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From "Scott Boag/CAM/Lotus" <Scott_B...@lotus.com>
Subject RE: Microsoft XML stuff
Date Thu, 13 Jul 2000 04:29:25 GMT

> '"pull" model parser' - does this mean optimizing based on the schema?

No.  A Sax-style parser is where you parse and catch events... which means
you have to set up a state machine in your ContentHandler... a task which
tends to be not very fun for most casual developers.  A pull model parser
would be where you would ask to parse up to the next node, handle the
event, and then continue parsing, perhaps all in a single loop.  I'm not
certain of the exact API, but the model is easier, if maybe not quite as
performant, for many tasks.  Ted may be able to tell you more about what
the API should look like, since he was thinking of this well over a year
ago.  I think the API would be something along the lines of a NodeIterator?

Note they have XMLTextReader and XMLNodeReader as concrete implementations
of this interface... which means you should be able to use the same code
over both an XML stream and a DOM tree.  I think.

> ditto for "data-friendly DOM" - does this mean a schema-centric DOM?
> or designed for large datasets?

No.  It means an API that is set up to be friendly for table-shaped data,
as in an export from ODBC rowsets, rather than irregular data as you might
find in a document.  At least 50% of XML used in business transactions is
likely to be table-shaped-regular, so this makes sense.  For the database
crowd.  Not sure of details.

> How is XmlNavigator different from the selectNodes() method, which has
been
> in MSXML for over 2 years?

It's an itterator object.  In one sense it's doing the same thing.  But I
think select nodes was returning a NodeList, or some such.  An XmlNavigator
provides cursor style access to the data.  The major methods on it seem to
be:
void Select(String xpath);
bool MoveNextSelected();
void MoveChildren(XmlNavigator other);

Don't take what I'm saying as gospel.  I'm just learning about this stuff,
and have somewhat incomplete data.

-scott




                                                                                         
                         
                    "Ed Staub"                                                           
                         
                    <estaub@media        To:     <general@xml.apache.org>       
                                  
                    one.net>             cc:     (bcc: Scott Boag/CAM/Lotus)          
                            
                                         Subject:     RE: Microsoft XML stuff            
                         
                    07/12/2000                                                           
                         
                    09:29 PM                                                             
                         
                    Please                                                               
                         
                    respond to                                                           
                         
                    general                                                              
                         
                                                                                         
                         
                                                                                         
                         



Scott,
Thanks for the report from the front.
Can you elaborate on these?
I might have understood, or I might not have...

'"pull" model parser' - does this mean optimizing based on the schema?

ditto for "data-friendly DOM" - does this mean a schema-centric DOM?
or designed for large datasets?

How is XmlNavigator different from the selectNodes() method, which has been
in MSXML for over 2 years?

-Ed


-----Original Message-----
From: Scott Boag/CAM/Lotus [mailto:Scott_Boag@lotus.com]
Sent: Wednesday, July 12, 2000 3:46 PM
To: general@xml.apache.org
Subject: Microsoft XML stuff



BTW, as I sit here in the Microsoft Developers Conference, they are talking
about a "pull" model parser.   Something to think about.  They call this an
XmlReader.

They are also talking about a data-friendly DOM -- i.e. a DOM that is
friendly and specialized for data-shaped XML, i.e. the kind of XML you
might get from a database.

They also have an XmlNavigator, which is basically a NodeIterator that is a
"lens" onto the XML tree, using XPath.  This is similar or exactly what I
am doing in the XPath module in Xalan2.

Their latest XSLT architecture looks suspiciously like TrAX.  Probably a
good thing.  Note that they are defining a SAX (like) api for their parser.

-scott





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