Impact Factor: isra (India) = 971 isi (Dubai, uae) = 829 gif

Impact Factor: 
ISRA (India) = 4.971 
ISI (Dubai, UAE) = 0.829 
GIF (Australia) = 0.564 
JIF = 1.500 
SIS (USA) = 0.912
РИНЦ (Russia) = 0.126
ESJI (KZ) = 8.997 
SJIF (Morocco) = 5.667 
ICV (Poland) 
 = 6.630 
PIF (India) 
 = 1.940 
IBI (India) 
 = 4.260 
OAJI (USA) = 0.350 
 
 
Philadelphia, USA
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to decompose data streams) until functions can be split 
into parts. 
Construction of specifications of elementary 
processes (at the level of algorithms). 
If necessary - making changes to the DFD of any 
levels as the details of the requirements are clarified. 
The result of completing all of these stages is a 
ready-made model of the functional requirements of 
the system and a clear understanding of the structure 
of the subject area. At the end of this stage, you can 
proceed to building the data model. 
ESSENCE-CONNECTION DIAGRAMS 
One of the most commonly used tools for 
developing data models are Entity-Relationship 
Diagrams (ERDs). ERDs provide a standard way to 
define data and the relationships between them. With 
their help, the detailing of the data stores of the 
designed system is carried out, the system components 
are determined, the ways of their interaction, 
including the identification of objects important for 
the subject area (entities), the properties of these 
objects (attributes) and their relations with other 
objects (links). 
This notation was introduced by Chen and was 
further developed by Barker. These diagramming 
techniques are used to design relational databases. 
An entity is a set of instances of real or abstract 
objects (people, events, states, ideas, objects, etc.) that 
have common attributes or characters. Any system 
object can be represented by only one entity, which 
must be uniquely identified. In this case, the name of 
the entity should reflect the type or class of the object, 
and not its specific instance (for example, PATIENT, 
not KIM N.I.). 
An 
independent 
entity 
represents 
the 
independent data that is always present in the system 
and the relationship. other entities may or may not 
exist. 
A dependent entity represents data that is 
dependent on other entities in the system. Therefore, 
it must always have relationships with other entities. 
An associated entity represents data that is 
associated with a relationship between two or more 
entities (see many-to-many relationships below). 
A relationship in its most general form is a 
relationship between two or more entities. Verb 
groups are used to name relationships (has, can own, 
defines). 
An unconstrained (mandatory) relationship is an 
unconditional relationship, that is, a relationship that 
always exists as long as there are related entities. 
A constrained (optional) relationship is a 
conditional relationship between entities. 
A substantially constrained relationship is used 
when the respective entities are interdependent in the 
system. 
Relationships 
are 
used 
to 
identify 
the 
requirements by which entities are involved in 
relationships. Each relationship connects an entity and 
a relationship and can only be directed from 
relationship to entity. 
The value of a link characterizes its type and, as 
a rule, is selected from the following set: 
{"0 or 1", "0 or more", "1", "1 or more", "p: q"} 
A pair of relationship values belonging to the 
same relationship determines the type of this 
relationship. The following types of relationships are 
used: 
1 * 1 (one-to-one); 
1 * N (one-to-many); 
N * M (many-to-many). 
Relationships of this type are used in the early 
design stages to clarify the situation. In the future, 
each of these relations must be converted into a 
combination of relations of types 1. 
2 (possibly with the addition of auxiliary 
associative entities and the introduction of new 
relationships). 
Demonstrating the relationship between the 
objects of a medical organization (polyclinic). 
According to this diagram, each doctor treats one or 
more patients. In addition, each patient may or may 
not be treated by one or more physicians. Each doctor 
conducts an outpatient appointment for which patients 
are registered (assigned). In the process of examining 
patients at an outpatient appointment, the doctor forms 
epicrises that affect the diagnosis. Every diagnosis for 
a patient must have an author - a doctor who is 
responsible for making the decision. 
Each entity has one or more attributes that 
uniquely identify each instance of the entity. 
Moreover, any attribute can be defined as key. 
Entity drill-down is accomplished using attribute 
diagrams that expose the attributes associated with an 
entity. An attribute diagram consists of a drillable 
entity, associated attributes, and domains that describe 
the attribute value ranges. In the diagram, each 
attribute is represented as a relationship between the 
entity and the corresponding domain, which is a 
graphical representation of the set of possible attribute 
values. All attribute links have meaning at their end. 
The attribute name underscore is used to identify a key 
attribute. 
An entity can be split and represented as two or 
more entity-categories, each of which has common 
attributes and / or relationships. The entity split into 
categories was called the general entity (at 
intermediate levels of decomposition, the same entity 
can be both a general entity and an entity-category). 
To demonstrate the decomposition of an entity 
into categories, categorization diagrams are used. 
Such a diagram contains a general entity, two or more 
entity-categories, and a special node - a discriminator, 
which describes how entities are decomposed. 
The ER-approach was further developed in the 
works of Barker, who proposed an original notation 
that made it possible to integrate the model description 
tools proposed by Chen at the top level. There is only 

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