Department «digital economy and information technology» subject "database"

DEPARTMENT «DIGITAL ECONOMY AND INFORMATION TECHNOLOGY»
SUBJECT "DATABASE"
SUBJECT3. BASIC DATA MODELS
BASIC DATA MODELS
A data model is a tool for modeling an arbitrary subject area.
Data Model –this is a set of rules for generating data structures in a database, operations on them, as well as integrity constraints that determine permissible connections and data values, the sequence of their changes. So,the data model consists of three parts:
Set of data structure types. Here we can draw an analogy with programming languages, which also have predefined types of data structures, such as scalar data, vectors, arrays, structures, etc.
A set of operators or inference rules that can be applied toany correct examplesdata typeslisted in,to find, infer or transform information contained in any parts of these structures in any combinations.
A set of general integrity rules that directly or indirectly define the set of consistent states of a database and/or the set of changes to its state.
BASIC DATA MODELS
Data structuring is based on the use of the concepts of “aggregation” and “generalization”. One of the first options for data structuring was proposed by the Association for Data Processing Languages ​​(Conference on Data Systems Languages, CODASYL).
Composition of data structures by versionCODASYL
Data element–the smallest named unit of data that the DBMS can access directly and with the help of which all other structures are built.For each data element, its type must be defined.
BASIC DATA MODELS
Aggregate – a named collection of data elements within a record that can be considered as a single whole.The unit may besimple(including only data elements) andcomposite(including, along with data elements, other aggregates).
Examples of units: a) simple and b) compound unit