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

Network Data Model (NDM)
Network model allows organize DB,structure which seems count general kind. Organization data V network models corresponds structuring data By versions CODASYL.Each vertex graph stores copies entities(records one type)And intelligence O group relationships With entities others types.Each recording Maybe keep arbitrary quantity values attributes(elements data And units),characterizing copy essence.For everyone type records stands out primary key–attribute,meaning whom allows definitely to identify recording among copies records given type.
Network Data Model (NDM)
Let's consider fragment DB"Company".Here records types DEPARTMENTS And ORGANIZATIONS-CUSTOMERS are owners records type PROJECTS And They connected group relationships respectively perform And order.Posts types DEPARTMENTS And PROJECTS are owners records type EMPLOYEES And They connected group relationships work And are being carried out.Posts type EMPLOYEES are owners records type CHILDREN.
Network Data Model (NDM)
The following operations on data are used in SMD: remember: entering information into the database; include in a group relationship:establishing connections between data; switch: change of ownership of a member of a set; update: data modification; extract: read data; delete:physical or logical deletion of data; exclude from group relationship: Breaking connections between data.
IN network models data provided special ways navigation And manipulation data.Apparatus navigation V graph models serves For establishing those records,To which will apply another operation manipulation data.Such records are called current.IN SMD possible transitions:
from the current instance of a record of a certain type to the next instance of a record of the same type;
from the current vertex to any vertex with which the current one is connected by a group relationship.