Re: [Xmldb-org-xupdate] Poorly defined update instruction

[John L. C. <jl...@po...>]

On Fri, Apr 29, 2005 at 10:41:28AM +0200, Wolfgang Meier wrote:
> >3) It would be useful for update to allow element, attribute, etc. as=20
> >content. That said, I'm not convinced it's worth the complexity, as you=
=20
> >can simply delete the element and reinsert it with the new content.
>=20
> I would like to propose a "replace" instruction for this purpose.
[...]
> Example:
>=20
> <xupdate:replace select=3D"/example/p[2]">
>   <quote>a <b>replaced</b> paragraph</quote>
> </xupdate:replace>

This is exactly the effect that I would like the update instruction to
have.  If we had such a replace operation, would there be any further
need for an update?  It seems that the most common use case for update
is a quick textual change within a #PCDATA element field; this could
easily be accomplished with a simple replace.  For example, the example
in the spec under the update instruction could be performed with:

---
<xupdate:replace select=3D"/addresses/address[2]/town/text()[1]"
  xmlns:xupdate=3D"http://www.xmldb.org/xupdate">New York</xupdate:replace>
---

> Concerning "update", I would still allow element, text etc. as content=20
> if the "select" xpath evaluates to one or more elements. Otherwise, the=
=20
> expression just updates the value of an attribute or text node.

As I mentioned above, with such a replace instruction, I no longer see
the point of update[0].  I actually think that either name for the
instruction - "update" or "replace" - would be fine, although keeping it
as "update" would be less disruptive.

Take care,

    John L. Clark

[0] In fact, I think this would simplify the spec even further - I no
longer see the need for a delete operation.  You could delete the "New
York" text with:

---
<xupdate:replace select=3D"/addresses/address[2]/town/text()[1]"
  xmlns:xupdate=3D"http://www.xmldb.org/xupdate"/>
---

or the whole town with:

---
<xupdate:replace select=3D"/addresses/address[2]/town"
  xmlns:xupdate=3D"http://www.xmldb.org/xupdate"/>
---