Web Services Essentials

XML-RPC Data Model

The XML-RPC specification defines six basic data types and two compound data types that represent combinations of types. While this is a much more restricted set of types than many programming languages provide, it’s enough to represent many kinds of information, and it seems to have hit the lowest common denominator for many kinds of program-to-program communications.

All of the basic types are represented by simple XML elements whose content provides the value. For example, to define a string whose value is “Hello World!”, you’d write:

<string>Hello World!</string>

The basic types for XML-RPC are listed in Table 2-1.

Table 2-1. Basic data types in XML-RPC

Type	Value	Examples
int or i4	32-bit integers between -2,147,483,648 and 2,147,483,647.	<int>27</int> <i4>27</i4>
double	64-bit floating-point numbers	<double>27.31415</double> <double>-1.1465</double>
Boolean	true (1) or false (0)	<boolean>1</boolean> <boolean>0</boolean>
string	ASCII text, though many implementations support Unicode	<string>Hello</string> <string>bonkers! @</string>
dateTime.iso8601	Dates in ISO8601 format: CCYYMMDDTHH:MM:SS	<dateTime.iso8601>20021125T02:20:04 </dateTime.iso8601> <dateTime.iso8601>20020104T17:27:30 </dateTime.iso8601>
base64	Binary information encoded as Base 64, as defined in RFC 2045	<base64>SGVsbG8sIFdvcmxkIQ== </base64>

Tip

For more information on how Base 64 encoding works, see section 6.8 of RFC 2045, “Multipurpose Internet Mail Extensions (MIME) ...