Collection Object Groups (COG) Design & Implementation
Purpose and Context
In Specify, individual specimens and samples are stored as Collection Objects (COs), each with a unique GUID and catalog record. However, when COs share a physical or contextual connection—such as being part of the same organism, mounted on a common medium, or co-located they can be grouped logically using Collection Object Groups (COGs).
See Collection Object Groups Discourse Post for background.
Flexibility in Abstraction
COGs allow collections to balance granularity versus simplicity. Collections may choose not to designate separate COs for closely related specimens, instead grouping them in a single record to reflect resource constraints or specific cataloging protocols. Conversely, COGs become essential when multi-component relationships are meaningful—for example, minerals embedded in a slab or multiple specimens on a herbarium sheet—improving efficiency in cataloging, querying, data exports, and managing loans or transactions.
Types of COGs and Business Logic
COGs can be categorized into three super types, each with distinct behaviors:
Super Type |
Description |
Key Behavior |
|---|---|---|
Consolidated |
Physically joined objects (e.g., a rock slab, microscope slide) |
Requires a primary CO; transactions treat group as a unit |
Discrete |
Related but separate objects (e.g., multiple plant species collected together) |
No primary CO required; each CO remains equally independent |
Drill Core |
Segmented cores ordered by depth/age |
Linear grouping with no primary CO required |
Implementation Details
COGs are defined via a COG Type record, setting both a user-friendly name and the super type.
Relationships are managed in the
collectionobjectgroupjoin(COJO) table, which stores the children (COs or other COGs); primary and substrate roles are also supported.For Consolidated COGs, marking a CO as primary ensures proper handling in reporting and transactional processes—such as loans, where including a preparation of a CO within a COG triggers inclusion of all related COG components.