Lecture Chapter 5: Modeling systems requirements - Events and things

Chia sẻ: Minh Vũ | Ngày: | Loại File: PDF | Số trang:9

Thêm vào BST

Báo xấu

54
lượt xem 3
download

Download Vui lòng tải xuống để xem tài liệu đầy đủ

Lecture "Chapter 5: Modeling systems requirements - Events and things" provides students with the knowledge: Models and modeling, types of models, overview of models used in analysis and design, types of models, overview of models used in analysis and design,... Invite you to consult.

Chủ đề:

Bình luận(0) Đăng nhập để gửi bình luận!

Lưu

Nội dung Text: Lecture Chapter 5: Modeling systems requirements - Events and things

5 5 Learning Objectives Chapter 5:  Explain the many reasons for creating information system models Modeling Systems Requirements: Events and Things  Describe three types of models and list some specific models used for analysis and design  Explain how events can be used to define system Systems Analysis and Design in a Changing requirements World, 3rd Edition  Identify and analyze events to which a system responds  Recognize that events trigger system activities or use cases Systems Analysis and Design in a Changing World, 3rd Edition 2 5 5 Learning Objectives (continued) Overview  Explain how the concept of things in the system  Document functional requirements by creating also defines requirements models  Explain the similarities and the differences  Models created during analysis phase activity: between data entities and objects Define system requirements  Identify and analyze data entities and objects  Two concepts define system requirements in needed in the system traditional approach and object-oriented  Read, interpret, and create an entity-relationship approach diagram  Events  Read, interpret, and create a class diagram  Things Systems Analysis and Design in a Changing World, 3rd Edition 3 Systems Analysis and Design in a Changing World, 3rd Edition 4 5 5 Models and Modeling Reasons for Modeling  Analyst describes information system requirements using a collection of models  Complex systems require more than one type of model  Models represent some aspect of the system being built  Process of creating model helps analyst clarify and refine design  Models assist communication with system users Systems Analysis and Design in a Changing World, 3rd Edition 5 Systems Analysis and Design in a Changing World, 3rd Edition 6
5 5 Overview of Models Used Types of Models in Analysis and Design  Different types of models are used in information  Analysis phase activity named “define system systems development requirements”  Mathematical - formulas that describe technical  Logical models aspects of the system  Provide detail without regard to specific technology  Descriptive - narrative memos, reports, or lists that  Design phase describe aspects of the system  Physical models  Graphical - diagrams and schematic  Provide technical details representations of some aspect of the system  Extend logical models Systems Analysis and Design in a Changing World, 3rd Edition 7 Systems Analysis and Design in a Changing World, 3rd Edition 8 5 5 Models Used in Analysis Models Used in Design Systems Analysis and Design in a Changing World, 3rd Edition 9 Systems Analysis and Design in a Changing World, 3rd Edition 10 5 5 Events Affecting a Charge Account Events and System Requirements Processing System  Events  Occurrences at a specific time and place  Trigger all system processing  Requirement definition  Determine relevant events  External events first  Temporal events second  Decompose system into manageable units Systems Analysis and Design in a Changing World, 3rd Edition 11 Systems Analysis and Design in a Changing World, 3rd Edition 12
5 5 Types of Events External Event Checklist  External  Outside system  Initiated by external agent or actor  Temporal  Occurs as result of reaching a point in time  Based on system deadlines  State  Something inside system triggers processing need Systems Analysis and Design in a Changing World, 3rd Edition 13 Systems Analysis and Design in a Changing World, 3rd Edition 14 5 5 Temporal Event Checklist Identifying Events  Can be difficult to determine  Often confused with conditions and responses  May be useful to trace a transaction’s life cycle  Certain events left to design phase  Systems controls to protect system integrity  Perfect technology assumption defers events Systems Analysis and Design in a Changing World, 3rd Edition 15 Systems Analysis and Design in a Changing World, 3rd Edition 16 5 Sequence of “Transactions” 5 Sequence of Actions that Lead up to Only for One Specific Customer One Event Affecting the System Resulting in Many Events Systems Analysis and Design in a Changing World, 3rd Edition 17 Systems Analysis and Design in a Changing World, 3rd Edition 18
5 5 Events Deferred Until the Design Phase Events in the RMO case  Important external events involve customers  Customer checks item availability, customer places order, customer changes or cancels order  Other external events involve departments  Shipping fulfills order, marketing sends promotion to customer, merchandising updates catalog  Temporal events include periodic reports  Time to produce order summary reports, Time to produce fulfillment summary reports Systems Analysis and Design in a Changing World, 3rd Edition 19 Systems Analysis and Design in a Changing World, 3rd Edition 20 5 5 Information about each Event Things and System Requirements in an Event Table  Define system requirements by understanding system information that needs to be stored  Store information about things in the problem domain that people deal with when they do their work  Analysts identify these types of things by considering each event in the event list  What things does the system need to know about and store information about? Systems Analysis and Design in a Changing World, 3rd Edition 21 Systems Analysis and Design in a Changing World, 3rd Edition 22 5 5 Procedure for Developing an Types of Things Initial List of Things  Step 1: Using the event table and information about each event, identify all nouns about system  Step 2: Using other information from existing systems, current procedures, and current reports or forms, add items or categories of information needed  Step 3: Refine list and record assumptions or issues to explore Systems Analysis and Design in a Changing World, 3rd Edition 23 Systems Analysis and Design in a Changing World, 3rd Edition 24
5 5 Relationships Naturally Occur Between Characteristics of Things Things  Relationship  Naturally occurring association among specific things  Occur in two directions  Number of associations is cardinality or multiplicity  Binary, unary, ternary, n-ary  Attribute  One specific piece of information about a thing Systems Analysis and Design in a Changing World, 3rd Edition 25 Systems Analysis and Design in a Changing World, 3rd Edition 26 5 5 Cardinality/Multiplicity of Relationships Attributes and Values Systems Analysis and Design in a Changing World, 3rd Edition 27 Systems Analysis and Design in a Changing World, 3rd Edition 28 5 5 Data Entities Objects  Objects do the work in system and store  Things system needs to store data about in information in object-oriented approach traditional IS approach  Objects have behaviors and attributes  Class: Type of thing  Modeled with entity-relationship diagram (ERD)  Object: Each specific thing  Methods: Behaviors of objects of the class  Requirements model used to create the database  Objects contain values for attributes and methods design model for relational database for operating on those attributes  An object is encapsulated – a self-contained unit Systems Analysis and Design in a Changing World, 3rd Edition 29 Systems Analysis and Design in a Changing World, 3rd Edition 30
5 5 Data Entities Compared with Objects Simple Entity-relationship Diagram Systems Analysis and Design in a Changing World, 3rd Edition 31 Systems Analysis and Design in a Changing World, 3rd Edition 32 5 5 Cardinality Symbols of Relationships Expanded ERD with Attributes Shown Systems Analysis and Design in a Changing World, 3rd Edition 33 Systems Analysis and Design in a Changing World, 3rd Edition 34 5 5 Customers, Orders, and Order Items University course enrollment ERD Systems Analysis and Design in a Changing World, 3rd Edition 35 Systems Analysis and Design in a Changing World, 3rd Edition 36
5 5 Refined University course enrollment ERD RMO Customer Support ERD Systems Analysis and Design in a Changing World, 3rd Edition 37 Systems Analysis and Design in a Changing World, 3rd Edition 38 5 5 A Generalization/Specialization The Class Diagram Hierarchy for Motor Vehicles  Models classes of objects instead of data entities  Generalization/specialization hierarchies  General superclasses to specialized subclasses  Inheritance allows subclasses to share characteristics of their superclasses  Aggregation (whole-part hierarchies)  Relates objects and its parts  Defines object in terms of its parts Systems Analysis and Design in a Changing World, 3rd Edition 39 Systems Analysis and Design in a Changing World, 3rd Edition 40 5 5 A Generalization/Specialization Aggregation or Whole-Part Relationships Hierarchy for Orders Systems Analysis and Design in a Changing World, 3rd Edition 41 Systems Analysis and Design in a Changing World, 3rd Edition 42
5 5 The Class Symbol for the Class Diagram Bank Account System Class Diagram Systems Analysis and Design in a Changing World, 3rd Edition 43 Systems Analysis and Design in a Changing World, 3rd Edition 44 5 5 Enrollment Class Diagram RMO Class Diagram with Association Class Systems Analysis and Design in a Changing World, 3rd Edition 45 Systems Analysis and Design in a Changing World, 3rd Edition 46 5 5 Where You Are Headed Summary  Analysis Phase: Define system requirements  Models created to: further learning process, reduce complexity, communicate with team members, and document requirements  Many types of models used:  Mathematical, descriptive, graphical  Key early step in modeling to identify and list:  Events that require a response from system  Things users deal with in work environment Systems Analysis and Design in a Changing World, 3rd Edition 47 Systems Analysis and Design in a Changing World, 3rd Edition 48
5 5 Summary (continued) Summary (continued)  Events are memorable, can be described, and  Things are what user deals with and system occur at specific time and place remembers, such as customer placing an order  External events occur outside system, triggered  Traditional approach uses entity-relationship by someone interacting with system diagrams (ERD) for data entities, attributes of data entities, and relationships between entities  Temporal events occur at defined point in time,  Things are shown as data entities such as end of day or end of month  Object-oriented approach uses class diagrams  State events based on internal system change for classes, attributes, methods of class, and associations among classes  Event table records event, trigger, source, activity or use case, response, and destination  Things are shown as objects belonging to a class Systems Analysis and Design in a Changing World, 3rd Edition 49 Systems Analysis and Design in a Changing World, 3rd Edition 50