Re: [xml-dev] Converting a variety of data formats, containing various k

[Michael Kay <mike@saxonica.com>]

> 
> Without giving this much thought; you could probably prove that all
> data modes that are "computationally  tractable" are reducible to a
> model that is isomorphic to a triple store. 

Generally I don't think different data models are isomorphic except in trivial cases: you can't usually find a 1:1 mapping between their value spaces. If you try to find a function F that maps from the XML value space to the JSON value space, for example, you will typically find that if it's lossless (ie. represents every distinct XML value using a different JSON value, and therefore has an inverse F'), then it won't be the case that F' maps every distinct JSON value to a distinct XML value.

Similarly if you map XML to a triple store, then the operation that reverses the mapping won't be useful as a general way of representing any triple store in XML.

If such isomorphisms existed, it wouldn't be necessary to employ half the programming profession at any point in time devising conversions from format A to format B.

Michael Kay
Saxonica