Dynamically EvolvingKlaim Nets

Lorenzo Bettinibettini@dsi.unifi.it

Joint work with

Michele Loreti, Rosario Pugliese

Dipartimento di Sistemi ed Informatica, Firenze

http://music.dsi.unifi.it

Dynamic Infrastructure It evolves over time:

New nodes can get connected Existing nodes can disconnect

Connections and disconnections can be temporary and unexpected

A connection can be established on the fly with wireless devices

Ad-hoc paths to services can be establish to enable communication among components

Dynamic Infrastructure The assumption that the underlying

network is always available may be too strong;

Permanent connection may not always be available;

The knowledge of the address of a remote host may be not sufficient to communicate with it;

Necessity of making Node Connectivity explicit in the language.

Communication Layer in Klaim is based on nodes’ location

knowledge, is influenced by:

Allocation environments; Tuple and Process distribution.

Connections and Disconnections

TS TSs1 s2

Two nodes are disconnected if one doesn’t know the locality of the other

Connections and Disconnections

TS TSs1 s2

s2

There is a (re)connection when one gets to know

about the other

Connections and Disconnections

TS TSs1 s2

Two nodes will be disconnected again when that knowledge is lost

s2

Node “Mobility”

TS TSs1 s2

TS

s3

s3s3

Node mobility corresponds to mobility of (knowledge of) links

If a process, that knows a node,

moves, then the known

node moves too.

s3

Clusters & SuperProcesses A Cluster is a collection of nodes There can be multiple clusters Two nodes can interact with each

other only if they stay in the same cluster

SuperProcesses are processes that: Can create new Clusters; Can add or remove their node to Clusters; Cannot move

New Actions Create a new cluster: newc(w) Add a node to a cluster: add(c) Remove a node from a cluster: rm(c)

Not indexed with a locality They act on the node they are

executed on.

sc2

s s

Example

c1newc(w)

add(c2)

rm(c1)

SyntaxN ::= s :: P c :: {s} N | N

P ::= nil out(et) act.P P | P act.P + act.P X A<…>

SP ::= P sact.SP SP | SP

act ::= out(t)@l in(t)@l read(t)@l eval(P)@l newloc(SP,u)

sact ::= add(c) rm(c) newc(w)

Connection Modes Tethered mode Disconnected mode Untethered mode

Tethered mode WAN connectivity is available Information can be accessed from

any point at any time

Idealized situation that takes place only for a limitedcomputers in a network.

Disconnected mode WAN connectivity is available Users can work offline When online a user works like in

Tethered Mode When a user goes online reconciliation

and/or notification can be needed.

Typical for a user that does not own a network access.The user works in isolation and, at some time, connectsto Internet (e.g. via a modem).

Untethered mode WAN connectivity is unavailable Local-area connectivity may still be

available Communication:

is enabled by wireless devices is limited to those devices that are in a

communication range

Usual form for a mobile user, that from time to time entersdifferent areas where connectivity is constrained (e.g. byfirewalls).

Tethered mode All nodes are in the same cluster

and there are no SuperProcesses.

Disconnected mode All nodes are in the same cluster Occasionally some node can be

removed and added

Untethered mode Multiple clusters are available Nodes can change cluster

Scenarios Location dependent connection Ad-hoc networking Disconnection

Location-dependent Connection A mechanical engineer visits a

plant in the Third World WAN connectivity is not available There is a single wireless access

point When connected engineer can

access plant’s resources (data and applications)

Location-dependent Connection

0101

Plant-access point

0101

add(cap

) Private area

cap

rm(cap)

cp

Ad hoc networking A team of experts meet in a site

where a new plant must be established

Experts can interact locally by using an ad hoc network, sharing data and resources

Occasionally connection to the headquarters might be needed to check additional information

Local area

Ad hoc networking

Head

qu

arte

rs H

ead

qu

art

ers

Local area

Disconnection A software engineer works in isolation At a given point she dials up and gets

reconnected to a virtual community server She downloads work updates She asks for help and goes offline

Later she reconnects to the virtual community: She contacts one of the connected experts She establishes a synchronous communication After acquiring enough information she logs off

Finally, when she ends her work, she logs on and uploads the artifacts

Disconnection

s2

0100

s2

c

add(c)rm(c)

add(c)rm(c)

add(c)

Remarks Proposed extensions can be

“expressed” in standard Klaim; Klaim’s Logical framework can be

automatically applied to extended Klaim;

Klaim’s Types for Access Control can be easily extended too.

Proposed extensions can be “expressed” in standard Klaim;

Klaim’s Logical framework can be automatically applied to extended Klaim;

Klaim’s Types for Access Control can be easily extended too.

Comparison with Ambients Clusters do not move Can intersect Represent a communication

ability, not necessarily an environment

Still locality-aware More similar to channels

Translation in standard Klaim A cluster c becomes a node sc

If s belongs to c then tuple (s) is in the TS of sc and (cluster, sc) in the TS of s

newc becomes newloc add(c) becomesout(self)@sc.out(cluster, sc)@self

rm(c) becomesin(self)@sc.in(cluster, sc)@self

Translation in standard Klaim Communication and migration

operations are translated into sequences of operations that first test for the presence of a cluster and then perform the operation

A counter should be used in order to exhaustively examine all the clusters to which a node belongs

Extending the implementation

Connecting to a Klava Nethostnet.dsi.unifi.it

$> java client2 hostnet.dsi.unifi.it 9999Connecting to hostnet.dsi.unifi.it:9999 ...Login as client2 ...Login successful!

$> java Klava.NetStarting Net on port 9999

150.217.14.14

Communication in Klava

Net

s1 s2

Extending the implementation

s1

s2

Net Net

s1 s2

Extending the implementation

s1

s2c1

c2

s3

c1

s1 s2

c2

s3

Future work Extend the implementation Apply the extensions to our

existing frameworks Merge with Structured Nets

Structured Nets Ordering relation on nodes (<): is-

parent-of Routing function (): the nodes

that have to be crossed to reach a site

System operations (sys(t)): to access and modify the structure of the net