Dodatkowe przykłady dopasowywane są do haseł w zautomatyzowany sposób - nie gwarantujemy ich poprawności.
Simply described, a conceptual schema is the first step in organizing the data requirements.
Storage technology can change without affecting either the logical or the conceptual schema.
The seven steps of the conceptual schema design procedure are:
The table/column structure can change without (necessarily) affecting the conceptual schema.
Conceptual schema, a map of concepts and their relationships.
The use of conceptual schema has evolved to become a powerful communication tool with business users.
The conceptual schema describes all the data items and relationships between them, together with integrity constraints (later).
There is only one conceptual schema per database.
In contrast, the Entity Types define the conceptual schema of the data.
The set of facts instantiates the conceptual schema by assertion to describe one possible world.
It should be emphasised that the data model which we have called the conceptual schema was developed independently of both machine and software considerations.
With the proper technology, the resulting conceptual schema can be used to control transaction processing in a distributed database environment.
A conceptual schema specifies the kinds of facts or propositions that can be expressed using the model.
The conceptual schema represents the basic underlying structure of data as viewed by the enterprise as a whole.
Logical data independence indicates that the conceptual schema can be changed without affecting the existing schemas.
A conceptual schema must have three important characteristics:
A conceptual schema or conceptual data model is a map of concepts and their relationships used for databases.
Conceptual schema: describes the semantics of a domain (the scope of the model).
The logical schema and conceptual schema are sometimes implemented as one and the same.
The states of a created conceptual schema are transformed into an explicit mapping, the database schema.
These are consolidated into a single conceptual schema that is the superset of all of those external views.
At the center, the conceptual schema defines the ontology of the concepts as the users think of them and talk about them.
Because a conceptual schema represents the semantics of an organization, and not a database design, it may exist on various levels of abstraction.
The entity-relationship model is a data model, referred to in this book as the conceptual schema or conceptual model.
Over the next twenty years, various groups attempted to define standards for the conceptual schema and its mappings to databases and programming languages.