[OSM-legal-talk] Substantial meaning
frederik at remote.org
Thu Apr 23 23:34:06 BST 2009
> Has there been any discussion on what people here feel 'substantial'
> means in the context of the definitions of the ODbL? I've banged
> around the wiki looking but might might have missed it.
It hasn't been discussed a lot. I guess you have read the
often-referred-to pp28-32 of
http://edina.ac.uk/projects/grade/gradeDigitalRightsIssues.pdf which of
course are not specific to OSM.
RichardF once summarised;
> Dr Waelde also notes that under EU database right it's not just a
> matter of percentage, but also of a "qualitative analysis". To me it
> appears clear that a single street name isn't substantial, the whole
> of Cambridge is. We could spend hours discussing this but I suspect it
> comes down to "don't take the piss".
I could think of a number of ways of defining substantialness. Any
workable definition must
1. be compatible with the EU database directive
2. be absolute (no "more than 0.01% of data means substantial")
3. be practical
For the sake of 2. and 3., I would define something like this:
"A substantial extract is an extract that covers more than one square
kilometre *and* more than 25 features, where a "feature" is either a way
with all its nodes and tags, or a single tagged node."
This would mean that an area of 1000 x 1000 metres could always be fully
extracted as insubstantial and used for any purpose. That's roughly the
size of Green Park in London. It is not something of a huge value; it is
something that can be mapped in an hour, or make it half a day if you
want all house numbers and pubs in a densely populated area. For a
densely populated area, the 25-feature constraint will always be met
within a square kilometre and thus ineffective. For a sparsely populated
area, it might be possible to fully extract a larger area as long as it
contains less than 25 features.
The 25-feature constraint becomes interesting when someone does queries;
one could extract the 25 highest mountains or the 25 largest buildings
or 25 catholic churches that are within 100 metres of a pub. Because
whole ways are allowed, the 25-feature constraint might even allow the
extraction of the whole motorway network of a small country.
When you think about what you can do with 25 features, always bear in
mind that you must not combine multiple insubstantial extracts - if you
manage to extract the motorway network of a small country in 25 features
then you cannot also get the coastline or the primary roads, even if
someone else extracts them for you or if you do it another time.
Of course the numbers can be changed but I think that a definition like
this is easy to understand and apply. There is some potential for abuse
because someone could quickly connect all things of interest to him into
one large way and then extract that but I think such behaviour could be
ruled out by proper wording.
Our goal in defining "substantial" must not be to allow as little as
possible. The database directive allows free use of insubstantial
extracts, and says the database owner must not disallow such use. If we
try to circumvent the rule by issuing a definition of "substantial" that
basically makes everything that is useful also substantial then we are
in breach of the database directive.
Frederik Ramm ## eMail frederik at remote.org ## N49°00'09" E008°23'33"
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