The purpose of this QoS is to avoid delivering "stale" data to the application.
Each data sample written by the DataWriter has an associated 'expiration time' beyond which the data should not be delivered to any application. Once the sample expires, the data will be removed from the DataReader caches as well as from the transient and persistent information caches.
Thetype exposes the following members.
Gets or sets the expiration time duration. The default value is infinite, which means samples never expire.
Determines whether the specified object is equal to the current object.(Inherited from Object.)
Serves as the default hash function.(Inherited from Object.)
Gets the Type of the current instance.(Inherited from Object.)
Returns a string that represents the current object.(Inherited from Object.)
The value of this policy may be changed at any time. Changes to this policy affect only data written after the change.
The 'expiration time' of each sample is computed by adding the duration specified by the Lifespan QoS to the source timestamp.
This QoS relies on the sender and receiving applications having their clocks sufficiently synchronized. If this is not the case and DDS can detect it, the DataReader is allowed to use the reception timestamp instead of the source timestamp in its computation of the 'expiration time'.