Re: [xml-dev] Processing binary data using XPath ... wow!

[Michael Kay <mike@saxonica.com>]

> 
> 1. The binary data is converted to base64 text (i.e., the binary is encoded as base64 text). The ExPath Binary Module provides XPath functions for searching and manipulating the binary data in its base64 form.


This isn't quite true.

XSD defines two data types for binary data, base64Binary and hexBinary. The names emphasize the lexical representation, but in both cases the value space is just a sequence of octets. The functions in the binary module use the base64Binary data type, but they are not interested in the lexical space, only in the value space. So they are actually manipulating binary data in binary form (just as boolean operations in XPath are manipulating boolean values, not the strings "true" and "false"); the conversion to/from base64Binary lexical representation (or hexBinary lexical representation) is done by the XML parser/validator/serializer, and is no concern of this module. The name of the data type is therefore misleading.

Michael Kay
Saxonica