Index: openacs-4/packages/acs-core-docs/www/groups-design.adp =================================================================== RCS file: /usr/local/cvsroot/openacs-4/packages/acs-core-docs/www/groups-design.adp,v diff -u -r1.1.2.2 -r1.1.2.3 --- openacs-4/packages/acs-core-docs/www/groups-design.adp 9 Jun 2016 08:44:49 -0000 1.1.2.2 +++ openacs-4/packages/acs-core-docs/www/groups-design.adp 23 Jun 2016 08:32:45 -0000 1.1.2.3 @@ -34,19 +34,19 @@

Historical Considerations

The primary limitation of the OpenACS 3.x user group system is -that it restricts the application developer to representing a "flat -group" that contains only users: The user_groups table may contain the +that it restricts the application developer to representing a +"flat group" that contains only users: The user_groups table may contain the group_id of a parent group, but parent-child relationship support is limited because it only allows one kind of relationship between groups to be represented. -Moreover, the Oracle database's limited support for tree-like +Moreover, the Oracle database's limited support for tree-like structures makes the queries over these relationships expensive.

In addition, the Module Scoping design in OpenACS 3.0 introduced a party abstraction - a thing that is a person or a group of people - though not in the form of an explicit table. Rather, the triple of scope, user_id, and group_id columns was used to identify the party. One disadvantage of this design convention is that it -increases a data model's complexity by requiring the programmer +increases a data model's complexity by requiring the programmer to:

Design Tradeoffs

The core of the Group Systems data model is quite simple, but it -was designed in the hopes of modeling "real world" organizations -which can be complex graph structures. The Groups System only -considers groups that can be modeled using directed acyclic graphs, -but queries over these structures are still complex enough to slow -the system down. Since almost every page will have at least one -membership check, a number of triggers, views, and auxiliary tables -have been created in the hopes of increasing performance. To keep -the triggers simple and the number of triggers small, the data -model disallows updates on the membership and composition tables, -only inserts and deletes are permitted.

The data model has tried to balance the need to model actual +was designed in the hopes of modeling "real world" +organizations which can be complex graph structures. The Groups +System only considers groups that can be modeled using directed +acyclic graphs, but queries over these structures are still complex +enough to slow the system down. Since almost every page will have +at least one membership check, a number of triggers, views, and +auxiliary tables have been created in the hopes of increasing +performance. To keep the triggers simple and the number of triggers +small, the data model disallows updates on the membership and +composition tables, only inserts and deletes are permitted.

The data model has tried to balance the need to model actual organizations without making the system too complex or too slow. The added triggers, views, and tables and will increase storage requirements and the insert and delete times in an effort to speed @@ -82,8 +82,9 @@

parties

The set of all defined parties: any person, user, or group must have a corresponding row in this table.

persons

The set of all defined persons. To allow easy sorting of persons, the name requirement 30.10 is -met by splitting the person's name into two columns: first_names and last_name.

users

The set of all registered users; this table includes information -about the user's email address and the user's visits to the +met by splitting the person's name into two columns: +first_names and last_name.

users

The set of all registered users; this table includes information +about the user's email address and the user's visits to the site.

user_preferences

Preferences for the user.

groups

The set of all defined groups.

group_types

When a new type of group is created, this table holds additional knowledge level attributes for the group and its subtypes.

membership_rels

The set of direct membership relationships between a group and a party.

group_member_index

A mapping of a party P to the groups {Gi @@ -104,10 +105,10 @@ application developer. Membership constraints can be specified at creation time by passing a parent group to the constructor.

The membership_rels and composition_rels tables -indicate a group's direct members and direct components; these +indicate a group's direct members and direct components; these tables do not provide a record of the members or components that are in the group by virtue of being a member or component of one of -the group's component groups. Site pages will query group +the group's component groups. Site pages will query group membership often, but the network of component groups can become a very complex directed acyclic graph and traversing this graph for every query will quickly degrade performance. To make membership @@ -130,10 +131,8 @@ appropriaterel_id from the membership_rels table.

group_approved_member_map

A mapping of a party to the groups the party is an approved member of (member_state is -'approved'); this mapping includes the type of relationship by -including the appropriaterel_id -from the membership_rels -table.

group_distinct_member_map

A person may appear in the group member map multiple times, for +'approved'); this mapping includes the type of relationship +by including the appropriaterel_id from the membership_rels table.

group_distinct_member_map

A person may appear in the group member map multiple times, for example, by being a member of two different groups that are both components of a third group. This view is strictly a mapping of approved members to @@ -201,8 +200,8 @@

User

acs_user.new creates a new user and returns the user_id. -The function must be given the user's email address and the full -name of the user in two pieces: first_names and last_name. All other fields are optional. +The function must be given the user's email address and the +full name of the user in two pieces: first_names and last_name. All other fields are optional. The interface for this function is:

 function acs_user.new (
   user_id            users.user_id%TYPE,
@@ -230,13 +229,13 @@
 );

acs_user.receives_alerts_p -returns 't' if the user should receive email alerts and 'f' -otherwise. The interface for this function is:

+returns 't' if the user should receive email alerts and
+'f' otherwise. The interface for this function is:
 function acs_user.receives_alerts_p (
   user_id       users.user_id%TYPE
 ) return varchar;
 
Use the procedures acs_user.approve_email and acs_user.unapprove_email to specify whether
-the user's email address is valid. The interface for these
+the user's email address is valid. The interface for these
 procedures are:
 procedure acs_user.approve_email (
   user_id       users.user_id%TYPE
@@ -248,10 +247,11 @@
 
Group

 acs_group.new creates a new
 group and returns the group_id.
-All fields are optional and default to null except for object_type which defaults to 'group',
-creation_date which defaults to
-sysdate, and group_name which is required. The interface
-for this function is:
+All fields are optional and default to null except for object_type which defaults to
+'group', creation_date
+which defaults to sysdate, and
+group_name which is required.
+The interface for this function is:
 function acs_group.new (
   group_id           groups.group_id%TYPE,
   object_type        acs_objects.object_type%TYPE,
@@ -271,8 +271,9 @@
 ) return varchar;
 

 acs_group.member_p returns
-'t' if the specified party is a member of the specified group.
-Returns 'f' otherwise. The interface for this function is:
+'t' if the specified party is a member of the specified
+group. Returns 'f' otherwise. The interface for this
+function is:
 function acs_group.member_p (
   group_id      groups.group_id%TYPE,
   party_id      parties.party_id%TYPE,
@@ -281,9 +282,10 @@
 Relationship

 membership_rel.new creates a
 new membership relationship type between two parties and returns
-the relationship type's rel_id.
-All fields are optional and default to null except for rel_type which defaults to membership_rel.
-The interface for this function is:
+the relationship type's rel_id. All fields are optional and default
+to null except for rel_type
+which defaults to membership_rel. The interface for this function
+is:
 function membership_rel.new (
   rel_id             membership_rels.rel_id%TYPE,
   rel_type           acs_rels.rel_type%TYPE,
@@ -304,8 +306,8 @@
 

 membership_rel.approve sets
 the member_state of the given
-rel_id to 'approved'. The
-interface for this procedure is:
+rel_id to 'approved'.
+The interface for this procedure is:
 procedure membership_rel.approve (
   rel_id           membership_rels.rel_id%TYPE
 );
@@ -328,8 +330,8 @@
 

 membership_rel.deleted sets
 the member_state of the given
-rel_id to 'deleted'. The
-interface for this procedure is:
+rel_id to 'deleted'.
+The interface for this procedure is:
 procedure membership_rel.deleted (
   rel_id           membership_rels.rel_id%TYPE
 );
@@ -343,9 +345,9 @@
 
Composition
 Relationship

 composition_rel.new creates
-a new composition relationship type and returns the relationship's
-rel_id. All fields are optional
-and default to null except for rel_type which defaults to composition_rel.
+a new composition relationship type and returns the
+relationship's rel_id. All
+fields are optional and default to null except for rel_type which defaults to composition_rel.
 The interface for this function is:
 function membership_rel.new (
   rel_id             composition_rels.rel_id%TYPE,