I'm currently trying to learn the construction of class diagrams for an upcoming exam, although I'm having difficulties knowing how to identify classes based on a use case specification (or any similar description of a system).
I understand people here can be reluctant to help with education based questions, I just wanted to clarify that I'm not asking for the work to be done for me, I just need to be pointed in the right direction.
I'm going over a past revision paper which contains a use case specification for the process of 'purchasing an ice cream' at a vending machine. The first question is to identify 9 typical classes from this specification.
I understand a class is like an object and usually identified by a noun, although my confusion is how I am able to extract 9 classes as I can only seem to find 6, that is if they're even correct:
Customer, Student, Staff, Touch Screen, Change Dispenser, and Member Card.
Here is the use case specification, apologies for the length:
Ben & Jerry’s company has just installed a new vending machine at a
University; it has a variety of ice creams available, in the format of
tubs or mini-tubs of different flavours. Products are subsidised for
students and staff but not for the rest of users; such that a customer
can insert a member card in a card reader and the subsidised prize for
the selected ice cream is displayed. You have designed a use case
model of the system, and identified a single use case (“purchase an
ice cream”) where the main actors are the customers.
ID: VM1
Name: Purchase a tub
Main Actors:
Subsidised customer (staff and students) 2 Non-subsidised customer
Pre-conditions:
Machine is on and works perfectly fine
There is stock of drinks and coins
There is sufficient stock of coins in the machine for providing change
There is sufficient stock of products
Main Flow:
Machine displays a welcome message
Student/staff inserts member card
System validates member card
Customer selects the tub by pressing the touch screen
Machine displays the subsidised price for the selected ice cream
REPEAT until sufficient coins entered: 6.1 Customer enters coin 6.2 Touch screen displays the amount entered so far
System dispenses the tub
IF too many coins are entered change is delivered
Price is added to the weekly total amount
Machine resets
Post Condition: Ice cream purchased
Alternative flow 1:
IF customer does not have sufficient coins 6.1 Customer presses the return button 6.2 System returns the entered coins
Alternative flow 2:
IF validation is unsuccessful 3.1 Message informing user 3.2 Non-subsidised price is show 3.3 Use case continues main flow 4
If anybody can help I'd really appreciate it. Thanks
You have mostly identified a number of actors, few classes itself. To start your design, ask yourself what the system under consideration (SUC) is. Obviously a vending machine. Now look at the UC how this SUC acts. There are a couple of hints:
control resources (temperature, ice cream, tubs, etc.),
control collection of money,
control dispension of ice cream.
For these you can create controller classes which look to the outside and act accordingly (read temp -> turn on cooling; count money -> start vending; etc.)
The vending process with customer interaction is probably even more complex (show offers, make selection, pricing, etc.)
As you already guessed, this is no tutorial point. However, those are the basic steps to start the design. You can go on and create sequence diagrams to verify collaboration between the single classes (lots of exceptions like: temp controller starting to yell when temp does go up too much).
Related
For my internship, I need to implement a blockchain based solution to manage a drug supply chain. The management of this supply chain implies to track-and-trace (geolocate) a drug on the chain, but also to monitor the storage temperature to see if the cold chain is respected. For that I created a mock-up of the POC my Dapps (https://balsamiq.cloud/sum5oq5/p8lsped)and also I wanted to prepare myself by doing a UML and a use cases. However, I didn't find a lot of information about blockchain's UML and use cases besides two literatures which were quite different, so I don't know if what I did was correct or not...
The users of my Dapps will be the following ones:
The stakeholders (Manufacturers, Distributors and Retailers) which will use the Dapps to place orders and also monitor them. They also can search in the historic a specific order. Finally, trough IOT sensors they update the conditions of the order (temperature & location).
The administrator which roles is to update the Dapps and its rules. But also to add or delete user while also defining the rights that they have on the blockchain (I intend to use a permisionned blockchain). Finally, they are also here to help in case of technical problem.
The Dapps that I'm thinking about works in the following:
A user, the customer, can place an order (a list of products) to a
certain seller and choose the final destination of the order.
The order is then put together before being shipped or stocked in the
depots of one of the stakeholders (distributor or retailer) with a
description of the stocking and/or shipping condition of the product
(for example the product must be stocked or transported in a room
with a temperature of less than 5°C). During the shipping and
storing, an IOT device will feed the drops with the temperature and
geolocation of the product by updating the data each 5-10mn.
Obviously they will be a function that allows all the users to see
the history of the order passed and search inside a specific order.
In case where the temperature doesn't respect the temperature
recommended, then the smart-contract send an alert. The same if the
collocation of the product is "weird" like being in some European
countries and not in an Asian country, an alert will be sent again by
the smart-contractual. Finally, in the case where the product is sent
to the asked location by the customer, then the money for the order
will be paid to the seller.
So based on what I explained, I came here in hope that someone tell me if the use cases and UML that I did were correct or not.
I thank in advance anybody who'll take the time to help me.
Say there is 5 bags of potatoes, when it hits two bags, an order is sent to the supplier automatically. Who/What is the actor?
Clearly you have an actor to watch the queue like this:
Even if the Potato Watcher is something implemented inside the SUC, it would be an actor on its own. You may drag it inside the SUC boundary. In a final implementation it might be a system task to poll a queue or a subscriber to the queue. But from the added value viewpoint it's just a simple actor to watch a queue and do something with it.
Since "an order is sent... automatically" the system is the actor. Assuming you are automating using software system.
However in real life it all goes wrong and businesses are far away from sending orders automatically.
Badgerbadger, you need to be carefull about statement "sent an order".
It is easy to overlook actual business process and previous subfunction-level answers are giving a nudge.
More realistic scenario is that the system is the actor who just initiates the check of stocks, maybe orchestrates. And then there is a complicated process of getting approval, finding budget, checking if goods are really required to be ordered and so on. In theory all of those can be automated, but usually in practice there is a work for human actor as well. Of course you may be lucky and avoid all of this.
Example of pessimistic scenario to consider:
It was eight bags, but now hits three. John just bought five bags from us, hooray!
System automatically places an order and pays for 10 more bags.
In ten minutes someone ordered one more.
System automatically places an order again and pays for 10 more bags.
We don't have enough money on account so we are facing overdraft.
At the same time regular inspection found that one bag is rotten.
System: 10 more bags please!
Our colleague just told us that we've missed 20% discount from supplier on simultaneous orders of 25+ bags which can be obtained only by calling a company manager.
John cancels his order in an hour after placing it.
Now we have 36 bags and a hole in our budget.
And our marketing manager just told us that the green bags system ordered are actually now selling with a discount, we are getting rid of them in favour of new line of blue bags.
You have to possibilities here:
Each time the stock is used the system checks if the condition to order is met and if yes then order it. As ordering will probably involve another actor (e.g. supplier's system), you might need to model it as a separate UC and use extend relationship. In this case you will not have any additional actor initiating the order, only the actor initiating stock usage.
The system checks on a regular basis what stocks reached the automated order level and make a single mass order. In this case you'll have to model Scheduler as an actor (in reality it's another system running on the server so it's fine to call it an actor). Some people prefer modelling such actor as "time" but it's discouraged.
I'm pretty new to Maximo and I have a question about how things should be handled. We have a project of integrating our ERP with Maximo using MIF interfaces. I'd like to know how you performed this in your company as I'm sure we're not the only one facing this challenges.
Let's go pretty simple about the Inventory. Receiving will be performed in our ERP and sent to Maximo. "Consumption" and inventory movements will be performed in Maximo and interfaced back to our ERP. so far so good, standard process.
However, there's a difference in the real inventory vs the inventory from a Financial perspective. As an example, we have let's say 3 cutters (same part number, different serial number). We have 2 in the internal storage and 1 in the machine where its being used. Once it is in the machine, it's known as "consumed" by finance. So from a finance point of view, there's only 2 in stock. From the tooling guy however, there's 3! The one in the machine can be taken out and replaced by one of the two others.
How are things like that handled in maximo? Any help, advices would be appreciated.
Regards
M.
It depends on how you plan to track on the individual level (track cutters by individual asset tags or serial numbers) or on the group level (3 cutters with the same item number)
If the cutter is treated as inventory and not as an asset, once it is issued then it is considered used. You can opt to use "Condition Code" and give each item a value from 0 to 100. Think of this value as depreciation. If a cutter is swapped out, then the new cutter (100%) is issued, and the replaced cutter is disposed of or returned to the shelf with a diminished value (e.g. 25%).
Unsure if this is the right place to ask such question.
I have to define use cases for a Windows Service application and I have some issues.
It regards a Windows Service application that is programmed to perform some tasks periodically.
One of the use-cases is "The system looks up unpaid orders and sends reminder to customer".
Alistar Cockburn's definition of an Actor: "An actor is anyone or anything with behavior."
My questions now are:
1) In my scenario, who is the Actor or Actors?
2) Who are the stakeholders / interests?
I am not Mr. Cockburn, but...
Actor should be anyone (or anything) who comes into touch (/uses) with system. <= Easier definition for me.
1.) So in your case, customer should be actor.
2.) I was always creating use cases with just use cases and actors.. what are stakeholders and interests? They are imo just another actors. If not, it just adds complexity to tool, which should be simple. (IMO)
Btw: Is "The system looks up unpaid orders and sends reminder to customer". really a use case? Isn't that a scenario (part of a use case)?
Edit: Use cases should describe behaviour from end user point of view. So it really should be something like:
Scenario: Pay for order
Actor: Customer
Flow:
1. Customer requests unpaid orders from system (not specifing how).
2. System provides (shows) unpaid orders.
3. Customer chooses one order
4. System process selection and shows detail about selected order
5. Customer requests to make a payment (again not telling something like 'customer will click on button called "pay"')
6. System requests payment details from user
7. User fills details
8. System validates entered data
9. IF successful:
a.) Order payment is comleted, system redirects user to XXX.
10. ELSE go back to step 7
It might be a bit long... but that's basically how I am doing scenarios (which are grouped into one use case).
Hi im not used to UML but i have to create a Use case diagram for a system.
Id Appreciate(HELP!) if some one could make an example of a use case Any of the information i provide. the system rums on windows mobile phone 7
Mobile Location based GPS
User creates account,
User Creates Profile(identy) on the account
User Chooses Region
User Chooses to partcipate, then gets Assigned A location from servers online
User gaol of Reaching loaction met, User is Assigned Points(leader board updated), If the user Fails No points Valuse of location increases.
USer Can Equip tools, User Gets new Tools if Points Goals are reached.
User Can lookup point leaderboard, See users Rank
Please wip out paint for 2-3 mins and how me how to do one of these use cases !
And does each sentance need a use case ? or is it possilbe to give a use case to each of these lines ?
THANKs!
I can't help but ask: What benefit does creating a UML use case diagram, with stick men and bubbles, give you that the simple sentences you posted do not? I simply don't understand what the fascination with UML is all about.