1. CHAPTER 9: Structuring System Requirements: Conceptual Data Modeling Conceptual Data Modeling 1.1 MSIS 5653 Advanced Systems Development Dursun Delen, Ph.D. Department of Management Oklahoma State University

2. D. Delen MSIS 5653 – Advanced Systems Development Learning Objectives Define key data modeling terms Entity type Attribute Multi-valued attribute Relationship Cardinality Business Rule Associative entity Trigger Super-type, Subtype 10.2

3. D. Delen MSIS 5653 – Advanced Systems Development Learning Objectives Learn to draw Entity-Relationship (E-R) Distinguish between unary, binary, and ternary relationships, and give an example of each Define four basic types of business rules in an E-R diagram Explain the role of CASE technology in the analysis and documentation of data required in an information system Relate data modeling to process and logic modeling as different views describing an information system 10.3

4. D. Delen MSIS 5653 – Advanced Systems Development Structuring System Requirements in SDLC

5. D. Delen MSIS 5653 – Advanced Systems Development Conceptual Data Modeling Conceptual Data Model: “A detailed model that captures the overall structure of organizational data” Purpose is to show rules about the meaning and the interrelationships among data Entity-Relationship (E-R) diagrams are commonly used to show how data are organized Main goal of conceptual data modeling is to create accurate E-R diagrams Methods such as interviewing, questionnaires and JAD are used to collect information Consistency must be maintained between process flow, decision logic and data modeling descriptions 10.5

6. D. Delen MSIS 5653 – Advanced Systems Development Process of Conceptual Data Modeling First step is to develop a data model for the system being replaced Next, a new conceptual data model is built that includes all the requirements of the new system In the design stage, the conceptual data model is translated into a physical design Project repository links all design and data modeling steps performed during SDLC 10.6

7. D. Delen MSIS 5653 – Advanced Systems Development Relationship between Data Modeling and the SDLC

8. D. Delen MSIS 5653 – Advanced Systems Development Deliverables and Outcome Primary deliverable is the entity-relationship (E-R) diagrams There may be as many as 4 E-R diagrams produced and analyzed during conceptual data modeling: 1.Covers just data needed in the project’s application 2.E-R diagram for system being replaced 3.An E-R diagram for the whole database from which the new application’s data are extracted 4.An E-R diagram for the whole database from which data for the application system being replaced is drawn 10.8

9. D. Delen MSIS 5653 – Advanced Systems Development Figure 10-3 Sample conceptual data model diagram 10.9

10. D. Delen MSIS 5653 – Advanced Systems Development Deliverables and Outcome Second deliverable is a set of entries about data objects to be stored in repository or project dictionary Repository links data, process and logic models of an information system Data elements that are included in the DFD must appear in the data model and visa versa Each data store in a process model must relate to business objects represented in the data model 10.1010

11. D. Delen MSIS 5653 – Advanced Systems Development Gathering Information for Conceptual Data Modeling Two perspectives 1.Top-down Data model is derived from an intimate understanding of the business 10.11

12. D. Delen MSIS 5653 – Advanced Systems Development Gathering Information for Conceptual Data Modeling Two perspectives (Cont.) 2.Bottom-up Data model is derived from the process of reviewing business documents 10.12 ORDER NO CUSTOMER NO NAME ADDRESS CITY-STATE-ZIP ORDER DATE PROMISED DATE PRODUCT NO DESCRIPTION QUANTITY ORDRED UNIT PRICE

13. D. Delen MSIS 5653 – Advanced Systems Development Introduction to Entity- Relationship (E-R) Modeling Notation uses three main constructs Data entities Relationships Attributes Entity-Relationship (E-R) Model A detailed, logical representation of the data entities, associations and data characteristics for an organization Entity-Relationship (E-R) Diagram A graphical representation of an E-R model 10.13

14. D. Delen MSIS 5653 – Advanced Systems Development E-RNotation

15. Entity-Relationship (E-R) Modeling Key Terms Entity A person, place, object, event or concept in the user environment about which the organization wishes to maintain data Represented by a rectangle in E-R diagrams Entity Type A collection of entities that share common properties or characteristics 10.15

16. D. Delen MSIS 5653 – Advanced Systems Development Entity-Relationship (E-R) Modeling Key Terms Naming and Defining Entity Types An entity type name  Is a Singular Noun (CUSTOMER, STUDENT)  Should be descriptive and specific to organization (PURCHASE ORDER, CUSTOMER ORDER)  Should be concise (REGISTRATION vs. STUDENT REGISTRATION FOR CLASS)  (for Event Entity Type) should be the result of the event, not the activity or process of the event (ASSIGNMENT) An entity type definition should  Include unique characteristics for each instance  Make it clear what entities instances are included/not-incl  When an instance of the entity type is created/deleted 10.16

17. D. Delen MSIS 5653 – Advanced Systems Development Attribute A named property or characteristic of an entity that is of interest to an organization Entity-Relationship (E-R) Modeling Key Terms

18. D. Delen MSIS 5653 – Advanced Systems Development Entity-Relationship (E-R) Modeling Key Terms Naming and Defining Attributes An attribute type name  Is a noun (Customer_ID, Age, Minimum_Qty)  Should be unique  Should follow a standard format (Student_GPA, not GPA_of_Student) An attribute definition should  State what attribute is and why it is important  Make it clear what entities instances are included/not-incl in the attribute’s value  List all aliases/alternative names  Specify if the value is Required/Optional 10.18

19. D. Delen MSIS 5653 – Advanced Systems Development Entity-Relationship (E-R) Modeling Key Terms Candidate keys and identifiers Each entity type must have an attribute or set of attributes that distinguishes one instance from other instances of the same type Candidate key  Attribute (or combination of attributes) that uniquely identifies each instance of an entity type Identifier  A candidate key that has been selected as the unique identifying characteristic for an entity type 10.19

20. D. Delen MSIS 5653 – Advanced Systems Development Entity-Relationship (E-R) Modeling Key Terms Selection rules for an identifier 1.Choose a candidate key that will not change its value 2.Choose a candidate key that will never be null 3.Avoid using intelligent keys 4.Consider substituting single value surrogate keys for large composite keys (e.g., use Game_ID instead of Home_Team and Visiting_Team for the entity GAME) 10.20

21. D. Delen MSIS 5653 – Advanced Systems Development Entity-Relationship (E-R) Modeling Key Terms Multi-valued Attribute An attribute that may take on more than one value for each entity instance Represented on E-R Diagram in two ways: 1. double-lined ellipse 2. weak entity 10.21

22. D. Delen MSIS 5653 – Advanced Systems Development Entity-Relationship (E-R) Modeling Key Terms Relationship An association between the instances of one or more entity types that is of interest to the organization Association indicates that an event has occurred or that there is a natural link between entity types Relationships are always labeled with verb phrases 10.22

23. D. Delen MSIS 5653 – Advanced Systems Development Degree of Relationship Degree Number of entity types that participate in a relationship Three cases Unary (recursive)  A relationship between two instances of one entity type Binary  A relationship between the instances of two entity types Ternary  A simultaneous relationship among the instances of three entity types  Not the same as three binary relationships 10.23

24. D. Delen MSIS 5653 – Advanced Systems Development Figure 10-6 Example relationships of different degrees 10.24

25. D. Delen MSIS 5653 – Advanced Systems Development Cardinality The number of instances of entity B that can be associated with each instance of entity A Minimum Cardinality The minimum number of instances of entity B that may be associated with each instance of entity A Maximum Cardinality The maximum number of instances of entity B that may be associated with each instance of entity A 10.25

26. D. Delen MSIS 5653 – Advanced Systems Development Cardinality

27. Naming and Defining Relationships Relationship name is a verb phrase Avoid vague names (e.g., Has, Is_related_to) Guidelines for defining relationships  Definition explains what action is being taken and why it is important  Give examples to clarify the action  Optional participation should be explained  Explain the reason for any explicit maximum cardinality  Explain any restrictions on participation in the relationship  Explain extent of the history that is kept in the relationship  Explain whether an entity instance involved in a relationship instance can transfer participation to another relationship instance 10.27 Entity-Relationship (E-R) Modeling Key Terms

28. D. Delen MSIS 5653 – Advanced Systems Development Associative Entity An entity type that associates the instances of one or more entity types and contains attributes that are peculiar to the relationship between those entity instances 10.28

29. D. Delen MSIS 5653 – Advanced Systems Development Associative Entity: Example 10.29 Ternary Relationship

30. D. Delen MSIS 5653 – Advanced Systems Development Associative Entity: Example 10.30

31. D. Delen MSIS 5653 – Advanced Systems Development Representing Supertypes and Subtypes Subtype: A subgrouping of the entities in an entity type that is meaningful to the organization and that shares common attributes or relationships Supertype: A generic entity type that has a relationship with one or more subtype

32. D. Delen MSIS 5653 – Advanced Systems Development Representing Supertypes and Subtypes Business Rules for Supertype/Subtype Relationships: Total Specialization rule: Specifies that each entity instance of the supertype must be a member of some subtype in the relationship ( represented with || ) Partial Specialization rule: Specifies that an entity instance of the supertype is allowed not to belong to any subtypes ( represented with | ) Disjoint rule: Specifies that if an entity instance of the supertype is a member of one subtype, it cannot be a member of any other subtype ( represented with ”d” ) Overlap rule: Specifies that an entity instance can simultaneously be a member of two or more subtypes (represented with ”o” )

33. D. Delen MSIS 5653 – Advanced Systems Development Example: Supertype / Subtype Hierarchy

34. D. Delen MSIS 5653 – Advanced Systems Development Business Rules Specifications that preserve the integrity of a conceptual data model 1.Entity integrity (each instance of an entity type must have a unique non-null identifier) 2.Referential integrity (rules concerning the relationships between entity types) 3.Domains (constraints on valid values for attributes) 4.Triggering operation (business rules that protect the validity of attribute values) 10.34

35. D. Delen MSIS 5653 – Advanced Systems Development Domains The set of all data types and ranges of values that an attribute can assume Several advantages: 1.Verify that the values for an attribute are valid 2.Ensure that various data manipulation operations are logical 3.Help conserve effort in describing attribute characteristics 10.35

36. D. Delen MSIS 5653 – Advanced Systems Development Triggering Operations An assertion or rule that governs the validity of data manipulation operations such as insert, update and delete Includes the following components: User rule (Statement of the business rule to be enforced by the trigger) Event (Data manipulation operation that initiates the operation) Entity Name (Name of entity being accessed or modified) Condition (Condition that causes the operation to be triggered) Action (Action taken when the operation is triggered) 10.36

37. D. Delen MSIS 5653 – Advanced Systems Development Triggering Operations *** Responsibility for data integrity lies within scope of database management system, not individual applications 10.37

38. D. Delen MSIS 5653 – Advanced Systems Development The Role of CASE in Conceptual Data Modeling CASE tools provide two important functions: Maintain E-R diagrams as a visual representation of structured data requirements Link objects on E-R diagrams to corresponding descriptions in a repository Usually supports more than one E-R diagramming notations Most tools do not support drawing ternary or higher relationships 10.38

39. D. Delen MSIS 5653 – Advanced Systems Development Example: HB’s Inventory Management System +=

40. D. Delen MSIS 5653 – Advanced Systems Development Example: HB’s Inventory Management System

41. D. Delen MSIS 5653 – Advanced Systems Development Summary Process of conceptual data modeling Deliverables Gathering information Entity-Relationship Modeling Entities, Attributes, and Relations Candidate keys and identifiers Multivalued attributes Degree of relationship Cardinality Associative entities Domains and Triggering Operations Role of CASE 10.41

42. CHAPTER 11: Selecting the Best Alternative Design Strategy 2.42

43. D. Delen MSIS 5653 – Advanced Systems Development Learning Objectives Describe different sources of software Learn to assemble the various pieces of an alternative design strategy Learn how to generate at least three alternative design strategies Discuss selecting the best design strategy using both qualitative and quantitative methods Learn how to use the results of the analysis phase to update a Baseline Project Plan (BPP) Discuss design strategies and how they are applied to the Internet 11.4343

44. D. Delen MSIS 5653 – Advanced Systems Development Alternative Generation and Selection in SDLC

45. D. Delen MSIS 5653 – Advanced Systems Development Selecting the Best Alternative Design Strategy Two basic steps 1.Generate a comprehensive set of alternative design strategies 2.Select the one design strategy that is most likely to result in the desired information system Process Divide requirements into different sets of capabilities Enumerate different potential implementation environments that could be used to deliver the different sets of capabilities Propose different ways to source or acquire the various sets of capabilities for the different implementation environments 11.4545

46. D. Delen MSIS 5653 – Advanced Systems Development Selecting the Best Alternative Design Strategy Deliverables 1. At least three substantially different system design strategies for building the replacement information system 2. A design strategy judged most likely to lead to the most desirable information system 3. A Baseline Project Plan (BPP) for turning the most likely design strategy into a working information system 11.4646

47. D. Delen MSIS 5653 – Advanced Systems Development Generating Alternative Design Strategies Best to generate three alternatives Low-end  Provides all required functionality users demand with a system that is minimally different from the current system High-end  Solves problem in question and provides many extra features users desire Midrange  Compromise of features of high-end alternative with frugality of low-end alternative 11.4747

48. D. Delen MSIS 5653 – Advanced Systems Development Drawing Bounds on Alternative Designs Minimum Requirements Mandatory features versus desired features Forms of features  Data  Outputs  Analyses  User expectations on accessibility,response time and turnaround time 11.4848

49. D. Delen MSIS 5653 – Advanced Systems Development Drawing Bounds on Alternative Designs Constraints on System Development Date when system is needed Financial and human resources Elements of the system that cannot change Legal and contractual considerations Dynamics of the problem 11.4949

50. D. Delen MSIS 5653 – Advanced Systems Development Issues to Consider in Generating Alternatives Outsourcing The practice of turning over responsibility of some to all of an organization’s information systems applications and operations to an outside firm Can provide a cost effective solution Why would an organization outsource its information systems operations? Why would an organization dissolve its entire IS unit to bring in an outsider to manage it? 11.5050

51. D. Delen MSIS 5653 – Advanced Systems Development Issues to Consider in Generating Alternatives Sources of Software Hardware manufacturers Packaged software producers Custom software producers Enterprise solution software Application Service Providers In-house development 11.51

52. D. Delen MSIS 5653 – Advanced Systems Development …Sources of Software …

53. D. Delen MSIS 5653 – Advanced Systems Development Comparison of Software Sources

54. D. Delen MSIS 5653 – Advanced Systems Development Criteria for Choosing Off-the-Shelf Software Cost In-house versus purchased Functionality Mandatory, essential and desired features Vendor Support Installation Training Technical Support Viability of Vendor 11.54

55. D. Delen MSIS 5653 – Advanced Systems Development Criteria for Choosing Off-the-Shelf Software Flexibility Ease of customization Documentation User documentation Technical documentation Response Time Ease of Installation 11.55

56. D. Delen MSIS 5653 – Advanced Systems Development Validating Purchased Software Information Information from vendor Request For Proposal (RFP) or Quote For Proposals (QFP)  A document provided to vendors to ask them to propose hardware and system software that will meet the requirements of your new system Software evaluation period Customer references from vendor Independent software testing service Trade publications 11.56

57. D. Delen MSIS 5653 – Advanced Systems Development Hardware and Software Issues Existing Platform 1.Lower costs 2.Information system staff is familiar with operation and maintenance 3.Increased odds of successfully integrating system with existing applications 4.No added costs of converting old systems to new platform or transferring data New Hardware and System Software 1.Some software components will only run on new platform 2.Developing system for new platform gives organization opportunity to upgrade technology holdings 3.New requirements may allow organization to radically change its computing operations 11.57

58. D. Delen MSIS 5653 – Advanced Systems Development Implementation and Organizational Issues Implementation Issues Technical and social aspects of implementation need to be addressed Training Disruption of work Organizational Issues Overall cost and availability of funding Management support User acceptance 11.58

59. D. Delen MSIS 5653 – Advanced Systems Development Hoosier Burger’s New Inventory Control System Replacement for existing system 11.59

60. D. Delen MSIS 5653 – Advanced Systems Development Hoosier Burger’s New Inventory Control System 11.60 Three alternatives A. Low-end B. Midrange C. High-end

61. D. Delen MSIS 5653 – Advanced Systems Development Hoosier Burger’s New Inventory Control System Selecting the most likely alternative Weighted approach can be used to compare the three alternatives Left hand side of table contains decision criteria  Constants and requirements  Weights are arrived at by discussion with analysis team, users and managers Each requirement and constraint is ranked  1 indicates that the alternative does not match the request well or that it violates the constraint  5 indicates that the alternative meets or exceeds requirements or clearly abides by the constraint 11.61

62. D. Delen MSIS 5653 – Advanced Systems Development Hoosier Burger’s New Inventory Control System Quantitative Measures: Weights? Rankings? 11.62 According to the weights used, alternative C appears to be the best

63. D. Delen MSIS 5653 – Advanced Systems Development Updating the Baseline Project Plan (BPP) The Baseline Project Plan (BPP) was developed during project initiation and planning Baseline Project Plan (BPP) can be used as an outline of a status report at analysis phase Schedule will be updated to reflect actual activities and durations An oral presentation of project status is typically made at this phase 11.63

64. D. Delen MSIS 5653 – Advanced Systems Development Internet Development: Selecting the Best Alternative Design Strategy Pine Valley Furniture WebStore Requirements and constraints were compiled by consultant and team (see Table 11-8) 11.64

65. D. Delen MSIS 5653 – Advanced Systems Development Internet Development: Selecting the Best Alternative Design Strategy 11.65

66. D. Delen MSIS 5653 – Advanced Systems Development Internet Development: Selecting the Best Alternative Design Strategy Proposed system is a scalable, three-tier approach Scalable  The ability to seamlessly upgrade the system through either hardware upgrades, software upgrades or both Three-tier  Web Server Provides connection to the internet and presentation of HTML page  Applications Server Middle layer of software and hardware that lies between Web server and corporate network  Corporate network Existing organizational computing infrastructure 11.66

67. D. Delen MSIS 5653 – Advanced Systems Development Internet Development: Selecting the Best Alternative Design Strategy 11.67

68. D. Delen MSIS 5653 – Advanced Systems Development Summary Sources of Software Identifying requirements and constraints Generating alternative design strategies Selecting the best design strategy Updating a Baseline Project Plan (BPP) Selecting the best design strategy for Internet applications 11.68