SIMSCRIPT II.5 Programming Language

Modelling Concepts
sioned as N.CITY BY N.COUNTY BY N.STATE. The third defines a four-dimensional array
dimensioned in a similar way. Compound entities are defined by statements of the form:
every compound entity name list has attribute name list
and owns set name list.
As in the case of individual entity definitions, has and owns clauses can appear in the same or different
statements. The word have can be used for has and own for owns. By definition, the individual
entities of which compound entities are composed must exist. If a compound entity MAN AND
WOMAN is declared, there must be an entity type MAN and an entity type WOMAN.
A compound entity name list consists of entity names that have either been declared previously in
every or include statements, or, by their presence in a compound entity declaration, are declared
as entities of the type specified in the current background condition, that is, by the last permanent
entities or temporary entities statement. Three kinds of compound entities are possible:
those composed exclusively of permanent entities; those composed exclusively of temporary
entities; and those composed of both permanent and temporary entities.
Members of sets owned by compound entities can be either permanent or temporary entities. Set
membership is declared as usual. Moreover, "compound sets" can have any of their six set attributes
deleted and be defined as FIFO, LIFO, or ranked. The following statements might appear in a
program in conjunction with the first declaration above:
temporary entities
every CHILD belongs to a FAMILY and has an AGE
define FAMILY as a set ranked by AGE
without N and M attributes
Attributes of compound entities and sets owned by compound entities are subscripted. Subscripting
takes place in the order in which compound entities are defined. Thus, in the statements:
let BANK.ACCOUNT(I,J) = 1000
file this CHILD in FAMILY(MAN,WOMAN)
the variables I and MAN can range from 1 to N.MAN, and the variables J and WOMAN can range from
1 to N.WOMAN. Compound entities cannot belong to sets. In fact, compound entities have no independent
existence, but rather define the existence of compound attributes, subscripted by the
named component entities.
Arrays are allocated to "permanent" compound entities when their individual entities are created.
They need not be created together, although they usually are. Given the declarations:
permanent entities
every MAN has a JOB and a SALARY
every WOMAN owns some INVESTMENTS
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