of the type hierarchy in XQuery is available
in the specification .

When implementing an internal module, you will be working with the XDM types in
Java as opposed to XQuery. eXist has a Java class to model each of those XDM types.
An understanding of how to map from an XDM type as used in XQuery to eXist's
Java type is essential to enable you to create functions that accept parameters and
return values. All of eXist's XDM Java types for atomic types are in the package
org.exist.xquery.value . The type mappings are listed in Table 16-6 .

Table 16-6. XDM atomic value type mappings

XDM atomic value type eXist's Java class Notes

An interface.

item Item

An abstract class.

xs:anyAtomicType AtomicValue

Internally represented using java.lang.String .

xs:untypedAtomic UntypedAtomicValue

Internally represented using java.lang.String .
Provides utility methods for converting to/from
org.exist.xmldb.XmldbURI .

xs:anyURI AnyURIValue

Internally represented using java.io.Input
Stream and java.io.OutputStream . Actual
encoding/decoding is lazy, and uses either
Base64BinaryValueType or HexBinaryType ,
respectively.

xs:base64Binary BinaryValue

xs:hexBinary
xs:boolean

Internally represented using boolean .

BooleanValue

Internally represented using javax.xml.data
type.XMLGregorianCalendar .

xs:dateTime DateTimeValue

xs:date DateValue

xs:time TimeValue

xs:gDay GDayValue

xs:gMonth GMonthValue

xs:gMonthDay GMonthDay

xs:gYear GYearValue

xs:gYearMonth GYearMonthValue

Internally represented using javax.xml.data
type.Duration .

xs:duration DurationValue

xs:dayTimeDuration DayTimeDurationValue