Behavior tree: Difference between revisions

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=== Behavior tree notation ===

[[File:Core Elements of the Behavior Tree Notation.png|360px|thumb|Core elements of the behavior tree notation]]

A behavior tree is used to formally represent the ''fragment of behavior'' in each individual requirement. BehaviorIn general, behavior for a large-scale system in general, where [[Concurrency (computer science)|concurrency]] is admitted, appears abstractly as a set of [[communicating sequential processes]]. The behavior tree notation captures these composed component-states and represents them as a tree-like form.

Behavior is expressed in terms of components realizing states and components creating and breaking relations. Using the logic and graphic forms of conventions found in [[programming languages]], components can support actions, composition, events, control-flow, data-flow, and threads.<ref name = "dromey03K1-Dromey"/>

Traceability tags (see Section 1.2 of behavior tree notation<ref name = "BTNotation" />) in behavior tree nodes link the formal representation to the corresponding [[natural language]] requirement. Behavior trees accurately capture behavior expressed in the natural language representation of functional requirements. Requirements behavior trees strictly use the vocabulary of the natural language requirements but employ graphical forms for behavior composition in order to eliminate risk of ambiguity. By doing this, they provide a direct and clearly traceable relationship between what is expressed in the natural language representation and its [[formal specification]].<ref name="geneticDesign05">Dromey, R.G. [http://www.behaviorengineering.org/publications/dromey/Dromey-LNCS-Final2-new.pdf "Genetic Design: Amplifying Our Ability to Deal With Requirements Complexity"] {{Webarchive|url=https://web.archive.org/web/20110725054508/http://www.behaviorengineering.org/publications/dromey/Dromey-LNCS-Final2-new.pdf |date=25 July 2011 }}, in S.Leue, and T.J. Systra, Scenarios, Lecture Notes in Computer Science, LNCS 3466, pp. 95–108, 2005.</ref>

A basis of the notation is that behavior is always associated with some component. Component-states which represent nodes of behavior are composed sequentially or concurrently to construct a behavior tree that represents the behavior expressed in the natural language requirements. A behavior tree with leaf nodes may revert (symbolized by adding the [[caret]] operator "^") to an ancestor node to repeat behavior or start a new thread (symbolized by two carets "^^").

A behavior tree specifies state changes in components, how data and control is passed between components and how [[Threads (computer science)|threads]] interact. There are constructs for creating and breaking relations. There are also constructs for setting and testing [[State (computer science)|states]] of components, as well as mechanisms for [[inter-process communication]] that include [[message passing]] (events), shared variable blocking and [[Synchronization (computer science)|synchronization]].

For a complete reference to behavior tree notation, version 1.0, see: ''Behavior Tree Notation v1.0'' (2007).<ref name = "BTNotation">Behavior Tree Group, [[ARC Centre for Complex Systems]], 2007. [https://projects.ui.ac.id/attachments/download/300/Behavior-Tree-Notation-1.0.pdf Behavior Tree Notation v1.0 (2007) ] {{webarchive |url=https://web.archive.org/web/20160304003828/https://projects.ui.ac.id/attachments/download/300/Behavior-Tree-Notation-1.0.pdf |date=2016-03-04}}</ref>