'In-Line' data in EML2 using base64 encoding

[Peter McCartney]

Whats so bad about putting it in a separate file and sending both in a zip
package? just put the filename in the distribution/online/url element.
 
Peter McCartney (peter.mccartney at asu.edu <mailto:peter.mccartney at asu.edu> )
Center for Environmental-Studies
Arizona State University
 

-----Original Message-----
From: Dan Higgins [mailto:higgins at nceas.ucsb.edu] 
Sent: Friday, May 23, 2003 10:01 AM
To: Eml-Dev (eml-dev at ecoinformatics.org); Christopher Jones
Subject: 'In-Line' data in EML2 using base64 encoding


Hi All,
 
We at NCEAS have had several discussions about how to 'in-line' data in eml2
documents. One method is to encode arbitrary data in base64 format. The EML2
spec even says "encode the data using a text encoding algorithm such as
base64, and then include that in a CDATA section" in the 'inline'
documentation. 

In looking into the subject, I discovered the reference below which points
out that base64 encoded data DOES NOT need to be inside a CDATA section
since it contains no special XML characters!

Dan
-------------------------


from: http://www.xml.com/axml/notes/CDprob.html
<http://www.xml.com/axml/notes/CDprob.html> 



CDATA Sections and Binary Data


A lot of people would like a way to package up any old binary data and
include it in an XML file. The conventional XML answer to this would be to
store it separately and point at it with an unparsed
<http://www.xml.com/axml/target.html#dt-unparsed> entity. Which is fine, but
that's not what people want; they want to include the data right in the
file, which is a reasonable way to go if you're going to transmit it over
the network.

When you look at CDATA, you might get the impression that you could maybe
jam your binary data in a CDATA section. You'd be right, but you'd have to
guarantee that it never included a byte sequence that looks like ]]>. There
is a trick you can use to get around that, but it's awkward:

<![CDATA[Use *two* CDATA sections when you need to embed a "]]]]><![CDATA[>"
in the data ]]> 

Another way to go would be to encode the binary data in base64 or some other
technique that's guaranteed never to contain a <; but if you're going to do
that, you don't need a CDATA section; any old element would do. Perhaps this
is a good use for XML's notation
<http://www.xml.com/axml/target.html#notatn> attributes.

----------------------
from: http://lists.xml.org/archives/xml-dev/199910/msg00388.html
<http://lists.xml.org/archives/xml-dev/199910/msg00388.html> 

>As Tim says in his annotation, if you use Base64 then you don't need the

>CDATA section as _none_ of the XML reserved chars appear in the Base64

>character set (A-Za-z0-9/+).

-- 

*******************************************************************

Dan Higgins                                  higgins at nceas.ucsb.edu
<mailto:higgins at nceas.ucsb.edu> 

http://www.nceas.ucsb.edu/ <http://www.nceas.ucsb.edu/>     Ph: 805-892-2531

National Center for Ecological Analysis and Synthesis (NCEAS) 

735 State Street - Room 205

Santa Barbara, CA 93195

*******************************************************************

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