F RANCI S CO J.
GAL AN
AND
AHME D
RI V E RAS
UNI V E RS I T Y
OF
S E V I L L E
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
PROLE 2013 (
MADRID
)
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
CONTENT
1
.
Purpose
2
.
Conceptualization
3
.
Formalization
4
.
Service
matchmaking
5
.
Conclusions
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
PURPOSE
To
formalize
a
class
of
s
emantic
web
services
(SWS)
based
on
the
concept
of
executional
entailment
.
The
formalization
(
1
)
integrates
functional
and
procedural
aspects
,
(
2
)
facilitates
the
dynamic
integration
of
SWSs
with
databases
and
(
3
)
solves
the
problem
of
service
matchmaking
in
an
effective
way
.
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
CONCEPTUALIZATION
•
State
=
set
of
properties
which
are
true
in
the
system
under
consideration
.
•
Data
invariant
=
set
of
constraints
which
must
satisfy
any
possible
state
in
the
life
of
a
system
.
•
Canonical
state
=
prototypical
state
.
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
CONCEPTUALIZATION
•
S
ervice
request
=
outputs
or
effects
a
web
client
want
to
achieve
by
executing
a
hypothetical
service
.
•
S
emantic
web
service
(SWS)
=
specification
of
a
service
by
a
set
of
possible
sequences
of
states
.
•
Canonical
execution
=
prototypical
execution
of
a
semantic
web
service
.
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
CONCEPTUALIZATION
•
It
is
important
to
remark
:
•
By
state
,
we
mean
an
abstraction
of
a
(real)
state
in
the
execution
of
a
service
.
•
By
execution
of
a
SWS,
we
mean
an
abstraction
of
a
(real)
execution
of
a
service
.
•
The
execution
of
a
SWS
≠
choreography
(i
.
e
.
interaction
with
the
client
in
order
to
consume
the
service
)
.
•
The
execution
of
a
SWS
≠
orchestration
(i
.
e
.
interaction
with
other
sevices
in
order
to
implement
the
functionality
of
the
service
)
.
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
CONCEPTUALIZATION
.
EXAMPLES
•
Service
request
(
generic
)
:
//
Buy
a
product
in
stock
with
delivery
before
invoicing
Service
r
equest
:
buy
(
p,c
)
{
Pre
:
product
p
is
in
stock
}
{
Int
1
:
product
p
is
delivered
to
customer
c
}
{
Post
:
product
p
is
delivered
to
customer
c
and
an
invoice
is
issued
}
Service
requests
(concrete)
:
//
Someone
want
to
buy
a
PC
with
delivery
before
invoicing
=
buy
(
PC,c
)
//
JN
want
to
buy
a
PC
with
delivery
before
invoicing
=
buy
(PC,JN)
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
CONCEPTUALIZATION
.
EXAMPLES
•
Semantic
web
service
:
//
Sell
a
product
in
stock
to
a
customer
with
delivery
before
invoicing
Service
:
sell
(
p,c
)
{
Pre
:
product
p
is
in
stock
}
{
Transaction
:
add
customer
c,
deliver
product
p
to
customer
c,
issue
an
invoice
and
consider
p
as
a
sold
product
{
Post
:
product
p
is
sold
to
customer
c,
p
is
delivered
to
c
and
an
invoice
is
issued
to
formalize
the
selling
of
p
to
c}
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
CONCEPTUALIZATION
.
EXAMPLES
Data
i
nvariant
:
//
For
every
sold
product
must
exist
a
customer
,
a
delivery
and
an
invoice
.
//
E
very
product
which
has
been
delivered
to
a
customer
can
not
be
in
//
stock
.
//
Customers
and
products
are
disjoint
sets
of
individuals
.
//
…
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
CONCEPTUALIZATION
.
EXAMPLES
State
:
PC
is
a
product
in
stock
(PC
is
a
concrete
individual)
.
Canonical
State
:
p
is
a
product
in
stock
(
p
is
a
protoypical
individual)
.
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
CONCEPTUALIZATION
.
EXAMPLES
Execution
:
state
1
:
PC
is
a
product
in
stock,TV
is
a
product
,
RB
is
a
customer
.
state
2
:
PC
is
a
product
in
stock
,
TV
is
a
product
,
JN
is
a
customer
,
RB
is
a
customer
.
state
3
:
PC
is
delivered
to
JN,
TV
is
a
product
,
RB
is
a
customer
.
state
4
:
product
PC
is
delivered
to
JN,
an
invoice
is
issued
to
JN
in
order
to
formalize
the
selling
of
PC,
TV
is
a
product
,
RB
is
a
customer
.
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
CONCEPTUALIZATION
.
EXAMPLES
Canonical
execution
:
state
1
:
p
is
a
product
in
stock
.
state
2
:
p
is
a
product
in
stock,
c
is
a
customer
.
state
3
:
p
is
a
product
in
stock,
c
is
a
customer
,
p
is
delivered
to
c
.
state
4
:
p
is
a
product
in
stock,
c
is
a
customer
,
p
is
delivered
to
c,
an
invoice
is
issued
in
order
to
formalize
the
selling
of
p
to
c
.
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
FORMALISM
state
:
a
set
of
ground
atoms
.
e
.
g
.
state
=
{
product
(PC),
stock
(PC)
}
canonical
state
:
a
set
of
atoms
with
labelled
nulls
,
e
.
g
.
state
=
{
product
(
p
),
stock
(
p
)
}
being
p
a
labelled
null
(
protoypical
individual)
.
A
formula
Y
(X,Y
)
where
is
a
conjunction
of
atoms
can
be
translated
to
a
canonical
state
by
replacing
each
variable
in
Y
(X,Y)
by
a
labelled
null
.
eg
.
canonical(
s(
supplies
(
s,p
)
product
(p
)))
{
supplies
(
s
,
p
),
product
(
p
)}
.
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
FORMALISM
Similarity
between
canonical
state
and
state
:
Given
a
canonical
state
s
1
and
a
(concrete)
state
s
2
,
we
say
that
s
2
is
similar
to
s
1
,
s
1
s
2
,
iff
there
is
a
substitution
such
that
s
1
s
2
.
e
.
g
.:
canonical
state
:
s
1
=
{
product
(
p
),
stock
(
p
)
}
state
:
s
2
=
{
product
(PC),
stock
(PC),
product
(TV),
customer
(RB)
}
s
1
s
2
with
=
{
p
/PC
}
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
FORMALISM
Data
invariant
:
a
(
finite
)
set
of
formulas
of
the
form
X(
(X)
Y
(X,Y))
or
X(
(X)
false)
inv
1
:
//
For
every
sold
product
must
exist
a
customer
,
a
delivery
and
an
invoice
.
p(
product
(p)
sold
(p)
c(
customer
(c)
delivery
(
p,c
)
invoice
(
p,c
))
//
Every
product
which
is
delivered
can
not
be
in
stock
.
p,c
(
product
(p)
delivery
(
p,c
)
stock(p)
false
)
//
Customers
and
products
are
disjoint
sets
of
individuals
.
p,c
(
product
(p)
delivery
(
p,c
)
stock(p)
false
)
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
FORMALISM
E
xecution
:
(
finite
)
sequence
of
states
satisfying
an
invariant
.
It
is
denoted
as
<state
1
,
…
,
state
n
>
inv
e
.
g
.
<s
1
,s
2
,s
3
,s
4
>
inv
1
,
being
s
1
=
{
product
(PC),
stock
(PC),
product
(TV),
customer
(RB)
}
s
2
=
{
product
(PC),
stock
(PC),
customer
(JN),
product
(TV),
customer
(RB)
}
s
3
=
{
product
(PC),
delivery
(PC,JN),
customer
(JN),
product
(TV),
customer
(RB)
}
s
4
=
{
product
(PC
),
delivery
(PC,JN),
customer
(JN),
invoice
(PC,JN),
sold
(PC),
product
(TV),
customer
(RB)
}
Notational
conventions
:
<
state
1
, …
>
inv
denotes
an
execution
which
starts
from
state
1
.
<…,
state
n
>
inv
denotes
an
execution
which
ends
in
state
n
.
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
FORMALISM
C
anonical
execution
:
execution
composed
of canonical
states
only
.
e.g
.:
<state
1
,state
2
,state
3
,state
4
>
inv1
,
where
state
1
=
{
product
(
p
),
stock
(
p
)
}
state
2
=
{
product
(
p
),
stock
(
p
),
customer
(
c
)
}
state
3
=
{
product
(
p
)
,
customer
(
c
),
delivery
(
p
,
c
)
}
state
4
=
{
product
(
p
)
,
customer
(
c
),
delivery
(
p
,
c
),
invoice
(
p
,
c
),
sold
(
p
)
}
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
FORMALISM
Given
a
canonical
execution
e
1
and
an
execution
e
2
,
we
say
that
e
2
is
similar
to
e
1
,
e
1
e
2
,
iff
|
e
1
|=|
e
2
|
and
there
is
a
substitution
such
that
,
for
each
s
i
in
e
1
and
t
i
in
e
2
,
s
i
t
i
.
E
.
g
.
:
e
1
e
2
with
={
p
/
PC,
c
/JN}
and
being
e
2
:
s
1
=
{
product
(PC
),
stock
(PC),
product
(TV),
customer
(RB)
}
s
2
=
{
product
(PC),
stock
(PC),
customer
(JN),
product
(TV),
customer
(RB)
}
s
3
=
{
product
(PC),
delivery
(PC,JN),
customer
(JN),
product
(TV),
customer
(RB)
}
s
4
=
{
product
(PC),
delivery
(PC,JN),
customer
(JN),
invoice
(PC,JN),
sold
(PC
),
product
(TV),
customer
(RB)
}
e
1
:
state
1
=
{
product
(
p
),
stock
(
p
)
}
state
2
=
{
product
(
p
),
stock
(
p
),
customer
(
c
)
}
state
3
=
{
product
(
p
)
,
customer
(
c
),
delivery
(
p
,
c
)
}
state
4
=
{
product
(
p
)
,
customer
(
c
),
delivery
(
p
,
c
),
invoice
(
p
,
c
),
sold
(
p
)
}
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
FORMALISM
Transaction
:
a
set
of
formulas
of
the
form
:
r(X)
Y(
(X,Y))
where
r
is
a
relation
symbol
and
a
formula
recursively
written
from
the
following
elements
:
(a)
primitive
consult
(
consult
),
(b)
primitive
update
(
add
,
del
),
(c)
(
restricted
)
paralell
conjunction
(
),
(d)
serial
conjunction
(
),
(e)
(
restricted
)
transaction
invocation
,
(f)
(
restricted
)
existential
quantification
(
)
and
(h)
negation
(
)
.
e
.
g
.
productInStock
(p)
consult
(
product
(p))
sell
2
(
p,c
)
productInStock
(p)
s(
consult
(
provider
(s))
(
add
(
provision
(
p,s
))
add
(stock(p)
)
)
sell
1
(
p,c
))
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
FORMALISM
The
semantics
of
a
transaction
is
formalized
by
executional
entailments
of
form
<state
1
,
…
,
state
n
>
inv
|=
.
<
state
>
inv
|=
consult
(r(C))
iff
r(C)
state
.
<
state
>
inv
|=
consult
(
r(X))
iff
there
is
C
such
that
r(C)
state
.
r(C
)
state
1
<state
1
,state
2
>
inv
|=
del(r(C
))
iff
state
2
=
state
1
–
{r(C)}
.
r(C)
state
<
state
>
inv
|=
del(r(C))
r(C
)
state
1
<
state
1
,
state
2
>
inv
|=
add
(r(C
))
iff
state
2
=
state
1
{r(C)}
.
r(C)
state
<
state
>
inv
|=
add
(r(C
))
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
FORMALISM
<state
1
,
…
,
state
n+
1
>
inv
|=
1
…
n
iff
<
state
1
,
state
2
>
inv
|=
1
and
<
state
2
,
…
,
state
n+
1
>
inv
|=
2
…
n
<
state
1
,state
n+
1
>
inv
|=
1
…
n
iff
for
every
serial
conjunction
of
1
,
…
,
n
,
,
we
have
that
<
state
1
,
…
>
inv
|=
and
<
…
,
state
n+
1
>
inv
|=
<state
1
,
…
,
state
n
>
inv
|=
r(C)
iff
r(X
)
Y(
(X,Y
))
and
<state
1
,… ,
state
n
>
inv
|=
Y(
(C,Y
))
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
FORMALISM
<
state
1
,
…
,
state
n
>
inv
|=
X(
(
X))
iff
<
state
1
,
…
,
state
n
>
inv
|=
(C)
where
C
satisfies
the
safeness
condition
(C
is
computed
by
a
consult
)
.
<state
1
,
…
,
state
n
>
inv
|=
iff
<
state
1
,
…
,
state
n
>
inv
|
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
FORMALISM
Service
request
:
sequence
of
formulas
{
Pre
}
{
Int
1
},
…
,
{
Int
n
}
{
Post
}
w
here
each
formula
is
of
the
form
Y
(X,Y
),
being
is
a
conjunction
of
atoms
.
e
.
g
.
//
Buy
a
product
in
stock
with
delivery
before
invoincing
Service
r
equest
:
buy
(
p,c
)
{
Pre
:
product
(p)
stock(p)}
{
Int
1
:
product
(p)
customer
(c)
delivery
(
p,c
)}
{
Post
:
product
(p)
customer
(c)
delivery
(
p,c
)
invoice
(
p,c
)}
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
FORMALISM
Service
request
:
g
{
Pre
}
{
Int
1
}
…
{
Int
J
}
{
Post
}
SEM(g)
=
the
canonical
execution
of
g
+
all
executions
similar
to
the
canonical
one
.
(
the
canonical
execution
of
g)
state
1
=
canonical(
Pre),
state
2
=
canonical(
Int
1
),
…
state
J+
1
=
canonical(
Int
J
)
,
state
J+
2
=canonical(
Post
)
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
FORMALISM
•
Semantic
web
s
ervice
:
pre/post
specification
extended
with
a
transaction
of
the
form
r
1
,
…
,
r
n
where
precondition
and
postcondition
are
formulas
of
the
form
Y(
(
X,Y))
and
each
i
,
with
i=
1
..
n,
is
a
transactional
formula
.
•
e
.
g
.:
//
Sell
a
product
in
stock
with
delivery
before
invoincing
•
Service
:
sell
1
(
p,c
)
{
Pre
:
product
(p)
and
stock(p)}
{
Transaction
:
sell
1
(
p,c
)
慤
(
捵獴c浥m
⡣⤩
(
add
(
delivery
(
p,c
))
del(stock(p)))
(
add
(
invoice
(
p,c
))
del(
sold
(p
)))
{
Post
:
product
(p)
sold
(p)
customer
(c)
delivery
(
p,c
)
invoice
(
p,c
)}
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
FORMALISM
Service
:
r
{
Pre
}
{
Transaction
:
r
1
,
…
,
r
k
}
{
Post
}
SEM(r)
=
k
canonical
executions
of
r
+
all
executions
similar
to
some
canonical
execution
of
r
such
that
<
state
1
,
…
,
state
n
>
inv
|=
j
,
with
j=
1
..
k,
such
that
state
1
|=
Pre
and
state
n
|=
Post
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
SERVICE
MATCHMAKING
It
is
the
mechanism
which
maps
appropriate
SWSs
to
service
requests
.
We
propose
a
matchmaking
method
based
on
two
phases
:
(
phase
1
)
p
rototypical
matchmaking
and
(
phase
2
)
concrete
matchmaking
.
The
purpose
of
the
prototypical
matchmaking
is
to
select
those
SWSs
which
may
satisfy
the
service
request
.
This
selection
is
based
on
canonical
executions
.
The
purpose
of
the
concrete
matchmaking
is
to
select
those
SWSs
which
can
satisfy
the
service
request
.
This
selection
is
based
on
(concrete)
executions
.
If
every
canonical
state
in
a
service
request
is
included
in
an
state
of
the
canonical
execution
of
the
SWS
then
we
can
conclude
that
the
SWS
may
satisfy
the
service
request
.
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
PROTOTYPICAL
SERVICE
MATCHMAKING
In
order
to
know
which
SWSs
may
satisfy
a
service
request
,
we
propose
the
construction
of
a
matrix
in
order
to
compare
the
canonical
execution
of
the
service
request
with
the
canonical
execution
of
the
SWS
.
As
we
can
see
,
every
canonical
state
in
the
service
request
is
contaned
in
some
state
of
the
canonical
execution
of
the
SWS
.
Therefore
,
we
can
conclude
that
the
SWS
may
satisfy
the
service
request
.
sell
buy
state
1
state
2
state
3
state
4
state
5
state
1
state
2
state
3
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
CONCRETE
SERVICE
MATCHMAKING
The
second
phase
of
the
matchmaking
focuses
on
the
selection
of
those
SWSs
which
can
satisfy
the
service
request
.
A
SWS
can
satisfy
a
service
request
if
it
can
develop
some
execution
similar
to
the
canonical
execution
of
the
service
request
.
Problem
:
the
construction
of
(concrete)
executions
are
expensive
because
we
have
to
access
to
the
web
for
extracting
the
current
state
of
the
system
.
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
CONCRETE
SERVICE
MATCHMAKING
We
assume
that
the
execution
of
a
SWS
does
not
affect
the
whole
state
of
the
system
.
Therefore
,
we
propose
to
access
to
the
web
for
extracting
the
affected
substate
only
.
To
check
an
invariant
is
usually
an
expensive
task
.
A
way
to
palliate
this
cost
is
by
following
a
solution
inspired
by
the
RETE
algorithm
.
Due
to
the
form
of
the
rules
in
an
invariant
,
we
must
only
check
those
rules
whose
antecedents
are
satisfied
in
each
state
of
the
execution
of
the
SWS
.
X(
(X)
Y
(X,Y
))
or
X(
(X)
false)
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
CONCRETE
SERVICE
MATCHMAKING
Suppose
that
a
client
want
to
achieve
the
service
request
buy
(PC,JN)
and
the
prototypical
matchmaking
has
selected
buy
(
p,c
)
as
a
SWS
which
may
satisfy
it
.
We
access
to
the
web
in
order
to
extract
the
current
state
of
the
system
but
restricted
to
the
substate
affected
by
the
execution
of
buy
(PC,JN)
.
(
scenario
1
)
state
1
=
{
product
(PC),
customer
(JN),
delivery
(PC,JN)
}
The
precondition
of
buy
(PC,JN)
is
{
product
(PC),
stock(PC)
}
As
we
can
verify
,
state
1
|
Pre
(
conclusion
:
service
matchmaking
fails
)
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
CONCRETE
SERVICE
MATCHMAKING
(
scenario
2
)
state
1
=
{
product
(PC),
customer
(JN),
stock(PC)
}
The
execution
of
,
the
transaction
in
buy
,
can
begin
from
state
1
because
state
1
|=
Pre
Let
<
state
1
,
state
2
,
state
3
,
state
4
>
be
the
execution
of
buy
(PC,JN)
,
being
state
2
=
{
product
(PC),
stock
(PC),
customer
(JN
)
}
state
3
=
{
product
(PC),
delivery
(PC,JN),
customer
(JN
)
}
state
4
=
{
product
(PC),
delivery
(PC,JN),
customer
(JN),
invoice
(PC,JN),
sold
(PC
)
}
As
we
can
verify
,
<
state
1
,
state
2
,
state
3
,
state
4
>
|=
and
state
4
|=
Post
(
conclusion
:
service
matchmaking
is
successful
)
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
CONCLUSIONS
We
have
proposed
a
formalism
for
specifying
and
executing
semantic
web
services
based
on
the
concept
of
executional
entailment
.
The
formalism
has
been
designed
having
in
mind
three
main
requirements
:
(
1
)
integration
of
functional
and
procedural
aspects
,
(
2
)
dynamic
integration
of
SWSs
with
databases
and
(
3
)
effective
solution
to
the
problem
of
service
matchmaking
.
F RANCI S CO J.
GAL AN
AND
AHME D
RI V E RAS
UNI V E RS I T Y
OF
S E V I L L E
SEMANTIC
WEB
SERVICES
IN A
TRANSACTIONAL
CONTEXT
PROLE 2013 (
MADRID
)
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