Re: More pain and sufferring with Tropashko's materialized path...

vadimtro_invalid_at_yahoo.com (Vadim Tropashko) wrote:

>Mark Johnson <102334.12_at_compuserve.com> wrote in message news:<ttasqvgjh5v48p40i6ebhkbpu9n81fg42u_at_4ax.com>...

>For balanced trees yes. For unbalanced trees, for instance, tree
>degrading into a list,

>1
>1.1
>1.1.1
>1.1.1.1
>...

>it's still a problem.

I don't know if my other message got to your server. But I can see that you might still have the problem of geometric expansion. You don't need to use the path, at all. But in creating your 'single integer key', you seem to retain the binary shifting previously used for denom and numer. So 1.1, is twice 1, and 1.1.1, is twice 1.1, and so on.

Am I correct in thinking that 'siblings', list ordering, is accomplished by shifting the key from the prevous item, and adding 1 to it? So that 1.1.2 is the key for 1.1.1 shifted, plus 1?

>Celko's Nested Sets encoding is dense, while Binary Rationals are
>sparce, indeed. This is the price one have to pay for nonvolatile
>encoding schema.

Don't you have to recalcuate every key in a sub-tree if you relocate it? with this single key method.

>> And I wonder, from that trop4 URL, that you suggest an 'adjacency
>> list' is synonymous with a table of contents, or XML tree, or the
>> like. That is, is the adjacency model still the description of any
>> particular XML tree, say for example, even if that is stored as nested
>> sets for purposes of rapid query and retrieval - assuming some custom
>> 'parser'? I might well misunderstand. But I thought the adjacency
>> model wasn't based on the tree being a tree, but on how the tree was
>> represented in a table.

That is, did you mean the adjacency model was synonymous with a simple table of contents, or outline, or rather that the one-way link-up was what is meant by the adjacency model? or something else more general? Received on Tue Nov 11 2003 - 13:21:54 CET