Information Systems Development 37C Lecture: Final notes. 30 th March 2017 Dr. Riitta Hekkala

Transcription

1 Information Systems Development 37C00200 Lecture: Final notes 30 th March 2017 Dr. Riitta Hekkala

2 The course should have given you Introduction to the information system development process Understanding of the importance of effective communication and integration with users and systems Systems development and design techniques (Use Case Diagram, Class diagram, ER-diagram, Relational database model, and how to refine relations with a set of rules called the normal forms) Basic knowledge on management issues in globally distributed teams + basic knowledge on outsourcing

3 Importance and Benefits of Use cases They are in a tracking format and help to understand functionality They represent the goal of an interaction between an actor and the system They improve communication between vendors and software users They are important for product and software development, and they improve security issues

4 Assignment 1

5 What does object-orientedness mean? A modeling principle that describes everything in a system using two elements: 1) Objects, 2) Interactions between these objects Object-oriented system analysis = Analysis on how to define the system behavior with meaningful objects and their interactions Ship product Digital inventory Customer X Change address Warehouse worker Y Customer DB Objects Interactions Objects

6 Objects know and can do things Vehicle Is a Weight Power source Max speed Calculate CO2 emissions Is a Data (know) Function (do) Is a Car Seat count Tyre size How much fuel left Put air conditioning on Ship Crew size Cargo contents Bicycle Tyre size Handle bar type 6

7 Assignment 2 Customer favoriterecipes RecipeCatalogue recipes BankGateway makepayment() addtofavorites() 1 addrecipe() findrecipe() 1 Warehouse * Recipe ingredients * 1 deliverers isavailable() order() 1 1 * * Delivery Ingredient Product quantity substance quantity substance deliver() is a * Substance * CourierDelivery 1 name 1 deliver()

8 ER model elements Entity Relationship Attribute Entity: person, object, event or concept about which data is to be maintained Entity type: collection of entities with common characteristics; Entity instance: single entity Relationship: Association between the instances of one or more entity types. Relationships can be thought of as verbs, linking two or more entities. Attribute: named property or characteristic of an entity 8

9 Identifier Attributes Candidate key Attribute (or combination of attributes) that uniquely identifies each instance of an entity type EMPLOYEE SSN NAME - Every entity (unless it is a weak entity) must have a minimal set of uniquely identifying attributes, which is called the entity's primary key. Weak entity cannot exist without entity with which it has a relationship. Instructor Year Course CName CourseDesc CNumber Section Belong_To Credits SectionNumber 9 Semester

10 Assignment 3

11 Assignment 4 N 1 WORKS_FOR EMPLOYEE MANAGES CONTROLS N WORKS_ON! DEPENDENTS_OF

12 Assignment 4

13 Assignment 4: From Conceptual Model to Relational Model and Normalization

14 Phase 1 ü Create a relation that includes all the simple attributes of entity ü Include all the simple component attributes of composite attributes ü Choose one of the key attributes of entity as primary key for R ü If the chosen key of E is composite, the set of simple attributes that form it will together form the primary key of R Information Systems Development 14

15 Phase 1 EMPLOYEE FNAME MINIT LNAM E SSN BDATE ADDRESS SEX SALA RY DEPARTMENT DNAME DNUMBER PROJECT PNAME PNUMBER PLOCATION Information Systems Development 15

16 Phase 2 ü For each weak entity type with owner entity type create a relation, and include all simple attributes and simple components of composite attributes of weak entity as attributes of relation ü In addition, include as foreign key attributes of relation the primary key attribute(s) of the relation(s) that correspond to the owner entity type(s) Information Systems Development 16

17 After phase 2 EMPLOYEE ESSN DEPENDENT_NAME SEX BDATE RELATION SHIP Information Systems Development 17

18 Phase 3 ü For each binary 1:1 relationship type relation: identify the relations that correspond to the entity types participating in relation (Manages: managers ssn + manager start date MGRSSN + MGRSTARTDATE) ü Include the simple attributes of the 1:1 relationship Information Systems Development 18

19 Phase 3 (binary 1:1 relationship) DEPARTMENT DNAME DNUMBER MGR SSN MGR STARTDATE Information Systems Development 19

20 Phase 4 ü For each regular binary 1:N relationship type identify the relation that represent the participating entity type at the N-side of the relationship type ü Include as foreign key in the primary key of the relations that represent the other entity type participating in relationship Information Systems Development 20

21 Phase 4: regular binary 1:N relationship EMPLOYEE F NAME MINIT LNA ME SS N B DATE AD- DRESS SEX SALA RY SUP ER- SSN DNA ME PROJECT PNAME PNUMBER PLOCATION DNUM Information Systems Development 21

22 Phase 5 binary M:N relationship ü Include as foreign key attributes in the primary keys of the relations that represent the participating entity types; their compination will form the primary key ü Many employees works on project: works_on attributes: employee ssn, project number, hours Information Systems Development 22

23 Phase 5: regular binary M:N relationship Works_on ESSN PNO HOURS Information Systems Development 23

24 Phase 6: Multivalued attribute ü If a multivalued attribute is composite, we include its components ü In this case department number and department location Information Systems Development 24

25 Phase 6: Multivalued attribute(s) Dept_locations DNUMBER DLOCATION Information Systems Development 25

26 Conclusion: Relational database model, and how to refine relations with a set of rules called the normal forms 1. Regular entity type 2. Weak entity type 3. Binary 1:1 relationship 4. Binary 1:N relationship 5. Binary M:N relationship 6. Multi-valued attribute(s) Information Systems Development 26

27 Final exam 6 th April, from 1pm to 4pm 19 th May, from 2pm to 5pm 3 rd possibility during next autumn? The exam will include concepts definitions and an essay The other half will be applied questions i.e. you need to draw some diagrams (e.g. use case diagram, ER diagram, relational model or to refine relations with a set of rules called the normal forms) 27