A marking scheme is a description of how something, or a set of things (i.e. assignments), is to be marked. Each scheme is composed of a set of sections which are organized in a tree structure rooted at a root section. Marking schemes don't contain any data about how a particular thing is marked; only about how something should be marked.
As an example, suppose an instructor has to mark a number
of Java assignments. The name of the assignment is "Assignment 1",
and it has to do with for and while
loops. There are several criteria on which to mark the assignment:
1) the for loop; 2) the while loop; 3)
the comments in the code. Item number (3) has two more criteria
that have to be marked: 1) Javadoc comments; 2) inline comments.
A scheme for marking this assignment might look like this:

For more information about the different components of a marking scheme, see the following: