SLIDE 1
A Formal Model and Composition Language for Context-Aware Service Protocols
A Formal Model and Composition Language for Context-Aware Service Protocols Introduction
A Formal Model and Composition Language for Context-Aware Service - - PowerPoint PPT Presentation
A Formal Model and Composition Language for Context-Aware Service - - PowerPoint PPT Presentation
A Formal Model and Composition Language for Context-Aware Service Protocols A Formal Model and Composition Language for Context-Aware Service Protocols Javier Cubo, Carlos Canal, Ernesto Pimentel, Gwen Sala un University of M alaga, Spain
SLIDE 2
SLIDE 3
A Formal Model and Composition Language for Context-Aware Service Protocols Definitions Values, Types, Operators
Values, Types, Operators
◮ Let Type(∋ t) be a set of types. For a given type t ∈ Type,
we write Valt for the set of possible values for t. We write Val =
t∈Type Valt. ◮ Let Op(∋ f ) be a set of operators. An operator signature Σ
- ver Op is a mapping Σ ∈ Op → Type+ × Type defining the
types for each of the operators allowed in expressions.
◮ Let x ∈ X be a set of variables. Then the set of valid
expressions of signature Σ over X is written Σ(X).
SLIDE 4
A Formal Model and Composition Language for Context-Aware Service Protocols Definitions Contexts
Contexts
◮ A context attribute A ∈ A is a string. Examples are
language, temperature, etc.
◮ A context signature T is a mapping
T : A → Type × Bool × Bool, with T(A) = (tA, sA, pA), where
◮ tA is the type of A; ◮ sA determines if A is static (true) or dynamic; ◮ pA determines if A is public (true) or private.
◮ A context C of type T is a mapping C : A → Val with
C(A) ∈ ValtA, as above.
SLIDE 5
A Formal Model and Composition Language for Context-Aware Service Protocols Definitions Context-Aware Transition Systems
Context-Aware Transition Systems
◮ A context-aware label ℓ is one of:
◮ τ
(internal action);
◮ ?(B, a, (x1, . . . , xn))
(reception of message);
◮ !(B, a, (E1, . . . , En))
(emission of message);
where B means Boolean expression and a is a message name.
◮ An atomic context-aware protocol P is a 6-tuple
(p, L, S, sI, SF, φ) where:
◮ p is the name of the protocol; ◮ L is a set of transition labels, as above; ◮ S is a set of states; ◮ sI is the initial state; ◮ SF is the set of correct final states; ◮ φ : S × L → S is a transition function.
SLIDE 6
A Formal Model and Composition Language for Context-Aware Service Protocols Definitions Composing Context-Aware Protocols
Composing Context-Aware Protocols
Context-aware protocols can be built up through expressions: P ::= Patomic | P.P | P + P | P D P where D is a data dependency of the form (p1, ℓ1) < (p2, ℓ2), implying that label ℓ1 in protocol p1 must be executed before label ℓ2 in protocol p2.
SLIDE 7
A Formal Model and Composition Language for Context-Aware Service Protocols Semantics Multiple protocols
Operational semantics of multiple protocols
si, Ei a!E → s′
i, Ei
sj, Ej a?x → s′
j, Ej
i, j ∈ 1..n i = j E′
j = Ej †
- x → [
[E] ]Ej
- . . . , si, Ei, . . . sj, Ej, . . .
a!E →
- . . . , s′
i, Ei, . . . s′ j, E′ j, . . .
- si, Ei τ
→ s′
i, Ei
i ∈ 1..n
- . . . , si, Ei, . . .
τ →
- . . . , s′
i, Ei, . . .
SLIDE 8
A Formal Model and Composition Language for Context-Aware Service Protocols Semantics Protocol composition
Operational semantics of composition language
s1, E1
ℓ1
→ s′
1, E1
- (p1, ℓ1) < (p2, ℓ2)
- ∈ D
¬in a loop(s1, ℓ1, φ1) D′ = remove
- (p1, ℓ1), D)
s1, E1 D s2, E2
ℓ1
→ s′
1, E1 D′ s2, E2
s1, E1
ℓ1
→ s′
1, E1
- (p1, ℓ1) < (p2, ℓ2)
- ∈ D
in a loop(s1, ℓ1, φ1) s1, E1 D s2, E2
ℓ1
→ s′
1, E1 D s2, E2
SLIDE 9
A Formal Model and Composition Language for Context-Aware Service Protocols Detecting dependencies
Detecting dependencies
◮ Algorithm 1: Find possible dependencies (semantic matching); ◮ User: Manually selects among the results of Algorithm 1; ◮ Algorithm 2: Transitive closure of the user’s choices.
SLIDE 10
A Formal Model and Composition Language for Context-Aware Service Protocols Concluding remarks