<id>        ::= \$?[a-zA-Z_][a-zA-Z_0-9]*
 <ids>       ::= <id> ('.' <id>)*
 <number>    ::= 0x[0-9a-fA-F]+
                 | [0-9]+
 <string> ::= (  '"' anything except newline or unescaped double quote '"'
               | '"""' anything other than three double quotes '"""'
               | \' anything except newline or unescaped single quote \'
               | \'\'\' anything other than three single quotes \'\'\')
 <qualified_string> ::= <string>
                      | <id> <base_string>
 <bool>   ::= true
              | false
 <uri>    ::= [a-zA-Z]+':'[a-zA-Z0-9_.-%%3aNo.]+
 <traversal> ::= <id>? ':' <id>?
               | <traversal> ':' <id>?

<description>    ::= <qualified_string>
<module_name>    ::= <ids>
<tag_name>       ::= <ids>
<pattern_name>   ::= <id>
<table_name>     ::= <id>
<identify_name>  ::= <id>
<node_kind>      ::= <id>
<attribute_name> ::= <id>
<variable>       ::= <ids>
<scope>          ::= <ids>
<function>       ::= <ids>
<version_number> ::= <number> '.' <number>

<module>      ::= tpl <version_number>  module <ids> ';'
                  <metadata>?
                  ( <definition> ';' )+
<metadata>   ::= metadata
                  ( <id> := <qualified_string>+ )+
                  end metadata;
<definition> ::= <import>
                  | <pattern>
                  | <table>
                  | <identify>
<import> ::= from <module_name> import <id> <version_number> (as <id>)?
                                   (',' <id> <version_number> (as <id>)?)*

<tags> ::= tags <tag_name> (',' <tag_name>)*

<pattern>      ::= pattern <pattern_name> <version_number>
                   <description>
                   <metadata>?
                   <overview>
                   <constants>?
                   <triggers>
                   <pattern_body>         
                   <removal>*
                   end pattern
<table>        ::= table <table_name> <version_number>
                   <table_row>*
                   end table
<identify>     ::= identify <identify_name> <version_number>
                   <tags> ';'
                   <node_kind> <attribute_name> (',' <attribute_name>)+
                   '->'
                   <attribute_name> (',' <attribute_name>)+ ';'
                   <table_row>*
                   end identify
<table_row>    ::= <table_key> '->' <table_value> ';'
                   | default '->' <table_value> ';'
<table_key>    ::= <table_value>
<table_value>  ::= <constant_expression> (',' <constant_expression>)*

<overview> ::= overview
                ( <overview_entry> ';' )*
                end overview
 <overview_entry> ::= <implements>
                    | <overrides>
                    | <requires>
                    | <tags>
 <overrides>  ::= overrides <pattern_name> ( ',' <pattern_name> )*
 <requires>   ::= requires <pattern_name> ( ',' <pattern_name> )*

<constants> ::= constants
                 ( <pattern_constant> )+
                 end constants ';'
<pattern_constant> ::= <id> ':=' <constant_expression> ';'

<triggers>          ::= triggers (scope <node_kind>)?
                         <trigger_condition>*
                         end triggers ';'
<trigger_condition> ::= on <trigger_match_list> ';'
<trigger_match_list> ::= <trigger_match_kind>
<trigger_match_kind> ::= <id> ':=' ( relationship )? <id> <trigger_fires_list>?
                          where <trigger_match>
<trigger_fires_list> ::= <trigger_fires> ( ',' <trigger_fires> )*
<trigger_fires> ::= created
                   | modified
                   | destroyed
                   | confirmed
<trigger_match> ::= <trigger_match_and>
<trigger_match_and> ::= <trigger_match_attribute>
                       | <trigger_match_and> and <trigger_match_attribute>
<trigger_match_attribute> ::= <id> '=' <constant_expression>
                             | <id> exists
                             | <id> in <constant_expression>
                             | <id> matches <constant_expression>
                             | '(' <trigger_match_and> ')'

<pattern_body> ::= body
                     <statements>
                   end body ';'

<removal> ::= removal
               on <variable> ':=' <node_kind> <removal_kind>
                                  ( where <trigger_match> )?';'
               <statement_list>
               end removal ';'
<removal_kind> ::= aged
                 | unconfirmed

<statement_list> ::= ( <statement> ';' )*
<statement> ::= <empty_statement>
              | <assignment_statement>
              | <function_call>
              | <if_statement>
              | <for_statement>
              | <break_statement>
              | <continue_statement>
              | <stop_statement>
<empty_statement> ::=

<assignment_statement> ::= <lvalue_list> ':=' <logical_expression>
<lvalue_list> ::= <lvalue> ( ',' <lvalue> )*
<lvalue> ::= <ids>
           | <lvalue> '[' <logical_expression> ']'

<if_statement> ::= if <logical_expression> then <statements>
                   (elif <logical_expression> then <statements>)*
                   (else <statements>)?
                   end if

<for_statement> ::= for <variable> in <logical_expression> do
                    <statements>
                    end for
<break_statement>    ::= break
<continue_statement> ::= continue

<stop_statement> ::= stop

<function_call> ::= <function> '(' <arg_list>? ')'
<arg_list> ::= <arg_spec> (',' <arg_spec>)*
<arg_spec> ::= <logical_expression>
             | <id> ':=' <logical_expression>

<expand_expression> ::= expand '(' <arg_list> ')'

<logical_expression>  ::= <and_test>
                        | <logical_expression> or <and_test>
<and_test>            ::= <not_test>
                        | <and_test> and <not_test>
<not_test>            ::= <comparison>
                        | not <not_test>
<comparison>          ::= <or_expression>
                        | <or_expression> <relational> <or_expression>
                        | '*' <relational> <or_expression>
                        | <or_expression> is? not? defined
<relational>          ::= '<' | '<=' | '>' | '>=' | '=' | '<>' | in
                        | not in | has subword | has substring | matches
<or_expression>       ::= <xor_expression>
                        | <or_expression> '|' <xor_expression>
<xor_expression>      ::= <and_expression>
                        | <xor_expression> '^' <and_expression>
<and_expression>      ::= <shift_expression>
                        | <and_expression> '&' <shift_expression>
<shift_expression>    ::= <add_expression>
                        | <shift_expression> '<<' <add_expression>
                        | <shift_expression> '>>' <add_expression>
<add_expression>      ::= <multiply_expression>
                        | <add_expression> '+' <multiply_expression>
                        | <add_expression> '-' <multiply_expression>
<multiply_expression> ::= <unary_expression>
                        | <multiply_expression> '*' <unary_expression>
                        | <multiply_expression> '/' <unary_expression>
                        | <multiply_expression> '%' <unary_expression>
<unary_expression>    ::= <primary>
                        | '-' <unary_expression>
                        | '+' <unary_expression>
                        | '~' <unary_expression>
<constant_expression> ::= <logical_expression>
<primary>             ::= <atom>
                        | <function_call>
                        | <search_expression>
                        | <expand_expression>
                        | <subscript>
                        | <list_expression>
                        | <attribute>
                        | <keyword_expression>
                        | <group_expression>
<subscript>           ::= <primary> '[' <logical_expression> ']'
<list_expression>     ::= '[' ( <logical_expression> ',' )* <logical_expression>? ']'
<scoped_attribute>    ::= <scope> '.' <attribute>
<attribute>           ::= <ids>
                        | <ids> '.' <key_expression>
<key_expression> ::= '#'
                   | '##'
                   | '#id'
                   | '#' <traversal>
                   | '#' <traversal> '.' <attribute>
                   | '#' <string> '(' <attributes> ')'
<keyword_expression>  ::= structure
<group_expression>    ::= '(' <expression> ( ',' <expression> )* ','? ')'
<atom>                ::= none
                        | <bool>
                        | <qualified_string>
                        | <number>

<search_expression> ::= search '('
                        <flags>?
                        <search_in>?
                        <kind_list>
                        <with_funcs>?
                        <where_clause>?
                        <traversals>?
                        <order_by_clause>?
                        <locale>?
                        <show>?
                        <search_process_with>?
                        ')'
<flags> ::= flags '(' <id> ( ',' <id> )* ')'
<search_in> ::= in <id>
              | in <string>
<kind_list> ::= '*'
              | <kind_comma_list>
<kind_comma_list> ::= <node_kind> ( ',' <node_kind> )*

<with_funcs> ::= with <with_func> ( ',' <with_func> )*
<with_func> ::= <id> '(' <search_expression_commalist> ')' as <id>

<traversals> ::= <traverse_or_expand>+
<traverse_or_expand> ::= <traverse_clause>
                       | <expand_clause>
                       | <step_in_clause>
                       | <step_out_clause>
<traverse_clause> ::= traverse <traversal> <with_funcs>? <where_clause>?
<expand_clause>   ::= expand   <traversal> <with_funcs>? <where_clause>?
<step_in_clause>  ::= step in  <traversal> <with_funcs>? <where_clause>?
<step_out_clause> ::= step out <traversal> <with_funcs>? <where_clause>?

<where_clause> ::= where <search_logical_expression>

<order_by_clause> ::= order by <order_by_commalist>
                    | order by taxonomy
<order_by_commalist> ::= <order_by> ( ',' <order_by> )*
<order_by> ::= <search_value_expression> <direction>?
<direction> ::= desc

<locale> ::= locale <string>
           | locale <id>

<show> ::= show <show_list>?
<show_list> ::= <show_clause> ( ',' <show_clause> )*
<show_clause> ::= <search_value_expression> <as>?
                | explode <search_value_expression> <as>?
                | summary
                | '*'
<as> ::= as <id>
       | as <string>
<search_logical_expression> ::= <search_and_expression>
                              | <search_logical_expression> or <search_and_expression>
<search_and_expression> ::= <search_and_expression>
                          | <search_and_expression> and <search_not_expression>
<search_not_expression> ::= <search_comparison>
                          | not <search_not_expression>
<search_comparison> ::= <search_value_expression> '=' <search_value_expression>
                      | <search_value_expression> '<>' <search_value_expression>
                      | <search_value_expression> >=' <search_value_expression>   
                      | <search_value_expression> '>' <search_value_expression>
                      | <search_value_expression> '<=' <search_value_expression>
                      | <search_value_expression> '<' <search_value_expression>
                      | <search_value_expression> has subword <search_value_expression>
                      | <search_value_expression> has substring <search_value_expression>
                      | <search_value_expression> matches <search_value_expression>
                      | <search_value_expression> not matches <search_value_expression>
                      | <search_value_expression> in <search_value_expression>
                      | <search_value_expression> not in <search_value_expression>
                      | <search_value_expression> defined
                      | <search_value_expression> is defined
                      | <search_value_expression> not defined
                      | <search_value_expression> is not defined
                      | '*' '=' <search_value_expression>
                      | '*' has subword <search_value_expression>
                      | '*' has substring <search_value_expression>
                      | '*' matches <search_value_expression>
                      | <search_value_expression>
<search_value_expression> ::= <search_multiply_expression>
                            | <search_value_expression> '+' <search_multiply_expression>
                            | <search_value_expression> '-' <search_multiply_expression>
<search_multiple_expression>
               ::= <search_unary_expression>
                 | <search_multiply_expression> '/' <search_unary_expression>
                 | <search_multiply_expression> '*' <search_unary_expression>
<search_unary_expression> ::= <search_primary_expression>
                            | '-' <search_unary_expression>
<search_primary_expression> ::= <search_value>
                              | <id> '(' <search_expression_commalist>? ')'
                              | '[' <search_expression_commalist>? ']'
                              | '(' <search_logical_expression> ')'
<search_value> ::= nodecount '(' <traversals>? ')'
                 | nodes '(' <traversals>? ')'
                 | <number>
                 | <string>
                 | <search_attribute>
<search_attribute_commalist> ::= <search_attribute> ( ',' <search_attribute> )*
<search_attribute> ::= <id>
                     | <search_key_expression>
                     | <search_at_expression>
<search_key_expression> ::= '#'
                          | '##'
                          | '#id'
                          | '#' <traversal>
                          | '#' <traversal> '.' <search_attribute>
                          | '#' <string> '(' <search_attribute_commalist> ')'
<search_expression_commalist> ::=
           <search_value_expression> ( ',' <search_value_expression> )*
<search_process_with> ::= processwith <search_process_with_func_list>
<search_process_with_func_list>
                      ::= <search_process_with_func>
                        | <search_process_with_func_list> ',' <search_process_with_func>
<search_process_with_func> ::= <id>
                             | <id> '(' <search_expression_commalist>? ')'