1. Designations 2. Definitions 3. Refutable descriptions 4. Rough sketches

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1 Previously: Four important kinds of description 1. Designations 2. Definitions 3. Refutable descriptions 4. Rough sketches Data requirements Often specified using both 1. Designations and 2. Definitions Week 6 1

2 Data requirements Data requirements are central to many different kinds of systems Why? Data requirements are important whether you are documenting Domain level or Product level requirements. What? Data requirements are the common to many different templates for specifying requirements Why? Four styles of data requirements 1. Data Model ER diagram Class diagram Really database design, BUT very precise requirements 2. Data dictionary Definitions of the data As an explanation of the data model, if it is used Meanings, value ranges Synonyms Default values Week 6 2

3 Data Model Week 6 3

4 Data modelling for a hotel GUEST STAY Guest in a hotel Description: The Guest is the person or company who has to pay the bill. A Guest has one or more Stay records. A company Guest may have none. The people staying in the Rooms are also called guests, but are not Guests in the system. Synonym: Customer is a synonym for Guest, but in the system we only use Guest. Week 6 4

5 Data Modelling for a hotel GUEST GuestID Guestname Address Credit card number STAY Room Number CheckIndate StayType RoomType CheckoutDate GuestID Guestname Name: Guestname Description: The name stated by the Guest. For companies, the official company name since the bill is sent there. Size: 50 chars (text) Longer names exist, but better truncate at registration time than at print out time. We call Guestname a data element Week 6 5

6 To specify Data Elements in a DD: 1. Name i.e. designation 2. Description brief explanation 3. Size how many characters or digits, etc. 4. Range/Limits required value limits or range 5. Accuracy required 6. Precision required. Accuracy and precision Precision refers to the acceptable margin of error Week 6 6

7 Roomrate 1. Name Roomrate 2. Description How much the room costs per night in Euros before discounts and or charges are applied. 3. Size 2 or 3 digits 4. Range Accuracy required 100% 6. Precision required within Hospital Clinic Appointments PATIENT PID Firstname Surname Telephone Paymethod APPOINTMENT PID Date Time Clinic Week 6 7

8 Did the patient turn up? PATIENT APPOINTMENT ATTENDANCE Entity: The attendance entity contains details of client appointments and attendances for a specific session. A client may attend who had an appointment booked or a person may attend without a previously booked appointment; this is known as an unscheduled attendance. The attendance record for a client who had a booked appointment but did not attend (DNA) is marked as a Did not attend Attribute Description Type Size Validation ID (PK) A unique identifier for each appointment/attendance Numeric 10 Date Date of appointment/attendance Date 10 Appointment Time Time of appointment/attendance Time 5 Status Indicates if the if the attendance is pending (ie booked appointment), attended or did not attend Text 50 Unscheduled Did Not Attend Reason Indicates if the attendance was unscheduled and did not have a prior booked appointment Logical 1 Reason why the client did not attend Text 30 Required if Status = Did not attend Session Id (FK) Primary key in Session Entity Numeric 8 Client Id (FK) Primary key in Client Entity Numeric 8 Staff Id (FK) Primary key in Staff Entity Numeric 8 Week 6 8

9 Source: NHS Data Dictionary (online) Entity: The attendance entity contains details of client appointments and attendances for a specific session. A client may attend who had an appointment booked or a person may attend without a previously booked appointment; this is known as an unscheduled attendance. The attendance record for a client who had a booked appointment but did not attend (DNA) is marked as a Did not attend Attribute Description Type Size Validation ID (PK) A unique identifier for each appointment/attendance Numeric 10 Date Date of appointment/attendance Date 10 Appointment Time Status Time of appointment/attendance Time 5 Indicates if the if the attendance is pending (ie booked appointment), attended or did not attend Text 50 Unscheduled Indicates if the attendance was unscheduled and did not have a prior booked appointment Logical 1 Did Not Attend Reason why the client did not attend Text 30 Required if Reason Status = Did not attend Session Id (FK) Primary key in Session Entity Numeric 8 Client Id (FK) Primary key in Client Entity Numeric 8 Staff Id (FK) Primary key in Staff Entity Numeric 8 Data dictionary vs Glossary 1. Name Discount 2. Description How much the price of the Room is reduced, relative to the Roomrate. 3. Size 1 or 2 digits 4. Range Accuracy required 100% 6. Precision required n/a Discount: a deduction from the usual cost of a room, typically given for prompt or advance payment or to a special category of Guests. Week 6 9