Vendor Interoperability

When communicating with other DDS vendors, the following settings enable compliance with the DDS-XTYPES specification.

All Vendors — XTYPES Compliance Mask

The NDDS_XTYPES_COMPLIANCE_MASK environment variable configures RTI Connext to use DDS specification-compliant behavior for type compatibility:

export NDDS_XTYPES_COMPLIANCE_MASK=0x000001a9

This mask enables several interoperability flags:

Comply with DDS-XTYPES 1.3 specification serialization rules
Enable strict type validation for cross-vendor communication

The Python start scripts (start_autopilot.sh, start_globalvector_consumer.sh) include this line commented out — uncomment it when interoperating with other vendors.

This can also be done programmatically if necessary for a specific endpoint. See RTI Connext XTYPES Compliance Documentation for full details on mask values and API usage.

Cyclone DDS

To ensure interoperability with Eclipse Cyclone DDS, the CycloneInterop QoS profile in qos/umaa_qos_lib.xml is provided as a convenience.

Data Representation

Eclipse Cyclone DDS uses XCDR2 serialization by default
RTI Connext determines the serialization format based on the data type’s extensibility kind (XCDR for final types, XCDR2 for appendable/mutable types)

CycloneInterop configures DataReaders to accept both XCDR and XCDR2 data representations:

<datareader_qos>
  <representation>
    <value>
      <element>XCDR_DATA_REPRESENTATION</element>
      <element>XCDR2_DATA_REPRESENTATION</element>
    </value>
  </representation>
</datareader_qos>

This ensures readers can receive data from writers using either serialization format.

See RTI Connext DATA_REPRESENTATION QoS Documentation for more details.

Serialize Key with Dispose

RTI Connext uses a key hash for instance handles. When a dispose message is the first message received for a given instance, the receiver may not have the key values needed to identify it. CycloneInterop configures DataWriters to serialize the key value alongside dispose messages so that receivers (including Cyclone DDS) can correctly identify the instance:

<datawriter_qos>
  <protocol>
    <serialize_key_with_dispose>true</serialize_key_with_dispose>
  </protocol>
</datawriter_qos>

This ensures cross-vendor dispose handling works correctly for keyed topics.

Type Extensibility Kind

The default type extensibility in Cyclone DDS is @final instead of @appendable, which is the default according to the DDS-XTYPES specification. This mismatch may cause deserialization errors in Connext applications. It is recommended to explicitly set @appendable on the Cyclone side to align with the standard.

Using `CycloneInterop` in Python

To apply the Cyclone interoperability profile in your Python component, inherit from or compose with the CycloneInterop profile in your QoS XML. Since the SDK uses AssignerQoS by default, you can layer the profile on top by setting it as the base for your custom QoS:

<qos_profile name="MyCycloneProfile" base_name="UMAAQoSLib::CycloneInterop">
    <!-- Additional QoS overrides here -->
</qos_profile>

Alternatively, set the compliance mask environment variable before launching your application:

export NDDS_XTYPES_COMPLIANCE_MASK=0x000001a9
./start_autopilot.sh --domain-id 0