1. 44220: Database Design & Implementation Modelling the ‘Real’ World Ian Perry Room: C41C Ext.: 7287 E-mail: I.P.Perry@hull.ac.ukI.P.Perry@hull.ac.uk http://itsy.co.uk/ac/0708/sem2/44220_DDI/

2. Ian PerrySlide 244220: Database Design & Implementation: Modelling the ‘Real’ World Last Lecture ended with this … This Lecture: Explores the complex idea of ‘Data Modelling’.

3. Ian PerrySlide 344220: Database Design & Implementation: Modelling the ‘Real’ World What is this?

4. Ian PerrySlide 444220: Database Design & Implementation: Modelling the ‘Real’ World And this? Any of the family of aquatic birds, especially those having short legs, webbed feet, and a broad blunt bill. Collins Concise English Dictionary

5. Ian PerrySlide 544220: Database Design & Implementation: Modelling the ‘Real’ World And this?

6. Ian PerrySlide 644220: Database Design & Implementation: Modelling the ‘Real’ World And this? Duck What do they have in common? They are ALL, depending upon your information requirements, perfectly adequate models of a Duck.

7. Ian PerrySlide 744220: Database Design & Implementation: Modelling the ‘Real’ World So, what is a Model? Always remember that; Models ARE NOT the Real thing. They are: the appearance of reality. an analogue of the real world. a simplified representation of reality. the abstraction of meaning (the semantics). We build models for a purpose, so; being clear as to the purpose of a model is the key to success.

8. Ian PerrySlide 844220: Database Design & Implementation: Modelling the ‘Real’ World Every-day Models Model Duck: Purpose; to show shape, colour, size, etc. Model Aeroplane: Purpose; to show general structure, identification of parts, flight characteristics, etc. Data Model: Purpose; the representation of objects of interest to an enterprise, allowing data to be structured (i.e. given meaning) and manipulated (for specific purposes).

9. Ian PerrySlide 944220: Database Design & Implementation: Modelling the ‘Real’ World The Data Abstraction Process Requires us to focus on the critical aspects of the real world’s richness. no model is complete! All models require decisions about: what to include & what to exclude? These decisions represent someone’s view of a particular reality, i.e.; what is important, and MUST be included. what is not important, and can be left out.

10. Ian PerrySlide 1044220: Database Design & Implementation: Modelling the ‘Real’ World Data Models in the Plural The complexity of the database design process means that we must use a hierarchy of data models: Conceptual Data Model Logical Data Model Physical Data Model Successful database design requires; an orderly, and rigorous, progression through this ‘Data Modelling Stack’.

11. Ian PerrySlide 1144220: Database Design & Implementation: Modelling the ‘Real’ World The ‘Data Modelling Stack’

12. Ian PerrySlide 1244220: Database Design & Implementation: Modelling the ‘Real’ World Conceptual Data Model Initial ‘view’ of the Objects of interest; their properties, relationships, semantics. An integrated ‘view’ of the whole; which is compromise free AND Software & Hardware independent. Conceptual Data Modelling, is all about; ‘capturing’ WHAT real-world Objects MUST be included, i.e. to suit a particular purpose. We will build Conceptual Models using: Entity Relationship (ER) Diagrams

13. Ian PerrySlide 1344220: Database Design & Implementation: Modelling the ‘Real’ World Logical Data Model Logical Data Modelling, is all about; ‘deciding’ HOW to best represent the properties of the Objects of interest, and the relationships between them. We will build these using: Database Schema A Database Schema: defines the single, integrated, data collection that is the whole database. within the constraints of a chosen/imposed theoretical framework.

14. Ian PerrySlide 1444220: Database Design & Implementation: Modelling the ‘Real’ World Theories of Logical Modelling Several to choose from, e.g.: Hierarchical, Relational, Object-based, etc. Each Logical Modelling Theory comes with its own: Data Definition Language (DDL) Data Manipulation Language (DDM) Data Query Language (DQL) Software availability tends to influence the Logical Modelling Theory chosen here: As we will be using Microsoft Access (a Relational DataBase Management System), our logical choice must be Relational.

15. Ian PerrySlide 1544220: Database Design & Implementation: Modelling the ‘Real’ World Physical Data Model Physical Data Modelling, is all about; ‘mapping’ a Logical Data Model onto a specific Physical Storage System. This process may be influenced by; both Software specific & Hardware specific considerations. i.e. one may have to compromise the Logical Data Model; in order to make it ‘fit’ the Software (in our case Microsoft Access) that will be used build, maintain & manipulate the Physical Data Model.

16. Ian PerrySlide 1644220: Database Design & Implementation: Modelling the ‘Real’ World Database Design & Development Analyse a business situation; in order to ‘discover’ the purpose. Develop a conceptual data model; from the above analysis. Develop a logical data model (constrained by a particular database theory); from the conceptual data model. Implement a physical data model (constrained by software availability); based on the logical data model. Manipulate i.e. test the physical data model; to prove it ‘suits’ the purpose discovered by the original analysis.

17. Ian PerrySlide 1744220: Database Design & Implementation: Modelling the ‘Real’ World DDI Assessment Method Assignment 1 (50%) [01 Apr, 2008] Develop; an ‘appropriate’ Conceptual Data Model for a Case Study organisation. Develop; a ‘robust’ Logical Data Model based on the Conceptual Data Model. Assignment 2 (50%) [08 May, 2008] Implement; a ‘accurate’ Physical Data Model based on the Logical Data Model. Manipulate; the Physical Data Model to ‘prove it can’ Answer Specific Questions from the Case Study.

18. Ian PerrySlide 1844220: Database Design & Implementation: Modelling the ‘Real’ World This Week’s Workshop In this Workshop we will begin to explore some of the decisions we must make as we attempt to construct a model of ‘real’ world ‘things’. Working alone, or in a small team, consider the following ‘things’ that exist in the ‘real’ world. University, Computer, Sports Activity. For each of the above; list as many as you can imagine (try to be as creative & inventive as you can) of the ways that it might be modelled. For each way of modelling the above ‘things’; indicate who might regard this form of model as a meaningful and useful abstraction that captures its essential aspects.