Glossary of eXpress Modeling Terms
Attribute – A measurable physical or abstract property of an entity.
Symbol – A picture that helps convey information about an element in a system, device or process. Symbols are stored in symbol libraries. Once dropped into a design, a symbol becomes an object; until then, a symbol has no function and no purpose.
Symbol Library – A collection of related symbols that can be used to build objects in eXpress.
Object – A symbol that has been added to a design. Although they are created from symbols, objects differ in that they possess additional characteristics that are automatically added as they are added to a design. There are five types of objects: components, assemblies, connectors, I/O flags and annotations.
Component – An object that contains internal port dependency definitions that establish the relationships between inputs and outputs. Components are the most basic of the five eXpress object types.
Assembly – An object that inherits detailed lower-level designs into an upper-level design. An assembly is a component that has been hierarchically linked to a lower-level design.
I/O Flag – An object that describes how signals enter or leave a design. An I/O flag represents an input or output of a design. I/O flags differ from connectors in that diagnostic and reliability calculations exclude them as a source of failure. The ports on an I/O flag have no inter-dependencies.
Input Flag – An I/O flag that represents a design input. An I/O flag with only output ports.
Output Flag – An I/O flag that represents a design input. An I/O flag with only input ports.
Terminal Output Flag – An output flag connected to a net that is only connected to output ports on other objects. A terminal output flag can be represented as a terminal event within a dependency model.
Internal Output Flag – An output flag connected to a net that is connected to at least one input, control or bidirectional part on another object. Although an internal output flag can be represented as an event within a dependency model, it cannot be represented as a terminal event.
Bidirectional Flag – An I/O flag that represents bidirectional input/output to a design. An I/O flag with at least one bidirectional port or mixed input and output ports.
Connector – A specialized object that is a cross between an I/O flag and a component. Like components, connectors have functions, attributes (including failure rates) and are considered by diagnostic and reliability calculations to be a possible source of failure. Like I/O flags, connectors have no port-to-port dependencies; every port on a connector is isolated.
Annotation – An object that can be placed within a design without impacting its diagnostic and reliability characteristics. Annotations are non-functional objects that are used exclusively for annotating the design.
