wiki:S3/S3Hierarchy

Version 5 (modified by Dominic König, 8 years ago) ( diff )

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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

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