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Mobile transaction models

Kangaroo transaction model (paper 4) Margaret H. Dunham, Abdelsalam Helal, Santosh

Balakrishnan: A Mobile Transaction Model That

Captures Both the Data and Movement Behavior,MONET 2(2), 1997, pp 149-162

Moflex transaction model (paper 5)

Kyong-I Ku, Yoo-Sung Kim: Moflex Transaction

Model for Mobile Heterogeneous Multidatabase

Systems, RIDE, 2000, pp 39-46 Paper 2 & 3

Analyzing mobile transaction models

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Discussion navigation


Why? How? Evaluation?

ACIDMobility

Disconnection

MotivationGoals

Challenges

Requirements

AssumptionsStructure

Protocols

Algorithm

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Kangaroo transaction model

A transaction model to Capture the movement behavior of transactions

In a multidatabase environment

Where mobile transactions do not originate and end at the

same site

Requirements Build on existing multidatabase systems and do not

duplicate support provided by source systems

Capture movement of mobile transaction and data access Move transaction control as mobile units move

Flexibiilty in terms of atomicity

Support long-lived transactions

Correctness criteria from ACID to unrestricted

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Reference model

Data access agent

Support data access from mobile transaction to source

systems

Forwarding transaction requests

Mobile transaction manager

Execution status, logging, checkpointing Uses, but does not maintain location information of the

mobile hosts

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Assumptions A mobile environment as anextension of a distributed

system

Links between nodes change dynamically

Target

Mobile heterogeneous and multidatabase system

Complete autonomy of the component DBMS and the various

multidatabase systems

Concepts

Open nested and split transactions

Transaction management function moves with the mobile

units (through the DAAs)

Avoiding message overhead

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Structure

Concepts Kangaroo transaction (KT)

Pouch, Equivalent KT

Joey transaction (JT) Unit of execution at one base station

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Design structure vs. execution structure

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Slow movement vs. fast movement structure

Empty Joey transaction?

Why?

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Processing modes Compensating and Split (default)

Compensating

Joey transaction vs. Component (local) DBMS

Abort of KT

When a JT fails Commit of KT

Number of active Joey is 0

Serializability

KT: no gurantee

JT sub-transactions: serializable in compensating mode

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Summary Consistency & Concurrency

Relies on underlying database

Database system model

Heterogeneous multidatabase

Mobility

Hand-off processes between MSS (via DAA)

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Analysing Kangaroo transaction model

Place of

execution

Compensable

transactionsConcurrency

handling

Mobility

support

Disconnection

support

Replication

support

Geographical

localization

Final state

Mobile

techniques

Physical

limitations

Particular

characteristics

Relating physical

aspects

Relating transaction

execution

Relating the models

adaptability

Relating implementation

issues

OK X X

MSS? OK OK

Cond. of

execution

X

X X

Connection X Start & end points

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Transaction definition Mobile transactions (KT) are initiated by mobile hosts

Transaction type

Open nested and Split

Execution model

Completed executed in wired network Execution at mobile host

Transaction request

Execution at wired network

Coordination and transaction execution

Operation mode Movement in connected mode

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ACID? None

Local DBMS

Mobility

Hand-off between MSS (through DAAs)

Disconnection None

M fl t ti d l

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Moflex transaction model

A transaction model to Support the management of mobility, heterogeneity and

flexibility

In the definition and execution of mobile transaction

Location dependent sub-transactions

Effective support hand-over (~ hand-off)

Heterogeneous multidatabase system

Logical integration of local database systems

Autonomous

M fl t ti d l hit t

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Moflex transaction model - architecture

Compare to [Mad+02],[Hir+01],[SRA04,[DHB]

M fl t ti d l

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Moflex transaction T is a 7-tuple M: set of sub-transactions

Compensable or non-compensable

S: success-dependencies in M

F: failure-dependencies in M

compensable or contingency?

: external-dependencies on M

P: time

Q: cost

L: location

H: hand-over control rules on M

J: acceptable join rules on M G: acceptable goal states of T

M fl t ti d l

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Execution states Tuple of states of each sub-transactions

Successful execution

Abort conditions

No subtransaction is executing

No more subtransaction can be scheduled

Current execution state is not equivalent to one of G

T(t1, t2, t3, tn)

X(x1, x2, x3, xn)

Xi:

N: not submitted for execution

E: being executed

S: successfully completed

F: failed

X ~ X G


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Hand-over control rules

Acceptable join rule

Join(): Automatic

User(): Manual


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Architecture

Analysing Moflex transaction model

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Place of

execution

Compensable

transactionsConcurrency

handling

Mobility

support

Disconnection

support

Replication

support

Geographical

localization

Final state

Mobile

techniques

Physical

limitations

Particular

characteristics

Relating physical

aspects

Relating transaction

execution

Relating the models

adaptability

Relating implementation

issues

OK X X

MSS? OK OK

Cond. of

execution

Connection Location

dependent

OK

OK OK

X


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Transaction definition Mobile hosts initiate the 7-tuple

Transaction type

Multi-transactions and location dependent transactions

Execution model

Completed executed in wired network Execution at mobile host

Definition of mobile transaction

Execution at wired network

Coordination and transaction execution

Operation mode Movement in connected mode


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ACID? None

Local DBMS

Mobility

Hand-off control rules

Location dependent sub-transactions Split operations

Disconnection

None

M bil t ti d l

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Kangaroo

Moflex


Transaction type

Execution model

Execution at mobile hostExecution at wired network

Operation mode

Transaction properties

ACID

Analyzing framework

Other issues

Structure mobility

design vs. execution states

Location dependent transactions

System architectureProtocols, e.g., commit, abort

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