obset

Obset is a term used in theoretical computer science and discussions of distributed state to denote a set-like data structure that integrates object identity with observability semantics. The name combines notions of objects and observation, emphasizing that membership can depend on what an observer has witnessed. The term is not standardized and appears mainly in speculative or foundational discussions.

Definition and structure

An obset is typically described as a carrier set O together with a family of visibility predicates Vis, parameterized by observer and time. Elements may become visible to a process only after certain events or observations. Operations commonly associated with an obset include add(o) to introduce an element, observe(o) to record that an observer has witnessed the element, and query operations to determine membership under a given observation context. The precise axioms vary by formulation, but the central idea is that observation status can influence which elements are considered members by a particular process.

Applications

In distributed systems and formal verification, obsets are used to model state where agents have partial or delayed visibility. They provide a framework for reasoning about convergence, causality, and consistency when different processes accumulate knowledge at different times. Obsets are related to, and sometimes contrasted with, CRDTs (conflict-free replicated data types) and patterns such as observed-remove sets, which capture similar notions of change and observable history.

Variants

Some formulations distinguish strong obsets, where membership is fully determined by observation, from weak obsets, where membership may retain some observer-independent aspects. Variants differ in how observability interacts with updates and how convergence is defined.

See also

Observed-remove set, CRDTs, event structures. Etymology: combines observable and object set.