1. Chris Russell O2.41 02920 41 6431 crussell@cardiffmet.ac.uk
Business Analysis
Introduction to Classes
Chris Russell
O2.41
Lecture BA15 Introduction to Classes

2. Lecture BA15 Introduction to Classes
Session schedule
Business Analysis Schedule
Academic Year
Semester 2
Week
Topic 1
Introduction 2
Investigate situation: rich picture, context diagrams 3
Consider perspectives: types of participation, CATWOE, Power-Interest, Thomas-Kilmann 4
Analyse needs 1: Use Cases 5
Analyse needs 2: structured techniques 6
Define requirements 1a: SSADM 7
Define requirements 1b: SSADM
EASTER 8
Define requirements 2: UML 9
Generic assignment feed-forward and task review 10
Balance good enough software against quality costs; Prioritise requirements 11
Assignment submisison
Lecture BA15 Introduction to Classes

3. Activities and Paradigms
Investigate Situation
Consider Perspectives
Analyse Needs
Define Requirements
Socio-technical
Rich picture
CATWOE
Types of participation
Thomas-Kilmann
Power-Interest X
Functional
Level 0 diagram
Structured techniques
DFD, ERM and ELH
Object-Oriented
Context diagram
Use Cases
Class and Sequence diagrams
Lecture BA15 Introduction to Classes

4. Lecture BA15 Introduction to Classes
Contents
UML compared to SSADM
Purpose
Basic notation
Basic guidelines
Example
Lecture BA15 Introduction to Classes

5. Lecture BA15 Introduction to Classes
UML compared to SSADM
Using use cases does not necessitate the adoption of UML for the entire design.
The most common alternative, at least in the UK, is the Structured Systems Analysis and Design Methodology (SSADM).
Whereas UML emphasises decomposing a problem space by objects, SSADM emphasises decomposing a problem space by functions and processes, resulting in a hierarchical breakdown of processes composed of sub-processes.
Thus a more process-intensive system might be more appropriately modelled using SSADM and a more data-intensive system might be more appropriately modelled using UML.
Lecture BA15 Introduction to Classes

6. Process-intensive and data-intensive?
Lecture BA15 Introduction to Classes
Object-oriented versus function-oriented decomposition (Larman 1998)

7. Lecture BA15 Introduction to Classes
Yes, then…
If the system, like this library information system, may be decomposed by objects or processes, the choice between UML and SSADM must be made according to other criteria.
Therefore, there follows a brief assessment of these two methodologies…
Lecture BA15 Introduction to Classes

8. Lecture BA15 Introduction to Classes
Data
UML
Subsumes data within the class to which it relates, reflecting the object-oriented approach.
Not representing data stores or files may cause problems in presenting an easily recognised analysis to the client or a suitable analysis for a designer to build upon.
SSADM
Data flow diagram is concerned with data stores and files and the flow of data from and to these.
Such stores and files may also form part of the entity relationship diagram.
Lecture BA15 Introduction to Classes

9. Lecture BA15 Introduction to Classes
Conditions
UML
The sequence diagram is effective in representing the optionality and the parallel nature of condition checks.
SSADM
The entity life history diagram is effective in representing the optionality and the parallel nature of condition checks.
Lecture BA15 Introduction to Classes

10. Lecture BA15 Introduction to Classes
Users
UML
The sequence diagram and use cases are readily understandable by someone with knowledge of the business but not systems analysis.
SSADM
The data flow diagram and the entity life history are readily understandable by someone with knowledge of the business but not systems analysis.
Lecture BA15 Introduction to Classes

11. Lecture BA15 Introduction to Classes
Development
UML
The class-focused approach of UML – for instance, the detail of attributes, operations and multiplicity – deliberately lends itself to object-oriented programming languages.
A very useful technique for validating a system design is to take each use case in turn and check that the design allows the use case to be carried out.
SSADM
The process-focused approach of SSADM lends itself primarily to functional programming languages – or functional use of object-oriented languages.
Lecture BA15 Introduction to Classes

12. Lecture BA15 Introduction to Classes
Time
UML
The sequence diagram can express time conditions; indeed, time may even be represented by lines on the chart.
SSADM
Does not provide a diagram which can adequately represent real-time, especially ‘hard’ real time.
An entity life history diagram will represent sequence, the ordering of events across time, but will not represent the actual, required or conditional time periods between events.
Lecture BA15 Introduction to Classes

13. Lecture BA15 Introduction to Classes
Endurance
UML
By being a data-driven approach leads, potentially, to a more enduring analysis, design and subsequent development.
As a use case has value for a particular actor, that actor will stay connected with the use case throughout the development and possible redevelopment of the program.
SSADM
The functions required are likely to change more with time than data, leading to a less enduring analysis, design and subsequent development.
Lecture BA15 Introduction to Classes

14. Lecture BA15 Introduction to Classes
Purpose
Analyse requirements in the form of a conceptual, static, data-oriented model
Depict the detailed design of object-oriented software
These two purposes require two different styles of class diagram
Lecture BA15 Introduction to Classes

15. Lecture BA15 Introduction to Classes
Basic notation
Name
Top box
Attributes
Middle box
Operations
Bottom box
Relationships (discussed next week)
Line
Lecture BA15 Introduction to Classes

16. Lecture BA15 Introduction to Classes
Guidelines for name
A template from which objects are instantiated (i.e. created)
Singular noun
Derived from problem domain and unambiguous
Typed in bold text and centred
Lecture BA15 Introduction to Classes

17. Guidelines for attributes
Information that is pertinent to their instances
In analysis attributes are ordinarily in the Attribute Name format whilst in design they are in the attributeName format
In analysis an incomplete list can be indicated by use of an ellipsis (…) at the end of the list
In design they take certain types e.g. Boolean, integer
Domain terminology, not generic
Lecture BA15 Introduction to Classes

18. Guidelines for operations
Functionality that the object supports
Strong imperative verb e.g. in analysis Verb Noun format whilst in design verbNoun format
In design parameters and return types are added
In analysis an incomplete list can be indicated by use of an ellipsis (…) at the end of the list
Domain terminology, not generic
If not using – a class may have only one box – leave a blank placeholder as similar naming conventions can cause confusion between attributes and operations
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19. Lecture BA15 Introduction to Classes
Identifying classes
An appropriate starting-point for arriving at classes are the use cases
Looking back to the share advice example, most of the use cases imply a class, thus:
Views Chart becomes the class Chart,
Retrieves Share Price becomes the class SharePrice,
Calculates Moving Averages becomes the class MovingAverage,
Sends becomes the class .
Their changed names reflect the more data-oriented nature of classes.
Subscribe Address and Unsubscribe Address can be combined in a class called Registration.
Lecture BA15 Introduction to Classes

20. Analysis or design example?
Lecture BA15 Introduction to Classes

21. Description of operations…
SharePriceRetriever() returns a Double
This method “manages” the retrieving of the HTML page containing the share price, its parsing to find the price and the conversion of this price to a Double (so that it may be stored in a Vector).
makeDouble(String numberString) returns a Double
This method “strips” the share price token of extraneous characters and space, and then converts the String to a Double so that it may be stored in a Vector object.
Lecture BA15 Introduction to Classes

22. …Description of operations
getPage(String urlString) returns a String
This method reads the HTML page into a character array and then assigns this array to a String.
parsePage(String htmlStringText)
This method parses the String for tokens, that is, data contained between the HTML tags.
getToken(int index) returns a String
getToken(String searchString, int offset) returns a String
findToken(String tokenString) returns an Integer
These methods find the token containing the share price.
Lecture BA15 Introduction to Classes