Language Syntax

<query> ::= SELECT  <select_target>
            CLUSTER <cluster>
            FROM    <source>
            WHERE   <condition>

<select_target> ::= x | y | z | t | image_object |
                    audio_object | video_object | type

<cluster> ::=  * | <x_cluster> | <y_cluster> | <z_cluster> |
               <t_cluster>  

<x_cluster> ::=  <x_val> | <x_val> <x_cluster>

<x_val> ::= <val> | OPEN <val>

<source> ::= <query> | <source_name>

<condition> ::=  <string>