Gerard Freriks wrote:
> Thanks.
>
> But I'm curious in:
> Why?
>
> Why is you solution more safe?
A) You are definitively bookending the string.
This is exactly the same as you do within the ADL e.g.
["at0002"] = <
description = <"*">
text = <"Procedure started date time">
>
The adl above does not say:
description = *
text = Procedure started due time.
etc.
why is that?
& Would that be the same as:
description = *
text =
Procedure started due time.
?
B) Even worse is the fact that an XML element can contain many text
children even where it may look like there is just one. This can cause
all sorts of fun.
e.g.
http://www.informit.com/articles/article.aspx?p=31273&seqNum=12&rl=1
"The text of an element is considered *normalized* when it contains no
two adjacent Text nodes, as was shown above. In general, deserializing
an XML document into a DOM will yield normalized elements. However, when
new Text nodes are inserted into the hierarchy, one can wind up with a
denormalized element. While completely legal, various XML technologies
have a difficult time handling denormalized elements. XPath, for
example, depends on a normalized document tree structure to behave
properly. Performing an XPath traversal against a document with
denormalized elements would yield unexpected results. This can be
prevented using the Node.normalize method, which recursively normalizes
all ancestor Text nodes. Consider the following Java code:
import org.w3c.dom.*;
void appendText(Document doc, Node elem) {
int nChildren = elem.getChildNodes().getLength();
Node text1 = doc.createTextNode("hello ");
Node text2 = doc.createTextNode("world");
elem.appendChild(text1);
elem.appendChild(text2);
text2.splitText(2);
assert(elem.getChildNodes().getLength() == nChildren + 3);
elem.normalize();
assert(elem.getChildNodes().getLength() == nChildren + 1);
}
As shown in Figure 2.12
<javascript:popUp('/content/images/chap2_0201709147/elementLinks/02fig12.gif')>,
after the call to Text.splitText, there are three new Text node
children. However, after the call to Node.normalize, the three adjacent
Text nodes are folded into a single node containing the string "hello,
world"."
> Why is your solution more efficient?
A) File sizes are smaller/the XML is less verbose.
B) The fact that you know exactly where the string starts and finishes
means that using Sax etc can be much faster as there is no need to
normalize.
i.e. at present you would already have more verbose xml & then the only
safe option is to always normalize the whole document before processing it.
C) XML attribute values are structural vs a function in most of the XML
processing languages e.g. XSLT or XPath.
e.g. compare /a/b/@c vs /a/b/text() or /a/b[@c="bob"] vs /a/b[text() =
"bob"]
> Why is your solution a better Best Practice?
>
In part for the reasons above.
In part because experiences of failures because of the ambiguities wrt
the text child in XML have driven people to be pretty careful about
using text unless you really need to.
If you want a single string containing a value which will not contain
child elements e.g.
Good use for text child:
some <strong>bold text</strong> in some documentation
Bad use for text child:
at003
Again I would refer you yo your very own ADL which in essence has
adopted the exact same solution to avoiding an textual ambiguities via
markup such as:
["at0030"] = <
description = <"*">
text = <"Material used">
>
["at0031"] = <
description = <"*">
text = <"Procedure comments">
>
["at0032"] = <
description = <"*">
text = <"Procedure comments">
>
["at0033"] = <
description = <"*">
text = <"Procedure end date time">
>
were say the first element above to be rewritten it could be seen as
<at0030 description="*" text="Material used"/>
Adam
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