Inserting into XML tables at arbitrary points

[Simone Bettini]

At 15:04 -0800 19-03-2002, Bill Humphries wrote:
>On Tuesday, March 19, 2002, at 02:12 PM, Greg Pierce wrote:
>
>>Can I ask exactly what you're trying to accomplish with arbitrary insertion?
>>
>>It seems the correct approach to this is to edit the XML before 
>>compiling it to a table.
>
>Who's doing the editing though, if it's a domain expert familiar 
>with XML markup, then yes, the right thing to do is edit the text, 
>check for well-formedness, validate against DTD or schema if 
>necessary, then compile.
>
>However, my users' expect a visual editing interface, and would run 
>screaming for Gilroy if I asked them to edit markup. They aren't 
>programmers.

There is another point too, xml.compile and xml.decompile are quite 
slow verbs when applied to huge docs and/or tables.

In our CMS, that heavily uses xml tables we use the second approach 
and modify tables, but pay attention not to assign huge tables, as 
it's another processor intensive task.

A better approach imho would be to shif all items in table down in place:

on insertAt(theTableAdr, theItemName, theItemValue, thePosition) {
	local {
		tAdr;
		tPos;
		tTableSize = sizeOf(theTableAdr^)};
	for tPos = tTableSize downto thePosition {
		local {
			tAdr = @theTableAdr^[tPos];
			tName = xml.convertToDisplayName(tAdr^);
			tNewName =string.padWithZeros(tPos+1,5) + 
"000\t" + tName};
		theTableAdr^.[tNewName] = tAdr^;
		delete(tAdr)};
	local {
		tNewName =string.padWithZeros(thePosition,5) + 
"000\t" + theItemName};
	theTableAdr^.[tNewName] = theItemValue}

(i didn't test this function, so be careful using it)

But be careful, would the tag of the table have any attributes, or 
the tag contain data then you would have /atts at the beginning and 
one or more /pcdata somewhere inside the table, shifting down all 
items by one:

<test num='1'>
	bye bye
	<item>Hi</item>
	<item>Hi2</item>
	<item>Hi3</item>
	bye2
	</test>

generates a table like this:

>00001000	test
	>/atts
		>num	1
	>00002000\t/pcdata	bye bye
	>00003000\titem		Hi
	>00004000\titem		Hi2
	>00005000\titem		Hi3
	>00006000\t/pcdata	bye2

So if you want to use such approach be sure at least no pcdata will 
be included in your tables, and if you need to have any atts modify 
the above script to deal with /atts table presence (you just need to 
verify wether a /atts object is defined in the table and in such a 
case shift positions accordingly)
-- 

Simone

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