Snippets (text quotes and extracts from authoritative sources)

A Snippet is a short quote or extract (typically a phrase, a sentence, or at most a few sentences) from an authoritative source document such as a specification, technical manual, or design manual. Throughout this site, content is often related to supporting Snippets and each Snippet page links back to the content pages that reference it! The Snippet and Note concepts are very closely related and they support each other.

The Snippet concept is also at the heart of the Parsing Analysis recipe for UML® and SysML®

Kind Snippet quote/extract Source UML keywords SysML keywords Keywords
CONSTRAINT If the triggers of an AcceptEventAction are all for ChangeEvents and/or CallEvents, then the AcceptEventAction has no result OutputPins (unless the AcceptEventAction is an AcceptCallAction ...) Unified Modeling Language 2.5.1 AcceptEventAction, ChangeEvent, CallEvent, Trigger, OutputPin, AcceptCallAction
INFO If the upperBound evaluates to *, then there is no limit on the number of tokens the ObjectNode may hold. Unified Modeling Language 2.5.1 Activity, ObjectNode, token, object token, ObjectNode::upperBound, ValueSpecification, UnlimitedNatural, *
INFO If there is a defaultValue specified for a Property, this default is evaluated when an instance of the Property is created in the absence of a specific setting for the Property or a constraint in the model that requires the Property to have a specific val Unified Modeling Language 2.5.1 Property, Property::defaultValue UML, Unified Modeling Language
INFO If there is no outgoing Transition inside the composite State, then the incoming Transition simply performs a default State entry. Unified Modeling Language 2.5.1 State, StateMachine, Transition, PseudostateKind, PseudostateKind::entryPoint, default entry rule, default State entry
INFO If two quarks have unaligned spins, the spin vectors add up to make a vector of length S = 0 and has only one spin projection (Sz = 0), etc. Wikipedia
INFO If we had chosen velocity (the derivative of position with respect to time), then we would have been in the awkward situation of trying to describe the behavior of a spring in terms of velocities, not positions. Modelica By Example Modelica, acausal connection
INFO In 1982, the International Union of Pure and Applied Chemistry (IUPAC) recommended that for the purposes of specifying the physical properties of substances, standard pressure should be precisely 100 kPa (1 bar). Wikipedia standard atmosphere, standard temperature pressure, 1 bar
INFO In a prime focus design no secondary optics are used, the image is accessed at the focal point of the primary mirror. Wikipedia reflecting telescope, reflector, optical telescope, telescope, primary mirror, prime focus reflector
INFO In a SysML block with constraint properties, the constraints correspond to the same equations in Modelica ... except the SysML parameters in those constraints correspond in Modelica to the properties they are bound to in SysML. SysPhS-1.1 Constraint ConstraintBlock, constraint parameter, BindingConnector SysPhS, Modelica, SysML, Systems Modeling Language
INFO In a SysML block with constraint properties, the constraints correspond to the same equations in Modelica ... except the SysML parameters in those equations correspond in Modelica to the properties they are bound to in SysML SysPhS-1.1 Constraint ConstraintBlock, constraint parameter, constraint property SysPhS, SysML, Systems Modeling Language, Modelica
INFO In a well-formed model, such a Transition should have a corresponding external Transition outgoing from the same exit point, representing a continuation of the terminating Transition. Unified Modeling Language 2.5.1 State, StateMachine, Transition, PseudostateKind, PseudostateKind::exitPoint, Vertex, TransitionKind::external
INFO In addition to identifying keywords, guillemets are also used to distinguish the usage of stereotypes. Unified Modeling Language 2.5.1 «keyword», Stereotype, guillemets UML, MagicDraw UML
INFO In addition, a State may also have an associated exit Behavior, which, if defined, is executed whenever the State is exited. Unified Modeling Language 2.5.1 State, StateMachine, Behavior, State::exit
INFO In addition, behavior allocation may also include the allocation of Behaviors to BehavioralFeatures of Blocks (e.g., Operations). OMG Systems Modeling Language (SysML) 1.6 Behavior, BehavioralFeature, Operation Allocate, allocation, «allocate», Block functional allocation
INFO In an imperfect lens L, all the rays do not pass through a focal point. The smallest circle that they pass through C is called the circle of least confusion. Wikipedia optics, lens, circle of confusion, blur circle
EXAMPLE, INFO In an instance of Operating Car, which is one execution of it, instances of Brake Pressure and Modulation Frequency are linked to the execution instance when they are in the object nodes of the activity. OMG Systems Modeling Language (SysML) 1.6 AggregationKind::composite, Association, Activity, ObjectNode «activity», SysML specification figure, AdjunctProperty
INFO In case of simple States, a completion event is generated when the associated entry and doActivity Behaviors have completed executing. If no such Behaviors are defined, the completion event is generated upon entry into the State. Unified Modeling Language 2.5.1 StateMachine, State, completion, completion transition, implicit trigger, Transition, Trigger, completion event, Trigger::event, State::entry, State::doActivity
INFO In cases where a Transition terminates on a history Pseudostate when the State has not been entered before (i.e., no prior history) or it had reached its FinalState, there is an option to force a transition to a specific substate, using the default ... Unified Modeling Language 2.5.1 State, StateMachine, Vertex, Pseudostate, history, PseudostateKind::deepHistory, PseudostateKind::shallowHistory, default history mechanism
NOTATION In cases where the metaclass of a subject is ambiguous, the keyword . corresponding to the notation for the metaclass of Classifier (see 9.2.4) shall be shown in guillemets above the name. Unified Modeling Language 2.5.1 UseCase, UseCase Diagram, UseCase::subject, Classifier, «keyword», Stereotype, guillemets, metaclass
INFO In chemistry and in various industries, the reference pressure referred to in standard temperature and pressure (STP) was commonly 1 atm (101.325 kPa) but standards have since diverged; Wikipedia standard atmosphere, standard temperature pressure, 1 atm
INFO In contrast to Associations, which specify links between any instance of the associated Classifiers, Connectors specify links between instances playing the connected parts only. Unified Modeling Language 2.5.1 Connector, instance, link, Association, Classifier
INFO In contrast to Associations, which specify links between any suitably-typed instance of the associated Classifiers, Connectors specify links between instances playing the connected roles only. Unified Modeling Language 2.5.1 Connector, instance, StructuredClassifier, roles, Association
INFO In contrast to traditional digital models, digital twins can connect with the physical ‘twin’ they model, changing alongside the physical system via real-time sensors and actuators. ANZLIC 2019 - Principles for Spatially Enabled Digital Twins of the Built and Natural Environment in Australia digital twin, Digital Twin Instance, sensor, actuator, control loop, ANZLIC-2019
INFO In diagrams of optical systems, virtual rays are conventionally represented by dotted lines. Wikipedia optics, image, light ray, focus point, real image, virtual image
CONSTRAINT In each Region of the StateMachine or composite State owning the entryPoint, there is at most a single Transition from the entry point to a Vertex within that Region. Unified Modeling Language 2.5.1 State, Pseudostate, PseudostateKind::entryPoint, StateMachine, composite State, Vertex, Transition, Region
INFO In effect, the latter is a continuation of the external incoming Transition, with the proviso that the execution of the entry Behavior of the composite State (if defined) occurs between the effect Behavior of the incoming Transition and the effect ... Unified Modeling Language 2.5.1 State, StateMachine, Transition, PseudostateKind, PseudostateKind::entryPoint, Vertex, Transition::source, Transition::effect, Behavior
INFO In either case, users of a block are only concerned with the features of its ports, regardless of whether the features are surfaced by proxy ports, or handled by full ports directly. OMG Systems Modeling Language (SysML) 1.6 Port FullPort, "standard" Port, ProxyPort
INFO In Figure 50, amplifiers, low-pass filters, and high-pass filters, each have an input and an output. Since they are similar in this sense, a generalized TwoPinSignalComponent component has an input u and an output y. SysPhS-1.1 SysPhS, signal processing, amplifier, high-pass filter, low-pass filter
INFO In Figure 9-16, the item flow classifier (EnginePart) is a supertype of the classifiers of the item flows in the decomposition. OMG Systems Modeling Language (SysML) 1.6 Connector, InformationFlow::conveyed ItemFlow, AssociationBlock
INFO In Figure 9-17, the item flow classifier (Engine) composes the classifiers of the items flows in the decomposition from Figure 9-17. OMG Systems Modeling Language (SysML) 1.6 Connector, InformationFlow::conveyed ItemFlow, AssociationBlock
INFO In general, a StateMachine can have multiple Regions, each of which may contain States of its own, some of which may be composites with their own multiple Regions, etc. Unified Modeling Language 2.5.1 State, StateMachine, Region, composite State, State::/isComposite
INFO In general, a ValueSpecification is a model element that is considered semantically to yield zero or more values. Unified Modeling Language 2.5.1 ValueSpecification
INFO In geometrical optics, a focus, also called an image point, is the point where light rays originating from a point on the object converge. Wikipedia optics, image, light ray, focus point, focus, image point
INFO In many English-speaking countries, however, the most common shape of a handwritten Arabic digit 1 is just a vertical stroke; that is, it lacks the upstroke added in many other cultures. Wikipedia litre, units, scientific unit system, volume, SI unit, SI alternative unit, ISO-80000
INFO In modern physics, antimatter is defined as matter which is composed of the antiparticles (or "partners") of the corresponding particles of 'ordinary' matter. Wikipedia
INFO In nonideal fluid dynamics, the Hagen–Poiseuille equation ... is a physical law that gives the pressure drop in an incompressible and Newtonian fluid in laminar flow flowing through a long cylindrical pipe of constant cross section. Wikipedia Hagen–Poiseuille equation, fluid flow, hydraulics
INFO In optical engineering, the objective is the optical element that gathers light from the object being observed and focuses the light rays to produce a real image. Wikipedia optical astronomy, optics, objective, light, light ray
INFO In optics, an image is defined as the collection of focus points of light rays coming from an object. Wikipedia optics, image, light ray, focus point
INFO In optics, the f-number of an optical system such as a camera lens is the ratio of the system's focal length to the diameter of the entrance pupil ("clear aperture"). It is also known as the focal ratio, f-ratio, or f-stop Wikipedia optics, f-number, f-ratio, f-stop, focal length
INFO In order to understand one specific class of connector semantics, it is first necessary to understand a bit more about acausal formulations of physical systems. An acausal approach to physical modeling identifies two distinct classes of variables. Modelica By Example Modelica, acausal connection
INFO, NOTATION In other words, the internal property shown with a path name in the left-hand side of Figure 8-1 is equivalent to the innermost nested box shown at the right. OMG Systems Modeling Language (SysML) 1.6 Property multi-level property path, pathname dot notation, nested Property
INFO In particle physics, a baryon is a type of composite subatomic particle which contains an odd number of valence quarks (at least 3). Wikipedia
INFO In particle physics, a fermion is a particle that follows Fermi–Dirac statistics and generally has half odd integer spin 1/2, 3/2 etc. These particles obey the Pauli exclusion principle. Wikipedia
INFO In particle physics, a hadron ... is a subatomic composite particle made of two or more quarks ... Wikipedia
INFO In particle physics, a lepton is an elementary particle of half-integer spin (spin ​1⁄2) that does not undergo strong interactions. Wikipedia
INFO In particle physics, every type of particle is associated with [an] antiparticle with the same mass but with opposite physical charges (such as electric charge). Wikipedia
INFO In particle physics, mesons are hadronic subatomic particles composed of one quark and one antiquark, bound together by strong interactions. Wikipedia
NOTATION In particular, there is scope for confusion between a UseCase appearing visually contained in a boundary rectangle representing a Classifier that is its subject, and appearing visually contained in a compartment of a Classifier that is its owner... Unified Modeling Language 2.5.1 UseCase, UseCase::subject, Classifier
INFO In physics, a vapor or vapour is a substance in the gas phase at a temperature which means that the vapor can be condensed to a liquid by increasing the pressure on it without reducing the temperature of the vapor. Wikipedia vapour, Psychrometrics, gas
INFO In quantum mechanics and particle physics, spin is an intrinsic form of angular momentum carried by elementary particles, composite particles (hadrons), and atomic nuclei. Wikipedia
INFO In ray diagrams ... real rays of light are always represented by full, solid lines; perceived or extrapolated rays of light are represented by dashed lines. Wikipedia optics, image, light ray, focus point, virtual image, real image
INFO In software engineering, dependency injection is a technique in which an object receives other objects that it depends on. These other objects are called dependencies. Wikipedia software engineering, dependency injection
INFO In some cases, multiple concurrent executions of an ExecutableNode may be ongoing at one time (see the semantics of isLocallyReentrant=true for Actions ... ). In this case, the ExecutableNode holds one control token for each concurrent execution. Unified Modeling Language 2.5.1 Behavior, Activity, Activity Diagram, ExecutableNode, implicit join, ControlFlow, ActivityNode::incoming, token, control token
INFO In some contexts, especially in photography and astronomy, aperture refers to the diameter of the aperture stop rather than the physical stop or the opening itself. Wikipedia optical telescope, telescope, aperture, optics, astronomy, astrophotography
INFO In the 20th century, many new types of telescopes were invented, including radio telescopes in the 1930s and infrared telescopes in the 1960s. Wikipedia telescope, optical telescope, astronomy
INFO In the case of the profile diagram, profile definitions can be captured on a package diagram and the parametric diagram. OMG Systems Modeling Language (SysML) 1.6 Diagram, Object Diagram, Communication Diagram, Interaction Overview Diagram, Timing Diagram, Deployment Diagram, Profile Diagram SysML Package Diagram, SysML Parametric Diagram
INFO In the Gregorian design, the primary mirror creates a real image before the secondary mirror. This allows for a field stop to be placed at this location, so that the light from outside the field of view does not reach the secondary mirror. Wikipedia telescope, Gregorian reflector, field stop, optics, primary mirror, secondary mirror
INFO In the UK and Ireland, as well as the rest of Europe, lowercase l is used with prefixes, though whole litres are often written in full (so, "750 ml" on a wine bottle, but often "1 litre" on a juice carton). Wikipedia litre, units, scientific unit system, volume, SI unit, SI alternative unit, ISO-80000, United Kingdom, Ireland, Europe
INFO In theory, a particle and its anti-particle (for example, a proton and an antiproton) have the same mass, but opposite electric charge and other differences in quantum numbers. For example, a proton has positive charge while an antiproton has negative ... Wikipedia
INFO In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary Wikipedia heat, thermodynamics, energy, energy transfer
INFO In thermodynamics, heat is energy in transfer to or from a thermodynamic system, by mechanisms other than thermodynamic work or transfer of matter. Wikipedia heat, energy, energy transfer, thermal transfer, thermodynamics
INFO In this example, a constraint block BinaryElectricalComponentConstraint defines parameters and constraints common to resistors, inductors, capacitors, and sources, as shown in Figure 40. SysPhS-1.1 Constraint constraint parameter, ConstraintBlock, Block SysPhS
INFO In this example, a constraint block BinarySignalComponentConstraint defines the parameters for one input (ip) and one output (op), common to amplifiers, low-pass filters, and high-pass filters, as shown in Figure 51. SysPhS-1.1 Constraint ConstraintBlock, constraint parameter SysPhS, signal processing, amplifier, high-pass filter, low-pass filter
INFO In this example, constraint blocks PipeConstraint and TankConstraint define parameters and equations for pipes and tanks, respectively, as shown in Figure 61. SysPhS-1.1 Constraint constraint parameter, ConstraintBlock
INFO In this example, ports are typed by RealSignalOutElement and RealSignalInElement from the signal flow library ... which both have a flow property rSig typed by Real, from SysML, as shown in Figure 49. SysPhS-1.1 Port "standard" Port, FlowProperty, Real SysPhS, signal processing
INFO In this section, we’ll discuss relatively simple engineering domains. These are ones where a connector deals with only one through and one across variable. Conceptually, this means that only one conserved quantity is involved with that connector. Modelica By Example Modelica, acausal connection
CONSTRAINT incoming_control_one_input_parameter If the DecisionNode has a decisionInputFlow and an incoming ControlFlow, then any decisionInput Behavior has one in Parameter ... Unified Modeling Language 2.5.1 DecisionNode, ActivityEdge, ActivityNode::incoming, ControlFlow, DecisionNode::decisionInputFlow, DecisionNode::decisionInput, Parameter, Parameter::direction, ParameterDirectionKind::in, Behavior::inputParameters(), Behavior, TypedElement, object token, token, TypedElement::type, Type
INFO Infrared and optical astronomy are often practiced using the same telescopes, as the same mirrors or lenses are usually effective over a wavelength range that includes both visible and infrared light. Wikipedia infrared, infrared astronomy, mirror, lens
INFO Infrared astronomy is the branch of astronomy and astrophysics that studies astronomical objects visible in infrared (IR) radiation. Wikipedia infrared, infrared astronomy, mirror, lens
INFO Infrared radiation with wavelengths just longer than visible light, known as near-infrared, behaves in a very similar way to visible light, and can be detected using similar solid state devices ... Wikipedia far infrared, near infrared, infrared astronomy
CONSTRAINT initial - ... It is the source for at most one Transition, which may have an associated effect Behavior, but not an associated trigger or guard. Unified Modeling Language 2.5.1 PseudostateKind::initial, Transition, Transition::effect, Transition::guard
SEMANTIC initial - An initial Pseudostate represents a starting point for a Region; that is, it is the point from which execution of its contained behavior commences when the Region is entered via default activation. Unified Modeling Language 2.5.1 PseudostateKind::initial, Region
INFO Initial value compartments may be specified within nested properties, which then apply only in the particular usage context defined by the outermost containing block. OMG Systems Modeling Language (SysML) 1.6 compartment initial values, initialValues compartment, context-specific values
SEMANTIC InitialNodes are an exception to the rule that ControlNodes cannot “hold” tokens, but only manage their flow. Unified Modeling Language 2.5.1 Activity, InitialNode, ControlNode, control token, InitialNode
INFO Instances of a structured DataType are considered to be equal if and only if the structure is the same and the values of the corresponding attributes are equal. Unified Modeling Language 2.5.1 Type, DataType, Classifier, structured DataType
INFO InstanceSpecification::classifer : Classifier [0..*] ... The Classifier or Classifiers of the represented instance. If multiple Classifiers are specified, the instance is classified by all of them. Unified Modeling Language 2.5.1 instance, InstanceSpecification, InstanceSpecification::classifier, Classifier
INFO InstanceSpecification::slot : Slot [0..*] ... A Slot giving the value or values of a StructuralFeature of the instance. An InstanceSpecification can have one Slot per StructuralFeature of its Classifiers, including inherited features. ... Unified Modeling Language 2.5.1 instance, InstanceSpecification, InstanceSpecification::slot, Slot, StructuralFeature, Classifier
INFO InstanceSpecification::slot : Slot [0..*] ... It is not necessary to model a Slot for every StructuralFeature, in which case the InstanceSpecification is a partial description. Unified Modeling Language 2.5.1 instance, InstanceSpecification, InstanceSpecification::slot, Slot, StructuralFeature, Classifier
INFO InstanceSpecification::specification : ValueSpecification [0..1] ... A specification of how to compute, derive, or construct the instance. Unified Modeling Language 2.5.1 instance, InstanceSpecification, InstanceSpecification::classifier, ValueSpecification
INFO Instead of the client specifying which service it will use, the injector tells the client what service to use. The "injection" refers to the passing of a dependency (a service) into the object (a client) that would use it. Wikipedia software engineering, dependency injection
EXAMPLE Interactions in block definition diagrams appear as regular blocks, except the «interaction» keyword may be used to indicate the Block stereotype is applied to an interaction, as shown in Figure 12-1 OMG Systems Modeling Language (SysML) 1.6 Interaction «interaction», SysML Block Definition Diagram
EXAMPLE Interactions in block definition diagrams can also appear with the same notation as InteractionUses. OMG Systems Modeling Language (SysML) 1.6 Interaction, Association, Parameter, InteractionUse SysML Block Definition Diagram
CONSTRAINT Interface blocks cannot have behaviors, including classifier behaviors or methods, or internal parts. OMG Systems Modeling Language (SysML) 1.6 InterfaceBlock, ~InterfaceBlock
INFO InterfaceBlock ... for example, in flow properties are conjugated as out flow properties and provided features are conjugated as required features. OMG Systems Modeling Language (SysML) 1.6 InterfaceBlock, ~InterfaceBlock, conjugation, ~InterfaceBlock::original, DirectedFeature, FlowProperty, FlowProperty::direction, FlowDirectionKind, DirectedFeature::featureDirection, FeatureDirectionKind, FlowDirectionKind::in, FlowDirectionKind::out, FeatureDirectionKind::provided, FeatureDirectionKind::providedrequired
CONSTRAINT InterfaceBlock::1_no_behavior Interface blocks shall not own or inherit behaviors, have classifier behaviors, or methods for their behavioral features. OMG Systems Modeling Language (SysML) 1.6 InterfaceBlock, ~InterfaceBlock
CONSTRAINT InterfaceBlock::2_no_part Interface blocks composite properties are either ports, value properties or flow properties. OMG Systems Modeling Language (SysML) 1.6 Port, AggregationKind::composite InterfaceBlock, ~InterfaceBlock, value property, FlowProperty
CONSTRAINT InterfaceBlock::3_interfaceblock_typed_ports Ports owned by interface blocks shall only be typed by interface blocks. OMG Systems Modeling Language (SysML) 1.6 InterfaceBlock, ~InterfaceBlock
CONSTRAINT InterfaceBlock::isconjugated_not_used Any port typed by an InterfaceBlock shall have its isConjugated property set to false. OMG Systems Modeling Language (SysML) 1.7beta1 Port::isConjugated InterfaceBlock, ~InterfaceBlock
INFO Interfaces may also be used to specify required Interfaces, which are specified by a Usage dependency between the BehavioredClassifier and the corresponding Interfaces. Unified Modeling Language 2.5.1 BehavioredClassifier, Interface, Usage, required Interface
INFO internal - Implies that the Transition, if triggered, occurs without exiting or entering the source State (i.e., it does not cause a state change). This means that the entry or exit condition of the source State will not be invoked. Unified Modeling Language 2.5.1 Transition, TransitionKind, Transition::kind, Enumeration, TransitionKind::internal, State::entry, State::exit
INFO Internal connectors to ports are the ones inside the ports owner (specifically, they are the ones that do not have a UML partwithPort on the connector end linked to the port, assuming NestedConnectorEnd is not applied to that end, or if NestedConnectorEnd OMG Systems Modeling Language (SysML) 1.6 Port, ConnectorEnd::partwithPort, internal Connector NestedConnectorEnd
CONSTRAINT, INFO Internal connectors to proxy ports can be typed by association blocks, including when the connector is binding. Association OMG Systems Modeling Language (SysML) 1.6 Port, Feature, Connector, internal Connector ProxyPort, BindingConnector, AssociationBlock
EXAMPLE, INFO Inversely, the InternalCombustionEngine can read the isControlOn property of the PowerControlUnit across the connector to determine if the unit is still operating, and possibly shut down if it is not. OMG Systems Modeling Language (SysML) 1.6 Connector HSUV sample problem, provided Feature, required Feature, part property, Block
INFO InvocationAction::argument : InputPin [0..*] The InputPins that provide the argument values passed in the invocation request. Unified Modeling Language 2.5.1 InvocationAction, InvocationAction::argument
INFO InvocationAction::onPort : Port [0..1] For CallOperationActions, SendSignalActions, and SendObjectActions, an optional Port of the target object through which the invocation request is sent. Unified Modeling Language 2.5.1 InvocationAction, InvocationAction::onPort
isControl : Boolean [1..1] = false Indicates whether the Pin provides data to the Action or just controls how the Action executes. Unified Modeling Language 2.5.1 Pin, Pin::isControl
INFO Isobaric volumetric heat capacity C(P,v) J⋅cm−3⋅K−1 of liquid Water at 100 °C = 4.2160 Wikipedia volumetric heat capacity, thermodynamics, joule, kelvin, water, celsius
INFO Isobaric volumetric heat capacity C(P,v) J⋅cm−3⋅K−1 of liquid Water at 25 °C = 4.1796 Wikipedia volumetric heat capacity, thermodynamics, joule, kelvin, water, celsius
EXAMPLE, INFO It assumes a constant 100hp at the drive wheels, 4000lb gross vehicle weight, and constant values for Cd and Cf. OMG Systems Modeling Language (SysML) 1.6 Timing Diagram, Constraint constraint parameter, ConstraintBlock
INFO It captures the definition of blocks in terms of properties and operations, and relationships such as a system hierarchy or a system classification tree OMG Systems Modeling Language (SysML) 1.6 Diagram, Feature, Relationship, Association, Generalization, part, Property, Operation Block, SysML Block Definition Diagram systems engineering, Model-Based Systems Engineering, SysML, Systems Modeling Language