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   RE: XInclude [was: XLink transformations]

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  • From: "Bullard, Claude L (Len)" <clbullar@ingr.com>
  • To: Paul Grosso <pgrosso@arbortext.com>, xml-dev@xml.org
  • Date: Wed, 26 Jul 2000 15:03:40 -0500

Sorry to be tedious, Paul.  I want to be sure 
I understand the different abstractions 
so I can present them correctly.  I understand 
your answer. 

In a relational system, data in a view 
can be appended to the recordset (table) thus 
creating new records versus say an update 
in which new values are written into 
preexisting records.  The SQL is an 
Insert Into.  So

INSERT INTO target [(field1, field2
VALUES (value1, value2)


UPDATE table SET newvalue WHERE criteria

Simply, INSERT creates new records and 
UPDATE overwrites existing records.

In the table, order of records is not a 
guaranteed abstract property as a means to 
identify a record (identity is invariant 
to transform by insertion).
While the operations of first, last, 
previous and next (navigating recordsets) 
is enabled, only by comparing a value can 
one determine the identity of the record.  
Thus, recordset walking is often an expensive 
but unavoidable operation and the implementor 
writes a routine using the Previous/Next/Last/First 
methods to get and set values. 

XInclude is operationally an Insert Into 
except that there is also the concept of the 
abstract property of position in the target; 
that is, the inclusion or insert occurs at the position 
of the XInclude statement.  Order is preserved.  
Positions of information items following the 
inclusions increment.  In the relational system, 
this is unimportant.  In the tree, it can be.

When comparing these systems, it is important 
for the implementor to understand the 
properties of position and order in the abstract information 
set and how the XInclude operation affects it.   This 
can determine on which side of mixed systems 
certain operations are best performed.  

Len Bullard
Intergraph Public Safety

Ekam sat.h, Vipraah bahudhaa vadanti.
Daamyata. Datta. Dayadhvam.h

-----Original Message-----
From: Paul Grosso [mailto:pgrosso@arbortext.com]

...I think the answer is that you are not mistaken;
XInclude preserves order.  As I said earlier:

"All information in the included bit is included 
at the including point"



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