The Tallis Toolset
Expressions are text strings that are evaluated by the Tallis Engine in order to obtain information about the current state of a process-description during its enactment. The value of an expression is dependent on the state of the process.
Conditions are expressions that evaluate to truth-values; they occur in the several task attributes:
|State trigger||An expression that has to be true before the task can be executed (if false, the task remains dormant and waits for it to become true).|
|Precondition||An expression that has to be true before the task can be executed (if false, the task is discarded).|
|Cycle until||An expression defining the conditions under which a task stops cycling.|
|Abort Condition(Plans)||An expression defining the conditions under which a plan’s state is set to discarded.|
|An expression defining the conditions under which a plan’s state is set to completed.|
|An expression defining the conditions under which the argument applies.|
|An expression defining the conditions under which a candidate is recommended.|
Expressions can also evaluate to an integer, a real number, a text string, a set of integers, a set of real numbers, a set of text strings, or to the special value unknown.
An assertion is a text string describing values to be assigned to data items during the enactment of a process-description. Assertions occur in postconditions:
|Postcondition||An assertion that is executed when the task has been performed; often used to specify information that will be needed by subsequent tasks.|
PROforma functions can be integrated to create complex expressions.
|AND||Expression AND Expression||Returns TRUE if all its arguments are TRUE, returns FALSE if any argument is FALSE. If either operand evaluates to UNKNOWN then the resulting expression evaluates to FALSE.|
|OR||Expression OR Expression||Returns TRUE if any argument is TRUE, returns FALSE if all arguments are FALSE. If either operand evaluates to UNKNOWN then the resulting expression evaluates to FALSE.|
|NOT||not(Expression)||Returns TRUE for a FALSE argument and FASLE for a TRUE or UNKNOWN argument.|
|IF||if(Expression, value_if_true, value_if_false)||Returns one value if the specified Expression evaluates to TRUE and another value if it evaluates to FALSE.|
|isknown||isknown(Expression)||Returns FALSE if Expression is UNKNOWN, returns TRUE otherwise.|
|result_of||result_of(Decision: Single candidate selection)||Returns the decision’s committed candidate if a single candidate was committed; returns UNKNOWN otherwise.|
|result_set||result_set(Decision: Multi candidate selection)||Returns the decision’s set of committed candidates; returns UNKNOWN if no candidate were committed.|
|is_completed||is_completed(Task)||Returns TRUE if a Task is in the State, returns FALSE if a Task is not in the State.|
|netsupport||netsupport(Decision, Candidate)||Returns Net Support value for Candidate of Decision.|
|>||Number/TextString > Number/TextString||A real number may be compared with an integer but a text string may only be compared with another text string. If either of the operands of a comparison evaluates to UNKNOWN then the resulting expression evaluates to FALSE.|
|<||Number/TextString < Number/TextString|
|>=||Number/TextString >= Number/TextString|
|=<||Number/TextString =< Number/TextString|
|=||Number/TextString = Number/TextString|
|!=||Number/TextString != Number/TextString|
|+||Number + Number||If either of the operands of an arithmetic operator evaluates to UNKNOWN then the resulting expression also evaluates to UNKNOWN.|
|-||Number - Number|
|*||Number * Number|
|/||Number / Number|
|ln||ln(Number)||Returns the natural logarithm of a number|
|exp||exp(Number)||Returns e raised to the power of a given number|
|sin||sin(angle: radians)||Returns the sine of an angle.|
|cos||cos(angle: radians)||Returns the cosine of an angle.|
|tan||tan(angle: radians)||Returns the tangent of an angle.|
|asin||asin(number)||Returns the arcsine of a number in radians.|
|acos||acos(number)||Returns the arccosine of a number in radians.|
|atan||atan(number)||Returns the arctangent of a number in radians.|
|abs||abs(Number)||Returns the absolute value of a number.|
|random||random()||Returns a random number greater than or equal to 0 and less than 1.
Note: two occurrences of random() that are evaluated without an intervening change in engine state will return the same value. For instance, if a task has the precondition random() = random() then this precondition will always evaluate to true.
|Include(s)||Set includes Member||Returns TRUE if Set includes Member, returns FALSE if Set does not include Member. If either operand evaluates to UNKNOWN then the resulting expression evaluates to FALSE.
Note: Exp1 oneof Exp2 is equivalent to Exp2 includes Exp1
|oneof||Member oneof Set|
|nth||nth(n,Set)||Returns the nth Member in a Set, returns UNKNOWN if the Set does not have an nth Member.
nth(2,["fee","fi","fo","fum"]) evaluates to "fi"
nth(4,[2,3,5]) evaluates to unknown.
|count||count(Set)||Returns the number of Members in a Set.|
|max||max(Set)||Returns the largest value in a set of values.
Note: Text strings are compared lexicographically ignoring case, e.g., max(["bb","bbb","AAA"]) evaluates to "bbb".
|min||min(Set)||Returns the smallest value in a set of values.|
|sum||sum(Set)||Returns the sum of members of a Set.
sum evaluates to 0.
sum([1,1,2,3,5]) evaluates to 12.
|union||union(Set1,Set2)||Returns all Members of both Sets.
Note: Unlike a set theoretic union the PROforma union operator does not eliminate duplicates.
union([1,2+2,5],[5,2,1]) evaluates to [1,4,5,5,2,1].
|diff||diff(Set1,Set2)||Returns Members of Set1 that are not Members of Set2.
diff([1,2+2,5,6],[5,2,1]) evaluates to [4,6].
|intersect||intersect(Set1,Set2)||Returns Members of Set1 that are also Members of Set2.
intersect([1,2+2,5],[5,2,1]) evaluates to [1,5].
|Now||now()||Returns the current engine time.|
|completed_time||completed_time(Task)||Returns the “engine time” at which a Task last entered a State (or UNKNOWN if the Task has not entered the State).
If Task1 has a state trigger Now() – completed_time(Task2) > 1000 it wouldn’t start until 1 second (i.e. 1000 milliseconds) after Task2 has completed.
|# (concatenate)||TextString # TextString||Joins several text strings into one text string.
Example: the expression "more " # "beans" evaluates to the text string more beans.
|forever()||forever()||Always evaluates to FALSE. It is intended to be used as a cycle until condition for tasks that cycle forever.|
In this section you will find expression that are frequently used in preconditions, state triggers and postconditions.
Preconditions are typically used in combination with scheduling constraints. Different expressions are characteristic of preconditions, depending on the workflow pattern.
A point where, based on a decision, one of several tasks is chosen. Preconditions control task activation and typically have the following structure:
Result_of(Decision) = Candidate
A point where, based on a decision, a number of tasks are chosen. Preconditions control task activation and typically have the following structure:
Result_set(Decision) includes Candidate
If more than one candidate can trigger task activation, the expression can be structured as follows:
result_set(Decision) = [Candidate1, Candidate2, Candidate3]
A point where, based on workflow data, one or more of several tasks are chosen. Preconditions control task activation and typically have the following structure:
Data Item Comparison Operator Value
State triggers are commonly used in dataflow without scheduling constraints. They monitor state and the data changes in the process-description, and typically have the following structure:
Data Item Comparison Operator Value
or one of the following:
Assertions that typically take the form:
Data Item = Value
Data Item = if(Expression, value_if_true, value_if_false)
The Expression Editor is accessible from every field in the task properties window that contains an expression (e.g., State Trigger, Precondition, Cycle Until). To display it, click on the ellipsis (…) button to the right of the field.
The figure below is a screen capture of the Expression Editor:
Expressions are typed in the Condition field.
You can add functions to the Condition field by double-clicking the function buttons. Function buttons have two modes:
The placeholders and what they stand for:
You can add data items or data item values to the Condition field by double-clicking a selected item. The Range Values list displays the values of the selected data item.
You can add decisions or candidates to the Condition field by double-clicking a selected item. The Candidates list displays the candidates of the selected decision.