Cause-effect graph
Encyclopedia
In software testing
, a cause–effect graph is a directed graph
that maps a set of causes to a set of effects. The causes may be thought of as the input to the program, and the effects may be thought of as the output. Usually the graph shows the nodes representing the causes on the left side and the nodes representing the effects on the right side. There may be intermediate nodes in between that combine inputs using logical operators such as AND and OR.
Constraints may be added to the causes and effects. These are represented as edges labelled with the constraint symbol using a dashed line. For causes, valid constraint symbols are E (exclusive), O (one and only one), and I (at least one). The exclusive constraint states that both causes1 and cause2 cannot be true simultaneously. The Inclusive (at least one) constraint
states that at least one of the causes 1, 2 or 3 must be true. The OaOO (One and Only One) constraint states that only one of the causes 1, 2 or 3 can be true.
For effects, valid constraint symbols are R (Requires) and M (Mask). The Requires constraint states that if cause 1 is true, then cause 2 must be true, and it is impossible for 1 to be true and 2 to be false. The mask constraint states that if effect 1 is true then effect 2 is false. (Note that the mask constraint relates to the effects and not the causes like the other constraints.
The graph's direction is as follows:
Causes --> intermediate nodes --> Effects
The graph can always be rearranged so there is only one node between any input and any output. See conjunctive normal form
and disjunctive normal form
.
A cause–effect graph is useful for generating a reduced decision table
.
Software testing
Software testing is an investigation conducted to provide stakeholders with information about the quality of the product or service under test. Software testing can also provide an objective, independent view of the software to allow the business to appreciate and understand the risks of software...
, a cause–effect graph is a directed graph
Directed graph
A directed graph or digraph is a pair G= of:* a set V, whose elements are called vertices or nodes,...
that maps a set of causes to a set of effects. The causes may be thought of as the input to the program, and the effects may be thought of as the output. Usually the graph shows the nodes representing the causes on the left side and the nodes representing the effects on the right side. There may be intermediate nodes in between that combine inputs using logical operators such as AND and OR.
Constraints may be added to the causes and effects. These are represented as edges labelled with the constraint symbol using a dashed line. For causes, valid constraint symbols are E (exclusive), O (one and only one), and I (at least one). The exclusive constraint states that both causes1 and cause2 cannot be true simultaneously. The Inclusive (at least one) constraint
states that at least one of the causes 1, 2 or 3 must be true. The OaOO (One and Only One) constraint states that only one of the causes 1, 2 or 3 can be true.
For effects, valid constraint symbols are R (Requires) and M (Mask). The Requires constraint states that if cause 1 is true, then cause 2 must be true, and it is impossible for 1 to be true and 2 to be false. The mask constraint states that if effect 1 is true then effect 2 is false. (Note that the mask constraint relates to the effects and not the causes like the other constraints.
The graph's direction is as follows:
Causes --> intermediate nodes --> Effects
The graph can always be rearranged so there is only one node between any input and any output. See conjunctive normal form
Conjunctive normal form
In Boolean logic, a formula is in conjunctive normal form if it is a conjunction of clauses, where a clause is a disjunction of literals.As a normal form, it is useful in automated theorem proving...
and disjunctive normal form
Disjunctive normal form
In boolean logic, a disjunctive normal form is a standardization of a logical formula which is a disjunction of conjunctive clauses. As a normal form, it is useful in automated theorem proving. A logical formula is considered to be in DNF if and only if it is a disjunction of one or more...
.
A cause–effect graph is useful for generating a reduced decision table
Decision table
Decision tables are a precise yet compact way to model complicated logic.Decision tables, like flowcharts and if-then-else and switch-case statements, associate conditions with actions to perform, but in many cases do so in a more elegant way....
.