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Subject: Re: [provision] The modification problem gets worse...
Jeff,
Your argument here and in your previous message is predicated on the
assumption that the RAs in my scenario hold the state of the data while in
yours they do not. In yours they simply request a modification that is
independent of the current state of the data. You argue that this is not a
race condition problem and that your scenario will not suffer from it.
Let's go through it again using your implementation:
RA 1 Entry RA2
create
A: 1,2
B: 3,4
read
A:1,2
B:3,4
replace
B: 5,6
A:1,2
B:5,6
replace
B:3,5
A:1,2
B:3,5
This is how the current specification works and according to you this is
fine. I'm not sure that I see much of a difference in the end result.
Please explain.
Gerry
|---------+---------------------------->
| | Jeff Bohren |
| | <jbohren@opennetw|
| | ork.com> |
| | |
| | 03/13/2003 05:22 |
| | AM |
| | |
|---------+---------------------------->
>------------------------------------------------------------------------------------------------------------------------------|
| |
| To: provision@lists.oasis-open.org |
| cc: |
| Subject: [provision] The modification problem gets worse... |
| |
>------------------------------------------------------------------------------------------------------------------------------|
In a previous posting I have shown how the current proposal by Gerry Woods
will cause data corruption when doing modifications. I have shown this
using a very simple case. Gerry has suggested that this could be overcome
by a modification mechanism that uses XPath in combination with ldap like
modification semantics. Although this alternative has not been fully
fleshed out, it will not work either. Even theoretically it will fail. Let
me explain why.
Suppose a record has data that looks like:
<A>
<B>
<C>foo1</C>
<C>foo2</C>
<C>foo3</C>
</B>
<B>
<C>foo4</C>
<C>foo5</C>
<C>foo6</C>
<B>
</A>
No suppose RA1 wants to change the first B component. It would have to
issues a modification request with an XPath that refers to B where B has
foo1, foo2, and foo3. Now suppose the modification changes the record so
that it looks like:
<A>
<B>
<C>foo1</C>
<C>bar8</C>
<C>foo3</C>
</B>
<B>
<C>foo4</C>
<C>foo5</C>
<C>foo6</C>
<B>
</A>
Now suppose at a later time RA2 wants to remove the first B component from
A. It would have to issues a modification request with an XPath that refers
to B where B has foo1, foo2, and foo3. This request would now fail. There
is no automatic way for RA2 to reconcile the differences.
Jeff Bohren
Product Architect
OpenNetwork Technologies, Inc
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