Re: Another "Against the Grain" column on XML

[Ken North <ken_north@compuserve.com>]

<< And frankly, doing so using an RDBMS has frequently felt like programming
a Turing machine. Sure you can do anything that way, and you know you can.
But it sure is the hard way. This is complex multidemsional __information__
and splitting it into 2D tables is work, and then getting it back in a
useful way is a major task for the server.

Perhaps I'm misreading your posting. I'm addressing my comments to points I
believe you are trying to make:

1. You implied XML is complex information for which two-dimensional
operations are inadequate.

Presumably you have collections of multi-dimensional XML documents. How
exactly does that work? Does a single document instance consist of
multi-dimensional data?  What syntax, for example, do you use to define the
dimensionality of an element? How do you ensure each element has unique
coordinates in a 2-n dimensional space? The XML spec talks about start-tag,
end-tag, type and so on but I see no reference to defining dimensions.

Or do you have a multi-dimensional collection --  each document instance has
unique coordinates?

2. You implied the relational model means having to map data into a 2D model
when doing queries.

Some SQL implementations support multi-dimensional expressions. You can, for
example, run queries that operate on a data cube. You can also write star
schemas for multi-dimensional data sets. That's a common technique for data
warehouse design.

What query tool do you use that supports multi-dimensional expressions when
querying or navigating through XML documents? Do you have, for example,
software that let's you write XPath with dimensions (e.g., reference the
dimension of a node-set or an axis)?