Tuple Flow - modelint/shlaer-mellor-metamodel GitHub Wiki

Certain Relational Actions such as Rank Restrict Action and Restrict Action are capable of outputting either a Table Flow or a Tuple Flow.

A Tuple Flow is emitted when the selection cardinality is ONE. And this cardinality only guarantees that zero or one tuple will be generated as output.

Any Action, such as the the Extract Action that receives a Tuple Flow must then verify that a tuple input is present at runtime and then throw an exception if the Tuple Flow is empty.

So care must be taken when defining an Activity that produces intermediate Tuple Flows. If an empty Tuple Flow might be enabled by some producer Action, an intermediate Decision Action could test the value to avoid a downstream exception.

Identifiers

1. ID + Activity + Domain

Attributes

No non-referential attributes