Information Technology Reference
In-Depth Information
-
Public view
: The provider of the service
P
may want to hide internal de-
tails of
P
, and describe only communication capabilities of
P
, i.e. an ab-
stract version of
P
. Technically, we search to derive a canonical
P
such that
Strat
(
P
)=
Strat
(
P
).
-
Operating guideline
:Arequesterof
P
is usually interested in all potential
strategies of
P
. Technically we search for a concise description of
Strat
(
P
).
A given requester service
R
rises a couple of questions at the broker's job,
including
-
E
cient search
: The broker may administer a large provider repository
P
of
provider services. Ecient algorithms are mandatory to find a service
P
∈P
that is compatible with
R
. Such algorithms of course depend on the kind of
information available to the broker about both
R
and
P
,aswellasonthe
organization of
.
-
Adaption
: For a given provider service
P
, the composition
P
P
R
may only
be “almost reasonable”. The broker may (automatically) construct a service
A
(“adapter”) such that
R
is a strategy for
P
⊕
⊕
A
. In technical terms we are
behind a solution
X
of the problem
R
∈
Strat
(
P
⊕
X
)
.
This is equivalent to the problem
(
R
⊕
X
)
∈
Strat
(
P
)
.
-
Composed adaption
: As a special case of the general adaption problem, an
adapter may be just some other service in the depository. Even more, the
broker may compose two or more services
P
1
,...,P
n
such that
P
1
⊕
...
⊕
P
n
is compatible to
R
. Formulated differently, the repository
R
may be virtually
extended by the n-fold composition of all its services.
A concrete modeling technique for services should provide ecient algorithms
to answer the above questions and to construct corresponding services.
4S rv eN s
Above we compiled a number of requirements at a proper framework for the no-
tion of services. Here we strive for a more concrete, operational model that would
meet those requirements. To this end we suggest
open workflow nets
(
oWFN
)as
a staring point to model services. Before launching into details, we justify and
motivate this approach.
4.1
The Motivation for Open Workflow Nets
As outlined in Sect. 2.2 already, the essential components of a service are its
interface and its internal control. Here we stick to those two aspects:
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