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

Mark Johnson <102334.12_at_compuserve.com> wrote in message news:<ttasqvgjh5v48p40i6ebhkbpu9n81fg42u_at_4ax.com>...
> I just saw this. The problem was the sparse use of integers as your
> integer pairs exploded from binary shifting, correct? which as soon as
> the very idea of shifting enterred your mind you knew would be at
> least a potential overflow problem. This below avoids those geometric
> progressions?

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. Note, that you have the same problem for materialized path encoding. If you String datatype length is limited to say 2000 characters, then you'll be unable to accomodate hierarchies deeper than 1000 levels. The difference is that for integers the length is much smaller, but this is deficiency of the integer computer representation, not the encoding model.  

> I wonder, too, if there is a bias in favor of small lists, in any
> case, in a 'flattened' substitute for the adjacency model, which
> itself hides each subdirectory by the single local link, and is what
> Celko was attempting to 'flatten' out, correct, and what your method
> attempted to refine for the maintenance overhead of his method?

I'm not sure I understand your comment about bias in favor of small lists.

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.  

> 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.

I'm sorry, but I don't know what XML is, and have no idea why parsing is relevant. Received on Sun Nov 09 2003 - 21:49:56 CET