Value Assignment Alternatives 

Use

Value assignment alternatives are needed for setting characteristic values.

You define these when you set up your table structure. A value assignment alternative describes which table fields are key fields and which table fields are data fields. Key fields are used to find a table line whose data fields can be used to infer values.

In the following table, characteristic MODEL is defined as a key field to infer values for characteristics COLOR and LENGTH.

Characteristics

Value assignment alternatives

MODEL

X

Color

  

Length

  

 

Features

Value Assignment Alternatives in Procedures (Actions)

You can only define one value assignment alternative for procedures (actions). Once the table has been used in a procedure (action) with Released status, you can no longer change the first value assignment alternative.

Value Assignment Alternatives in Constraints

Setting Values

In constraints, you can define several characteristics for which the constraint sets values. To set these values, value assignment alternatives must be maintained to allow correct access.

OBJECTS:

B is_a (300) Bike where MOD = Model; Typ = Bike_type; FH = Frame_height.

RESTRICTIONS:

(MODEL = MOD, Bike_type = Typ, T_Frame_height = FH).

INFERENCES:

MOD, TYP, FH.

This constraint is for setting values for all three characteristics, so you need to define three value assignment alternatives:

Characteristics

A1

A2

A3

MODEL

X

    

BIKE_TYPE

  

X

  

T_FRAME_HEIGHT

    

X

 

Once the table has been used in a constraint with ‘ Released’ status, you can no longer change existing value assignment alternatives. You can only create new value assignment alternatives for the table.

You cannot define a new value assignment alternative that is a subset of an existing value assignment alternative.

Restricting Values

You do not need to define value assignment alternatives when you use tables in constraints to restrict allowed values.

Unique Value

The key fields must set one value only, not two or more.

Table T1

MODEL

COLOR

LENGTH

A

red

100

A

blue

100

B

red

200

C

red

50

 

If the value assigned to MODEL is ‘A’, a single value cannot be inferred for COLOR. Characteristic COLOR can have either the value ‘red’ or the value ‘blue’. For this reason, a value cannot be set.