The OMG DDS (Data Distribution Service) is a standard for data distribution which is widely used as the foundation for operational systems such as air traffic control and management, combat systems, distributed telemetry and control, etc. On the other hand, HLA (High Level Architecture) is a communication and coordination standard which is widely adopted in the distributed simulation community. DDS is increasingly gaining adoption in distributed simulation, especially for those systems that require high throughput, low latencies and scalability. In addition, the use of DDS in simulation provides native interoperability between operational and simulated systems, thus eliminating integration overhead and complexities. This presentation introduces DDS and HLA, provide an apple-to-apple comparison between the two standards and show how DDS and HLA systems can be seamlessly integrated together.

1. Distributed Simulations
with DDS and HLA
OpenSplice DDS
Angelo CORSARO, Ph.D.
Chief Technology Officer
OMG DDS Sig Co-Chair
PrismTech
angelo.corsaro@prismtech.com
José-Ramón Martínez-Salio
Technical Sales Engineers Director
NADS
jrmartinez@nexteleng.es

2. Context
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☐ DDS is increasingly being adopted in simulation applications either
side-by-side with HLA or as a replacement
OpenSplice DDS
☐ This webcast provides an objective comparison of DDS and HLA
allowing attendees to understand the value that each of these
technologies can bring

3. OpenSplice DDS
Genesis

4. DDS and HLA Goals
DDS HLA
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☐ Foster interoperability and ☐ Foster interoperability and
portability of Distributed portability of Distributed
OpenSplice DDS
Operational Systems Simulation Systems
☐ Address functional and ☐ Address functional
non-functional requirements and (some)
requirements of non functional requirements
Operational Systems of Simulation Systems

5. Standard Scope
DDS HLA
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Application Federate
Data Centric Publish Subscriber (DCPS) Run-Time Infrastructure (RTI)
Content Federation Object Time
Ownership Durability
Subscription Management Managenent Management
OpenSplice DDS
Minimum Profile Ownership Data Distribution Declaration
Management Management Management
DDS Interoperability Wire Protocol - DDSI-RTPS
UDP/IP
Application
☐ DDS and HLA define standardized ways of describing application Data.

6. Standardization History
DDS-ISO-Java
DDS-RMI
UML4DDS DDS4CCM DDS-ISO-C++
DDS-Security
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Dec
DDS-TCP/IP
DDS v1.1 DDS v1.2 DDSI v2.0 DDSI v2.1 DDS-XTopics
Dec Jan Apr Jan March
Sep
2005 2006 2007 2008 2009 2010 2011 2012
OpenSplice DDS
HLA Evolved
DDS v1.0
Dec
1996 1997 1998 1999 2000 2001 2003 2004
HLA
HLA v1.3 HLA
IEEE 1516

7. [DDS/HLA ]
Similarities and Differences
DDS HLA
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API Standard Yes Yes
No
Wire Protocol Standard Yes
(essentially underspecified)
OpenSplice DDS
Data Modeling Standard Yes (IDL, XML, XSD, UML) Yes (OMT, XML)
Static Declaration of FOM
Discovery Fully Dynamic
Dynamic Matching Pub/Sub
Implementation Dependent
Architectural Style Fully Distributed (Most implementation have a
centralized broker)

8. [DDS/HLA ]
Similarities and Differences
DDS HLA
Per Topic with Content Per Object Attribute
Subscription Model
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Filters and Queries Per Interaction
2 QoS Policies (Reliability
QoS 22 QoS Policies
and Ordering)
OpenSplice DDS
‣ Dependency on globally
‣ No dependency on global
defined FOM
Coupling knowledge
‣ Time coupling
‣ Time decoupling
‣ Sophisticated time
Time Management ‣ Basic Timestamping
management service

9. DDS in Defense and Aerospace
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OpenSplice DDS
Integrated Modular Vetronics Training & Simulation Systems Naval Combat Systems
Air Traffic Control & Management Unmanned Air Vehicles Aerospace Applications

10. DDS in Commercial Applications
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OpenSplice DDS
Agricultural Vehicle Systems Large Scale SCADA Systems Smart Cities
Train Control Systems Complex Medical Devices High Frequency Auto-Trading

11. DDS and HLA Fundamentals
OpenSplice DDS

12. Data Distribution Service
For Real-Time Systems
DDS provides a Topic-Based Publish/
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Subscribe abstraction based on: Data
Reader
Data
Writer
☐ Topics: data distribution subject’s
OpenSplice DDS
Data
Reader
Data TopicD
Writer
DataWriters: data producers
TopicA
☐
Data
TopicB Reader
Data
Writer
☐ DataReaders: data consumers TopicC
...
Data Data
Writer Reader
DDS Global Data Space

13. Data Distribution Service
For Real-Time Systems
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☐ DataWriters and DataReaders
are automatically and Data
Reader
dynamically matched by the Data
Writer
DDS Dynamic Discovery
OpenSplice DDS
Data
Reader
Data TopicD
Writer
TopicA
☐ A rich set of QoS allows the Data
Reader
TopicB
control existential, temporal,
Data
Writer
TopicC
...
and spatial properties of data Data Data
Writer Reader
DDS Global Data Space

14. HLA Federation
☐ An HLA Federation is a collection of Federates (essentially HLA applications)
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sharing a common Federation Object Model (FOM)
☐ Each Federate can publish/subscribe a subset Objects Attributes and
Interactions defined by the Federation FOM.
OpenSplice DDS
Federate A Federate B ... Federate K
Federation Object Model
<FOM>
<Shared object classes>
<Shared interaction classes>
<More>
</FOM>
RTI (Run-Time Infrastructure)

15. DDS Topics
“Circle”, “Square”, “Triangle”, ...
☐ A Topic defines a class of streams
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☐ A Topic has associated a unique Name
name, a user defined extensible
type and a set of QoS policies Topic
Typ
S
OpenSplice DDS
DURABILITY,
Qo
☐ QoS Policies capture the Topic
e
DEADLINE,
ShapeType
non-functional invariants PRIORITY,
…
☐ Topics can be discovered or
locally defined struct ShapeType {
@Key
string color;
long x;
long y;
long shapesize;
};

16. Instances and Samples
“Circle”, “Square”, “Triangle”, ...
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Name
Topic
Typ
S
OpenSplice DDS
DURABILITY,
Qo
e
DEADLINE,
ShapeType
PRIORITY,
…
struct ShapeType {
@Key
string color;
long x;
long y;
long shapesize;
};

17. HLA Objects
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☐ HLA Objects identify a
class of instances whose (objects
(class Shape
attributes can be (attribute color reliable timestamp ShapeSpace)
individually published/ (attribute
(attribute
x best_effort timestamp ShapeSpace)
y best_effort timestamp ShapeSpace)
OpenSplice DDS
subscribed )
(attribute shapesize reliable timestamp ShapeSpace)
)
☐ QoS are controlled at
an attribute-level
☐ Object attributes can be bound to spaces and dimensions to
organize/partition the data distribution

18. HLA Interactions
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☐ HLA Interactions are
used to model
consumable events
OpenSplice DDS
(interactions
☐ Interactions are (class ShapeCollision reliable timestamp ShapeSpace
published/subscribed as (attribute x)
(attribute y)
atomically )
)
☐ QoS is attached with the
interaciton

19. Polymorphism
DDS HLA
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☐ DDS is equipped with a ☐ HLA provides supports for
structural type system where traditional subtype polymorphism
subtype relationships are as supported in declarative
deduced based on type nominal type systems
OpenSplice DDS
properties as opposed to
syntactical declaration ☐ HLA supports only single
inheritance
☐ This means that a subscription
for a type X matches a ☐ This means that a subscription for a
publication for a type Y iff Y <: type X matches a publication for a
X (the subtype property is type Y iff Y <: X
antisymmetric, reflexive, and
transitive)

20. Polymorphism
Point GPoint
x: long x: long
y: long y: long
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z: long
t: long
Point3D
z: long
OpenSplice DDS
DDS HLA
☐ Point3D <: Point ☐ Point3D <: Point
☐ GPoint <: Point3D

21. Anatomy of a DDS Application
Domain (e.g. Domain 123)
Domain
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Participant
Topic
Partition (e.g. “Telemetry”, “Shapes”, )
OpenSplice DDS
T1 Publisher
T1 T3 Subscriber
Topic Instances/Samples Tx
Ty
Tb
Ta DataWrter DataReader
Tc

22. OpenSplice DDS
Federation
Spaces
Y.d
X.a
K
X.b I
Y.c
J
Federate
Ambassador
Anatomy of a HLA Application
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23. Data Selection
DDS HLA
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☐ Pub/Sub granularity is the ☐ Pub/Sub granularity are
Topic attributes for Object and
☐ Data can be organized the whole class for an
Interaction
OpenSplice DDS
into Partitions. Partitions
matching is based on ☐ Data can be organized in
regular expression
Spaces and Dimensions
☐ Content Filters and
Queries can be used to
select the data that is
received

24. DDS Partitions Matching
Domain
Partitions DDS Publishers and
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☐
Subscribers can specify a
M:0:0 M:0:1 M:0:2 list of regular expressions
representing the partitions
to join
OpenSplice DDS
M:1:0 M:1:1 M:1:2
☐ Actual partition can be
any string, but some
M:2:0 M:2:1 M:2:2 structure can be given in
order mimic hierarchy

25. DDS Partitions Matching
Domain
Partitions
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M:0:0 M:0:1 M:0:2 M:0:*
OpenSplice DDS
M:1:0 M:1:1 M:1:2
M:2:0 M:2:1 M:2:2

26. DDS Partitions Matching
Domain
Partitions
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M:0:0 M:0:1 M:0:2
OpenSplice DDS
M:1:0 M:1:1 M:1:2
M:2:0 M:2:1 M:2:2
M:*:2

27. DDS Partitions Matching
Domain
Partitions
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M:0:0 M:0:1 M:0:2
OpenSplice DDS
M:1:0 M:1:1 M:1:2
M:2:0 M:2:1 M:2:2 M:0:0, M:1:1, M:2:2

28. Anatomy of a DDS Application
[DDS C++ API 2010]
Domain
Domain
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auto dp = DomainParticipant(domainId);
Participant
Session
// Create a Topic
auto topic = Topic<ShapeType>(dp, “Circle”) Publisher
Topic
Subscriber
OpenSplice DDS
// Create a Publisher / Subscriber
auto pub = Publisher(dp)
auto sub = Subscriber(dp)
Reader/Writers for User Defined for Types DataWriter
DataReader
// Create a DataWriter/DataWriter
auto writer = DataWriter<ShapeType>(pub, topic); Reader/Writer for
auto reader = DataReader<ShapeType>(sub, topic);
application defined
Topic Types

29. Anatomy of a DDS Application
[DDS C++ API 2010]
Domain
Domain
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auto dp = DomainParticipant(domainId);
Participant
Session
// Create a Topic
auto topic = Topic<ShapeType>(dp, “Circle”) Publisher
Topic
Subscriber
OpenSplice DDS
// Create a Publisher / Subscriber
auto pub = Publisher(dp)
auto sub = Subscriber(dp)
Reader/Writers for User Defined for Types DataWriter
DataReader
// Write data
writer.write(ShapeType(“RED”, 131, 107, 89)); Reader/Writer for
// But you can also write like this...
writer << ShapeType(“RED”, 131, 107, 89);
application defined
Topic Types
// Read new data (loaned)
auto data = reader.read();

30. Anatomy of an HLA Application
using namespace std;
int main( int argc, char *argv[] )
{
// 1. create the RTIambassador that we are going to work with
Federation RTI::RTIambassador* rtiamb = 0;
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rtiamb = new RTI::RTIambassador();
// 2. create the federation execution
rtiamb->createFederationExecution( "exampleFederation", "testfom.fed" );
cout << "Created federation" << endl;
// 3. join the federation execution
Federate RTI::FederateAmbassador* fedamb = new MyFedAmb();
rtiamb->joinFederationExecution( "myFederate", "exampleFederation", fedamb );
OpenSplice DDS
cout << "Joined federation" << endl;
// Pub/Sub...
// 4. resign from the federation execution
rtiamb->resignFederationExecution( RTI::DELETE_OBJECTS_AND_RELEASE_ATTRIBUTES );
cout << "Resigned from federation" << endl;
// 5. destroy the federation execution
rtiamb->destroyFederationExecution( "exampleFederation" );
cout << "Destroyed federation" << endl;
// 6. do some cleanup and exit
delete rtiamb;
return 0;
}

31. OpenSplice DDS
QoS

32. DDS QoS Model
☐ QoS-Policies control local and
end-to-end properties of DDS
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Type Matching
entities
QoS matching
QoS QoS QoS QoS QoS QoS QoS
☐ Local properties controlled by Topic
Name
QoS are related resource usage
Publisher Subscriber
... DataWriter writes Type reads DataReader
...
...
OpenSplice DDS
☐ End-to-end properties DomainParticipant DataWriter writes Type reads DataReader DomainParticipant
controlled by QoS are related Topic
Name
to temporal and spatial aspects QoS QoS QoS
of data distribution
☐ Some QoS-Policies are matched
based on a Request vs. Offered
Model thus QoS-enforcement

33. DDS QoS Policies
[T: Topic] [DR: DataReader] [DW: DataWriter] [P: Publisher] [S: Subscriber] [DP: Domain Participant]
QoS Policy Applicability RxO Modifiable
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USER_DATA DP, DR, DW N Y
TOPIC_DATA T N Y Configuration
GROUP_DATA P, S N Y
DURABILITY T, DR, DW Y N
OpenSplice DDS
DURABILITY T, DW N N
SERVICE Data Availability
HISTORY T, DR, DW N N
PRESENTATION P, S Y N
RELIABILITY T, DR, DW Y N
PARTITION P, S N Y
Data Delivery
DESTINATION T, DR, DW Y N
ORDER
LIFESPAN T, DW N Y

34. DDS QoS Policies
[T: Topic] [DR: DataReader] [DW: DataWriter] [P: Publisher] [S: Subscriber] [DP: Domain Participant]
QoS Policy Applicability RxO Modifiable
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DEADLINE T, DR, DW Y Y
LATENCY T, DR, DW Y Y
BUDGET Temporal/
TRANSPORT T, DW N Y Importance
PRIORITY Characteristics
OpenSplice DDS
TIME BASED DR N Y
FILTER
OWNERSHIP T, DR, DW Y N
OWNERSHIP DW N Y Replication
STRENGTH
LIVELINESS T, DR, DW Y N Fault-Detection

35. OpenSplice DDS
Partition
Data Delivery
Reliability
Presentation
Data Delivery
Order
Destination
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36. Data Availability
History
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Data
OpenSplice DDS
Lifespan Durability
Availability
Ownership
Ownership
Strength

37. Temporal Properties
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TimeBasedFilter Deadline
[Inbound]
OpenSplice DDS
Throughput LatencyBudget Latency
[Outbound]
TransportPriority

38. HLA QoS Policies
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☐ HLA provides roughly only two policies, one for controlling the
reliability and the other for controlling the ordering of data
OpenSplice DDS
☐ HLA ties policies with data thus does not allow different producer/
consumers to refine the QoS with which data is produced/
consumed

39. Time Management
DDS HLA
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☐ Along with automatic time- ☐ HLA provides support for:
stamping based on real-time, ☐ Event Driven Simulation
DDS provides an API for time- ☐ Time Stepped Simulation
OpenSplice DDS
stamping messages ☐ Parallel Discrete-Event Simulation
☐ This API can be used to
☐ Wall-clock-time Simulation
implement logical clocks
☐ The HLA Time Service provides
primitives to coordinate and
control the advancement of time

40. DDS Performance
OpenSplice DDS

41. Local Latency
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☐ Inter-Core latency can be as
low as 10 usec!
Latency distribution
OpenSplice DDS
☐
predictable with:
☐ IQR <= 0.5 usec
☐ 99% - Min <= 4 usec

42. Head of Line Blocking
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☐ Concurrent application
w/o real-time
networking might
OpenSplice DDS
provoke unbounded
priority inversion
☐ ...OpenSplice can avoid
this...

43. The Lane’s Effect
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☐ The proper configuration
of network lanes can
eliminate (or bound) the
OpenSplice DDS
priority inversion
introduced by the head-
of-line blocking

44. OpenSplice DDS
Real-Time Determinism
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45. Integration DDS and HLA
-Live Demo-
OpenSplice DDS

46. OpenSplice DDS
Summing Up

47. Concluding Remarks
DDS provides a very powerful and high-performance infrastructure
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☐
for data distribution
☐ When compared to HLA, DDS stands out for its support for
evolvability and dynamic systems/federations
OpenSplice DDS
☐ On the down-side, DDS is a technology that was designed for
Operational Systems, as such it does not provide mechanisms such
as Time Management. However these mechanisms can easily be
implemented over DDS

48. OpenSplice DDS

49. References
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OpenSplice | DDS Escalier
¥ #1 OMG DDS Implementation ¥ Fastest growing JVM Language ¥ Scala API for OpenSplice DDS
¥ Open Source ¥ Open Source ¥ Open Source
¥ www.opensplice.org ¥ www.scala-lang.org ¥ github.com/kydos/escalier
OpenSplice DDS
¥ Simple C++ API for DDS ¥ DDS-PSM-Java for OpenSplice DDS ¥ DDS-based Advanced Distributed
¥ Open Source ¥ Open Source Algorithms Toolkit
¥ github.com/kydos/simd-cxx ¥ github.com/kydos/simd-java ¥ Open Source
¥ github.com/kydos/dada

50. :: Connect with Us ::
¥opensplice.com ¥forums.opensplice.org
¥@acorsaro
¥opensplice.org ¥opensplicedds@prismtech.com ¥@prismtech
OpenSplice DDS
¥ crc@prismtech.com
¥sales@prismtech.com
¥youtube.com/opensplicetube ¥slideshare.net/angelo.corsaro