# Class: StateVariable
URI: [tvbo:StateVariable](https://w3id.org/tvbo/StateVariable) ```{mermaid} classDiagram class StateVariable click StateVariable href "./StateVariable.html" StateVariable <|-- FieldStateVariable click FieldStateVariable href "./FieldStateVariable.html" StateVariable : coupling_variable StateVariable --> "0..1" Boolean : coupling_variable click Boolean href "../http://www.w3.org/2001/XMLSchema#boolean.html" StateVariable : definition StateVariable --> "0..1" String : definition click String href "../http://www.w3.org/2001/XMLSchema#string.html" StateVariable : derivative_initial_value StateVariable --> "0..1" Float : derivative_initial_value click Float href "../http://www.w3.org/2001/XMLSchema#float.html" StateVariable : description StateVariable --> "0..1" String : description click String href "../http://www.w3.org/2001/XMLSchema#string.html" StateVariable : distribution StateVariable --> "0..1" Distribution : distribution click Distribution href "./Distribution.html" StateVariable : domain StateVariable --> "0..1" Range : domain click Range href "./Range.html" StateVariable : equation StateVariable --> "0..1" Equation : equation click Equation href "./Equation.html" StateVariable : equation_order StateVariable --> "0..1" Integer : equation_order click Integer href "../http://www.w3.org/2001/XMLSchema#integer.html" StateVariable : equation_type StateVariable --> "0..1" String : equation_type click String href "../http://www.w3.org/2001/XMLSchema#string.html" StateVariable : evict_equation StateVariable --> "0..1" Equation : evict_equation click Equation href "./Equation.html" StateVariable : grounding StateVariable --> "*" Uriorcurie : grounding click Uriorcurie href "../http://www.w3.org/2001/XMLSchema#anyURI.html" StateVariable : history StateVariable --> "0..1" TimeSeries : history click TimeSeries href "./TimeSeries.html" StateVariable : initial_value StateVariable --> "0..1" Float : initial_value click Float href "../http://www.w3.org/2001/XMLSchema#float.html" StateVariable : label StateVariable --> "0..1" String : label click String href "../http://www.w3.org/2001/XMLSchema#string.html" StateVariable : name StateVariable --> "1" String : name click String href "../http://www.w3.org/2001/XMLSchema#string.html" StateVariable : noise StateVariable --> "0..1" Noise : noise click Noise href "./Noise.html" StateVariable : record StateVariable --> "0..1" Boolean : record click Boolean href "../http://www.w3.org/2001/XMLSchema#boolean.html" StateVariable : stimulation_variable StateVariable --> "0..1" Boolean : stimulation_variable click Boolean href "../http://www.w3.org/2001/XMLSchema#boolean.html" StateVariable : symbol StateVariable --> "0..1" String : symbol click String href "../http://www.w3.org/2001/XMLSchema#string.html" StateVariable : unit StateVariable --> "0..1" String : unit click String href "../http://www.w3.org/2001/XMLSchema#string.html" StateVariable : variable_of_interest StateVariable --> "0..1" Boolean : variable_of_interest click Boolean href "../http://www.w3.org/2001/XMLSchema#boolean.html" ``` ## Inheritance * **StateVariable** * [FieldStateVariable](../classes/FieldStateVariable.qmd) ## Class Properties | Property | Value | | --- | --- | | Class URI | [tvbo:StateVariable](https://w3id.org/tvbo/StateVariable) | ## Slots | Name | Cardinality and Range | Description | Inheritance | | --- | --- | --- | --- | | [name](../slots/name.qmd) | 1
[xsd:string](http://www.w3.org/2001/XMLSchema#string) | Globally unique identifier for the entity | direct | | [symbol](../slots/symbol.qmd) | 0..1
[xsd:string](http://www.w3.org/2001/XMLSchema#string) | | direct | | [label](../slots/label.qmd) | 0..1
[xsd:string](http://www.w3.org/2001/XMLSchema#string) | | direct | | [definition](../slots/definition.qmd) | 0..1
[xsd:string](http://www.w3.org/2001/XMLSchema#string) | | direct | | [domain](../slots/domain.qmd) | 0..1
[Range](../classes/Range.qmd) | | direct | | [description](../slots/description.qmd) | 0..1
[xsd:string](http://www.w3.org/2001/XMLSchema#string) | | direct | | [equation](../slots/equation.qmd) | 0..1
[Equation](../classes/Equation.qmd) | | direct | | [unit](../slots/unit.qmd) | 0..1
[xsd:string](http://www.w3.org/2001/XMLSchema#string) or 
[UnitEnum](../enums/UnitEnum.qmd) | Physical unit of measurement | direct | | [record](../slots/record.qmd) | 0..1
[xsd:boolean](http://www.w3.org/2001/XMLSchema#boolean) | Whether to include this element in simulation output files | direct | | [grounding](../slots/grounding.qmd) | *
[xsd:anyURI](http://www.w3.org/2001/XMLSchema#anyURI) | External ontology IRIs (typically GO, ChEBI, UBERON, CL, MeSH) that this enti... | direct | | [variable_of_interest](../slots/variable_of_interest.qmd) | 0..1
[xsd:boolean](http://www.w3.org/2001/XMLSchema#boolean) | | direct | | [coupling_variable](../slots/coupling_variable.qmd) | 0..1
[xsd:boolean](http://www.w3.org/2001/XMLSchema#boolean) | Whether this state variable is transmitted to connected nodes through the cou... | direct | | [equation_type](../slots/equation_type.qmd) | 0..1
[xsd:string](http://www.w3.org/2001/XMLSchema#string) | How to interpret ``equation | direct | | [evict_equation](../slots/evict_equation.qmd) | 0..1
[Equation](../classes/Equation.qmd) | Optional reverse recurrence for a **sliding-window** reduction: the per-step ... | direct | | [equation_order](../slots/equation_order.qmd) | 0..1
[xsd:integer](http://www.w3.org/2001/XMLSchema#integer) | Order of the time derivative on the LHS | direct | | [noise](../slots/noise.qmd) | 0..1
[Noise](../classes/Noise.qmd) | | direct | | [stimulation_variable](../slots/stimulation_variable.qmd) | 0..1
[xsd:boolean](http://www.w3.org/2001/XMLSchema#boolean) | | direct | | [initial_value](../slots/initial_value.qmd) | 0..1
[xsd:float](http://www.w3.org/2001/XMLSchema#float) | Value this state starts at | direct | | [derivative_initial_value](../slots/derivative_initial_value.qmd) | 0..1
[xsd:float](http://www.w3.org/2001/XMLSchema#float) | Initial value for the first time derivative, used when equation_order > 1 | direct | | [distribution](../slots/distribution.qmd) | 0..1
[Distribution](../classes/Distribution.qmd) | Distribution for sampling initial conditions per node | direct | | [history](../slots/history.qmd) | 0..1
[TimeSeries](../classes/TimeSeries.qmd) | | direct | ## Usages | used by | used in | type | used | | --- | --- | --- | --- | | [Observation](../classes/Observation.qmd) | [source](../slots/source.qmd) | any_of[range] | [StateVariable](../classes/StateVariable.qmd) | | [Dynamics](../classes/Dynamics.qmd) | [state_variables](../slots/state_variables.qmd) | range | [StateVariable](../classes/StateVariable.qmd) | | [Noise](../classes/Noise.qmd) | [targets](../slots/targets.qmd) | range | [StateVariable](../classes/StateVariable.qmd) | | [TuningObjective](../classes/TuningObjective.qmd) | [target_variable](../slots/target_variable.qmd) | range | [StateVariable](../classes/StateVariable.qmd) | | [Coupling](../classes/Coupling.qmd) | [incoming_states](../slots/incoming_states.qmd) | range | [StateVariable](../classes/StateVariable.qmd) | | [Coupling](../classes/Coupling.qmd) | [local_states](../slots/local_states.qmd) | range | [StateVariable](../classes/StateVariable.qmd) | ## Identifier and Mapping Information ### Schema Source * from schema: https://w3id.org/tvbo ## Mappings | Mapping Type | Mapped Value | | --- | --- | | self | tvbo:StateVariable | | native | tvbo:StateVariable | ## LinkML Source ### Direct
```yaml name: StateVariable from_schema: https://w3id.org/tvbo slots: - name - symbol - label - definition - domain - description - equation - unit - record - grounding slot_usage: record: name: record ifabsent: 'True' attributes: variable_of_interest: name: variable_of_interest deprecated: Use 'record' instead. A state variable is recorded in the output when record=true (the default); set record=false to suppress it. 'variable_of_interest' is retained for backward compatibility and is ignored by the TVB/jax/rateml codegen. from_schema: https://w3id.org/tvbo rank: 1000 ifabsent: 'True' domain_of: - StateVariable range: boolean coupling_variable: name: coupling_variable description: Whether this state variable is transmitted to connected nodes through the coupling function. In TVB terms, this determines the cvar indices (state variables extracted from history and fed into the coupling function). The coupling function may override this via its incoming_states attribute. from_schema: https://w3id.org/tvbo rank: 1000 ifabsent: 'False' domain_of: - StateVariable range: boolean equation_type: name: equation_type description: 'How to interpret ``equation.rhs`` when advancing this state: ''differential'' (default) integrates it as ``dx/dt = rhs``; ''algebraic'' is a constraint ``0 = rhs`` / ``x ~ rhs`` (DAE); ''recurrence'' is a discrete per-step update ``x_next = rhs`` (no integrator applied), used by an observation''s auxiliary ``dynamics`` for online reductions/accumulators (e.g. a running sum ``x_next = x + f``) — the symbolic, backend-independent sibling of the continuous ''differential'' form. Algebraic equations are used by ModelingToolkit.jl backend.' from_schema: https://w3id.org/tvbo rank: 1000 ifabsent: string(differential) domain_of: - StateVariable range: string evict_equation: name: evict_equation description: 'Optional reverse recurrence for a **sliding-window** reduction: the per-step downdate that removes the sample leaving the window, the inverse of ``equation`` (which folds an arriving sample in). Only meaningful when ``equation_type: recurrence`` on an observation''s auxiliary ``dynamics``. When present, the observer is a windowed reduction — its state is maintained by ``equation`` (add) and ``evict_equation`` (evict) and rebuilt exactly from the window on resync — rather than a cumulative accumulator over the whole trajectory (``equation`` alone). Absent for ordinary state variables and cumulative reductions.' from_schema: https://w3id.org/tvbo rank: 1000 domain_of: - StateVariable range: Equation equation_order: name: equation_order description: Order of the time derivative on the LHS. Default 1 means dx/dt = rhs (first-order ODE). Order 2 means d²x/dt² = rhs (second-order ODE), etc. Higher-order ODEs are automatically lowered to coupled first-order systems by backends like ModelingToolkit.jl via mtkcompile. from_schema: https://w3id.org/tvbo rank: 1000 ifabsent: int(1) domain_of: - StateVariable range: integer noise: name: noise from_schema: https://w3id.org/tvbo domain_of: - Stimulus - StateVariable - Integrator range: Noise inlined: true stimulation_variable: name: stimulation_variable from_schema: https://w3id.org/tvbo rank: 1000 domain_of: - StateVariable range: boolean initial_value: name: initial_value description: 'Value this state starts at. Absent means undeclared: the consumer supplies its own fallback via ``tvbo.utils.initial_value``, which documents why this slot carries no schema default.' from_schema: https://w3id.org/tvbo rank: 1000 domain_of: - StateVariable - FreeParameter - SpatialField range: float derivative_initial_value: name: derivative_initial_value description: Initial value for the first time derivative, used when equation_order > 1. For a second-order ODE d²x/dt² = f, this sets dx/dt(0). Required by ModelingToolkit.jl to fully specify higher-order initial value problems. from_schema: https://w3id.org/tvbo rank: 1000 domain_of: - StateVariable range: float distribution: name: distribution description: Distribution for sampling initial conditions per node. If present, initial_value is used as fallback/mean. from_schema: https://w3id.org/tvbo domain_of: - ProcedureStep - StateVariable - Parameter - Noise - Prior - Coupling range: Distribution inlined: true history: name: history from_schema: https://w3id.org/tvbo rank: 1000 domain_of: - StateVariable range: TimeSeries inlined: true class_uri: tvbo:StateVariable ```
### Induced
```yaml name: StateVariable from_schema: https://w3id.org/tvbo slot_usage: record: name: record ifabsent: 'True' attributes: variable_of_interest: name: variable_of_interest deprecated: Use 'record' instead. A state variable is recorded in the output when record=true (the default); set record=false to suppress it. 'variable_of_interest' is retained for backward compatibility and is ignored by the TVB/jax/rateml codegen. from_schema: https://w3id.org/tvbo rank: 1000 ifabsent: 'True' owner: StateVariable domain_of: - StateVariable range: boolean coupling_variable: name: coupling_variable description: Whether this state variable is transmitted to connected nodes through the coupling function. In TVB terms, this determines the cvar indices (state variables extracted from history and fed into the coupling function). The coupling function may override this via its incoming_states attribute. from_schema: https://w3id.org/tvbo rank: 1000 ifabsent: 'False' owner: StateVariable domain_of: - StateVariable range: boolean equation_type: name: equation_type description: 'How to interpret ``equation.rhs`` when advancing this state: ''differential'' (default) integrates it as ``dx/dt = rhs``; ''algebraic'' is a constraint ``0 = rhs`` / ``x ~ rhs`` (DAE); ''recurrence'' is a discrete per-step update ``x_next = rhs`` (no integrator applied), used by an observation''s auxiliary ``dynamics`` for online reductions/accumulators (e.g. a running sum ``x_next = x + f``) — the symbolic, backend-independent sibling of the continuous ''differential'' form. Algebraic equations are used by ModelingToolkit.jl backend.' from_schema: https://w3id.org/tvbo rank: 1000 ifabsent: string(differential) owner: StateVariable domain_of: - StateVariable range: string evict_equation: name: evict_equation description: 'Optional reverse recurrence for a **sliding-window** reduction: the per-step downdate that removes the sample leaving the window, the inverse of ``equation`` (which folds an arriving sample in). Only meaningful when ``equation_type: recurrence`` on an observation''s auxiliary ``dynamics``. When present, the observer is a windowed reduction — its state is maintained by ``equation`` (add) and ``evict_equation`` (evict) and rebuilt exactly from the window on resync — rather than a cumulative accumulator over the whole trajectory (``equation`` alone). Absent for ordinary state variables and cumulative reductions.' from_schema: https://w3id.org/tvbo rank: 1000 owner: StateVariable domain_of: - StateVariable range: Equation equation_order: name: equation_order description: Order of the time derivative on the LHS. Default 1 means dx/dt = rhs (first-order ODE). Order 2 means d²x/dt² = rhs (second-order ODE), etc. Higher-order ODEs are automatically lowered to coupled first-order systems by backends like ModelingToolkit.jl via mtkcompile. from_schema: https://w3id.org/tvbo rank: 1000 ifabsent: int(1) owner: StateVariable domain_of: - StateVariable range: integer noise: name: noise from_schema: https://w3id.org/tvbo owner: StateVariable domain_of: - Stimulus - StateVariable - Integrator range: Noise inlined: true stimulation_variable: name: stimulation_variable from_schema: https://w3id.org/tvbo rank: 1000 owner: StateVariable domain_of: - StateVariable range: boolean initial_value: name: initial_value description: 'Value this state starts at. Absent means undeclared: the consumer supplies its own fallback via ``tvbo.utils.initial_value``, which documents why this slot carries no schema default.' from_schema: https://w3id.org/tvbo rank: 1000 owner: StateVariable domain_of: - StateVariable - FreeParameter - SpatialField range: float derivative_initial_value: name: derivative_initial_value description: Initial value for the first time derivative, used when equation_order > 1. For a second-order ODE d²x/dt² = f, this sets dx/dt(0). Required by ModelingToolkit.jl to fully specify higher-order initial value problems. from_schema: https://w3id.org/tvbo rank: 1000 owner: StateVariable domain_of: - StateVariable range: float distribution: name: distribution description: Distribution for sampling initial conditions per node. If present, initial_value is used as fallback/mean. from_schema: https://w3id.org/tvbo owner: StateVariable domain_of: - ProcedureStep - StateVariable - Parameter - Noise - Prior - Coupling range: Distribution inlined: true history: name: history from_schema: https://w3id.org/tvbo rank: 1000 owner: StateVariable domain_of: - StateVariable range: TimeSeries inlined: true name: name: name description: Globally unique identifier for the entity. from_schema: https://w3id.org/tvbo/common slot_uri: schema:name identifier: true owner: StateVariable domain_of: - BrainAtlas - CommonCoordinateSpace - ParcellationEntity - StudyLayout - StudyTemplate - StudyDirectory - StudyFile - DBSProtocol - ClinicalScale - ClinicalScore - SoftwarePackage - SoftwareRequirement - SoftwareEnvironment - Figure - Event - Tractogram - ResultEntity - Activity - CachedArray - MeasureSpec - NamedArray - GraphGenerator - Binding - ProcedureStep - File - StateValue - Observation - Dynamics - StateVariable - Distribution - Parameter - CouplingInput - Argument - Function - FunctionCall - Callable - DerivedParameter - DerivedVariable - DataSource - OptimizationStage - Exploration - Inference - Prior - Likelihood - UpdateRule - Algorithm - Option - BranchSwitch - Continuation - Coupling - EnvironmentVariable - SchedulerDirective - Reducer range: string required: true symbol: name: symbol from_schema: https://w3id.org/tvbo rank: 1000 owner: StateVariable domain_of: - ToolUnit - StateVariable - Parameter - CouplingInput - DerivedParameter - DerivedVariable range: string label: name: label from_schema: https://w3id.org/tvbo rank: 1000 slot_uri: rdfs:label owner: StateVariable domain_of: - ParcellationTerminology - Subject - Session - Dataset - Contact - SoftwareEnvironment - Figure - Panel - Inset - Layer - Colorbar - Rule - Equation - Stimulus - Event - Parcellation - Tractogram - Matrix - Phenotype - Network - Node - Edge - Observation - Dynamics - StateVariable - Parameter - Function - FunctionCall - DerivedVariable - RandomStream - DataSource - OptimizationStage - Exploration - ExplorationAxis - FreeParameter - Inference - AlgorithmStage - TuningObjective - Continuation - Coupling - RegionMapping - SimulationExperiment - SimulationStudy - TimeSeries - NDArray - SpatialDomain - Mesh - SpatialField - FieldStateVariable - DifferentialOperator - BoundaryCondition - PDESolver - PDE range: string definition: name: definition from_schema: https://w3id.org/tvbo rank: 1000 slot_uri: skos:definition owner: StateVariable domain_of: - Equation - StateVariable - Parameter - Function - DifferentialOperator range: string domain: name: domain from_schema: https://w3id.org/tvbo aliases: - range - boundaries rank: 1000 owner: StateVariable domain_of: - ClinicalScale - ClinicalScore - StateVariable - Distribution - Parameter - ExplorationAxis - FreeParameter - PDE range: Range description: name: description from_schema: https://w3id.org/tvbo rank: 1000 slot_uri: dcterms:description owner: StateVariable domain_of: - CommonCoordinateSpace - Dataset - StudyLayout - StudyTemplate - StudyDirectory - StudyFile - ClinicalScore - SoftwarePackage - SoftwareRequirement - SoftwareEnvironment - Figure - Panel - Equation - Stimulus - Event - Tractogram - Matrix - ResultEntity - Activity - Phenotype - MeasureSpec - NamedArray - Network - GraphGenerator - ProcedureStep - File - Node - Edge - Observation - Dynamics - StateVariable - Parameter - CouplingInput - Argument - Function - FunctionCall - Callable - DerivedParameter - DerivedVariable - RandomStream - DataSource - OptimizationStage - Exploration - ExplorationAxis - FreeParameter - Inference - Prior - Likelihood - UpdateRule - AlgorithmStage - TuningObjective - Algorithm - BranchSwitch - Continuation - Integrator - Coupling - RegionMapping - SimulationExperiment - Study - ResultBinding - TimeSeries - NDArray - SpatialDomain - Mesh - SpatialField - FieldStateVariable - BoundaryCondition - PDESolver - PDE - Reducer range: string equation: name: equation from_schema: https://w3id.org/tvbo rank: 1000 slot_uri: tvbo:Equation owner: StateVariable domain_of: - Stimulus - Event - ProcedureStep - Observation - StateVariable - Parameter - Function - FunctionCall - DerivedParameter - DerivedVariable - Noise - UpdateRule - DifferentialOperator - BoundaryCondition range: Equation inlined: true unit: name: unit description: 'Physical unit of measurement. `UnitEnum` is the curated vocabulary — each of its values is vendored from QUDT (`ontology/tvb-o-units.ttl`) and can be reasoned about dimensionally. The range is deliberately open beyond it: a unit nobody has curated yet is recorded as written and reported `uncurated`, because a closed range forces the author to either misdeclare the quantity or leave it undeclared, and both lose more than an unrecognised string does. An uncurated unit carries no dimensional claim, so a check involving it reports `underdetermined` rather than guessing. Promote one with `tvbo units add `, which pulls its QUDT record into the vendored module — so every unit TVBO *reasons* about stays authoritative, and only what it *records* is open.' from_schema: https://w3id.org/tvbo rank: 1000 slot_uri: qudt:unit owner: StateVariable domain_of: - CommonCoordinateSpace - ToolUnit - MeasureSpec - NamedArray - Edge - Observation - StateVariable - Parameter - Argument - DerivedParameter - DerivedVariable - ExplorationAxis - Integrator - TimeSeries - NDArray - SpatialField range: string any_of: - range: UnitEnum - range: string record: name: record description: Whether to include this element in simulation output files. Applicable to state variables (default true), derived variables (default false), and network nodes (default true). On an observation it forces (true) or suppresses (false) persistence in the result; left unset, a terminal observation (one not consumed by another observation or a loss) is recorded and an intermediate one is not. Set false to suppress recording. from_schema: https://w3id.org/tvbo rank: 1000 ifabsent: 'True' owner: StateVariable domain_of: - Node - Observation - StateVariable - DerivedVariable - Exploration range: boolean grounding: name: grounding description: 'External ontology IRIs (typically GO, ChEBI, UBERON, CL, MeSH) that this entity is a surrogate / abstraction / model of. Realized as the `tvbo:surrogate_of` object property, carried inline with the YAML data instance. Multiple IRIs allowed: a single parameter may abstract several biological processes (e.g. a synaptic conductance grounding both GO:0060079 (excitatory PSP) and GO:0007268 (chemical synaptic transmission)).' from_schema: https://w3id.org/tvbo rank: 1000 slot_uri: tvbo:surrogate_of owner: StateVariable domain_of: - StateVariable - Parameter - DerivedVariable range: uriorcurie multivalued: true class_uri: tvbo:StateVariable ```