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Some schema languages use string regular expressions to check lexical space of
attributes and character data. The regex strings often become uncomprehensible,
such as
(([a-zA-Z][0-9a-zA-Z+\-\.]*:)?/{0,2}[0-9a-zA-Z;/?:@&=+$\.\-_!~*'()%]+)?(#[0-9a-zA-Z;/?:@&=+$\.\-_!~*'()%]+)?
for any URI.
Providing a structured syntax, similar to that for XML, would help reading and debugging
them, for example,
s-pattern="""
comment = "\(([^\(\)\\]|\\.)*\)"
atom = "[a-zA-Z0-9!#$%&'*+\-/=?\^_`{|}~]+"
atoms = atom "(\." atom ")*"
person = "\"([^\"\\]|\\.)*\""
location = "\[([^\[\]\\]|\\.)*\]"
local-part = "(" atoms "|" person ")"
domain = "(" atoms "|" location ")"
start = "(" comment " )?" local-part "@" domain "( " comment ")?"
"""
instead of
pattern=
"(\(([^\(\)\\]|\\.)*\) )?"
~ """([a-zA-Z0-9!#$%&'*+\-/=?\^_`{|}~]+(\.[a-zA-Z0-9!#$%&'*+\-/=?\^_`{|}~]+)*|"([^"\\]|\\.)*")"""
~ "@"
~ "([a-zA-Z0-9!#$%&'*+\-/=?\^_`{|}~]+(\.[a-zA-Z0-9!#$%&'*+\-/=?\^_`{|}~]+)*|\[([^\[\]\\]|\\.)*\])"
~ "( \(([^\(\)\\]|\\.)*\))?"
Why isn't it done?
David
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