Information Technology Reference
In-Depth Information
Definition 3.
Requirements database:
A requirements database, denoted
Δ
is the set
of all information elicited or otherwise acquired during the
RE
of a system-to-be.
Remark 1.
Since
Δ
should include all information elicited or otherwise acquired in
RE
, it should include all instances of domain assumptions (i.e. invariants in the appli-
cation domain), goals, softgoals, quality constraints, and tasks that we elicited, found
through refinement or otherwise identified during
RE
. One can view
Δ
as a repository
of information that is usually found in what is informally referred to as a “require-
ments model”. The notation used in the definition of the requirements problem, note
that
Δ
=
K
∪
T
∪
G
∪
Q
∪
S
.
Remark 2.
Below, we will use the term
requirement
to abbreviate “member of the re-
quirements database
Δ
”. I.e., we will call every member of
Δ
a requirement.
To get to the definition of the
runtime requirements adaptation problem
, we start intro-
ducing the
Context
concept. In [15], we discussed how this definition relates to existing
conceptions and use of
Context
in the AI and RE literatures (e.g., [12,6,20,1]).
Definition 4.
Context:
An instance
C
of the
Context
concept is a set of information that
is presupposed by the stakeholders to hold when they communicate particular require-
ments. We say that every requirement depends on one or more contexts to say that the
requirement would not be retracted by the stakeholders in every one of these contexts.
Firstly, we need a language to write this information that is presupposed, and is thereby
in the set of information that we call a particular context. We develop that language be-
low. Secondly, the dependence of a requirement on a context means that every require-
ment is specific to one or more contexts, and thus, requirements need to be annotated by
contexts, which begs additional questions on how the engineer comes to determine con-
texts. At this point, we revise the Techne language to allow information that is included
in contexts. This results in adding one more sort.
Definition 5.
Techne for SAS:
The language
L
SAS
is a finite set of expressions, in
∈L
SAS
satisfies the following
BNF
specification
2
:
which every expression
φ
x
::=
(
p
)
|
(
p
)
|
(
p
)
|
(
p
)
|
(
p
)
(4.1)
k
g
q
s
t
q
::=
(
p
)
(4.2)
c
w
::=
x
|
q
(4.3)
n
n
y
::=
w
i
→
w
|
w
i
→⊥
(4.4)
i
=1
i
=1
φ
::=
w
|
(
y
)
|
(
y
)
(4.5)
k
c
Remark 3.
We used (indexed/primed p, q, r) as an arbitrary atomic statement, every
φ
an arbitrary complex statement, and every x an arbitrary label to represent Techne
labeled propositions i.e. domain assumption (
k
(p)), a goal (
g
(p)), etc., to distinguish
from these basic labeled propositions the context propositions (i.e., propositions about
2
In BNF: “
::=
” reads “defines”; “
|
” reads “or”.
