A Ticket Booking System For Theatre
The purpose of the online ticket booking system is to provide another way for purchasing cinema tickets in advance. It is an automatic system. This paper presents a formal use of the Object Oriented analysis and Design, we will illustrate our system by providing Use Case Diagrams with Specifications, Activity Diagrams, Class Diagrams, Sequence Diagrams, State Machines and Communication Diagrams on the functionalities of the system, also we will provide some process description and data dictionary.
The goals of our system are:
Record performance details
Record customer details
Record tickets sold
Print tickets
Print address labels for telephone booking
Task 1: Functional Modelling
Identification of Actors & Use Cases
Analyzing the existing system we figured out that, there are two main scopes to be covered in the system. The scopes are Performance Planning and Ticket Booking. We used the below table to identify the Actors and the Use Cases for the system.
User
Role
Use Case
Theatre Manager
Performance planning
Define the type of the performance and name it.
Performance scheduling
Define date and time of the performance.
Artist booking
Book an artist for the performance.
Ticket pricing
Determine a price for the ticket.
Clerk
Check schedule
Check the performance schedule for a particular show on a date.
Check seat availability
Checks for available seats
Capture customer information
Record customer details
Check ticket price
Check for ticket price for particular show.
Sell ticket
Record tickets sold.
Print ticket
Print ticket for the customer.
Print address label
Print address label for telephone booking.
Use Case Diagram
Following diagram shows the overall view of the Ticket Booking System for Theatre.
Figure 1: Use Case Diagram (Performance Planning & Ticket Booking)
Use Case Specification
Table 1: Use Case of Performance Planning
Number:
UC01
Req. Doc Ref:
Name:
Performance Planning
Status:
Actors:
Theatre Manager
Pre-requisites:
User should be logged in the system.
Goal:
Defining the performance type and naming it.
Use Case Relationships:
Extend:UC02, UC03
Include:
Association:
Generalization:
Description:
Index
Actor Event
1
User enters the name of the performance.
2
User enters the type of the performance.
3
System checks for all required data entry.
4
System connects to the database.
5
System writes data into the database.
6
System shows a confirmation message after successful database writes.
Alternatives:
Index
Actor Event
A 3.1
Enter required information.
A 4.1
Check network connectivity
A 4.2
Check database connectivity
A 4.3
Check database user role
A 5.1
Theatre manager gets notification of unsuccessful operation.
Table 2: Use Case of Performance Scheduling
Number:
UC02
Req. Doc Ref:
Name:
Performance Scheduling
Status:
Actors:
Theatre Manager
Pre-requisites:
User should be logged in the system.
Performance planning (UC01) should be inserted into the system.
Goal:
Define date and time of the performance.
Use Case Relationships:
Extend:
Include:
Association:
Generalization:
Description:
Index
Actor Event
1
User selects the desired performance from the system.
2
User enters the date of the performance.
3
User enters the time of the performance.
4
System checks for all required data entry.
5
System connects to the database.
6
System writes data into the database.
7
System shows a confirmation message after successful database writes.
Alternatives:
Index
Actor Event
A 3.1
Enter required information.
A 5.1
Check network connectivity
A 5.2
Check database connectivity
A 5.3
Check database user role
A 6.1
Theatre manager gets notification of unsuccessful operation.
Table 3: Use Case of Artist Booking
Number:
UC03
Req. Doc Ref:
Name:
Artist Booking
Status:
Actors:
Theatre Manager
Pre-requisites:
User should be logged in the system.
Performance planning (UC01) should be inserted into the system.
Goal:
Book an artist for the performance.
Use Case Relationships:
Extend:
Include:
Association:
Generalization:
Description:
Index
Actor Event
1
User selects the desired performance from the system.
2
User enters the name of the desired artist.
3
System checks for all required data entry.
4
System connects to the database.
5
System writes data into the database.
6
System shows a confirmation message after successful database writes.
Alternatives:
Index
Actor Event
A 3.1
Enter required information.
A 4.1
Check network connectivity
A 4.2
Check database connectivity
A 4.3
Check database user role
A 5.1
Theatre manager gets notification of unsuccessful operation.
Table 5: Use Case of Schedule Checking
Number:
UC04
Req. Doc Ref:
Name:
Schedule Checking
Status:
Actors:
Clerk
Pre-requisites:
User should be logged in the system.
Performance scheduling (UC02) should be inserted into the system.
Goal:
Check the performance schedule for a particular show on a date.
Use Case Relationships:
Extend: UC01
Include:
Association:
Generalization:
Description:
Index
Actor Event
1
User selects a desired performance and a date.
2
System shows a confirmation message for the availability of the performance.
3
System allows the user to perform the next event (UC06).
Alternatives:
Index
Actor Event
A 1.1
System notifies the user that the performance is unavailable on the desired date.
Table 6: Use Case of Check Seat Availability
Number:
UC05
Req. Doc Ref:
Name:
Check Seat Availability
Status:
Actors:
Clerk
Pre-requisites:
User should be logged in the system.
Schedule checking (UC05) should be performed by the user.
Goal:
Checks for available seats.
Use Case Relationships:
Extend:
Include:
Association:
Generalization:
Description:
Index
Actor Event
1
User selects a desired performance and a date.
2
System shows a confirmation message for the availability of the seat.
3
System allows the user to perform the next event (UC07).
Alternatives:
Index
Actor Event
A 1.1
System notifies the user that the seat is unavailable for the desired performance.
Table 7: Use Case of Capturing Customer Information
Number:
UC06
Req. Doc Ref:
Name:
Capture Customer Information
Status:
Actors:
Clerk
Pre-requisites:
User should be logged in the system.
Seat checking (UC06) should be performed by the user.
Goal:
Record customer details.
Use Case Relationships:
Extend:
Include:
Association:
Generalization:
Description:
Index
Actor Event
1
User enters the name, address and telephone number of the customer.
2
System checks for all required data entry.
3
System connects to the database.
4
System writes data into the database.
5
System shows a confirmation message after successful database writes.
Alternatives:
Index
Actor Event
A 2.1
Enter required information.
A 3.1
Check network connectivity
A 3.2
Check database connectivity
A 3.3
Check database user role
A 4.1
User gets notification of unsuccessful operation.
Table 8: Use Case of Checking Ticket Price
Number:
UC07
Req. Doc Ref:
Name:
Check Ticket Price
Status:
Actors:
Clerk
Pre-requisites:
User should be logged in the system.
Ticket pricing information (UC04) should be entered into the system.
Goal:
Check for ticket price for particular show
Use Case Relationships:
Extend: UC01
Include:
Association:
Generalization:
Description:
Index
Actor Event
1
User selects a desired performance form the system.
2
System shows the defined pricing for the ticket.
Alternatives:
Index
Actor Event
A 2.1
Price not found is notified to the user.
Table 9: Use Case of Selling Ticket
Number:
UC08
Req. Doc Ref:
Name:
Selling Ticket
Status:
Actors:
Clerk
Pre-requisites:
User should be logged in the system.
Check ticket price (UC08) should be performed by the user.
Goal:
Record tickets sold.
Use Case Relationships:
Extend:
Include:
Association:
Generalization:
Description:
Index
Actor Event
1
User selects the desired performance from the system.
2
User enters ticket selling date and the ticket price for the desired performance.
3
System checks for all required data entry.
4
System connects to the database.
5
System writes data into the database.
6
System shows a confirmation message after successful database writes.
Alternatives:
Index
Actor Event
A 3.1
Enter required information.
A 4.1
Check network connectivity
A 4.2
Check database connectivity
A 4.3
Check database user role
A 5.1
Theatre manager gets notification of unsuccessful operation.
Table 10: Use Case of Printing Ticket
Number:
UC09
Req. Doc Ref:
Name:
Printing Ticket
Status:
Actors:
Clerk
Pre-requisites:
User should be logged in the system.
Check ticket price (UC08) should be performed by the user.
Goal:
Print ticket for the customer
Use Case Relationships:
Extend:
Include:
Association:
Generalization:
Description:
Index
Actor Event
1
User triggers the print command for the sold ticket.
Alternatives:
Index
Actor Event
A 1.1
Printer not found notification will be given to the user.
Table 11: Use Case of Checking Ticket Booking Type
Number:
UC10
Req. Doc Ref:
Name:
Check Ticket Booking Type
Status:
Actors:
Clerk
Pre-requisites:
User should be logged in the system.
Print ticket (UC10) should be performed by the user.
Goal:
Determine the ticket booking type.
Use Case Relationships:
Extend:
Include:
Association:
Generalization:
Description:
Index
Actor Event
1
User selects the booking type to identify whether the ticket was booked over phone.
Alternatives:
Index
Actor Event
Table 12: Use Case of Printing Address Label
Number:
UC11
Req. Doc Ref:
Name:
Print Address Label
Status:
Actors:
Clerk
Pre-requisites:
User should be logged in the system.
Ticket booking type (UC11) should be performed by the user.
Goal:
Print address label for telephone booking
Use Case Relationships:
Extend: UC11
Include:
Association:
Generalization:
Description:
Index
Actor Event
1
User triggers the print command to print the address label.
Alternatives:
Index
Actor Event
Activity Diagram
Based on the system observation, a high level activity diagram is drawn modelling the process of ticket booking for theatre. The activity diagram will bring everybody on a common ground for understanding the system functionalities.
Figure 2: Activity Diagram (Performance Planning & Ticket Booking)
Task 2: Structural Modelling
Class Diagram (attributes & operations)
The following diagram depicts the relationships between the classes for Ticket Booking System along with the attributes and the operations.
Figure 3: Class Diagram (Performance Planning & Ticket Booking)
Task 3: Behavioural Modelling
Sequence Diagram
The following diagram is a sequence diagram for buying ticket. There are few things I want to state, that this is just one of the sequences of buying ticket. There could be more alternative sequence for buying ticket. For example, we can choice a performance before buying ticket. But the overall structures of all buying ticket sequence are similar, so, others sequence will not be shown.
Figure 4: Sequence Diagram (Performance Planning & Ticket Booking)
State Machine Diagram
Below diagram is used to give an abstract description of the behaviour of the ticket booking system. This behaviour is analyzed and represented in series of events that could occur in one or more possible states. Hereby “each diagram usually represents objects of a single class and tracks the different states of its objects through the system.
Figure 5: State Machine Diagram (Performance Planning & Ticket Booking)
Communication Diagram
Communication diagram is similar to sequence diagrams, but it provides an overview of the relationships between objects, rather than focusing on the order of messages between objects, as the software executes.
Figure 6: Communication Diagram (Performance Planning & Ticket Booking)
Task 4: Data Protection Law
Introduction
In Bangladesh Cyber Acts are in a process to be implemented. The Government of Bangladesh has formed National Council for Science and Technology (NCST). The Executive Committee for NCST has also been formed to implement policies formulated by the Council. Currently NCST is working with the general boundaries to protect the ICT industry and specific laws are yet to be decided. For our application we can follow the acts and regulations from UK.
Laws, Regulations and Best Practices
The Data Protection Act gives individuals the right to know what information is held about them. It provides a framework to ensure that personal information is handled properly. The Act works in two ways. Firstly, it states that anyone who processes personal information must comply with eight principles, which make sure that personal information is:
Fairly and lawfully processed
Processed for limited purposes
Adequate, relevant and not excessive
Accurate and up to date
Not kept for longer than is necessary
Processed in line with your rights
Secure
Not transferred to other countries without adequate protection
The second area covered by the Act provides individuals with important rights, including the right to find out what personal information is held on computer and most paper records.
Data protection laws should be adequate enough to maintain the below options at a minimum-
How to access information
This allows one to find out what information is held about him/her on a computer and within some manual records, such as medical records, files held by public bodies and financial information held by credit reference agencies.
Correcting information
This allows one to apply to a court to order a data controller to correct, block, remove or destroy personal details if they are inaccurate or contain expressions of opinion based on inaccurate information.
Preventing processing of information
This means one can ask a data controller not to process information about him/her that causes substantial unwarranted damage or distress. The data controller is not always bound to act on the request.
Preventing unsolicited marketing
This means a data controller is required not to process information about one for direct marketing purposes if he/she asks them not to.
Preventing automated decision making
This means one can object to decisions made only by automatic means. For example, where there is no human involvement.
Claiming compensation
This allows one to claim compensation through the courts from a data controller for damage, and in some cases distress, caused by any breach of the act.
Exempt information
This allows one to ask the information commissioner to investigate and assess whether the data controller has breached the act.
There should be a committee (in our case NCTS could be the choice) that will have legal powers to ensure that organizations comply with the requirements of the data protection laws. It is notable here that these powers are focused on ensuring that organizations meet the obligations of the act.
To promote best practices the regulation-
The committee should carry out consensual audits with data controllers to assess their processing of personal information.
The committee should see auditing as a constructive process with real benefits for data controllers.
The committee should adopt, wherever possible, a participative approach including working closely with the data controller to agree the timing and scope of the audit.
Comply with Data Protection Law
A short checklist can help us to comply with the data protection laws in our system. Maintaining all the items in the checklist does guarantee compliance but it should mean that we are heading in the right direction.
We should store only the related information about the customer and the personnel’s involved with the system. And we need to make sure that we know what we are going to do with the information.
The person should know, what are the information we are holding. He/she should understand what it will be used for.
Information should be held securely whether it’s on the paper or on computer.
The system should prevent any unwanted access of its resources.
The information should be deleted as soon as there is no need for it.
Access control list should be created with a strict need to know to prevent data access from all kind of users of the system.
We should train the stuff in their duties and responsibilities under the act that we are putting them in to practice.
Recommendations
Being a strategic regulator means that, in so far as we have a choice, we have to be selective with our interventions. We will therefore apply our limited resources in ways that deliver the maximum return in terms of a sustained reduction in data protection risk. That is the risk of harm through improper use of personal information.
There are priorities we have to set. We need to focus most attention on situations where there is a real likelihood of serious harm. We also need to focus on situations where our intervention is most likely to make a long term as well as a short term difference. When we intervene we must do so in a way that gives us the best possible return and remember that we will often be at our most effective when working closely with others. We are entitled to have legitimate expectations of those who are in a position to influence data protection risk. Our effectiveness depends on them seeking and welcoming our reasonable interventions. Furthermore we have an important international role. Data protection risk in the Bangladesh is increasingly influenced by events worldwide.
Our risk-based approach is in line with good regulatory practice. It does not mean that we seek to remove all data protection risk. We do what we can to moderate the most serious risks and protect those who are most vulnerable to improper use of their information. But we will not try to take away freedom of choice and will remember that individuals themselves ought to be best placed to make decisions about their own interests. Part of our job is to equip individuals with the knowledge and tools to enable them to make their own well-informed decisions about the use and disclosure of their personal information.
Being a strategic regulator also means extending our approach beyond simply improving (through guidance, persuasion and regulatory action) the behaviour of organisations that handle personal information. We also have a legitimate role in informing and influencing the market or political environment in which they operate. Thus we will seek to have long term influence over government and the legislature at Westminster and in the devolved administrations as well as over representative bodies and other stakeholders, to ensure privacy friendly outcomes.
We will also seek to influence the legal framework that governs our own work to ensure that data protection requirements are simple, meaningful and proportionate and that we have the flexibility and tools to regulate effectively.
Building public confidence in data protection is the key in our approach. We protect people, not just information. This means we need to engage with the public and explain what we do in a way that they can easily understand and relate to.
This commitment is at the heart of how we approach our job as data protection regulator and will inform all our data protection tasks including complaints handling and the provision of advice.
Task 5: Ticket Printing
Produce Tickets
To protect the tickets from being forged or copied we can use a barcode on each ticket. We’ll print a unique 10-digit number as a barcode on the tickets, which will be checked at the entrance with the software and a simple barcode scanner. As each barcode can only be used once to enter, copied or forged tickets are rejected and the revenues are protected. By default, the tickets will be labeled with random numbers with 10 digits, which will serve as copy protection.
Figure 7: Sample barcode to print on tickets
Seat Allocation
Tickets will be printed with seat numbers, with serial numbers. Section names can be in different colours to facilitate orientation. For sections with an aisle a seat description can be added to the seat number (e.g. “left”, “right”), which helps the visitor to find the seat.
Figure 8: Sample barcode to print on ticket with seat no.
Hardware for printing tickets
There are numerous tickets available in the market but I found D-Link printers suitable for our system. Below are the details of the hardware-
Description: With the DSA-3100 and the DSA-3100P Ticket Printer, businesses and organizations can provide free or fee-based broadband Internet access to their customers or members. No complex billing system is required, guaranteeing a quick and convenient Internet experience for operators and their hot spot users. The DSA-3100P is hassle-free hot spot ticket printer that communicates with the DSA-3100 Public/Private Gateway to generate and print log-in usernames and passwords for the hot spot customers. Patented for easy loading, the DSA-3100P is connected to the DSA-3100 gateway via its RS-232 serial communication. With the DSA-3100P, the DSA-3100 gateway can manage and store up to 2,000 user accounts in its internal database and support up to 50 logged-in users at any time.
Features:
Printing Method: Thermal Dot Line Printing
Print Speed: 80 mm/Second
Connectivity: RS-232 Serial
Compatibility: D-Link DSA-3100 Public/Private Gateway
Specification:
Manufacturer
D-Link
Manufacturer Part #
DSA-3100P
Device Type
Thermal Line Label Printer
Media Handling
Media Type
Receipt Paper
Max Media Size
2.2″
Max Printing Width
1.9″
Roll Maximum Outer Diameter
3.3″
Total Capacity
1 Roll
Connectivity
Interfaces
1 x RS-232 Serial
Included Cables
1 x Serial Cable
Power Requirements
Power Supply
External, 3.5 V DC
Dimensions(H X W X D)
Unit
4.6″ x 3.8″ x 6.3″
Weight
Unit
0.9 lbs
Price: $375
Figure 9: D-Link DSA-3100P Ticket Printer
Task 6: Database Design
Database Design
Figure 10: Database Design (Performance Planning & Ticket Booking)
Data Dictionary
Table: Artist
Attribute
Data Type
Length
Primary Key
Ref. Table
ArtistID
Integer
Yes
ArtistName
Varchar
100
Table: Performance
Attribute
Data Type
Length
Primary Key
Ref. Table
PerformanceID
Integer
Yes
PerformanceName
Varchar
100
TicketPriceID
Integer
TicketPrice
ArtistID
Integer
Artist
Table: TicketPrice
Attribute
Data Type
Length
Primary Key
Ref. Table
TicketPriceID
Integer
Yes
PerformanceID
Integer
Performance
TicketPrice
Numeric
(18,2)
Table: PerformanceSchedule
Attribute
Data Type
Length
Primary Key
Ref. Table
ScheduleID
Integer
Yes
PerformanceID
Integer
Performance
PerformanceDate
Date
Table: Customer
Attribute
Data Type
Length
Primary Key
Ref. Table
CustomerID
Integer
Yes
Name
Varchar
100
Address
Varchar
250
Telephone
Varchar
20
Table: Sales
Attribute
Data Type
Length
Primary Key
Ref. Table
SalesID
Integer
Yes
PerformanceID
Integer
Performance
ScheduleID
Integer
PerformanceSchedule
TicketPriceID
Integer
TicketPrice
CustomerID
Integer
Customer
BookingType
Boolean
Table: SeatAllocation
Attribute
Data Type
Length
Primary Key
Ref. Table
SeatID
Integer
Yes
SalesID
Integer
Sales
SeatNoFrom
Integer
SeatNoTo
Integer
Task 7: Object-Orient Approaches vs. Standard Approaches
Standard Approaches
Standard approach includes many variations based on techniques used to develop information system with structured and modular programming. Standard analysis and design techniques are a software engineering methodology for describing systems as a hierarchy of functions. Below are the characteristics of Standard Approaches.
Approach for structured analysis consists of the following objects:
Data Flow Diagrams (DFD)
Shows processes and flow of data in and out of these processes.
Does not show control structures (loops)
Contains 5 graphic symbols (shown later)
Uses layers to decompose complex systems
Can be used to show logical and physical
Is a quantum leap forward to other techniques at the time, I.e. monolithic descriptions with globs of text.
Context Diagram
Represent all external entities that may interact with a system
This diagram pictures the system at the centre, with no details of its interior structure, surrounding by all its interacting systems, environment and activities.
The objective of a system context diagram is to focus attention on external factors and events that should be considered in developing a complete set of system requirements and constrains.
System context diagram are related to Data Flow Diagram
Context diagrams can be helpful in understanding the context in which the system will be part of software engineering.
Data Dictionary
A data dictionary or database dictionary is a file that defines the basic organization of a database.
A database dictionary contains a list of all files in the database, the number of records in each file, and the names and types of each data field.
Most database management systems keep the data dictionary hidden from users to prevent them from accidentally destroying its contents
Data dictionaries do not contain any actual data from the database, only book keeping information for managing it. Without a data dictionary, however, a database management system cannot access data from the database.
OO Approaches
Object-oriented software design is a design strategy where system designers think in terms of objects instead of operations or functions. The executing system is made up of interacting objects that maintain their own local state and provide operations on that state information. They hide information about the representation of the state and hence limit access to it. An object-oriented design process involves designing the object classes and the relationships between these classes.
Approach for object oriented analysis consists of the following objects:
Use cases: A use case in software engineering and systems engineering is a description of a system’s behaviour as it responds to a request that originates from outside of that system. In other words, a use case describes “who” can do “what” with the system in question. The use case technique is used to capture a system’s behavioural requirements by detailing scenario-driven threads through the functional requirements.
UML class diagrams: Unified Modelling Language (UML) is a standardized general-purpose modelling language in the field of software engineering. UML includes a set of graphical notation techniques to create visual models of software-intensive systems
Interaction diagrams: Interaction diagrams, a subset of behaviour diagrams, emphasize the flow of control and data among the things in the system being modelled:
Communication diagram: shows the interactions between objects or parts in terms of sequenced messages. They represent a combination of information taken from Class, Sequence, and Use Case Diagrams describing both the static structure and dynamic behaviour of a system.
Interaction overview diagram: are types of activity diagram in which the nodes represent interaction diagrams.
Sequence diagram: shows how objects communicate with each other in terms of a sequence of messages. Also indicates the lifespan of objects relative to those messages.
Timing diagrams: are specific types of interaction diagram, where the focus is on timing constraints.
It may also include some kind of user interface mock-up. Object oriented analysis is to develops a model that describe computer software as it works to satisfy a set of customer define requirements.
Below are the advantages and disadvantages of both the standard and object oriented approaches.
Standard Approaches
Object Oriented Approaches
Advantages
There are distinct milestones for SSAD which makes tracking easier for project management.
Since SSAD is very visual, it makes it easier for users/programmers to understand.
SSAD makes good use of it graphical analysis and tools such as DFD’s.
SSAD is a very well known and established methodology in the industry.
SSAD has been around for a long time and consequently is a mature technique.
SSAD allows for a means of requirements validation.
Finally SSAD is relatively simple and easy to understand.
In comparison to SSAD, the development time, the level of organization, the robustness, and the code reuse are all greatly enhanced by the OOAD methodology
In OOAD there is no separation between the analysis and design phases, which improves communication between the users from beginning to end of project development.
In OOAD analysts and programmers are not bound by the constraints of system implementation, so that they can formulate designs that conform to different execution environments.
Since objects relate to entities (things) with which we commonly interact there is usually a clear mapping between the real-world entities and the corresponding objects in the system. This significantly improves understanding of the design
In OOAD the software is resilient to change, resulting in a higher level of confidence in the correctness of the software which helps to reduce the risks in developing complex systems
In OOAD, when developing objects with complex interactions, the analyst thinks on a different level of detail than is possible with structured code. In this case the analyst thinks about which attributes the object needs to know and how it will act on those attributes.
OOAD improves the quality of the system due to program reuse. That observation implies an order-of-magnitude reduction in defects”
Disadvantages
Since SSAD is process-oriented, it ignores the non-functional requirements.
There is less direct management involvement in SSAD.
Since SSAD is non-iterative like the waterfall model, so that requirements changes would mean restarting the entire process.
In SSAD there is some but not enough user/analyst interaction.
Except for the logical design and the DFD’s, SSAD provides no other tools for communication with users, and therefore it is more difficult for users to measure progress.
In SSAD it is more difficult to decide when to stop functional decomposition and to start building the system.
SSAD does not always address the user’s requirements.
Finally, SSAD is not a good fit for object-oriented programming languages, as it was originally designed for structured programming languages and not object-oriented ones.
In OOAD the initial designs for the system may be too simplified to be adequate.
In OOAD there tends to be much more focus on code than in SSAD.
In OOAD there is not as much emphasis on team work as in SSAD.
In OOAD it is not an easy task to determine all the necessary classes and objects needed for the system.
Many times object-oriented programming is used in conjunction with analyzing the various functions of the system; however, these function based methods are inappropriate in OOAD.
Another major disadvantage of OOAD is the overemphasis of this object methodology in general where, in fact, another approach might be much better to use for the design and development of a system, depending on the particular circumstances.
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