admin

Class GroupDB

java.lang.Object

admin.GroupDB

public abstract class GroupDB
extends java.lang.Object

GroupDB is the repository of user group information.

Field Summary

Fields

Modifier and Type	Field and Description
(package private) java.util.Collection<GroupRecord>	data The collection of group data records.
(package private) UserDB	userDB Reference to GroupDB needed for change and delete methods.

Constructor Summary

Constructors

Constructor and Description
GroupDB()

Method Summary

Methods

Modifier and Type	Method and Description
(package private) abstract void	add(GroupRecord gr) Add the given GroupRecord to the given GroupDB.
(package private) abstract void	change(GroupRecord old_gr, GroupRecord new_gr) Change the given old GroupRecord to the given new record.
(package private) abstract void	delete(GroupRecord gr) Delete the given group record from the given GroupDB.
(package private) abstract GroupRecord	findById(java.lang.String id) Find a group by unique name.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

data

java.util.Collection<GroupRecord> data

The collection of group data records.

userDB

UserDB userDB

Reference to GroupDB needed for change and delete methods.

Constructor Detail

GroupDB

public GroupDB()

Method Detail

add

abstract void add(GroupRecord gr)

Add the given GroupRecord to the given GroupDB. The name of the given group must not be the same as a group already in the GroupDB. All group members must be registered users. The leader(s) of the group must be members of it.

      pre:
        //
        // All group members are registered users.
        //
        forall (String id ; gr.members.contains(id) ;
                exists(UserRecord ur ; userDB.data.contains(ur) ;
                    ur.id.equals(id)))

            &&

        //
        // All group leaders are members of the group.
        //
        forall (String id ; gr.leaders.contains(id) ;
            gr.members.contains(id));

      post:
        //
        // A group record is in the output db if and only if it is the new
        // record to be added or it is in the input db.
        //
        forall (GroupRecord gr_other ;
            data'.contains(gr_other) iff
                gr_other.equals(gr) || data.contains(gr_other));

delete

abstract void delete(GroupRecord gr)

Delete the given group record from the given GroupDB. The given record must already be in the input db. Typically the user runs the FindGroup operation prior to Delete to locate an existing record to delete.

      pre:
        //
        // The given GroupRecord is in the given GroupDB.
        //
        data.contains(gr);

      post:
        //
        // A group record is in the output db if and only if it is not the
        // existing record to be deleted and it is in the input db.
        //
        forall (GroupRecord gr_other ;
            data'.contains(gr_other) iff
                !gr_other.equals(gr) && data.contains(gr_other));

change

abstract void change(GroupRecord old_gr,
          GroupRecord new_gr)

Change the given old GroupRecord to the given new record. The old and new records must not be the same. The old record must already be in the input db. The new record must meet the same conditions as for the input to the AddGroup operation. Typically the user runs the FindGroup operation prior to Change to locate an existing record to be changed.

      pre:
        //
        // The old and new group records are not the same.
        //
        !old_gr.equals(new_gr)

            &&

        //
        // All group members are registered users.
        //
        forall (String id ; new_gr.members.contains(id) ;
                exists(UserRecord ur ; userDB.data.contains(ur) &&
                     ur.id.equals(id)))

            &&

        //
        // All group leaders are members of the group.
        //
        forall (String id ; new_gr.leaders.contains(id) ;
            new_gr.members.contains(id));

      post:
        //
        // A group record is in the output db if and only if it is the new
        // record to be added or it is in the input db, and it is not the old
        // record.
        //
        forall (GroupRecord gr_other ;
            data'.contains(gr_other) iff
                gr_other.equals(new_gr) ||
                    data.contains(gr_other) &&
                        !gr_other.equals(old_gr));

findById

abstract GroupRecord findById(java.lang.String id)

Find a group by unique name.

      post:
        //
        // If there is a record with the given name in the input db, then the
        // output record is equal to that record, otherwise the output record
        // is empty.
        //
        exists(GroupRecord gr_found ; data.contains(gr_found) ;
                gr_found.name.equals(id) && gr_found.equals(return))
            ||
        !exists(GroupRecord gr_found ; data.contains(gr_found) ;
                gr_found.name.equals(id)) && return == null;