TagSelector¶

class tracdap.metadata.TagSelector¶

A tag selector describes the selection of a unique object at a point in time.

A tag selector refers to a single object ID and provides criteria for selecting the object version and tag version. The available selection criteria are:

Select an explicit version number

Select the latest available version

Select the version that was live at specific point in time

A selector for an explicit version number will always match that exact version number. These “fixed” types of selector can be used to refer to elements of a repeatable job, because the versions they refer to will never change.

A selector for the latest version will select different versions over time, as they become available. These “variable” types of selector can be used by client applications that want to query the latest state of an object. If a job is set up using variable selectors, TRAC will convert them to fixed selectors for the particular versions that were selected before saving the job definition.

Criteria for object versions and tag versions can be “mixed and matched”, so e.g. latestObject = true with tagVersion = 1 is allowed.