Database administrators – DBA is responsible for authorizing access to the database, for coordinating and monitoring its
use, and acquiring software and hardware resources as needed.
Database designers – identify data to be stored in the database and choosing appropriate structures to represent and store
the data. Most of these functions are done before the database is implemented and populated with the data. It is the
responsibility of the database designers to communicate with all prospective users to understand their requirements and
come up with a design that meets these requirements.
End Users :
Casual End Users – occasionally access, may need different information each time. Use query language to specify
Naïve or parametric end users – main job is to query and update the database using standard queries and updates.
Sophisticated end users – engineers, scientists, analysts who implement applications to meet their requirements.
Stand alone users – maintain personal databases using ready made packages.
An applications architecture describes the behaviour of applications used in a business, focused on how they
interact with each other and with users. It is focused on the data consumed and produced by applications rather than their
internal structure. The applications architecture is specified on the basis of business and functional requirements. This
involves defining the interaction between application packages, databases, and middleware systems in terms of functional
1-Tier Architecture is the simplest, single tier on single user, and is the equivalent of running an application on a
personal computer. All the required component to run the application are located within it. User interface, business logic,
and data storage are all located on the same machine. They are the easiest to design, but the least scalable. Because they are
not part of a network, they are useless for designing web applications.
2-Tier Architectures supply a basic network between a client and a server. For example, the basic web model is a 2Tier Architecture. A web browser makes a request from a web server, which then processes the request and returns the
desired response, in this case, web pages. This approach improves scalability and divides the user interface from the data
layers. However, it does not divide application layers so they can be utilized separately. This makes them difficult to
update and not specialized. The entire application must be updated because layers aren‘t separated.
3- n-tier Application
An n-tier application program is one that is distributed among three or more separate computers in a distributed
network. The most common form of n-tier (meaning 'some number of tiers') is the 3-tier application, in which user
interface programming is in the user's computer, business logic is in a more centralized computer, and needed data is in a
computer that manages a database.
Database design and the e-r model
UNIT - 2
Database Design and the E-R model
Entity relationship model :
an entity–relationship model (ER model) is a data model for describing the data or information aspects of a
business domain or its process requirements, in an abstract way that lends itself to ultimately being implemented in a
database such as a relational database. The main components of ER models are entities (things) and the relationships that
can exist among them, and databases.
Fig: e-r model
An entity can be a real-world object, either animate or inanimate, that can be easily identifiable. For example, in a school
database, students, teachers, classes, and courses offered can be considered as entities. All these entities have some
attributes or properties that give them their identity.