47.4 DATATAG QosPolicy
The DATATAG QosPolicy can be used to associate a set of tags in the form of (name, value) pairs with a DataReader or DataWriter. The Access Control plugin may use the tags to determine publish and subscribe permissions.
The DATATAG QosPolicy is similar to the PropertyQosPolicy, except you cannot select whether or not a particular pair should be propagated (included in the built-in topic); data tags are always propagated. For example, with the Property QoS, it would be possible for a DomainParticipant to allow its own endpoint (DataReader or DataWriter) based on some required properties, and for a remote DomainParticipant to deny that same endpoint because the endpoint chose not to propagate the required properties to the remote DomainParticipant. To avoid such inconsistencies—and because other participants must know about a DomainParticipant’s security credentials—data tags in the DATATAG QosPolicy are always propagated.
This policy includes the member listed in Table 47.11 DDS_DataTagQosPolicy.
|
Type |
Field Name |
Description |
|
DDS_TagSeq |
tags |
A sequence of (name, value) string pairs. |
You can manipulate the sequence of tags (name, value pairs) with the standard methods available for sequences. You can also use the helper class, DataTagQosPolicyHelper, which provides another way to work with a DataTagQosPolicy object. The DataTagQosPolicyHelper operations are described in the following table. For more information, see the API Reference HTML documentation.
|
Operation |
Description |
|
get_number_of_tags |
Gets the number of data tags in the input policy. |
|
assert_tag |
Asserts the data tag identified by name in the input policy. (Either adds it, or replaces an existing one.) |
|
add_tag |
Adds a new data tag to the input policy. |
|
lookup_tag |
Searches for a data tag in the input policy given its name. |
|
remove_tag |
Removes a data tag from the input policy. |
47.4.1 Properties
This QosPolicy cannot be modified after the Entity has been created. There is no requirement that the publishing and subscribing sides use compatible values.
47.4.2 Related QosPolicies
44.4 DOMAIN_PARTICIPANT_RESOURCE_LIMITS QosPolicy (DDS Extension)
47.4.3 Applicable Entities
47.4.4 System Resource Considerations
44.4 DOMAIN_PARTICIPANT_RESOURCE_LIMITS QosPolicy (DDS Extension) contains several fields for configuring the resources associated with the data tags stored in this QosPolicy.