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From "Gerald B. Rosenberg" <...@newtechlaw.com>
Subject RE: Entire XML in memory?
Date Fri, 16 Jan 2004 00:25:36 GMT
I, too, am quite interested in this issue.

My fundamental question is why should any of an XML exist outside of the 
database in order to be worked upon.  Instead, why can't -- indeed why 
shouldn't -- v2 be (also) architected to leverage the existing XML handling 
capabilities of the hybrid databases, such as Oracle 9i and DB2.  O9i in 
particular provides native/raw XPath, XQuery and cursor capabilities using 
an SQL-centric syntax.  Using these native XML/DB capabilities would 
preserve the indexing, concurrency control, access rights, etc. provided by 
the database.  By instancing even only a block of the XML outside of the 
database, it seems you have to lock the corresponding portion of the 
database while providing your own XPath/XQuery/XMLCursor 
implementations.  That does not seem to be an efficient use of the database.

Of course not all DBs have these native XML capabilities.  Just my opinion 
that the current weight of development -- not scientific, just a bunch of 
web browsing and reading -- is tending toward integrating XML directly into 
the DBs, which is helped by XPath, XQuery and cursor operations being 
relatively well-accepted/well-defined standards.

Just as a reference point, my use-case scenario is a corpus of several 
thousand XML documents with multiple concurrent processes performing a 
progressive, essentially statistical analysis and update of the 
documents.  Each process will need to reference multiple documents at a 
time to perform group analysis.  At least one other process will be adding 
documents to the corpus.  Each document is likely to be fairly large: 100 - 
300kB.  (If the documents were not fundamentally XML, this would be a quite 
standard relational application.)

XMLBeans looks to provide the java-centric programming model that is most 
appropriate for my needs.  However, I am concerned with the apparent 
absence of concurrency capabilities and failure to take advantage of the DB 
indexing/performance capabilities.

Can you please comment on how (if) v2 will address these issues.  Have you 
yet established the back-end API.  If you have, I would really like to take 
a look at it.


At 02:02 PM 1/15/2004, you wrote:

>In v1, the document exists entirely in memory.  In v2, I am making the
>xml store backend pluggable so that one may provide alternate backends
>with different characteristics.  In addition to a high performance,
>in-memory store (the default), I will make a memory mapped backend which
>stores the XML in a memory mapped file and does not consume VM memory
>proportional to the size of the XML being worked on which will allow one
>to load very large documents.  I can imagine backends which
>incrementally load parts of a document.
>This architecture is very much incomplete and in flux.  Unless you want
>to be chasing my changes, I would give it a few months.
>- Eric
>-----Original Message-----
>From: Matthew Bishop [mailto:matt@thebishops.org]
>Sent: Thursday, January 15, 2004 1:17 PM
>To: xmlbeans-dev@xml.apache.org
>Subject: RE: Entire XML in memory?
>I'm interested in the answer to this one as well, though I think the
>is no, the whole doc is not in memory.  It may have different answers
>depending on how one navigates the instance, however.
>My interest is using XMLBeans in a J2ME PersonalProfile application.
>just started this today, and my initial impression is that v2's design
>are more in line with what I need to do.  Without reading the entire
>can I get a feel for how far along v2 is?
>Matt Bishop
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