ember js relationship property

my problem is that i have two models : stations and lines,

• stations is just a simple model containing name, addess....
• lines is a model containing a relationship to stations, so line record must contain a list to stations, but what i want to do is to assosiate a number to each station so that i can know the first station, then the second. its easly done with a database table containing a 3 field, one for the line_id one for the stations and one for the station order