Glossary
Hierarchical Task Networks
Hierarchical Task Networks
Terms related to structured representations for decomposing high-level objectives into manageable subtasks. Target: Engineers building complex, multi-step agent workflows.
Hierarchical Task Network (HTN)
A planning formalism that decomposes high-level tasks into networks of subtasks using methods until primitive, directly executable actions are reached.
Primitive Task
A task in an HTN that corresponds directly to an executable action or operator in the planning domain.
Compound Task
A high-level, abstract task in an HTN that must be decomposed into subtasks before it can be executed.
Method (HTN)
A schema in an HTN that defines a possible way to decompose a compound task into a network of subtasks, given certain preconditions are met.
Precondition
A logical condition that must be true in the current world state for a planning operator or HTN method to be applicable.
Effect
The changes to the world state that result from the execution of a primitive task or planning operator.
Task Decomposition
The core process in HTN planning where a compound task is recursively replaced by a network of subtasks using applicable methods.
Domain Description (HTN)
The formal specification of an HTN planning problem, including the set of tasks, methods, operators, and the initial state.
Operator
The formal representation of an executable action in a planning domain, defined by its preconditions and effects.
SHOP (Simple Hierarchical Ordered Planner)
A seminal HTN planning algorithm that performs task decomposition in a forward, depth-first manner, interleaving planning with state progression.
HTN Planning
A planning paradigm where the solution is generated by recursively decomposing tasks into smaller subtasks until a sequence of primitive actions is found.
Decomposition Tree
A tree structure that visually represents the hierarchical breakdown of a high-level task into its constituent subtasks during HTN planning.
Skeletal Plan
A partially specified plan, often generated early in HTN planning, that contains abstract tasks requiring further decomposition.
Task Schema
A template that defines a class of tasks, specifying its parameters and the constraints on how it can be decomposed or executed.
Plan Refinement
The iterative process in HTN planning of replacing abstract tasks in a skeletal plan with more concrete subtasks or primitive actions.
Initial Task Network
The starting point for an HTN planning problem, typically consisting of one or more high-level goal tasks to be decomposed.
Plan Verification
The process of formally checking that a generated plan is valid, executable, and achieves the desired goals from the initial state.
Ordering Constraint
A temporal relation specifying that one task or action must be performed before another within a plan.
Hierarchical Plan
A plan that maintains its hierarchical structure, showing the decomposition relationships between high-level tasks and their constituent actions.
Decomposition Method
Synonymous with 'Method (HTN)', it is a rule specifying how to break down a compound task into a subtask network.
Task Library
A curated collection of task schemas, methods, and operators that define the capabilities and knowledge for an HTN planner in a specific domain.
Planning Problem (HTN)
A formal problem instance for an HTN planner, consisting of a domain description, an initial world state, and an initial task network.
Solution Plan
A fully decomposed, executable sequence of primitive actions that, when executed from the initial state, achieves the specified goals.
Plan Execution
The phase where a generated plan's primitive actions are carried out in the real world or a simulated environment.
Replanning
The process of generating a new plan, often using HTN decomposition, when the execution of the current plan fails or the world state changes unexpectedly.
Conditional Task
A task whose decomposition or execution is contingent on the runtime evaluation of specific world state conditions.
Iterative Task
A task that involves repeating a subtask or a network of subtasks until a termination condition is satisfied.
Parallel Task
A compound task whose subtasks are intended to be executed concurrently, subject to resource and ordering constraints.
Sequential Task
A compound task whose subtasks must be executed in a strict, predefined order.
Resource Constraint
A limitation on the availability of consumable or reusable resources that must be respected during task decomposition and plan execution.
Partnered with leading AI, data, and software stack.
How We Work
Custom AI workflows for your Business
One-fit-all AI don't work for modern businesses. At Inferensys, we aim to understand your business & custom requirements; which we use to define most efficient agentic workflows, the data, and the tools for your business.
01
Review the use case
We understand the task, the users, and where AI can actually help.
Read more02
Pick the right approach
We define what needs search, automation, or product integration.
Read more03
Build the first useful version
We implement the part that proves the value first.
Read more04
Improve from there
We add the checks and visibility needed to keep it useful.
Read moreThe first call is a practical review of your use case and the right next step.
Talk to Us