Anonymous Users

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Moodle 2.0

Objective

To allow users to switch into an anonymous mode when using certain activities eg when posting to a forum, so that the user's real identity cannot be ascertained by other non-privileged users.

Possible Use Cases

Activity: for example a forum may be switched into anonymous mode by teacher rendering all posts anonymous.
User: a user may choose to participate in an activity anonymously. In this case the teacher would switch the activity into an optional mode. For example, the forum module, when posting to a forum in an optional anonymous mode, the student could choose at the time of posting whether the post should be anonymous;
Role Play: a teacher may choose to run the whole course in an anonymous mode to allow students to role play. In this case the anonymous mode will be forced to "yes" in the course settings.

Settings

Global

Course

Activity

User Profile

Code Changes

Status definitions

define('ANONYMITY_ON', 2);
define('ANONYMITY_OPTIONAL', 1);
define('ANONYMITY_INHERIT', 0);
define('ANONYMITY_OFF', -1);
define('ANONYMITY_DISABLED', -9999);

DB Tables

New table: anonymity_context

Record the anonymity status in given contexts

field	type	description
id	int(10) unsigned	auto-increment
contextid	int(10) unsigned	id from the context table
status	int(4) signed	anonymity status

New table: anonymity_user_context

Record user aliases for a particular context

field	type	description
id	int(10) unsigned	auto-increment
userid	int(10) unsigned	id from the user table
contextid	int(10) unsigned	id from the context table
alias	varchar(255)	the user's alias for this given context

Code

The fullname function in lib/moodlelib.php will be changed to return an anonymous name if applicable. We can take advantage of the Navigation 2.0 changes which ensure each page is linked to a specific context (That is, $PAGE->context will always to set to something sensible.)

As the fullname function may be called many times on a single page, it is extremely important that we keep the function as efficient as possible. It is also important that we implement these changes in a way that works in most instances without changes to the calling code.

function fullname($user, $override=false, $anonymous=false)

where the user object may also contain an alias property. The $anonymous parameter will only be checked if the anonymity status for the current context is set to optional.

What we return depends on:

anonymity status for the current context
$anonymous parameter
existing user alias in the anonymity_user_context table
alias property in the passed $user object
moodle/anonymity:viewanonymous permission for the current user
$CFG->anonymityuseraliases

So what do we return? The following table shows the possibilities for various scenarios

anonymity status	$anonymous	$CFG->anonmymityuseraliases	anonymity_user_alias.alias	$user->alias	moodle/anonymity:viewanonymous	return example
on	true	true	(not set)	(not set)	true	get_string('anonymous')."(Real Name)"
on	true	true	(not set)	(not set)	false	get_string('anonymous')
on	true	true	(not set)	"Fred Jones"	true	"Fred Jones (Real Name)
on	true	true	(not set)	"Fred Jones"	false	"Fred Jones"
on	true	true	"Bob Smith"	(not set)	false	Bob Smith
on	true	true	"Bob Smith"	(not set)	true	"Bob Smith (Real Name)"
on	true	true	"Bob Smith"	"Fred Jones"	false	"Fred Jones"
on	true	true	"Bob Smith"	"Fred Jones"	true	"Fred Jones (Real Name)"

backwards compatibility

If no anonymous mode is given then we check the current context to see if anonymous mode should be running. Check activity, course, global settings and determine anonymity status. We can grab the current context from the $PAGE object, otherwise find another way to do it.
If no alias property is defined in the user object then we return get_string('anonymoususer') ie a global, default string;

Documentation