module Grader;
	import File.File;
	export UserWorkSpace, Gradesheets, UserGrader, RequiresSaving;

	object UserWorkSpace
	  components: Gradesheets;
	  description: (*
		The user contains active gradesheets upon which the user is working.
	*);
	end UserWorkSpace;

	object Gradesheets
	  components: Gradesheet*;
	  description: (*
		Gradesheets is a list of the active gradesheets open in the UserWorkspace
	*);
	end Gradesheets;

	object Gradesheet
	  components: Row*;
	  description: (*
		A gradesheet is a collection of zero or more rows, 
		that represents a course grade sheet
	  *);
	end Gradesheet;

	object UserGrader
--	  components: file:File and requires_saving:RequiresSaving;
	  components: requires_saving:RequiresSaving;
	  description: (*
        	A UserGrader has a flag indicating if the GradeSheet
        	requires saving.
    	*);

	end UserGrader;

	object StudentInfo;	-- stub

	object Row extends StudentInfo
	  components: Column* and CourseGradeColumn;
	  description: (*
		Row is an individual students grade and personal 
		information. It consists of a student name, an ID, 
		a collection of zero or more columns, and a course 
		grade column.
	  *);
	end Row;

	object CourseGradeColumn
	  components: PointsCol and PercentageCol and LetterCol;
	  description: (*
		Course Grade Column is a default column created 
		by the system when roster is imported. The course 
		grade column has three subcolumns:  a course 
		points column, a course percentage column, and a 
		course letter grade column
	*);
	end CourseGradeColumn;

	object PointsCol =  Points;
	object PercentageCol =  Percentage;
	object LetterCol =  Symbol;

	object Points =  integer;
	object Percentage =  real;
	object Symbol =  string;

	object Column
	  components: ColumnValue and AVGColumn and SubColumn*;
	  description: (*
		Column is a category in the gradesheet that 
		contains a column value, a system defaulted 
		average column, and a collection of 0 or more 
		sub columns.
		*);
	end Column;

	object ColumnValue
	  components: Points or Percentage or Symbol;
	  description: (*
		ColumnValue is the component of a cell in points 
		form, percentage form or letter form	
		*);
	end ColumnValue;

	object AVGColumn
	  components: Points or Percentage or Symbol;
	  description: (*
		AVGColumn is a default column created by the 
		system when a new column is created that contains 
		the average of all subcolumns at the same level
		*);
	end AVGColumn;

	object 	SubColumn
	  components: SubColumnValue and SubColumn*;
	  description: (*
		SubColumn is an assignment in the grade sheet 
		that contains a value, and a collection of zero 
		or more subcolumns
		*);
	end SubColumn;

	object SubColumnValue
	  components: Points or Percentage or Symbol;
	  description: (*
		SubColumnValue is the component of a cell in 
		points form, percentage form or letter form
		*);
	end SubColumnValue;

	object RequiresSaving =  boolean
	  description: (*
        	True if a grader requires saving, which is the case if one or more
        	successful edit operations has been performed on the grader since the
        	most recent save.  The grader edit operations are ...
		*);
	end RequiresSaving;

	object PreviousState
	  components: ;
	  description: (*
        	PreviousState is the snapshot of scheduled items before the most
        	recently performed scheduling operation used by EditUndo.  The
        	Schedule, Change, and Delete operations save the previous state to
        	support Undo.
		*);
	end PreviousState;


end Grader;