This presentation introduces dscript, a framework that brings DDS-like publish/subscribe to the Web Browser. Beyond providing an inter-browser Pub/Sub abstraction, dscript provides with a semaless integratio with native DDS applications. Meaning that data can flow effortlessly from native DDS applications to the browser and viceversa.

1. OpenSpliceDDS
Angelo CORSARO, Ph.D.
Chief Technology Officer
OMG DDS Sig Co-Chair
PrismTech
angelo.corsaro@prismtech.com
DDS Web Programming
with dscript

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2013,
PrismTech
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OpenSpliceDDS
Motivation
☐ WebSockets have made it possible to efficiently push data to the
browser, yet provide a low level abstraction
☐ More and more “Real-Time Web” Applications need to produce as
well as consume real-time data streams
☐ Wouldn’t it be nice to have a DDS-like abstraction in JavaScript?
☐ i.e. to do pub/sub from JavaScript Applications

3. Copyright
2013,
PrismTech
–
All
Rights
Reserved.
OpenSpliceDDS
Motivation
☐ WebSockets have made it possible to efficiently push data to the
browser, yet provide a low level abstraction
☐ More and more “Real-Time Web” Applications need to produce as
well as consume real-time data streams
☐ Wouldn’t be nice to have a DDS-like abstraction in JavaScript to
feed Real-Time Web Applications with data coming from a DDS
System?

4. Copyright
2013,
PrismTech
–
All
Rights
Reserved.
OpenSpliceDDS
Motivation
☐ WebSockets have made it possible to efficiently push data to the
browser, yet provide a low level abstraction
☐ More and more “Real-Time Web” Applications need to display
real-time data streams
☐ In a sense, wouldn’t it be nice to be able to do Pub/Sub with a DDS-
like abstraction between Web Applications and DDS Applications
w/o any barriers???

5. Copyright
2013,
PrismTech
–
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Rights
Reserved.
OpenSpliceDDS
dscript
JavaScript/CoffeeScript framework
that extends the DDS abstraction
to the WebBrowser/Node.js

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2013,
PrismTech
–
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Reserved.
OpenSpliceDDS
Architecture
dscript is composed by two elements:
☐ Client Side (dscript.js): JavaScript/CoffeeScript framework that provides DDS-
like abstractions
☐ Server Side(dscript.play): A Router that transparently bridges data between
matching DDS entities, e.g. Browser-2-Browser, DDS-2-Browser and Browser-2-DDS
TopicA
TopicB
TopicC
TopicD
QoS
QoS
QoS
QoS
Data
Reader
Data
Reader
Data
Writer
Data
Writer
dscript.play
dscript
dscript.js
dscript.js
dscript.js
dscript.play
dscript

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OpenSpliceDDS
dscript.js
☐ dscript.js reduces the DDS concepts to Topics, DataReaders,
DataWriters and QoS. DomainParticipant and Publishers are
managed for you
☐ The API is reactive and considers DataReaders as the source for a
stream of data. This data can be handled by the application or
bound to a cache (notice the cache is not part of the
DataReader)

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2013,
PrismTech
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OpenSpliceDDS
Topic
circleTopic = new dds.Topic(0, 'Circle', 'org.omg.dds.demo.ShapeType')
squareTopic = new dds.Topic(0, 'Square', 'org.omg.dds.demo.ShapeType')
triangleTopic = new dds.Topic(0, 'Triangle', 'org.omg.dds.demo.ShapeType')
var myTopic = new dds.Topic(domainID, topicName, topicType);
myTopic = new dds.Topic(domainID, topicName, topicType)
JavaScript
CoffeeScript
var circleTopic = new dds.Topic(0, 'Circle', 'org.omg.dds.demo.ShapeType');
var squareTopic = new dds.Topic(0, 'Square', 'org.omg.dds.demo.ShapeType');
var triangleTopic = new dds.Topic(0, 'Triangle', 'org.omg.dds.demo.ShapeType');
Example:
Example:

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DataWriter
dwqos = new dds.DataReaderQos(
dds.History.KeepLast(10),
dds.Reliability.Reliable,
dds.TimeFilter(250))
cdw = new dds.DataWriter(circleTopic,dwqos)
shape = {}
shape.color = ’RED’
shape.x = 10
shape.y = 20
shape.shapesize = 30
cdw.write(shape)
dr = new dds.DataWriter(topic, qos)
CoffeeScript
Example:

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2013,
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OpenSpliceDDS
DataReader
drqos = new dds.DataReaderQos(
dds.History.KeepLast(10),
dds.Reliability.Reliable,
dds.TimeFilter(250))
cdr = new dds.DataReader(circleTopic,drqos)
dr = new dds.DataReader(topic, qos)
CoffeeScript
Example:

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OpenSpliceDDS
Binding a DataReader
☐ A DataReader can be bound to a user provided function that will
handle incoming data or to a cache
☐ Notice, that as you are in control of how data-readers are bound
to cache you can be very creative

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Binding to User Function
cdr.addListener((s) -> console.log(JSON.stringify(s)))
dr.addListener(f)
CoffeeScript
Example:

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Binding to a Cache
// Binding
bindShape = dds.bind((s) -> s.color)
ccache = new DataCache(historyDepth)
bindShape(cache, cdr)
// Working with the Cache
ccache.forEach(displayOnMyHTMLCanvas)
someCircles = ccache.takeWhile((s) -> s.x < s.y)
cache = new DataCache(historyDepth)
bind(keyMapper)(dr, cache)
CoffeeScript
Example:

14. OpenSpliceDDS
Demo!

15. OpenSpliceDDS
WebApp
Publish: Circle
Subscribe: Square
JavaFX native DDS App
Publish: Square
Subscribe: Circle
WebApp
Subscribe: Circle
Subscribe: Square

16. OpenSpliceDDS
Copyright
2013,
PrismTech
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Code
☐ https://github.com/nuvo-io/dscript.js
☐ https://github.com/nuvo-io/dscript.play
The demo is under dscript.js/demo/jshapes

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2013,
PrismTech
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OpenSpliceDDS