1. DATA MODELS

2. MODEL AND DATA MODEL
Model- is an abstraction or representation of the real world that reveals all features of interest to the users of the information in the model
Are created to better understand a process/ phenomenon/activity
A model is used to provide a representation of items, events and relationship sets between them and to provide all the basic concepts and rules for good communication between developers and users

3. Data model continued…
Hoberman (2009) defines a data model as a wayfinding tool for both business and IT professionals which uses a set of symbols and text to precisely explain a subset of real information to improve communication within the organization and thereby lead to a more flexible and stable application environment

4. Data model is a tool for data abstraction representing the organization itself and helps users clearly and accurately communicate their understanding of the organization data

5. DATA MODEL CATEGORIES
High Level/ Object Based/ Conceptual Based
They provide concepts that are close to the user or close to the way the user sees the database
They describe data at the conceptual and external view levels
Allows one to specify data constraints explicitly
e.g. ER model, Object oriented model, semantic model

6. E.g. hierarchical, relational and network
Implementation/ Record Based/ Representational
They are used to specify the logical structure of the database
The database is structured in fixed format records of several types and each record type defines a fixed number of fields/ attributes and each field is usually of a fixed length
E.g. hierarchical, relational and network

7. Physical/ Low Level data model
They provide concepts that describe the data of how data (metadata) is stored in the computer
Concepts at this level are meant for computer specialists and not meant for typical end users

8. RESEARCH
2- TIER AND 3 TIER ARCHITECTURE