Scales Improvements Specifications

Overview

Scales Improvements
Project state	Specification
Tracker issue	https://tracker.moodle.org/browse/MDL-17258
Discussion	-
Assignee	HQ

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One of the gradebook improvements is to allow teachers to enter a grade letter and have that converted to a number (e.g. b+ => 75). The feature already exists to do the reverse (enter a number and have the student see a letter). There is significant overlap with scales - and this is really just a scale with a custom mapping of items to points.

So - this specification is a break down of the changes that would be required to improve scales so that they can support a custom mapping of items -> points.

Create a scales API

The way scales are implemented currently (Moodle 2.7) is that the activity modules each re-implement the logic of retrieving a list of scale items for a given scale and creating a menu from it. The chosen item is then pushed to the gradebook via the "grade_update" method where the grade_item in the gradebook identifies the scale in use. It would be much better if there was a single function responsible for creating a form element that represents a scale. There are other bits of scales logic hard coded in modules such as getting the min and max for a scale, converting a scale item to a points value, getting a list of scale items, getting a normalized grade from a scale item and getting the closest scale item to a value specified in points.

We should create an api for these functions under \core\grade to encapsulate all this logic.