S3Hierarchy

Purpose

The S3Hierarchy toolkit can be used to perform lookups in hierarchical taxonomies. It analyses the parent-relationships of the records, and provides methods to access and search through the parent-, child- and sibling-axes of each record.

Example

Facility type as an example for a hierarchical taxonomy:

• Arts and Recreation
  • Recreation Centers
• Community Groups
  • Volunteer Opportunities
• Education
  • Adult Education
  • Guidance and Tutoring Programs
• Health and Mental Health
  • Dental Care
  • Health Centers
  • Health Clinics
  • Health Screening and Testing
  • Hospitals and Medical Centers
  • Mental Health Counseling
  • Mental Health Programs
  • Public Health Programs
  • Substance Abuse Programs
• Social Services
  • Children and Family Services
  • Public Information Services
  • Senior Services
  • Support Groups

Data Model

To store a hierarchical taxonomy, the database table must include a parent reference (self-reference). This can either be a foreign key to the table, or - if the table is a super-entity instance - a (second) reference to the super-entity.

The diagrams explain the two models:

Configuration

The hierarchy is configured in the model as the field name of the parent reference:

    self.configure(tablename, hierarchy="parent")

If categories (e.g. level) are to be used, the hierarchy is configured as tuple of parent reference and category field:

    self.configure(tablename, hierarchy=("parent", "level"))

Connecting to the Hierarchy

• tbw