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Re: Achieving interoperability in a world where different OS's

• From: Hermann Stamm-Wilbrandt <STAMMW@de.ibm.com>
• To: "Costello, Roger L." <costello@mitre.org>
• Date: Sun, 14 Dec 2014 12:49:43 +0100

CRLF may be an issue in case of juggling between different RE flavors as
well (as eg. in XSD processors).

4 years ago I had to fix this APAR:
http://www-01.ibm.com/support/docview.wss?rs=2362&uid=swg1IC72220

XML Schema Regular Expressions (SCRE) are anchored at start and end
automatically, and XSD processor does translate SCRE to PCRE. The fix was
to replace ")$" by ")(?!\n)$" in order to make sure that PCRE does not
match input "9\n" for (SCRE) "9"; the "(?!\n)" negative lookahead fixed the
issue:
http://www.regular-expressions.info/lookaround.html#lookahead


Mit besten Gruessen / Best wishes,

Hermann Stamm-Wilbrandt
Level 3 support for XML Compiler team & Fixpack team lead
IBM DataPower Gateways
https://www.ibm.com/developerworks/mydeveloperworks/blogs/HermannSW/
https://twitter.com/HermannSW/
http://stamm-wilbrandt.de/GraphvizFiddle/
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  From:       "Costello, Roger L." <costello@mitre.org>                                                                                             
                                                                                                                                                    
  To:         "xml-dev@lists.xml.org" <xml-dev@lists.xml.org>                                                                                       
                                                                                                                                                    
  Date:       12/13/2014 03:11 PM                                                                                                                   
                                                                                                                                                    
  Subject:     Achieving interoperability in a world where different OS's represent newline differently                                    
                                                                                                                                                    





Hi Folks,

Each operating system has its own convention for signifying the end of a
line of text:

Unix: the newline is a character, with the value hex A (LF).

MS Windows: the newline is a combination of two characters, with the values
hex D (CR) and hex A (LF), in that order.

Mac OS: the newline is a character, with the value hex D (CR).

This operating-system-dependency of newlines can cause interoperability
problems: the newlines in a string created on a Unix box will not be
understood by applications running on a Windows box.

Here is how the newline problem is resolved in XML and in JSON:

XML: all newlines are normalized by an XML parser to hex A (LF). So it
doesn't matter whether you create your XML document on a Unix box, a
Windows box, or a Macintosh box, all newlines will be represented as hex A
(LF).

JSON: multi-line strings are not permitted! So the newline problem is
avoided completely. You can, however, embed within your JSON strings the \n
(LF) or \r\n (CRLF) symbols, to instruct processing applications: "Hey, I
would like a newline here."

That is quite an interesting difference in approach between XML and JSON
for dealing with the newline problem!

Please let me know of any errors or confusion in the above explanation.
Thanks!

/Roger

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• Follow-Ups:
  • Re: Achieving interoperability in a world where differentOS's represent newline differently
    • From: Rick Jelliffe <rjelliffe@allette.com.au>

• References:
  • Achieving interoperability in a world where different OS'srepresent newline differently
    • From: "Costello, Roger L." <costello@mitre.org>