I have an Access db I wrote that I've used for my checkbook and budgeting for the last 3 years. I've never written a program before, but I've decided to write the db into a stand alone program. My only experience, besides the simple VBA in the db itself, is an Intro to C++ class and an OO Logic class.
Even though I know what I want the program to do (because it's what my db does now) I want to approach the planning and design as properly as possible, so I can write the program as properly as possible, so that feature additions and maintenance are easier.
I need help planning. I guess UML diagrams should be first. What UML diagrams do I need to do? And in what order? I tried to do a use-case but since the program only involves me, my money, the bank, and the stores, it seemed pointless. Or was I thinking about it wrongly? Do I need to diagram my money and my budget inside my account? I don't know. I need help on how to proceed. Thanks.
It's good to have a set of UML diagrams to keep track of what is happening, but to remember in the end that documentation decays - your code is your design. That said, UML are good for planning and recalling bits and parts. There's a large dose of personal experience involved here, so feel free to take what you want and leave out what you think don't applies.
Use Case Diagrams
Skip this, and just write use cases instead.
Class Diagrams
I find them useful for planning the big picture view of an architecture, but I usually would leave out all the method names, or only leave in the relevant . I use it to illustrate the logical model of your classes
Sequence Diagrams
One of the more useful diagrams especially for business logic, and flow of data. I always find myself sketching sequence diagrams for complicated data-flow and especially when there are events being dispatched.
Object Diagrams
Shows the interaction of objects at run-time. I usually draw those for complex object interactions, and not the 'academically correct' ones. I think it is less useful than sequence diagrams.
Flow diagrams
Good for websites if you have complicate flow
State Transitions
Important if your application has many states. Again, just sketch out the most complex system, there is no need to have one for every sub-system.
ER Diagram
I know this is not UML, but a good database design upfront is important, and an ER diagram would help you to organise and plan how different tables relate with each other
Since your application is for personal use, I think you only really need two diagrams, maybe three. You can use a Use Case diagram if you want, but you will probably be better off with just a list of use cases. Since no one else has stated it, a use case is a requirement where you state something you're going to use it for. These help you define what features you need.
Next you need the class diagrams for how you're going to organize your program. A class diagram shows which classes you have and how they're connected. This is useful for figuring out if your program is too complicated or if you're using the antipattern known as the blob. If you have a lot of lines connecting classes to each other, you might want to reorganize to see if you can make each class more cohesive and if you see very few classes, you might want to check for a blob antipattern. An antipattern is a common occurrence which is bad for readability or maintainability. Class cohesiveness is defined by if each class has exactly what it needs. For example, if you decide to have a class for your account, it doesn't need to know information which isn't related to your account, like the street address or name of your bank.
The last UML diagram I think you'll need is a sequence diagram which shows how different objects in your program will interact. This will help you better understand the interactions your classes are doing and decide if you need to better organize them if they're getting too complex.
Those are the UML diagrams you might need. You might also want a network diagram to understand how your database is going to connect to the bank's website and get the information you need.
The diagrams are there just to make you understand what you are doing and keep you on track. I guess you already know that. In your case, i Believe a detailed use case will suffice, just to make sure you handle all the features and dont forget anything. (Reminder: Use case is not a diagram. it is text)
Related
hello, my first question is how I can place cases to better readability? I want to make this diagram fit on a A4-sized paper.
But I am aware that this diagram may be badly made, so I ask you to advice, maybe I should share on the smaller part?
You need to to connect a use case only to its primary actor. So eventually you have to create a common role where the UC is used by this common actor role. Then your specific actors inherit from this common one. Like in #Amir's example International Student inherits from Student.
I'd simply up-vote the latter example but it has <<include>>/<<extend>> which is no favorable with use case synthesis. Moreover it uses a generalization which is very bad practice with UCs since a UC represent an individual added value and inheritance from added value does not make sense (unlike in a class context).
I don't understood your language (In your use-cases). Generally most of time we have some common feature so You can use inheritance in UML diagram. For example if you have different kinds of students (or Actors) that have some common feature you can do something like below picture:
I think there is too many of use cases. I had the same problem. Try using CRUD - https://books.google.co.uk/books?id=gKHfVZn1CkgC&pg=PA367&lpg=PA367&dq=crud+use+cases&source=bl&ots=g7C2qnzunP&sig=F3OtpNWT29NFyqFvmO-MBtTG98k&hl=en&sa=X&ved=0ahUKEwjAmKifh9_OAhWpCsAKHV9pA344ChDoAQg4MAU#v=onepage&q&f=false
Also, you can divide your diagram into few use case diagrams for each actor. Or put all actors on the one side of the diagram and use cases on other. Hope this helps.
I completely agree with the given suggestions (CRUD, inheritance and responsibility by roles) and I additionally recommend not to try to create an overview about the whole universe. Instead, try to separate your use cases into groups based on similarities, differences etc. and explain your modeling on smaller pieces.
Avoid too complex structures and mutual/cyclic dependencies - they are almost always a sign of poor design. Remember, you have to implement and test every connection in your diagram somehow. Less connections, less effort, less errors.
Im in a confusion on the sequence of drawing UML diagrams. I cannot understand where to start drawing them. Which diagram should come first if I have the scenario with me?
Start with Use Cases (and the related diagrams). Once Actors and Use Cases are identified, you can start designing a Class model. Create Collaborations realizing the Use Cases. Then inside show how the Instances of the Classes collaborate to actually realize what is needed for the Use Cases.
I recommend the ICONIX approach since that is what got me going a long time ago.
The other option is to start with Activity Diagram. I.e. make a business process analysis.
I always start with a problem-domain class diagram. (Some examples of what I mean are here and here.) Understanding the concepts in the domain and the relationships between them is extremely important. If you don't understand the problem domain, everything else will be confused and brittle, including business processes, requirements, use cases, and collaborations. Here is an example of an improper domain model, and here are the recommended corrections.
Firstly, I'm still quite new to UML; but, highly interested and am attempting to learn as much about it as I can.
With that said, I’m in a situation where I’m directed to assemble a ‘Context Diagram’. I feel as though I understand the concept of what a context diagram is and how to create one, so I think I’m ok there. Basically it is identifying the system and the components or actors it will interact with. It applies the focus on the system, and not the actors. Kind of like a Use case diagram, but not focusing on the actors. If I’m wrong, please tell me.
I read somewhere that Context Diagrams are not actually part of UML. I also read, somewhere, that, if you use a Context Diagram, it falls into the Component side of things. When I read about Domain models, it seems like it should be there.
For my current situation, I know a simple answer is to simply create the diagram and move on, as that is all that is required. But, for my interest to better understand and leverage UML, I know there is a right way and a wrong way. If I were in a case of a bigger project, what would be the right way?
Now here is where my question begins. I’m using Enterprise Architect, create my project, and start to create a model. Does it belong in a Domain Model or Component Model? What is the difference between these two? Or even more. As it is an aide to help identify requirements, should it go there? Or does is just simply depend on what and how I want to convey it?
The Domain Model is where you standardize the vocabulary that everyone on the project will use to communicate in a consistent manner. The development team are experts at software development, but they may not have any experience in the domain (e.g. banking, air traffic control, healthcare) in which they are being asked to work. So you get domain experts and modelling experts together to build a model that describes the domain, answering important questions like "how are account fees calculated?" and "how does a pilot know what route to follow?" and then this model is then passed to the development team to provide them with the important domain knowledge that they will need. I would use UML class diagrams to create a domain model.
A Context Diagram shows the system being modeled in relationship to external systems. It could show data flowing in from and out to external systems, modeled by a data flow diagram (not part of UML). It could show behavioral interactions between the system and external "actors", modeled by a UML use case diagram. It could show the system's physical connections to other systems, modeled by a SysML block diagram. Whichever you choose, it will be on page 1 of your design document, so choose wisely!
You (can) create context diagram by making any element composite. Then drag the element itself onto that diagram as link (not instance!) and highlight it by making the border a bit thicker. Finally insert related elements from the context menu (differs from EA version to version). Layout the diagram and now you have your element in the context.
A domain model is usually a class diagram showing the (business) domain on a higher abstraction level.
As you have said, Context Diagrams per se are not part of the UML spec. There are plenty of ways to do a context diagram, but the UML way is to use a Use Case diagram, with or without supporting narratives and scenarios. Start with this, which is a broad overview of different types of Context Diagrams. Then, investigate use case diagrams, use case narratives, and activity diagrams. If you need to go into more detail than a use case narrative can easily do, get into use case scenarios and sequence diagrams. Here is a pretty good use case narrative template (feel free to leave out sections such as "scope and level" if they are more than you need, and consider adding information about what triggers the use case and where you go when you finish it--these two are required for scenarios if you go that far).
Keep in mind that use case narratives and use case scenarios are often confused. (Some people will say that I am the confused one; I will invite you to judge the matter for yourself.) A narrative is an explanation of an entire (single) use case, and may be supported with an activity diagram. A scenario is an explanation of a single path through a single use case, and may be supported with a sequence diagram.
For example, a use case will generally have a basic flow of events, along with a number of alternate flows. The narrative describes the entire process. The basic flow and each alternate flow would each be a separate use case scenario.
I suspect that it's unlikely that you will have to get down to the level of use case scenarios. You will probably want to put a use case diagram together, and possibly prepare narratives and activity diagrams for each of the use cases in the diagram.
I am currently taking a course that gives an introduction to project planning. It is mostly about how to draw UML diagrams (blegh), but also has a few other topics.
One part in particular keeps bugging me. In the course they describe a method for going from a set of requirements to an initial class diagram, but everything about the method gives me this feeling that it is most definitely not the way to go. Let me first give an example before proceeding.
Let's consider a system that manages a greenhouse company. The company has multiple greenhouses, and every employee is assigned to his/her own greenhouse. A greenhouse has a location and a type of plant being grown in there. An employee has a name and phone number.
Here's what according to the course's method the class diagram would look like:
To me this looks like a database layout adapted for code. When I go about designing a program, I try to identify major abstractions. Like all the code that interacts with the database or the code that is responsible for the GUI are all different parts of the system. That would be what I consider to be an initial class diagram.
I simply can not imagine that this is a common way to start designing the architecture of a project. The classes look ugly, since if you take a slightly larger example the classes will be flooded with responsibilities. To me they look like data objects that have functionality to them they shouldn't have. It does not give me a clue on how to continue from here and get a general architecture going. Everything about it seems obsolete.
All I want to know if there's someone out there that can tell me if this is a common way to get a first class diagram on paper for reasons I am overlooking.
I would say it's reasonable to start with a logical model that's free of implementation constraints. That logical model is not necessarily concerned with physical implementation details (e.g. whether or not to use a database, what type of database, OS / UI choice, etc.) and thus represents just "real" business domain objects and processes. The similarity to a potential database implementation shouldn't be surprising for the simple example.
By understanding your business domain (through the logical model you've started to construct), you will be better placed to subsequently identify, for example, which architectural patterns are appropriate, what screens you need to build, and database elements to design. Possibly, there will be another part of the course that will aid you in this stage.
In practice, you will often know that you're intending to implement, say, a web-based application using MVC with a back-end database, and may look to model the implementation classes in parallel with your business items. For your course to use a method that emphasises the distinction between logical and physical stages doesn't sound unreasonable.
When I go about designing a program, I try to identify major
abstractions
Same principle in UML as well. You represent abstractions and their relationships and due to existing Visual Tools you can do a presentation of a system to stakeholders or even generate automatically stubs from your design.
I have to develop a CRUD application, that will be coded in php.
I have 3 main actors (Users, Administrators and Doctors -- this is for an hypothetical
hospital), each one with different Use Cases already defined.
Although I feel the Use Cases are more than enough to successfuly model the Class Diagram, I am being specifically asked to also include DataFlow Diagrams into the project's documentation.
I've been reading about DataFlow diagrams, and it seems you usually have first of all a Level 0 DataFlow Diagram, to which they call Context Diagram.
Being that this is basically a 3-tier application with 3 different Actors, how should I model the Context Diagram?
Being that a Context Diagram is supposed to just tell us what comes in and what comes out of our System, I can't imagine anything more interesting/descriptive than the following diagram:
Is this supposed to be something like this, or am I totally missing the point? This php page will connect to an Oracle database, but I guess that if the idea is to consider the System as a whole in the Context Diagram, I should "hide" that fact in the above diagram.
Where should I go on from here? I know I should "zoom" the System process to something more detailed. Maybe the next step would be to depict each one of the User Cases in a DataFlow diagram? Do I include repositories of data, already? For example, one for Users, other for Doctors and yet another for Administrators?
Thanks
Are you sure there's nothing else the system interacts with? e.g. diagnostics input, etc.?
If not then your context diag is basically ok - although I'd probably show each entity once and use double headed arrows. I'd agree with your reasoning for the db - it's part of the system, not external to it - so don't show it on the CD.
As for next steps, again you're on the right lines. Try modelling the flow for each Use Case as a DFD. DFDs are very useful for illustrating processing-intensive apps. Difficult to know if that's a good match to your problem or not.
You'll find DFDs are also useful for driving out and validating your Class Diagram. In fact, that's one of their strengths: datastores on the DFD should correlate with the contents of your class diagram (not necessarily one datastore to one class though). So do include datastores as you work through the processes. You'll find it drives out more than just the Actors.
hth.
Some remarks:
You DFD does not tell me much, except that Users, Administrators and Doctors use it, but it gives me no clue what they get from the system (except "Output Data"). IOW the context diagram does not give me the slightest idea, what the system does.
Admittedly, if the system is large, then it can be difficult to describe the dataflows in few words, but just about anything is better than "data".
The fact that the system is a 3tier architecture is irrelevant for the DFD. This is an implementation detail. DFDs are an analysis tool. You describe what you want the system to do, not how this is achieved.
I find it particularly useful to focus on the outgoing flows. While Users, Administrators and Doctors provide input to the system, this is most likely nothing they want to do. It is something they have to do in order to get the desired output.