You can define a grammar for Jaql using a top-down approach, starting with the grammar
select = "select" variables "from" classNames optionalWhere;
If your users are familiar with SQL, the words select and from will be familiar to them. For your own query language, you can use other words such as show or present. As a language designer, you should determine the keywords of your language according to the effect they will have on your users.
As a first cut, you can model variables and classNames as repetitions of words, separated by commas:
select = "select" variables "from" classNames optionalWhere; variables = commaList(variable); variable = Word; classNames = commaList(className); className = Word; optionalWhere = empty ...