]project-open[ Data-Model: Object-Relationships

Object-Relationships The ]project-open[ Data-Model , Frank Bergmann, 2010-09-22 This tutorial explains how to create generic relationships between OpenACS/]project-open[ objects. Such relationships include the “is-member-of” relationship between users and business objects, but also relationships like “is-employee-of”, “is-invoice-for”, “is-group-member-of” etc.

GUI Example ,[object Object],[object Object],[object Object]

Types of Relationships ,[object Object],[object Object],Company Other Company User Project Other User is_customer (1:n rel) is_member is_member (project manager) is_member is_friend (Sample N:M Relationships between a user and several ]po[ objects)

The acs_rels Table ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],rel_type object_id_two rel_id acs_rels object_id_one SELECT p.project_name, im_name_from_user_id(u.user_id) as user_name FROM acs_rels r, im_projects p, users u WHERE r.object_id_one = p.project_id and r.object_id_two = u.user_id user_id user . . . username (A sample SQL query to list all user-project memberships) The acs_rels table is essentially a generic mapping table for acs_objects. Once we come up with a way to associate attributes with relationship types, we could replace many of the ACS 3.x mapping tables like user_content_map, user_group_map, and user_group_type_modules_map with this one table. Much application logic consists of asking questions like "Does object X have a relationship of type Y to object Z?" where all that differs is X, Y, and Z. Thus, the value of consolidating many mapping tables into one is that we can provide a generic API for defining and querying relationships. In addition, we may need to design a way to enable "type_specific" storage for relationships (i.e., foreign key columns for one-to-many relationships and custom mapping tables for many-to-many relationships), instead of only supporting "generic" storage in the acs_rels table. This would parallel what we do with acs_attributes. project_id im_projects project_name . . . project_nr

Relationship Types ,[object Object],rel_id im_biz_object_members object_role_id ,[object Object],[object Object],percentage object_id object_type acs_objects rel_id acs_rels object_id_one object_id_two rel_type rel_id membership_rels member_state rel_id admin_rels rel_id composition_rels rel_id group_rels rel_type group_id rel_type acs_rel_type object_type_two role_one object_type_one role_two min_n_rels_one max_n_rels_one min_n_rels_two max_n_rels_two

Range and Domain Constraints ,[object Object],[object Object],[object Object],[object Object],[object Object],Object 1 Object 2 relationship Domain (Example: Person) Range (Example: Project) ( Relationship can be constraint to specific Domain and Range for consistency checking ) rel_type acs_rel_type object_type_two role_one object_type_one role_two min_n_rels_one max_n_rels_one min_n_rels_two max_n_rels_two

Exercises ,[object Object],[object Object]

Frank Bergmann [email_address] www.project-open.com

]project-open[ Data-Model: Object-Relationships

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]project-open[ Data-Model: Object-Relationships