[OSM-legal-talk] ODbL: How obscure/inaccessible can published algorithms be?

[Frederik Ramm]

Hi,

    OdbL has this requirement where, if you publish a produced work 
based on a derived database, you also have to publish either

(a) the derived database or
(b) a "diff" allowing someone to arrive at the derived database if he 
has the original, publicly available database or
(c) an algorithm that does the same.

Is that correct so far?

To use a simple example, let's say I build a WMS that works with OSM 
data. To make this perform well at low zooms, I have to combine ways 
into longer bits and simplify their geometry. The result is clearly a 
derived database that falls under the above, and in practice I would 
probably choose the "a" route and simply make a weekly PostGIS dump 
available for download and be done with it.

However, I wonder about the permitted ways of doing (c).

I guess it would probably permitted to specify a number of PostGIS 
commands that achieve the changes. - Let us assume for a moment that 
applying these PostGIS commands would require a machine with 192 GB of 
RAM and Quad Quadcore processors and still take two weeks to complete, 
putting it out of reach of many users. Would it still be permitted to do 
that?

Or, would it be allowable to say: "For simplification, a Douglas-Peucker 
algorithm <link to DP wikipedia entry> is used." (leaving open the exact 
implementation and parametrisation of DP - bear in mind that with some 
algorithms, how they work is easily explained but implementing them in a 
way that runs on standard hardware may be a hard task).

Or, would it be allowed to say: "For simplification, just load the data 
set into <name of horribly expensive proprietary ESRI program> and hit 
Ctrl-S X Y, then choose Export to PostGIS"?

What about: "For simplification, we did the following steps: <detailed 
instructions that are easy to follow>. These steps in this sequence are 
patented by us, so if you want to follow them, please apply to us for a 
license to use our patent."

Bye
Frederik