Modelling Business Information

Entity relationship and class modelling for Business Analysts

Keith Gordon

• Éditeur: BCS, The Chartered Institute for IT
• Année: 2017
• ISBN:
  9781780173559
• Sujet: Informatique
• Sous-sujet: Modélisation et conception de données

It is almost universally accepted that requirements documents for new or enhanced IT systems by business analysts should include a 'data model' to represent the information that has to be handled by the system. Starting from first principles, this book will help business analysts to develop the skills required to construct data models through comprehensive coverage of entity relationship and class modelling, in line with the BCS Data Analysis syllabus. In addition to covering the topics in the syllabus, the book also includes extra information of interest including data model quality and taking a requirement model into database design.

PART 1:
THE BASICS

The first part of the book (Chapters 1 to 6), which provides a general introduction to entity relationship modelling and UML class modelling, covers the requirements for the Data Analysis certificate that is part of the scheme for the BCS Advanced International Diploma in Business Analysis.

Chapter 1, Why business analysts should model information, provides an introduction to business analysis, systems, information, data and modelling and why these topics come together within the development of requirements for an IT system. The notations used within the book, the Ellis-Barker entity relationship notation and the UML class diagram notion, are introduced. The chapter finishes with a discussion of data analysis.

Chapter 2, Modelling the things of interest to the business and the relationships between them, introduces the basic modelling concept of the entity to represent something of interest to the business about which information needs to be recorded and the related concept of the entity types, the representation of a group of entity occurrences with common characteristics. The relationships between entity types are also introduced. Alongside the introduction of these concepts, the comparable concepts of object, object class and association are also introduced.

Chapter 3, Modelling more complex relationships, explores some of the more complex relationships that can exist between entity types or object classes. The topics covered are the resolution of many-to-many relationships and associations (including the oddity known as the ‘Bill of Materials’ structure), mutually exclusive relationships and associations, which leads to generalisation and specialisation, and, finally, a quick look at aggregation and composition.

Chapter 4, Drawing and validating information model diagrams, introduces a process for drawing an information model diagram. It then considers two techniques for validating an information model – the data navigation path and the Create-Read-Update-Delete (CRUD) matrix.

Chapter 5, Recording information about things, introduces the related concepts of the attribute, the unique identifier and the domain, and their representation on both entity relationship models and class models. The object-oriented concept of the operation is also introduced at the end of the chapter.

Chapter 6, Rationalising data using normalisation, involves a change of direction as we look at the process of relational data analysis (or normalisation). We need to look at the theory of the relational model of data – the ‘model’ that underpins all of the database management systems that use the SQL database language. Having understood the theory, we then look at the process of normalisation and the production of a ‘third normal form’ model.

These chapters should be read sequentially, from Chapter 1 through to Chapter 6. Revision exercises are provided at the end of Chapters 2 to 6.

1 WHY BUSINESS ANALYSTS SHOULD MODEL INFORMATION

This chapter provides an introduction to business analysis, systems, information, data and modelling and why these topics come together within the development of requirements for an IT system. The chapter finishes with a discussion of data analysis.

WHAT IS BUSINESS ANALYSIS?

Business analysis is a discipline that has been evolving for about 20 years. Its main purpose is to ensure that there is alignment between business needs and business change solutions. Many of these business change solutions involve the development of new – or the enhancement of existing – information technology (commonly abbreviated to IT) systems.

There is no fixed route to becoming a business analyst. Some business analysts have a strong information technology background and have developed an understanding of business in general and their business organisation in particular. Other business analysts have a strong business background and, where a solution involving information technology is concerned, they need to have obtained an understanding both of the capabilities provided by information technology and of how an information technology system is developed.

The word ‘system’ appears in the two preceding paragraphs because it is important for the business analyst to grasp hold of ‘systems thinking’. Whether the proposed business change solution involves the use of information technology or not, the business analyst is working with or specifying the requirements for systems. These systems may be business systems, information systems or information technology systems.

So, what is a system?

Professor Michael C. Jackson of the University of Hull has defined a system as

a complex whole the functioning of which depends on its parts and the interactions between those parts.³

Using this definition, the term ‘system’ can be applied to a hard, designed system such as a central heating system or to a soft, or human activity, system such as a business organisation.

A central heating system consists of a boiler, radiators, pipes and, importantly, a thermostat to keep the whole system under control. This is a ‘complex whole’, the functioning of which depends on all of those parts working together.

A business, whether in the private, public or not-for-profit sectors of the economy, consists of people (employees, suppliers and customers), organisations (headquarters, branches, departments) and processes (including ordering and receiving goods and selling goods). All businesses require information to manage their people, organisations and processes and, for most businesses these days, there is information technology providing support for the management of that information. So, a business can be seen as another ‘complex whole’, the functioning of which depends on the parts, the people, the organisations, the processes, the information and the technology, working together to achieve the goals of the business. There will also be checks and balances to ensure that the business remains effective and efficient – the equivalent of the thermostat in the central heating system.

Any business can, therefore, be considered as a system – a business system. Any system can have a number of subsystems, so a business system can also have subsystems.

One of the important subsystems of a business system is the information system, or set of information systems, which supports the business by managing the business’s information. I define an information system as:

a system that gets the right information to the right person in the right place at the right time.

We need, therefore, to think about information systemically. If there is a requirement for Sue in production to receive details of an important sales order as soon as it arrives in the business, then we need to arrange for that to happen. It could be that the arrangement is for the salesman, John, who has just completed the sale, to walk along the corridor to production to tell Sue about the sales order. The right information (details of the sales order) is being delivered to the right person (Sue) in the right place (the production department) at the right time (immediately) without the use of any technology. We have a technology-free information system! Yes, that is possible, but that information system still needs defining, developing, implementing and maintaining.

Most modern businesses require the information system to be supported by an information technology system – a collection of hardware, software and networks that function together to store and retrieve information.

The business analyst needs to think in terms of three levels of system: the business system itself; the subsystem that handles the information for the business (the information system); and the sub-subsystem that provides the technology to support the information system (the IT system). This is shown diagrammatically in Figure 1.1.

Figure 1.1 Three levels of system

Information is a key business resource in all business, even if the senior managers of most businesses fail to recognise that fact.

INFORMATION AND DATA

In my previous book, I explained the relationship between information and data. I repeat that explanation here, slightly edited, because this book is about modelling business information with a view to storing that information as data within an information system or an information technology system.

A...