DBMS data models. The relational data model. Technology development of Web-based applications

a database is modeled. Data Models are fundamental entities to introduce abstraction in a DBMS. Data models define how data is connected to each other and how they are processed and stored inside the system.
The very first data model could be flat data-models, where all the data used are to be kept in the same plane. Earlier data models were not so scientific, hence they were prone to introduce lots of duplication and update anomalies.

entities and relationships among them. While formulating real-world scenario into the database model, the ER Model creates entity set, relationship set, general attributes and constraints.
ER Model is best used for the conceptual design of a database.
ER Model is based on −
Entities and their attributes.
Relationships among entities.
These concepts are explained below.

having properties called attributes. Every attribute is defined by its set of values called domain. For example, in a school database, a student is considered as an entity. Student has various attributes like name, age, class, etc.
Relationship − The logical association among entities is called relationship. Relationships are mapped with entities in various ways. Mapping cardinalities define the number of association between two entities.
Mapping cardinalities −
one to one
one to many
many to one
many to many

Model. It is more scientific a model than others. This model is based on first-order predicate logic and defines a table as an n-ary relation.

tables called relations.
Relations can be normalized.
In normalized relations, values saved are atomic values.
Each row in a relation contains a unique value.
Each column in a relation contains values from a same domain.

creating Web Applications:
I. Client Side Scripting / Coding - Client Side Scripting is the type of code that is executed or interpreted by browsers.
Client Side Scripting is generally viewable by any visitor to a site (from the view menu click on "View Source" to view the source code).
Below are some common Client Side Scripting technologies:
HTML (HyperText Markup Language)
CSS (Cascading Style Sheets)
JavaScript
Ajax (Asynchronous JavaScript and XML)
jQuery (JavaScript Framework Library - commonly used in Ajax development)
MooTools (JavaScript Framework Library - commonly used in Ajax development)
Dojo Toolkit (JavaScript Framework Library - commonly used in Ajax development)