XML Companion, The, Third Edition

URL construction

A URL is a simple text string. This string can appear in any form. It can be printed on paper, and still be termed a URL. But a URL is most useful in electronic form. It can then be interpreted by software that needs to access the resource it identifies.

Syntax

The characters allowed in a URL string are restricted to digits, upper-case and lower-case letters, and a few symbols (though some additional symbols are allowed in specific parts of a URL):

0123456789
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
-_.!~*'()

All other characters are represented by an escape code comprising a percent symbol, '%', followed by a hexadecimal two-digit ASCII (see Chapter 29) character value ('%00' to '%FF'). For example, '%20' represents ...