SysML Block Definition Diagram

SysML Block Definition Diagram⌘

Block Definition Diagram⌘

• The Block Definition Diagram in SysML defines features of blocks and relationships between blocks such as associations, generalizations, and dependencies.
• It captures the definition of blocks in terms of properties and operations, and relationships such as a system hierarchy or a system classification tree.

Block⌘

• Blocks are modular units of system description.
• Each block defines a collection of features to describe a system or other element of interest.
• These may include both structural and behavioral features, such as properties and operations
• SysML allows blocks to have multiple compartments appearing in any order, each optionally with name.
• In SysML all properties of a block have the visibility public.

Block structure compartment⌘

• A compartment with the label “structure” may appear as part of a block definition to show connectors and other internal structure elements for the block being defined.

Relationships⌘

Generalization⌘

• relationship between a more general classifier and a more specific classifier
• each instance of the specific classifier is also an indirect instance of the general classifier
• the specific classifier inherits the features of the more general classifier

Association⌘

• A unidirectional association has a default multiplicity of 1 on its target end.

Part/Shared Association⌘

• A part or shared association has a default multiplicity of [0..1] on the black or white diamond end.

Containment⌘

ValueType⌘

• A ValueType defines types of values that may be used to express information about a system but has no identity.
• SysML defines ValueType as a stereotype of UML DataType.
• For example, the SysML “Real” ValueType expresses the mathematical concept of a real number, but does not impose any restrictions on the precision or scale of a fixed or floating-point representation that expresses this concept.

Primitive Value Types⌘

Enumeration⌘

• An Enumeration is a Value Type whose values are enumerated in the model as literals.

Unit and QuantityKind⌘

• 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 feets.

Unit and QuantityKind example⌘

Ports and Flows⌘

• Ports and flows are useful to enable design of modular, reusable blocks with clearly defined ways of connecting and interacting with their context of use.
• Flow properties specify the kinds of items that might flow between a block and its environment, whether it is data, material, or energy.
• The kind of items that flow is specified by typing flow properties.

Item Flow⌘

• Item flows specify the things that flow between blocks and/or parts and across associations or connectors.
• Item flows specify what “does” flow between blocks and/or parts in a particular usage context, e.g. water or gasoline.

Port⌘

• Ports are points at which external entities can connect to and interact with a block in different or more limited ways than connecting directly to the block itself.
• They are properties with a type that specifies features available to the external entities via connectors to the ports.
• SysML identifies two kinds of ports:
  • proxy port - exposes features of the owning block or its internal parts
  • full port - supports its own features, specifies separate elements of the system
• Proxy ports are always typed by interface blocks, a specialized kind of block that has no behaviors or internal parts.
• Ports that are not specified as proxy or full are simply called “ports.”

Interface⌘

• An Interface represents a declaration of a set of public Features and obligations that together constitute a coherent service.
• The set of Interfaces realized by a block are its Provided Interfaces, which represent the services and obligations that instances of that block offer to their clients.
• Required Interfaces specify services that a block needs in order to perform its function and fulfill its own obligations to its clients.

Instance Specification⌘

• An Instance Specification is a model element that represents an instance in a modeled system.
• They are often used to model example configurations of instances.
• They may be partial or complete representations of the instances that they correspond to.

Constraint Blocks⌘

• Constraint blocks provide a mechanism for integrating engineering analysis such as performance and reliability models with other SysML models.
• Can be used to specify constraints that represent mathematical expressions such as {F=m*a} and {a=dv/dt}.
• Is a block that contains the statement of a constraint so it may be applied in a reusable way to constrain properties of other blocks.
• Can be defined on Block Definition Diagram or Package Diagram and used on Parametric Diagrams