Overpass API EBNF

(* Overpass QL EBNF Grammar, experimental Version 0.2 by Stefan Keller *)

(* Query *)
query                  ::= ( global_option )* ( statement )+ ( output_statement )*

(* Global Options *)
global_option          ::= '[' option ( ';' option )* ']'
option                 ::= 'out:' format
                         | 'timeout:' number
                         | 'maxsize:' number
                         | 'bbox:' bbox
                         | 'date:' date
                         | 'diff:' date ',' date
                         | 'resolve-aliases:' boolean
                         | 'force:' boolean

boolean                ::= 'true' | 'false'

(* Statements *)
statement              ::= fetch_statement
                         | area_statement
                         | assignment_statement
                         | union_statement
                         | difference_statement
                         | intersection_statement
                         | recurse_statement
                         | foreach_statement
                         | if_statement
                         | print_statement
                         | make_statement
                         | count_statement

(* Fetch Statement *)
fetch_statement        ::= element_type ( filter )* ( search_area )? ( ';' | '{' ( statement )+ '}' )

element_type           ::= 'node' | 'way' | 'relation' | 'nwr'

(* Filters *)
filter                 ::= '[' attribute_filter ']'
                         | '[' attribute_regexp_filter ']'
                         | '[' attribute_negation_filter ']'
                         | '(' bounding_clause ')'
                         | '[if:' condition ']'

attribute_filter       ::= key operator value
attribute_regexp_filter::= key operator_regex regex_value
attribute_negation_filter ::= '!' key

operator               ::= '=' | '!='
operator_regex         ::= '~' | '!~'
regex_value            ::= '"' regex_pattern '"'

(* Bounding Clause *)
bounding_clause        ::= bbox
                         | 'around' ':' radius ( ',' lat ',' lon )?
                         | 'poly' ':' '"' coordinates '"'

(* Search Area *)
search_area            ::= '(' area_selector ')'

area_selector          ::= 'area' ( '.' variable )?
                         | 'area' '(' query ')'

(* Assignment Statement *)
assignment_statement   ::= variable '=' expression ';'

expression             ::= fetch_statement
                         | union_statement
                         | difference_statement
                         | intersection_statement
                         | recurse_statement
                         | '(' statement_list ')'

(* Union Statement *)
union_statement        ::= '(' statement_list ')'

statement_list         ::= statement ( ';' statement )* ( ';' )?

(* Difference Statement *)
difference_statement   ::= '(' statement ';' '-' statement ( ';' )? ')'

(* Intersection Statement *)
intersection_statement ::= '(' statement ';' statement ( ';' )? ')'

(* Recurse Statement *)
recurse_statement      ::= ( variable ':' )? element_type recurse_operator ';'

recurse_operator       ::= '>' | '<' | '<<' | '>>' | '>' letter

(* Foreach Statement *)
foreach_statement      ::= 'foreach' '(' variable ')' '{' ( statement )+ '}'

(* If Statement *)
if_statement           ::= 'if' '(' condition ')' '{' ( statement )+ '}'

(* Print Statement *)
print_statement        ::= 'print' ( variable )? ( output_modifiers )* ';'

(* Make Statement *)
make_statement         ::= 'make' 'area' '(' statement ')' '->' variable ';'

(* Count Statement *)
count_statement        ::= 'count' '(' element_type ')' ';'

(* Area Statement *)
area_statement         ::= 'area' area_filter '->' variable ';'

area_filter            ::= '[' attribute_filter ']'

(* Output Statement *)
output_statement       ::= 'out' output_modifiers* ';'
output_modifiers       ::= 'body' | 'skel' | 'tags' | 'meta' | 'geom' | 'center' | 'ids' | 'qt' | 'count' | 'bb'

(* Variable *)
variable               ::= '.' identifier

(* Identifier *)
identifier             ::= letter ( letter | digit | '_' )*

(* Key and Value *)
key                    ::= '"' identifier '"'
value                  ::= '"' string '"'

(* Condition *)
condition              ::= logical_expression
logical_expression     ::= logical_term ( ( 'and' | 'or' ) logical_term )*
logical_term           ::= '(' logical_expression ')'
                         | comparison
comparison             ::= expression comparison_operator expression

comparison_operator    ::= '=' | '!=' | '>' | '<' | '>=' | '<='

(* Expressions *)
expression             ::= variable
                         | function_call
                         | value
                         | number

function_call          ::= function_name '(' ( expression ( ',' expression )* )? ')'
function_name          ::= identifier

(* Numbers and Strings *)
number                 ::= digit+ ( '.' digit+ )?
digit                  ::= '0'..'9'
letter                 ::= 'a'..'z' | 'A'..'Z'
string                 ::= character*
character              ::= any character except '"'

regex_pattern          ::= character*

(* Bounding Box and Coordinates *)
bbox                   ::= number ',' number ',' number ',' number
radius                 ::= number
lat                    ::= number
lon                    ::= number
coordinates            ::= number ( ' ' number )+ ( ',' number ( ' ' number )+ )*

(* Date *)
date                   ::= '"' iso8601_date '"'
iso8601_date           ::= year '-' month '-' day 'T' hour ':' minute ':' second 'Z'
year                   ::= digit digit digit digit
month                  ::= digit digit
day                    ::= digit digit
hour                   ::= digit digit
minute                 ::= digit digit
second                 ::= digit digit

(* Format *)
format                 ::= 'json' | 'xml' | 'csv' | 'popup'

(* Terminals *)
character              ::= any character except '"'