[e-lang] XML support in E

[Thomas Leonard]

On Tue, 2010-01-12 at 17:06 -0500, Kevin Reid wrote:
> On Oct 26, 2009, at 13:08, Thomas Leonard wrote:
> 
> > Could someone give some simple examples showing how to read and write
> > XML using E?
[...]

> There is no E-styled XML library built into E; this is certainly  
> something which ought to be addressed.
> 
> Such a library should of course use immutable trees (vs. e.g. DOM  
> which is mutable) and have quasiliteral/pattern support for users.
> 
> E-on-JavaScript's Updoc-to-HTML component is an example of XML  
> manipulation in E: it uses the Java DOM libraries (and, when a real E  
> XML library exists, should be converted to use it).
>    http://wiki.erights.org/wiki/E-on-JavaScript
> 
> 
> There are two different approaches which could be used for an E XML  
> library: one is to use the Term-tree objects, and merely write an  
> xml__quasiParser which allows one to use the XML-in-TermL embedding,  
> as well as facilities for reading/writing XML documents. The other is  
> to have a distinct object type for XML tree nodes; this has the  
> advantage that its methods can be optimized for the needs of XML  
> applications, and its __printOn would show XML rather than TermL.
> 
> Parsing and printing could be handled for starters by using Java's  
> builtin XML facilities; I'm not sure exactly how much could be reused  
> vs. reimplented.
> 
> Questions:
> 
>    * Would you be interested in working on the project of an XML library
>      for E?
> 
>    * If I were to work on it, would you use it and give feedback?

We'd certainly be interested in testing any XML support. I don't think
I'd be able to help with the implementation though: a selling point for
E was compatibility with existing Java libraries, so telling my manager
I need to spend time implementing XML support is unlikely to fly ;-)

My main concern here is about speed. I temporarily used the JSON support
in part of my code, and it noticeably slows the GUI down when used, even
for quite small documents! Here's a little test case, timing how long it
takes to serialise an example document:

# Example document taken from http://jsonml.org/
def testData := ["table", ["class" => "MyTable", "style" => "background-color:yellow"], ["tr", ["td", ["class" => "MyTD", "style" => "border:1px solid black"], "#550758"], ["td", ["class" => "MyTD", "style" => "background-color:red"], "Example text here"]], ["tr", ["td", ["class" => "MyTD", "style" => "border:1px solid black"], "#993101"], ["td", ["class" => "MyTD", "style" => "background-color:green"], "127624015"]], ["tr", ["td", ["class" => "MyTD", "style" => "border:1px solid black"], "#E33D87"], ["td", ["class" => "MyTD", "style" => "background-color:blue"], "\u00a0", ["span", ["style" => "background-color:maroon"], "\u00a9"], "\u00a0"]]]

def jsonSurgeon := <elib:serial.deJSONKit>.makeSurgeon()

def timeIt(op) {
	op()
	for x in 1..3 {
		def start := timer.now()
		for y in 1..5 {
			op()
		}
		def finish := timer.now()
		println(`Took ${finish-start} ms`)
	}
}

println("Using jsonSurgeon...")
timeIt(fn { jsonSurgeon.serialize(testData) } )

println("Using normal printing...")
timeIt(fn { `$testData` } )

On my laptop, the results are:

Using jsonSurgeon...
Took 3533 ms
Took 2600 ms
Took 2323 ms
Using normal printing...
Took 6 ms
Took 5 ms
Took 6 ms

QuasiParser support would be very nice too (for ensuring correct
quoting, as you mentioned in a later email), and we'd certainly need
namespaces.

Thanks,


-- 
Dr Thomas Leonard
IT Innovation Centre
2 Venture Road
Southampton
Hampshire SO16 7NP

Tel: +44 0 23 8076 0834
Fax: +44 0 23 8076 0833
mailto:tal at it-innovation.soton.ac.uk
http://www.it-innovation.soton.ac.uk