Colin,
Martin, if it walks like a duck and quacks like a duck, then it had
better be a duck... What I mean with this, is if the grammar is so
English-like such that people are tempted to use constructions which are
not (or not quite) supported by the grammar, or if the way it works is
contrary to how the English language would interpret it, then "errors
will occur".
Now, the primary intention was to allow to transfer conditions from
sign-posted information as "natural" as possible. Due the fact that
space is limited and people must be able to read it during driving, they
use a extremely simplified language - mostly nouns plus words like
except, if, when, on, then...
You don't get a Nobel Prize for Literature for text like "except
vehicles less than 5m long" (also in several variants, e.g. "except
vehicles with length<5m").
But nevertheless your point is valid. If we give the impression computer
understands sentences, soon or later we will find things like
"tracktype:cond = grade2 if weather was good for more than 3 days,
grade3 after a day of rain, grade4 after a thunderstorm". I haven't
taken this into account.
> Plus, of course, that the majority of users will not have
English as their first language, and we have to make this accessible to
the man-in-the-street and not allow it to become so obfuscated that only
PhD's need apply.
As I said, for information (exceptions, conditions) typically
sign-posted, you typically don't need a PhD. The parser can understand
quite amazing amount of signs just with the nouns we have already
defined for vehicles plus the properties (length, weight - plus variants
like long) and a few the date and time (Su or Sunday, etc) things also
described for other tags.
For mappers that are not familiar with the English language, the benefit
of the proposal is clearly massively reduced.
[...] If you start with
the premise that the answer must be expressed in ANTLR and shouldn't
include brackets, that's putting the cart before the horse.
The objective was to be able to understand sign-posted sentences.
I picked ANTLR to play around - but no "must".
I also said I want to avoid to use brackets just for solving precedence
problems - thus mappers shouldn't have to add brackets if they are not
used on the sign.
But one clear issue is the lack of a bigger amount of examples.
> Human language is sadly not very precise: "except taxis AND bicycles"
does not mean, you must be in a vehicle that is both (it means if not
taxis AND if not bicycles),
The human language here is extremely precise to any fluent
English-speaker. It means what it says.
Yes, no ambiguity here. Picked a bad example.
"If I were king" I would be looking for a system that:
Huh, a new condition, added it to the parser.
"maxspeed:cond = 200 if your are king" ;-)
* makes common cases easy
* makes complex cases possible
* makes each rule as standalone as possible (one sign -> one rule)
* does not rely on the user's fluency in English grammar (knowledge of a
set of specific words, e.g. tags and functions, is fine)
Signs use extremely simplified language. Thus almost every word on the
sign has an essential meaning and has to be translated into a system
also using English nouns.
But I haven't forgot your valid point - if people think that it is
free-text English, then we will soon or later see fancy conditions.
* uses grammatical constructions which are familiar to most people, or
easily learnt
The normal form is not easy to learn - this has to be made in addition
to the own language -> English translation.
But translating simplified text from one language to a simplified
English may also be a problem. Thus no major advantage here for the
alternative proposal.
However, looking to most signs, you will see combinations of one or two
attributes plus time related information only. In this case the "normal
form" is no challenge (but same is true for the simplified
"sign-language" English).
Outlook:
Yet the parser cannot parse complex conditions, the extensibility
requirements is therefore not fulfilled. Thus there is no alternative
"sign-language" proposal yet. And it looks like it is not feasible with
reasonable effort or unreasonable restrictions/rules (then we better
stick to the normal form).
IMO, the work done may be helpful for an editor: People can enter the
sign-text and the editor converts it to normal form with standardized
nouns and conditions. This tool may support several languages instead of
just English.
martinq
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