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Bolt implementation notes ¶
Source code ¶
The Bolt source code is part of the BOINC source code distribution?. The files related to Bolt are:
Include files:
- bolt.inc: implementation of course document functions.
- bolt_db.inc: Bolt-specific DB abstraction layer.
- db_conn.inc: General DB abstraction layer.
- bolt_ex.inc: Exercise API functions.
- bolt_util.inc: Miscellaneous HTML.
User-visible files:
- bolt.php: List of courses.
- bolt_course_sample.php: Example course document.
- bolt_course.php: Home page for a particular course.
- bolt_sched.php: Scheduler: makes sequencing decisions and adds navigation.
Administrative files:
- bolt_refresh.php: Periodic task to send refresh emails.
- bolt_setup_sample.php: Example script to create a course.
How exercises are implemented ¶
The following information is intended for those who want to add new exercise types.
An exercise is a function that is called with three global variables:
- $bolt_ex_mode
- $bolt_ex_index
- $bolt_ex_score
If $bolt_ex_mode is BOLT_MODE_SHOW, the function should display the exercise, typically generating some "form" input items. $bolt_ex_index is a sequential index (0, 1, ...) indicating the order of this question in a file containing multiple questions; it should be included in form variable names.
If $bolt_ex_mode is BOLT_MODE_SCORE, the function should score the student's response (based on $_GET values) and should store the result (a floating-point number in [0..1]) in $bolt_ex_score.
If $bolt_ex_mode is BOLT_MODE_ANSWER, the function should display an "answer page" that shows the students the correct answers, and whether the student's responses were right or wrong.
Structures ¶
Database tables ¶
| Table name | What it represents |
| bolt_user | A student, their demographic info, and project-defined attributes |
| bolt_course | A course, and the name of its course structure file |
| bolt_enrollment | A student taking a course, and the ID of their last view |
| bolt_view | A view of an item, created when we show the item, and finalized when the student clicks on something |
| bolt_result | The result of a single exercise |
| bolt_xset_result | The result of a completed exercise set |
| bolt_select_finished | The completion of a select structure |
| bolt_refresh | The refresh/repeat of an exercise set, either pending or in progress |
| bolt_question | A question asked by a student |
Each table has a corresponding PHP class with names like BoltUser? etc.
PHP "unit" class hierarchy ¶
A "course structure" is a tree of objects of the following types:
Course state ¶
A course state represents a student's position in a course. It consists of an array that maps unit names to "unit state" structures. The contents of a unit state structure depends on the unit. Typically it includes the name of the current child, and its order in the unit's subunits.
A course state is like a call stack, and unit states are like stack frames. One difference: a course state can include records for units that the student is not currently in.
Each BoltView? record contains the course state when the view started.
BoltIter? ¶
This data structure is used within the Bolt scheduler. It includes:
top:: the root of the course structure.
state:: the course state (from the latest BoltView? record).
xset:: the xset we're currently in, if any.
item:: the current item
frac_done:: fraction of course completed so far
