Timed edit automaton is action sequence transformer which takes a sequence of actions as input and produces another sequence of actions according to the policy it implements. If the input action sequence obeys the policy then timed edit automaton produces same actions sequence or an equivalent action sequence. If the input action sequence does not obey the policy then the timed edit automaton produces modified action sequence. Timed edit automaton is suitable for implementing real-time transactional security property

1. Implementing Real-Time Transactional Security Property using
Timed Edit Automata
N.Rajamanickam and R.Nadarajan
PSG College of Technology, Coimbatore, India
Email: nrm@mca.psgtech.ac.in
http://dx.doi.org/10.1145/2523514.2523578
Abstract
Timed edit automaton is action sequence transformer which takes a sequence of
actions as input and produces another sequence of actions according to the policy
it implements. If the input action sequence obeys the policy then timed edit automaton produces same actions sequence or an equivalent action sequence. If the
input action sequence does not obey the policy then the timed edit automaton produces modified action sequence. Timed edit automaton is suitable for implementing
real-time transactional security property.
Operational Semantics
Delay Transitions
u ∈ I(q) u + d ∈ I(q)
(σ, q, u) − T E (σ, q, u + d)
→
d
Discrete Transitions
σ = ai : ti ; σ
δ(ai , q, g, u) = (b, q , r, u ) u ∈ g
u ∈ I(q) u ∈ I(q )
b
u ∈ I(q )
c
(σ, q, u) → T E (σ, q , u )
−
Timed Edit Automata
σ = a i : ti ; σ
δ(ai , q, g, u) = (null, q , r, u ) u ∈ g
u ∈ I(q) u ∈ I(q )
null
Q - countably infinite set of control locations
(TE-Insert)
(TE-Suppress)
(σ, q, u) − − T E (σ , q , u )
−→
δ(null, q, g, u) = (null, q , r, u ) u ∈ g
A - set of actions
(TE-Suppress-Insert)
(σ, q, u) → T E (σ , q , u )
−
δ(null, q, g, u) = (c, q , r, u ) u ∈ g
The timed edit automaton is a 6-tuple (Q, A, q0 , C, δ, I) where
(TE-Delay)
u ∈ I(q )
null
(TE-Null)
(σ, q, u) − − T E (σ, q , u )
−→
q0 - start control location
C - set of real valued clocks
δ : A∪{null}×Q×B(C)×U → A∪{null}×Q×2C ×U is deterministic transition
function
I : Q → B(C) assigns clock constraints to control locations
Here g ∈ B(C) is a clock constraint is called a guard. u denotes clock statuses, mapping from C to non negative real numbers. u ∈ g to mean that the clock values
denoted by u satisfy the guard g. u + d denotes the clock assignment that maps all x ∈ C to u(x) + d. [r → 0]u denotes the clock assignment that maps all clocks in r to
0 and agree with u for other clocks in C r where r ⊆ C.
Timed Market Policy
Here B(C) denotes set of clock constraints. U denotes set of all possible clock
statuses. null denotes no (input/output) action.
Transitions
TE-Delay is for the transition between two actions, if the timed edit automaton
is in the same control location.
TE-Suppress-Insert suppresses the current action ai and inserts the new action b
TE-Insert is a discrete transition without taking any input action.
TE-Suppress suppresses the current input action ai and inserts no input action.
TE-Null is a discrete transition without taking any input action and without
emitting any output action.
Conclusion
Our timed market polices is a real-time transactional security property. Real-time
transactional security property is a combination of security property, real time
property and transactional property. This timed market policy can be implemented
by using timed edit automaton. Timed edit automaton is a action sequence transformer which transforms the input actions sequence to another action sequence and
the output action sequence always obeys the policy.
Timed market policy enables an user to pay using two gateways for single transaction. First the user buys a service for the amount of n and then he/she pays a partial
payment p using gateway G1. If he/she pays the remaining amount n − p using gateway G2 within 60 seconds then the transaction will be allowed. If he/she try to pay
amount other than n − p or amount n − p is not been paid within 60 seconds then this transaction will be failed.