Re: [cgmo-webcgm] QUESTION: where are Text Nodes in the WebCGM DOM tree?

[Benoit Bezaire <benoit@itedo.com>]

Tuesday, July 5, 2005, 9:17:50 PM, Lofton wrote:

LH> I remember that Text Nodes were discussed and added to the
LH> WebCGM DOM model at Cologne.  At one point, there was a WebCGMText
LH> interface (that inherited from WebCGMNode), but it didn't add
LH> anything useful that wasn't available on the WebCGMNode interface
LH> (nodeType equals TEXT_NODE).  So it was removed.
Correct.

LH> I don't remember exactly where Text Nodes apply in our
LH> document tree.  They certainly apply to the content of a metadata
LH> node. For example, if this were in an XCF, 
And that's mostly what they are used for...

LH> <grobject ...>
LH>     <model:part-longdesc>Here is a verbose description of the
LH>         AJX-20054321-B part, complete with source and replacement
LH>         instructions. Blah...blah...
LH>     </model:part-longdesc>

LH> then after the XCF was applied, model:part-longdesc would be
LH> a child of the grobject, and it would have a Text Node child whose
LH> value is "Here is a verbose ...blah...". 

LH> Correct so far? 
Yes.

LH> And model:part-longdesc would be the parentNode of that Text
LH> Node?
Well, Attr nodes have a ownerNode, not a parentNode... but yes (same
concept).

LH>  (Text Node has no children, and since we can't have
LH> additional markup within application-specific metadata elements,
LH> there will be no siblings,
why do you say that?

LH> as there might be if part-longdesc could have child elements that
LH> split the text node into sibling-level pieces.)

LH> Correct?
No. Our implementation supports...
<grobject ...>
  <model:part-longdesc>Here is a verbose description
    <model:anotherNode>Some text</model:anotherNode>
  </model:part-longdesc>
</grobject>

LH> Is there anywhere else in the WebCGM DOM model that Text
LH> Nodes appear?
No, not in WebCGM.

LH> DOM2 suggests they might represent the content of Attr nodes:
I guess we diverged from that in an attempt to simplify things...

LH> [InterfaceText, p.60] 
LH> The Text interface inherits from CharacterData[p.47] and represents
LH> the textual content (termed character data in XML) of an Element[p.52]
LH> or Attr[p.51] . If there is no markup inside an element’s content,
LH> the text is contained in a single object implementing the Text
LH> interface that is the only child of the element. If there is
LH> markup, it is parsed into the information items [p.98] (elements,
LH> comments, etc.) and Text nodes that form the list of children of the element.
LH>  Interface Attr [p.51] The Attr interface represents an attribute
LH> in an Element[p.52] object. Typically the allowable values for the
LH> attribute are defined in a document type definition.
LH> Attr objects inherit the Node[p.34] interface, but since they are
LH> not actually child nodes of the element they describe, the DOM
LH> does not consider them part of the document tree. Thus, the Node
LH> attributes parentNode, previousSibling, and nextSibling have a
LH> null value for Attr objects. The DOM takesthe view that attributes
LH> are properties of elements rather than having a separate identity
LH> from the elements they are associated with; this should make it
LH> more efficient to implement such features as default attributes
LH> associated with all elements of a given type.
LH> [...]
LH> In XML, where the value of an attribute can contain entity
LH> references, the child nodes of the Attr node may be either
LH> Text[p.60] or EntityReference[p.65] nodes (when these are in use;
LH> see the description of EntityReference for discussion). Because
LH> the DOM Core is not aware of attribute types, it treats all
LH> attribute values as simple strings, even if the DTD or schema
LH> declares them as having tokenized [p.99] types.

LH> Consider the following example,
LH> ...
LH> <grobject apsid="someId" screentip="this object has
LH> as creentip" name="someName" model:part-number="AJX-20054321-B">
LH>     <model:part-longdesc>Here is a verbose description of the
LH>         AJX-20054321-B part, complete with source and replacement
LH>         instructions. Blah...blah...
LH>     </model:part-longdesc>
LH> </grobject>

LH> One reasonable interpretation of the DOM2 text suggests that
LH> there would be several more text nodes in the example now, the
LH> strings: "this object has a screentip",
LH> "someName","AJX-20054321-B", "Here is a verbose description...".  

LH> So the final question is:  are these considered to be Text Nodes
LH> in the WebCGM DOM model?
I don't see how someone, reading the current WebCGM wording could
conclude that these are Text nodes. No they are not (except "Here is a
verbose description...").

-- 
 Benoit   mailto:benoit@itedo.com

LH> Regards,
LH> -Lofton.
LH>    
LH>