Hi Yuri,
We have to decide what is most important - fidelity to the infinite
number of tagging styles out there, or the ability to get a basic set of
tagging grammar accepted in as many tools as possible.
Any rules grammar will always have limits of course. If the rules are
too complex to represent in a declarative way, that is in itself an
indication of the mess we have got ourselves into. If the "unwritten
rules" of OSM tagging are too complex to write down, then they need
sorting out first! Having a simple base to work from might be a good
first step. Automated chaos is still chaos.
I agree that the ultimate rules engine may well end up using e.g. JS as
a medium to express some of the subtleties of the rules. Once a JS
implementation has been published, then people can translate the JS
reference implementation into whatever language they need. But
separating the basic rules from the execution engine is nothing more
than architectural best practice, and there is no reason that the basic
rules should not be portable across runtime environments.
Can you think of any complex patterns which cannot (easily) be expressed
in a declarative way?
The real challenge here is not for the coders, but a perennial challenge
for the OSM community. How do we get to such a consensus about tagging
patterns, that we can actually say "this is correct" and "this is wrong
enough to warrant correction" without upsetting a large number of
people? As soon as a discussion is about right vs wrong, it degenerates
into mudslinging.
//colin
On 2017-12-24 20:37, Yuri Astrakhan wrote:
> Declarative rules are usually not very good. Every tool must understand every
> type of rule, and must be updated when new rule types are introduced. Plus
> declarative grammar is either too limiting, or eventually starts looking like
> a scripting language itself, and we end up building an execution environment
> in every tool.
>
> I think a better path is executing scripts inside other languages, e.g.
>
> * a JavaScript library ran by Java, Python, C++, ...
> * a lib that gets compiled into a webassembly for browser, or connected to
> other languages via native bindings (less tried path)
> The lib would need an API to * access local data state * access master OSM DB
> for additional data * access other tools like taginfo
>
> Integrating scripting environment may be difficult, but offers far greater
> benefits of rule consistency and flexibility.
>
> On Sun, Dec 24, 2017 at 7:30 AM, Colin Smale <colin.sm...@xs4all.nl> wrote:
>
> The technical differences between java and JS do not preclude generic
> thinking. Consider tzdata[1] for example, which does something analogous for
> time zone data.
>
> The "rules database" can be made portable, in the form of XML or JSON for
> example. The logic for using these rules can be described in a portable way.
> Then you add a set of compliance tests, and publish a reference
> implementation to demonstrate that is is possible to implement it. After
> that, the logic can be implemented in any language you like, checked against
> the compliance tests and the bindings published.
>
> Externalising the rules database enables updates and customisations for
> particular reasons. Depending on the specific use case and the associated
> non-functionals, validation could possibly be offered as a cloud service (not
> necessarily by OSM).
>
> //colin
>
> [1] https://en.wikipedia.org/wiki/Tz_database [1]
>
> On 2017-12-24 12:18, James wrote:
> ID is javascript, JOSM is java. So right there I already see a
> intercompatibility issue
>
> On Dec 24, 2017 6:12 AM, "François Lacombe" <fl.infosrese...@gmail.com> wrote:
>
> Hi
>
> Here is an idea I got regarding tagging validation in editors (iD, JOSM,
> others).
> Subsequently to wiki proposal voting and cleanups, it's currently necessarily
> to open issues in each editor repository to ask for new tagging validation
> rules.
>
> It can sometimes be time consuming to develop those new rules and such a work
> is done independently by each project maintainer. While each project have its
> own specific components, background logic is the same.
>
> Would a new lib called like osmtagvalidator or so in charge of doing conform
> validation to wiki be useful?
> It may be shared by any project involved in osm editing and preserve its
> resources for other valuable developments.
>
> For me, validation doesn't prevent users to use tags they want, but only warn
> them about possible mistakes.
>
> How would devs and users feel about this?
>
> All the best
>
> François
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