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1 BTEC HNC Systems Support Castle College 2007/8 Systems Analysis Lecture 7 Descriptors Events Events Tables.

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Presentation on theme: "1 BTEC HNC Systems Support Castle College 2007/8 Systems Analysis Lecture 7 Descriptors Events Events Tables."— Presentation transcript:

1 1 BTEC HNC Systems Support Castle College 2007/8 Systems Analysis Lecture 7 Descriptors Events Events Tables

2 2 BTEC HNC Systems Support Castle College 2007/8 Lecture Objectives At the end of this lecture you should be able to: Explain what is meant by an event Identify events which trigger the system Draw an events table and a Use Case model

3 3 BTEC HNC Systems Support Castle College 2007/8 Modelling Systems Recap We develop a model after completing fact finding One way to do this is to identify Users and Processes Once identified, we can produce Role Descriptors and Business Process descriptors

4 4 BTEC HNC Systems Support Castle College 2007/8 Using Events Tables Another method is to use ‘Events’ which trigger business processes Recap: In lecture 2 we examined how an Event could trigger 3 business processes. The event was called “Receive Sales Order” Question: What type of event is this?

5 5 BTEC HNC Systems Support Castle College 2007/8 A simple business model might consist of an Event 3 business processes and a result This event is a response to an external trigger

6 6 BTEC HNC Systems Support Castle College 2007/8 Types of Event Events trigger all the processes within a system There are three types of event: External Temporal State

7 7 BTEC HNC Systems Support Castle College 2007/8 External Events Occur outside the system and are usually initiated by a person The system is required to record details about an external event (e.g. customer places an order) Or the system is required to produce something in response to the request: (e.g. customer rings to follow up/chase an order)

8 8 BTEC HNC Systems Support Castle College 2007/8 Typical external events Actor wants some information –e.g. employee takes a call from a customer enquiring about an order they have placed Data needs to be updated –e.g. employee changes address Management wants some information –e.g. manager want to know who has holidays booked

9 9 BTEC HNC Systems Support Castle College 2007/8 Temporal Events Triggered by a specific time being reached Many systems produce daily, weekly, monthly and annual reports. These reports are triggered when a specific date and time are reached Some events are triggered after a certain amount of time has passed (e.g.) reminder produced 2 weeks after bill was sent

10 10 BTEC HNC Systems Support Castle College 2007/8 Typical Temporal Events Internal outputs required –Management reports e.g. summary of all sales –Operational reports (detail of daily operation) –Internal statements and documents (including payroll) External outputs required –e.g. Statements,bills and reminders

11 11 BTEC HNC Systems Support Castle College 2007/8 State Events Triggered by a certain state/particular condition becoming true (Similar to temporal events except that the time cannot be defined) e.g. Re-order stock because the number of items in stock have reached a specific minimum level (re-order level), or e.g. Bank sends out a letter to their customer as their account has gone overdrawn

12 12 BTEC HNC Systems Support Castle College 2007/8 Identifying Events …can be difficult! Following the process through can identify the sequence of events If there is no time delay between two or more interactions then they are the same event, otherwise they are different events

13 13 BTEC HNC Systems Support Castle College 2007/8 Events we are not interested in Events that the do not normally concern the users. These are dealt with during design e.g. Logging on, Passwords, Backups Error routines (not yet…) –Perfect World assumption – It helps to think that everything is perfect and concentrate on events that are required in a perfect world

14 14 BTEC HNC Systems Support Castle College 2007/8 Activity – practise Look at the following sequence of occurrences at a hotel- identify the events Look for things that occur together without any time delays What are the events? What do they involve? What would you call the events?

15 15 BTEC HNC Systems Support Castle College 2007/8 Activity: Hotel occurrences 1.Customer contacts the hotel to see if they have a room free for the following Saturday 2.The clerk checks the room bookings and finds a free room 3.Customer accepts the room and gives their personal details (e.g. name, address, etc.) to the clerk 4.The customer pays the deposit by credit card 5.The clerk updates the system to show the room is no longer free on Saturday and that it is booked to the customer 6.The customer rings the following day to order flowers for the room. This is added to the room booking for inclusion on the bill

16 16 BTEC HNC Systems Support Castle College 2007/8 Activity: Hotel occurrences 7.The customer turns up on Saturday and gives their name 8.The clerk uses the system to find the room number and gives the customer their room key 9.The clerk records that the room is now occupied 10.On Sunday the customer is leaving the hotel 11.The bill is calculated by the clerk 12.The customer pays the bill 13.The clerk records that the room is no longer occupied and that the customer has paid

17 17 BTEC HNC Systems Support Castle College 2007/8 Examine & Document Events For each event the analyst must determine the: –Trigger –Source & Actor –Activity/Use Case –Response –Destination

18 18 BTEC HNC Systems Support Castle College 2007/8 Trigger How does the system know the event has occurred? –For external events…data enters the system –For temporal events…it is the date or time –For state events… it is the condition that has been met (state has changed)

19 19 BTEC HNC Systems Support Castle College 2007/8 Source The source is: –for external events only –in other words who is supplying the data which will be typed in –Might be the actor or someone interacting with the actor NB Note the difference!

20 20 BTEC HNC Systems Support Castle College 2007/8 Activity or Use Case What process does the system carry out in response to the event trigger? Remember: Case when the system is used to produce…

21 21 BTEC HNC Systems Support Castle College 2007/8 Response and Destination Response: –What output (if any) is produced by the system Destination: –What actor gets this output?

22 22 BTEC HNC Systems Support Castle College 2007/8 Building an Events Table An Events Table can be built using one row for each event We call the first event ‘customer makes booking’ we can call our Use Case ‘create new booking’ We can tell from our description that an event is happening and that we need the customer to trigger it and an Actor to perform the process

23 23 BTEC HNC Systems Support Castle College 2007/8 Events Table: hotel booking Event: Customer makes booking Trigger: Customer Enquiry Source: Customer Actor: Hotel Clerk Activity (Use Case): Create new booking Response: Room booking confirmation Destination: Hotel Clerk and Customer

24 24 BTEC HNC Systems Support Castle College 2007/8 Events tables to Use Case diagrams We can use the Events table to define the elements of a Use Case model Question: How does this work? Answer : Our Events table has given us a Use Case -Create new booking

25 25 BTEC HNC Systems Support Castle College 2007/8 Recap on Use Case model elements The symbols we can use are as follows: Actor Association Use Case Use Case label >

26 26 BTEC HNC Systems Support Castle College 2007/8 Actors and Use Cases Our Event table tells there are 2 Actors or ‘Inter-actors’ involved with the system for the first event Only the Booking Clerk interacts directly with the system 1.The Booking Clerk 2.The customer (who provides the trigger and necessary input information)

27 27 BTEC HNC Systems Support Castle College 2007/8 Use Case model of the event Remember this is just a fragment! Hotel System Create New Booking Clerk

28 28 BTEC HNC Systems Support Castle College 2007/8 Over to you… It is now your turn to complete the Hotel occurrences example Complete the table, and then translate it into a Use Case diagram Remember that practice makes perfect

29 29 BTEC HNC Systems Support Castle College 2007/8 Answers 1.Customer contacts the hotel for a free room 2.Clerk checks room availability 3.Customer gives name and address 4.Customer pays deposit 5.Clerk updates system to show room booked 6. Customer rings to order flowers 7.Customer turns up 8.Clerk find room number and gives key 9.Clerk records room as occupied 10.Customer leaves 11.Bill calculated 12.Customer pays bill 13.Clerk records room empty and customer paid. Customer Makes Booking Customer Orders service Customer Checks in Customer Checks out

30 30 BTEC HNC Systems Support Castle College 2007/8 Events & Use Cases Practise Could you also construct an events table and Use Case diagram from this example?

31 31 BTEC HNC Systems Support Castle College 2007/8 Summary You should now know: What is meant by an event The different types of events and be able to give an example of each What is meant by a trigger, source, use case, response and destination How to draw an events table How to draw a simple Use Case example from your Events table

32 32 BTEC HNC Systems Support Castle College 2007/8 References Systems Analysis & Design Shelley Cashman and Rosenblat 6 th Ed. Thomson (2006) Eva and Skidmore (2004). Introducing Systems Development. Palgrave Macmillan Satzinger JW, Jackson RB and Burd SD (2004). Systems Analysis and Design in a Changing World. 3 rd edition. Thomson


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