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
INFO A DerivedQuantityKind may also be used to define a synonym kind of quantity for another kind of quantity. OMG Systems Modeling Language (SysML) 1.6 DerivedQuantityKind, QuantityKind
INFO A DerivedUnit is a Unit that represents a measurement unit that is defined as a product of powers of one or more other measurement units. OMG Systems Modeling Language (SysML) 1.6 Unit, DerivedUnit
INFO A DeriveReqt relationship is a dependency between two requirements in which a client requirement can be derived from the supplier requirement. OMG Systems Modeling Language (SysML) 1.6 Dependency, Dependency::client, Dependency::supplier DeriveReqt, Requirement
NOTATION A DirectedFeature has the same notation as other non-flow properties and behavioral features with a feature direction prefix (prov | reqd | provreqd), which corresponds to one the FeatureDirectionKind literals “provided,” “required,” and “providedrequired OMG Systems Modeling Language (SysML) 1.7beta1 DirectedFeature, DirectedFeature::featureDirection, FeatureDirectionKind, FeatureDirectionKind::provided, FeatureDirectionKind::providedrequired, FeatureDirectionKind::required
INFO A DirectedFeature indicates whether the feature is supported by the owning block (provided) for other connected blocks to use, or is to be supported by a connected block for the owning block to use (required), or both (providedRequired). OMG Systems Modeling Language (SysML) 1.7beta1 DirectedFeature, FeatureDirectionKind::provided, FeatureDirectionKind::required, FeatureDirectionKind::providedrequired, FeatureDirectionKind
INFO A diverging lens (one that is thicker at the edges than the middle) or a convex mirror forms a virtual image. Such an image is reduced in size when compared to the original object. Wikipedia optics, image, light ray, focus point, virtual image
INFO A FinalNode is a ControlNode at which a flow in an Activity stops. A FinalNode shall not have outgoing ActivityEdges. A FinalNode accepts all tokens offered to it on its incoming ActivityEdges. There are two kinds of FinalNode: Unified Modeling Language 2.5.1 Activity, Activity Diagram, ControlNode, FinalNode, ActivityFinalNode, FlowFinalNode, ActivityNode::outgoing, ActivityNode::incoming
INFO A flat secondary mirror reflects the light to a focal plane at the side of the top of the telescope tube. Wikipedia reflecting telescope, reflector, optical telescope, telescope, Newtonian reflector, secondary mirror
INFO A FlowFinalNode is a FinalNode that terminates a flow. All tokens accepted by a FlowFinalNode are destroyed. This has no effect on other flows in the Activity. Unified Modeling Language 2.5.1 Activity, Activity Diagram, ControlNode, FinalNode, FlowFinalNode, termination, token
INFO A FlowProperty signifies a single flow element to/from a block. A flow property has the same notation as a Property only with a direction prefix (in | out | inout). Flow properties are listed in a compartment labeled flow properties. OMG Systems Modeling Language (SysML) 1.6 Property FlowProperty, FlowProperty::direction, FlowDirectionKind::in, FlowDirectionKind::out, FlowDirectionKind::inout, FlowDirectionKind
NOTATION A FlowProperty signifies a single flow element to/from a block. A flow property has the same notation as a Property only with a direction prefix (in | out | inout). Flow properties are listed in a compartment labeled flow properties. OMG Systems Modeling Language (SysML) 1.6 FlowProperty, FlowProperty::direction, FlowDirectionKind, FlowDirectionKind::in, FlowDirectionKind::inout, FlowDirectionKind::out
INFO A ForkNode is a ControlNode that splits a flow into multiple concurrent flows. A ForkNode shall have exactly one incoming ActivityEdge, though it may have multiple outgoing ActivityEdges. Unified Modeling Language 2.5.1 Activity, Activity Diagram, ControlNode, ForkNode, ActivityNode::incoming, ActivityNode::outgoing
NOTATION A found Message is denoted with a small black circle at the starting end of the Message. OMG Systems Modeling Language (SysML) 1.6 Message, MessageEnd, found Message
INFO A free neutron is unstable, decaying to a proton, electron and antineutrino with a mean lifetime of just under 15 minutes (881.5±1.5 s). Wikipedia neutron
INFO A given BehavioredClassifier may implement more than one Interface and that an Interface may be implemented by a number of different BehavioredClassifiers. Unified Modeling Language 2.5.1 BehavioredClassifier, Interface, BehavioredClassifier::interfaceRealization, InterfaceRealization, provided Interface, required Interface
INFO a helium atom in the ground state has spin 0 and behaves like a boson, even though the quarks and electrons which make it up are all fermions. Wikipedia
INFO A JoinNode is a ControlNode that synchronizes multiple flows. A JoinNode shall have exactly one outgoing ActivityEdge but may have multiple incoming ActivityEdges. Unified Modeling Language 2.5.1 Activity, Activity Diagram, ControlNode, JoinNode, ActivityNode::outgoing, ActivityNode::incoming, ActivityEdge
SEMANTIC A LiteralBoolean is shown as either the word “true” or the word “false,” corresponding to its value. Unified Modeling Language 2.5.1 value, notation, LiteralBoolean, Boolean, true, false
SEMANTIC A LiteralBoolean specifies a constant value of the PrimitiveType Boolean. Unified Modeling Language 2.5.1 value, LiteralBoolean, PrimitiveType, Boolean
SEMANTIC A LiteralInteger is shown as a sequence of digits representing the decimal numeral for the Integer value. Unified Modeling Language 2.5.1 value, notation, LiteralInteger, Integer, decimal, digit, numeral
SEMANTIC A LiteralInteger specifies a constant value of the PrimitiveType Integer. Unified Modeling Language 2.5.1 value, LiteralInteger, PrimitiveType, Integer
SEMANTIC A LiteralNull is intended to be used to explicitly model the lack of a value. Unified Modeling Language 2.5.1 LiteralNull, value
SEMANTIC A LiteralReal is shown in decimal notation or scientific notation. Unified Modeling Language 2.5.1 value, notation, LiteralReal, Real, decimal, scientific notation
SEMANTIC A LiteralReal specifies a constant value of the PrimitiveType Real. Unified Modeling Language 2.5.1 value, LiteralReal, PrimitiveType, Real
INFO a LiteralSpecification may be used in a ValueSpecificationAction to produce a constant value. Unified Modeling Language 2.5.1 Action, ValueSpecificationAction, ValueSpecificationAction::result, LiteralSpecification
SEMANTIC A LiteralString is shown as a sequence of characters within double quotes. The String value is the sequence of characters, not including the quotes. The character set used is unspecified. Unified Modeling Language 2.5.1 value, notation, LiteralString, character, String
SEMANTIC A LiteralString specifies a constant value of the PrimitiveType String. Though a String is specified as a sequence of characters, String values are considered to be primitive in UML, so their internal structure is not specified as part of UML semantics. Unified Modeling Language 2.5.1 value, LiteralString, PrimitiveType, String
SEMANTIC A LiteralUnlimitedNatural is shown either as a sequence of digits or as an asterisk (*), where an asterisk denotes unlimited. Unified Modeling Language 2.5.1 value, notation, LiteralUnlimitedNatural, UnlimitedNatural, *, unlimited, digit
SEMANTIC A LiteralUnlimitedNatural specifies a constant value of the PrimitiveType UnlimitedNatural. Unified Modeling Language 2.5.1 value, LiteralUnlimitedNatural, PrimitiveType, UnlimitedNatural
INFO A LoopNode is a StructuredActivityNode that represents an iterative loop. A LoopNode consists of a setupPart, a test and a bodyPart, which identify subsets of the ExecutableNodes contained in the LoopNode. Unified Modeling Language 2.5.1 Activity, Activity Diagram, LoopNode, LoopNode::setupPart, LoopNode::test, LoopNode::bodyPart, ExecutableNode
INFO A LoopNode may also define a set of loopVariable OutputPins used to hold intermediate values during each loop iteration. These OutputPins may have outgoing ActivityEdges, in order to make the values they hold available within the test and bodyPart ... Unified Modeling Language 2.5.1 Activity, Activity Diagram, LoopNode, LoopNode::test, LoopNode::loopVariable, ActivityNode::outgoing, ActivityEdge, OutputPin
NOTATION A lost Message is denoted with a small black circle at the arrow end of the Message. OMG Systems Modeling Language (SysML) 1.6 Message, MessageEnd, lost Message
EXAMPLE, INFO A measure of effectiveness (moe) represents a parameter whose value is critical for achieving the desired mission cost effectiveness. OMG Systems Modeling Language (SysML) 1.6 «moe» Measure of Effectiveness
INFO A MergeNode is a control node that brings together multiple flows without synchronization. Unified Modeling Language 2.5.1 Activity, Activity Diagram, ControlNode, MergeNode
CONSTRAINT A MergeNode shall have exactly one outgoing ActivityEdge but may have multiple incoming ActivityEdges. Unified Modeling Language 2.5.1 Activity, Activity Diagram, ControlNode, MergeNode, ActivityNode::outgoing, ActivityNode::incoming
INFO A MessageEvent specifies the receipt by an object of either an Operation call or a Signal instance. Unified Modeling Language 2.5.1 Event, MessageEvent, object, Operation, Signal, CallEvent, SignalEvent, AnyReceiveEvent
INFO A modern perspective has a proton composed of the valence quarks (up, up, down), the gluons, and transitory pairs of sea quarks. Wikipedia
INFO A neutrino (denoted by the Greek letter ν) is a fermion (an elementary particle with spin of 1/2) that interacts only via the weak subatomic force and gravity. Wikipedia
INFO A neutron contains two down quarks with charge −​1⁄3 e and one up quark with charge +​2⁄3 e. Wikipedia neutron
INFO A null token removes all the tokens already there. OMG Systems Modeling Language (SysML) 1.6 ObjectNode, MultiplicityElement::/upper, InputPin, Action::/input, token, null token, null Overwrite, «overwrite»
INFO, NOTATION A parametric diagram is a restricted form of internal block diagram that shows only the use of constraint blocks along with the properties they constrain within a context. OMG Systems Modeling Language (SysML) 1.6 Property ConstraintBlock, MD:ConstraintParameter, constraint parameter, constraint property, SysML Parametric Diagram, value property
INFO A parametric diagram is defined as a restricted form of internal block diagram. A parametric diagram may contain constraint properties and their parameters, along with other properties from within the internal block context. OMG Systems Modeling Language (SysML) 1.6 Property SysML Parametric Diagram, constraint parameter, constraint property, MD:ConstraintParameter
NOTATION A part belonging to a block, for example, may be typed by another block. The part defines a local usage of its defining block within the specific context to which the part belongs. OMG Systems Modeling Language (SysML) 1.6 Property, TypedElement, TypedElement::type, part Block, block property, part property systems engineering, Model-Based Systems Engineering, SysML, Systems Modeling Language
EXAMPLE, INFO A part or shared association has a default multiplicity of [0..1] on the black or white diamond end. A unidirectional association has a default multiplicity of 1 on its target end. OMG Systems Modeling Language (SysML) 1.7beta1 Association, AggregationKind, multiplicity, AggregationKind::composite, AggregationKind::shared, MultiplicityElement::upperValue, MultiplicityElement::lowerValue, MultiplicityElement, MultiplicityElement::/lower, MultiplicityElement::/upper, Property::isNavigable(), DirectedRelationship::/target
NOTATION A part or value property is always shown on an internal block diagram with a solid-outline box. OMG Systems Modeling Language (SysML) 1.6 Property part property, value property, MD:PartProperty, MD:ValueProperty
INFO A pathname dot notation can be used to refer to nested properties within a block hierarchy. OMG Systems Modeling Language (SysML) 1.6 Constraint ConstraintBlock, SysML Parametric Diagram, block property, NestedConnectorEnd, pathname dot notation, nested Property mathematics, equation
INFO A PhSConstant has values that do not change during simulation runs. Values can change between simulation runs. SysPhS-1.1 SysPhS, SysML, Systems Modeling Language
INFO A PhSVariable has values that can vary over time in a continuous or discrete fashion. SysPhS-1.1 SysPhS, SysML, Systems Modeling Language
INFO A Port has the ability, by setting the property isBehavior to true, to specify that any requests arriving at this Port are handled by the Behavior of the instance of the owning EncapsulatedClassifier, rather than being forwarded to any contained instances Unified Modeling Language 2.5.1 Port::isBehavior, Port, Behavior, EncapsulatedClassifier
INFO a predefined guard “else” (represented as an Expression with “else” as its operator and no operands) may be used for at most one outgoing edge. This guard evaluates to true only if the token is not accepted by any other outgoing edge from the DecisionNode Unified Modeling Language 2.5.1 DecisionNode, Activity Diagram, [else]
SEMANTIC A PrimitiveType defines a predefined DataType, without any substructure. A PrimitiveType may have algebra and operations defined outside of UML, for example, mathematically. Unified Modeling Language 2.5.1 Type, DataType, PrimitiveType mathematics
INFO A principal focus or focal point is a special focus: For a lens, or a spherical or parabolic mirror, it is a point onto which collimated light parallel to the axis is focused. Wikipedia optics, principal focus, focal point, mirror, lens, spherical mirror, parabolic mirror
NOTATION A property can represent a role or usage in the context of its enclosing block. A property has a type that supplies its definition. OMG Systems Modeling Language (SysML) 1.6 Property, TypedElement, TypedElement::type Block, block property, value property, constraint property, part property, reference property systems engineering, Model-Based Systems Engineering, SysML, Systems Modeling Language
INFO A Property may be marked as being a derived union, by setting isDerivedUnion to true. This means that the collection of values denoted by the Property in some context is derived by being the strict union of all of the values denoted ... Unified Modeling Language 2.5.1 Property, Property::isDerivedUnion, Property::subsettedProperty
INFO A Property may be marked as the subset of another subsettedProperty. In this case, calculate a set by eliminating duplicates from the collection of values denoted by the subsetting property in some context. Unified Modeling Language 2.5.1 Property, Property::subsettedProperty
INFO A Property may represent an attribute of a Classifier, a memberEnd of an Association, or in some cases both simultaneously. Unified Modeling Language 2.5.1 Property, Association, Association::memberEnd, Association::ownedEnd, Property::association, Property::owningAssociation
INFO, NOTATION A property name shown inside or outside the property box may take the form of a multi-level name. This form of name references a nested property accessible through a sequence of intermediate properties from a referencing context. OMG Systems Modeling Language (SysML) 1.6 Property multi-level property path, pathname dot notation
INFO A property typed by a Block that does not have composite aggregation is classified as a reference property. OMG Systems Modeling Language (SysML) 1.7beta1 Property, AggregationKind, Property::aggregation, AggregationKind::shared, AggregationKind::none Block, part property, reference property, shared property, MD:SharedProperty, MD:ReferenceProperty, MD:BlockProperty
INFO A property typed by a SysML Block that has composite aggregation is classified as a part property, except for the special case of a constraint property ... OMG Systems Modeling Language (SysML) 1.6 Property, AggregationKind, Property::aggregation, AggregationKind::composite Block, part property, MD:PartProperty
INFO A property typed by a SysML ValueType is classified as a value property, and always has composite aggregation. OMG Systems Modeling Language (SysML) 1.6 Property, AggregationKind, Property::aggregation, AggregationKind::composite Block, value property, MD:ValueProperty
INFO A proton is a subatomic particle, symbol p or p+, with a positive electric charge of +1e elementary charge and a mass slightly less than that of a neutron. Wikipedia
NOTATION A provided Interface may be shown using the lollipop notation ... attached to the Port. Unified Modeling Language 2.5.1 Interface, InterfaceRealization
INFO A providedRequired feature specifies a symmetric dependency between two connected blocks whereby a block’s internal use of such a feature is delegated to the connected block with the corresponding feature and conversely that block’s internal use of ... OMG Systems Modeling Language (SysML) 1.7beta1 DirectedFeature, FeatureDirectionKind::provided, FeatureDirectionKind::required, FeatureDirectionKind::providedrequired, FeatureDirectionKind
INFO A Pseudostate is an abstraction that encompasses different types of transient Vertices in the StateMachine graph. A StateMachine instance never comes to rest in a Pseudostate, instead, it will exit and enter the Pseudostate within a single ... step Unified Modeling Language 2.5.1 Vertex, StateMachine, Pseudostate, Abstraction, run-to-completion, Pseudostate::kind, Pseudostate::state, Pseudostate::stateMachine abstraction
INFO A quantity kind is a kind of quantity that may be stated in terms of defined units, but does not restrict the selection of a unit to state the value. A unit is a particular value in terms of which a quantity of the same quantity kind may be expressed. OMG Systems Modeling Language (SysML) 1.6 DataType ValueType, Unit, QuantityKind, ValueType::quantityKind, ValueType::unit
INFO A QuantityKind is a kind of quantity that may be stated by means of defined units. For example, the quantity kind of length may be measured by units of meters, kilometers, or feet. OMG Systems Modeling Language (SysML) 1.6 QuantityKind, Unit, Unit::quantityKind, ValueType::quantityKind scientific unit system
INFO A quark is a type of elementary particle and a fundamental constituent of matter. Wikipedia
INFO A real image ... is an image which is located in the plane of convergence for the light rays that originate from a given object. Wikipedia optics, image, light ray, focus point, virtual image
INFO A real image is the collection of focus points actually made by converging rays, while a virtual image is the collection of focus points made by extensions of diverging rays. Wikipedia optics, image, light ray, focus point, real image, virtual image
INFO A real image occurs where rays converge, whereas a virtual image occurs where rays only appear to diverge. Wikipedia optics, image, light ray, focus point, virtual image, real image
NOTATION A reference property is shown by a dashed-outline box, consistent with UML. OMG Systems Modeling Language (SysML) 1.6 Property reference property, MD:ReferenceProperty
INFO A reflecting telescope (also called a reflector) is a telescope that uses a single or a combination of curved mirrors that reflect light and form an image. Wikipedia telescope, optical telescope, astronomy
A Region is a top-level part of a StateMachine or a composite State, that serves as a container for the Vertices and Transitions of the StateMachine. Unified Modeling Language 2.5.1 Region, StateMachine, composite State, Vertex, Transition
NOTATION A reply Message (messageSort equals reply) has a dashed line with either an open or filled arrow head. OMG Systems Modeling Language (SysML) 1.6 Message, MessageEnd, Message::messageSort, MessageSort, MessageSort::reply
INFO A reply-message-label is used for reply Messages. It has the following form ... Unified Modeling Language 2.5.1 reply-message-label, Message, Message::messageSort, MessageSort, MessageSort::reply
INFO A reply-message-label may optionally have an assignment-target given to the left of the message-name, with a corresponding returned value denoted by the optional value-specification given after a colon at the end of the reply-message-label. Unified Modeling Language 2.5.1 reply-message-label, Message, Message::messageSort, MessageSort, MessageSort::reply, ValueSpecification
INFO A request that arrives at a Port that has a delegation Connector to one or more Properties or Ports on Properties will be passed on to those targets for handling. Unified Modeling Language 2.5.1 Port, Connector, Connector::kind, ConnectorKind, ConnectorKind::delegation
NOTATION A required Interface may be shown by the socket notation attached to the Port. Unified Modeling Language 2.5.1 Interface, Usage
INFO A requirement is a stereotype of both Class and Abstract Requirement. OMG Systems Modeling Language (SysML) 1.6 Class Requirement, «system», AbstractRequirement requirements engineering
INFO A requirement is defined as a stereotype of UML Class subject to a set of constraints. OMG Systems Modeling Language (SysML) 1.6 Class, Stereotype Requirement, SysML Requirements Diagram requirements engineering
INFO A requirement may specify a function that a system must perform or a performance condition that a system must satisfy. OMG Systems Modeling Language (SysML) 1.6 Requirement, Satisfy, «system» requirements engineering, function, system, performance condition
INFO A requirement specifies a capability or condition that must (or should) be satisfied. OMG Systems Modeling Language (SysML) 1.6 Requirement, Satisfy requirements engineering
INFO A requirement specifies a capability or condition that must (or should) be satisfied. A requirement may specify a function that a system must perform or a performance condition a system must achieve. OMG Systems Modeling Language (SysML) 1.6 Requirement requirements engineering
INFO A Satisfy relationship is a dependency between a requirement and a model element that fulfills the requirement. OMG Systems Modeling Language (SysML) 1.6 Dependency Requirement, Satisfy, AbstractRequirement::/satisfiedBy requirements engineering, requirements analysis
INFO A segmented mirror is an array of smaller mirrors designed to act as segments of a single large curved mirror. ... They are used as objectives for large reflecting telescopes. Wikipedia reflecting telescope, reflector, optical telescope, telescope, segmented mirror, mirror
INFO A semantic triple, or RDF triple or simply triple, is the atomic data entity in the Resource Description Framework (RDF) data model. Wikipedia semantic triple, semantic web, RDF, OWL
INFO A sensor is a transducer that receives and responds to a signal or stimulus from a physical system. It produces a signal, which represents information about the system Wikipedia sensor, control system
INFO A SignalEvent represents the receipt of an asynchronous Signal instance. Unified Modeling Language 2.5.1 Event, MessageEvent, SignalEvent, Trigger, Trigger::event, Message, Operation, object, Signal, SignalEvent::signal
INFO A slave requirement is a requirement whose text property is a read-only copy of the text property of a master requirement. The text property of the slave requirement is constrained to be the same as the text property of the related master requirement. OMG Systems Modeling Language (SysML) 1.6 Dependency::supplier, Dependency::client AbstractRequirement, Requirement, Copy, AbstractRequirement::/master, AbstractRequirement::text requirements engineering
INFO A sling psychrometer gives a dry-bulb temperature of 78°F and a wet-bulb temperature of 65°F. Determine other moist air properties from this information. CED Engineering course PDF: 'Air Conditioning Psychrometrics (A.Bhatia)' thermodynamics, Psychrometrics, humid air, temperature, dry bulb temperature, wet bulb temperature, relative humidity, absolute humidity, psychrometer, sling psychrometer
INFO A Slot designates that an entity modeled by an InstanceSpecification has a value or values for a specific StructuralFeature. OMG Systems Modeling Language (SysML) 1.6 Slot, InstanceSpecification::slot, StructuralFeature, Slot::definingFeature, Slot::owningInstance, Slot::value
INFO A stakeholder represents a role, group, or individual who has concerns that will be addressed by the View of the model. OMG Systems Modeling Language (SysML) 1.6 Actor, Class Stakeholder, View
CONSTRAINT A Stakeholder stereotype can only be applied to UML::Actor or UML::Class which are not a UML::Association. OMG Systems Modeling Language (SysML) 1.6 Actor, Class Stakeholder
INFO A standard requirement includes properties to specify its unique identifier and text requirement. Additional properties such as verification status, can be specified by the user. OMG Systems Modeling Language (SysML) 1.6 Requirement, SysML Requirements Diagram, AbstractRequirement::text, AbstractRequirement::id requirements engineering
SEMANTIC A StartObjectBehaviorAction is a CallAction that starts the execution either of a directly instantiated Behavior or of the classifierBehavior of an object. The object to be started is taken from the object InputPin. Unified Modeling Language 2.5.1 Action, InvocationAction, CallAction, Behavior, CallBehaviorAction, StartObjectBehaviorAction::object, Behavior, BehavioredClassifier::classifierBehavior, InputPin
INFO A State is said to be active if it is part of the active state configuration. Unified Modeling Language 2.5.1 State, StateMachine, Region, composite State, State::/isComposite, State::/isSimple, state configuration, valid state configuration, active state configuration
INFO A State may also have an associated doActivity Behavior. This Behavior commences execution when the State is entered (but only after the State entry Behavior has completed) and executes concurrently with any other Behaviors that may be associated ... Unified Modeling Language 2.5.1 State, StateMachine, Behavior, State::doActivity
INFO A State may have an associated entry Behavior. This Behavior, if defined, is executed whenever the State is entered through an external Transition. Unified Modeling Language 2.5.1 State, StateMachine, Behavior, State::entry, Transition, external Transition
A StateMachine or composite State may contain multiple Regions representing behaviors that may occur in parallel. Unified Modeling Language 2.5.1 Region, StateMachine, composite State, Vertex, Transition
CONSTRAINT A stereotype must be contained, directly or indirectly, in a profile. Unified Modeling Language 2.5.1 Stereotype, Profile