Types

type Book =  book [
               @year  [ Integer ],
               title  [ String ],
               author [ String ]{1,*}
             ]
type Bib = bib [ Book{0,*} ]
let book0 : Book =  book [
                      @year  [ 1999 ],
                      title  [ "Data on the Web" ],
                      author [ "Abiteboul" ],
                      author [ "Buneman" ],
                      author [ "Suciu" ]
                    ]
let bib0 : Bib = ...