Fujitsu UDS/SQL V2.5 사용자 설명서
CODASYL model
General information
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U929-J-Z125-9-76
2.2 Data models
The UDS/SQL database system supports both the network model (CODASYL model) and
the relational model. It encompasses the principles and capabilities of both the CODASYL
and the relational models in a single system. UDS/SQL can be regarded as the implemen-
tation of a coexistence model of a database. The following sections briefly describe the
CODASYL model, the relational model, the relative merits of the two models, and the
coexistence model.
the relational model. It encompasses the principles and capabilities of both the CODASYL
and the relational models in a single system. UDS/SQL can be regarded as the implemen-
tation of a coexistence model of a database. The following sections briefly describe the
CODASYL model, the relational model, the relative merits of the two models, and the
coexistence model.
2.2.1
The CODASYL model
A major user demand is that database systems are compatible. The standardization of
database systems has thus been the goal of powerful user associations for many years.
The Conference on Data System Languages (CODASYL) has developed widely accepted
recommendations for the standardization of database systems. This association is already
well-known for its achievements in application portability thanks to its development of the
programming language COBOL.
database systems has thus been the goal of powerful user associations for many years.
The Conference on Data System Languages (CODASYL) has developed widely accepted
recommendations for the standardization of database systems. This association is already
well-known for its achievements in application portability thanks to its development of the
programming language COBOL.
CODASYL was constituted in 1959 by US producers and users, and, notably, with the
participation of the US Administration.
Since 1965, this association has concentrated partly on data organization and databases.
When the basic results of the different study groups were published, they described a
database concept which has been continually improved.
participation of the US Administration.
Since 1965, this association has concentrated partly on data organization and databases.
When the basic results of the different study groups were published, they described a
database concept which has been continually improved.
The CODASYL model provided the basis for the implementation of the UDS/SQL database
system.
system.
In the CODASYL model, a database contains not only records, but also the relationships
between the records. This is why it is also referred to as the network model.
between the records. This is why it is also referred to as the network model.
The following diagram (
) shows an example of a networked data structure, which is
represented by boxes and arrows. A box symbolizes a type of record. In this example, the
records that describe the suppliers are grouped together in the record type SUPPLIER. All
records of the given record type have the same structure. For each supplier, the SUPPLIER
record type contains a record which defines the name and the city of that supplier. NAME
and CITY are record elements names.
records that describe the suppliers are grouped together in the record type SUPPLIER. All
records of the given record type have the same structure. For each supplier, the SUPPLIER
record type contains a record which defines the name and the city of that supplier. NAME
and CITY are record elements names.
Another record type shown in
is the record type ARTICLE. The record types
ARTICLE and SUPPLIER are connected by an arrow, which indicates that a relationship
exists between the record types. Such relationships are referred to as set relationships or
simply sets.
exists between the record types. Such relationships are referred to as set relationships or
simply sets.