The document describes Distributed Shared Memory (DSM), a technology that enables a distributed in-memory database for JavaScript applications. DSM allows multiple clients to access and modify the same data simultaneously. It resolves merge conflicts automatically and notifies clients of data changes. Developers can focus on building interactive web collaboration software without dealing with networking, databases, or concurrency issues. DSM supports both persistent storage and transient data sharing across clients in real-time.

1. Distributed
Shared
Memory
A labs.ericsson.com API
http://labs.ericsson.com/apis/distributed-shared-memory/

2. ericsson labs APIs
Maps & positioning communication security
Mobile Mobile SMS Send & Mobile Group Voice Mobile Web Security Oauth2
Location Maps Receive Push Mixer Bootstrap CAPTCHA Framework
Web Async Identity Management Key Management
Maps Voice Framework Service
Web technologies NFC & sensors User & network information
Web Web Background Mobile Sensor Mobile Network
Tag Tool
Connectivity EventSource Service
Actuator Link Identification Probe
Web Device Mobile Network
Distributed Web Real-Time
Real- Sensor Networking
Connectivity Shared Memory Communication Application Platform Look-up
Look-
Machine learning Media and graphics
Face
Cluster Text-to-Speech
Text- to-
Detector
Constructor
© Ericsson AB 2010 | Page 2

3. Distributed shared memory
› Distributed Shared Memory enables a distributed in-
memory database for JavaScript applications
– Get a replica of a DSM storage with a
specified address from a DSM server
– Register a listener and be notified when
data is changes by other users
– Modify data locally and synchronize
changes in the background with
other replicas
› Merge conflicts are automatically
resolved
© Ericsson AB 2010 | Page 3

4. Why distributed shared memory?
› Let web developers focus on developing highly interactive
and responsive web-based collaboration software without
having to deal with complicated issues such as
– networking protocols
– database management
– concurrency control
› Also, using a local replica where data can be modified
directly without a lock or blocking improves user
experience
› Synchronizing application states among multiple clients
› Implement group-wares or collaborative web services
supporting simultaneous real-time interactions
© Ericsson AB 2010 | Page 4

5. Main Features
› Makes it possible for multiple JavaScript clients to address and
manipulate the same data at the same
› Plain JavaScript Lib (no browser plug-in required)
› High performance and low delay
› Optimistic replication to resolve merge conflicts
› Event-driven (register a listener and be notified when data change)
› Support for both ordered arrays/lists and unordered key-value hash
tables
› Support for both persistent storage (disk) and transient data (RAM)
› Automatic garbage collection
› Time-to-live (specify how long time a value should be stored)
› Possibility to link DSM storages to build graph databases
© Ericsson AB 2010 | Page 5

6. Use cases
Examples of usage
› E-learning
› Tele-care, e.g. remote health care and specialist
consultation, remote monitoring etc.
› Call center support
› Collaborative work, e.g. a shared whiteboard or other
collaborative editing systems etc.
© Ericsson AB 2010 | Page 6

7. Merge conflicts are resolved
› All clients (and servers) DSM SW contains predefined rules
how to resolve conflicts
“Adjust” or transform
incoming operation to
match local changes
© Ericsson AB 2010 | Page 7

8. JavaScript API
› Simple and easy to use to API
// get a replica of hash://simpleTest
var hash = memCtrl.get(“hash://simpleTest”);
// update the web page when the replica is cloned
hash.onReady = function () {
document.getElementById(“myTextfield”).value = hash.get(“myKey”);
};
// handle changes to the replica
hash.onUpdate = function (op) {
document.getElementById(“myTextfield”).value = op.value;
};
// update the local replica
hash.set(“myKey”, “myValue”);
// send the operation to all other replica clients in the background
hash.submit();
© Ericsson AB 2010 | Page 8

9. Example applications
Shared Whiteboards Collaborative Workspaces
Shared JavaScript Apps, e.g. a Shared Map Widget
© Ericsson AB 2010 | Page 9

10. © Ericsson AB 2010 | Page 10