Learners are engaged in solving real-world problems: the WTDS can provide diverse real-world ERD problems (as shown in Table 3) for learner practice by slightly modifying its parameters.
This research adopts timely diagnostic feedback to aid ERD learning with systematic hints once learners encounter learning barriers during the diagram-drawing process.
Step 1: Presetting the correct ERD by an instructor
The first step is for an instructor to draw the correct ERD. To facilitate computing, the graphic information is converted into numeric data in a two-dimensional matrix, [R.sub.correct].
2 as an example, suppose that the left part is the correct ERD by an instructor.
Step 2: Comparing the ERD results of all testees with the correct ERD
After a testee finishes his or her ERD, the corresponding matrix [R.sub.test] is obtained through Formula (1).
Thus, when drawing an ERD, the common scenario is that a student submits the result only after finishing the ERD, and then receives feedback from the web server, or delayed feedback.
When drawing an ERD, the process flows of timely feedback are as follows: Whenever a user executes a drawing step on a browser, this action triggers the local AJAX engine for submitting the request to the web server.
The first phase generates a diagnostic database, which consists of the correct ERD answer, frequent itemsets, and association rules.
When a student performs a drawing on ERD, the system determines if this step is correct.
To enable students to practice diverse ERD models, five different ERD models were established based on the proposed system, including School, Sales, Publisher, Enterprise, and Hotel, as shown in Table 3.