2.2. Data Distribution Service (DDS)

Reliability Related Policies

RELIABILITY.  Selects either best effort or guaranteed delivery mechanism.

BEST_EFFORT

no special mechanism to guarantee delivery

RELIABLE

guarantee delivery at transport protocol level

OWNERSHIP.  Configures potential redundancy at publisher side.

SHARED

deliver messages from all writers

EXCLUSIVE

deliver messages from live writer with highest strength

OWNERSHIP_STRENGTH.  Set writer strength to be used with EXCLUSIVE OWNERSHIP policy.

Presentation Related Policies

PRESENTATION.  Determines how change messages are presented to application.

coherent access

group change messages into explicitly delimited transactions

ordered access

preserve order of change messages

access scope

scope access options

INSTANCE

access options apply at instance scope

TOPIC

access options apply at Topic object scope

GROUP

access options apply at Publisher or Subscriber object scope

DESTINATION_ORDER.  Determines how to handle concurrent updates.

BY_SOURCE_TIMESTAMP

value with highest source timestamp will be visible

BY_RECEPTION_TIMESTAMP

value with highest reception timestamp will be visible

History Related Policies

DURABILITY.  Availability of data for late joining readers.

VOLATILE

writer does not keep any history

TRANSIENT_LOCAL

history kept in writer local memory

TRANSIENT

history kept in session local memory

PERSISTENT

history kept in persistent storage

HISTORY.  How much history to keep.

KEEP_LAST

keep limited history with configurable depth

KEEP_ALL

keep all history within resource limits

RESOURCE_LIMITS.  What are the available resource limits.

max_samples

maximum number of samples managed across all instances

max_instances

maximum number of managed instances

max_samples_per_instance

maximum number of samples managed per single instance

Timing Related Policies

DEADLINE.  Guarantee periodic updates to all topic instances.

  • publisher can guarantee maximum update period

  • subscriber can require maximum update period

LATENCY_BUDGET.  Hint on available latency reserve.

TRANSPORT_PRIORITY.  Hint on requested transport priority.

LIVELINESS.  Configure how entity liveliness is determined.

AUTOMATIC

service tracks Entity object liveliness

MANUAL_BY_TOPIC

publisher must periodically assert liveliness per Topic object

MANUAL_BY_PARTICIPANT

publisher must periodically assert liveliness per Participant object

LIFESPAN.  Message expiration time. Relies on having synchronized clock.

TIME_BASED_FILTER.  Minimum separation time for incoming messages.

Miscellaneous Policies

USER_DATA

attaches arbitrary data to Entity objects

TOPIC_DATA

attaches arbitrary data to Topic objects

GROUP_DATA

attaches arbitrary data to Publisher and Subscriber objects

PARTITION

define a partition name for logical domain partitioning