An extension of OCL for expressing uncertainty in integrity constraints
UML diagrams can be annotated with OCL (Object Constraint Language) constraints that describe the business logic and the integrity constraints of the system being designed. Nevertheless, sometimes designers are uncertain about how these constraints should be defined. Maybe they don't have enough information, maybe there are alternative definitions or maybe they want to postpone the decision until a later stage of the design.
This package provides an extension of the Object Constraint Language for expressing uncertainty within an integrity constraint. This extension augments OCL with primitives for describing alternatives and unknowns within OCL expressions.
Examples of the syntax for "Uncertain OCL":
- A constraint that may or may not become part of the specification
[? <constraint> ]
- A subexpression that may have one of many alternative values
[ <expression>, ..., <expression> ]
- A subexpresion whose value is undecided or not specified at this point
unknown
- A numeric constant that may take any value within a given range
<value>..<value>
The directory examples/ includes several samples of uncertain OCL invariants.
The tool receives a set of uncertain constraints and produces the list of
concrete realizations of the OCL constraints, i.e., considering all potential
alternative ways to define the OCL invariants. For instance, an invariant
with an uncertain constant [2..5] will produce four variants of the specification,
each with a different invariant include a different concrete value for the constant.
The tool is implemented in Java and uses JFlex and CUP (included in the distribution) to parse the input.
The scripts compile.shand execute.sh can be used to compile and execute
the tool. The tool reads the uncertain constraints from the standard input
and emits the concrete OCL constraints to the standard output.
This tool is part of joint work by Loli Burgueño, Jordi Cabot and Robert Clarisó on dealing with uncertainty in OCL specifications.
You can contact the authors at <rclariso AT uoc.edu>.