What kind of UML diagram is this?
(source: tripod.com)
This is a class diagram, with added stereotypes
This is Class Diagram in a very abstract or initial form because all relationship are shown as Association.
Usually we start with such class diagram and then keep on refining by converting association (arrow as shown above) into more stronger relationship like generalization,composition,implementation etc.
Association is considered as weaker form of relationship between classes. So final class diagram should have fewer associations.
What is the emphasis or goal of this diagram? If it's the classes and relationships, then it's a class diagram. If it's the mapping between the classes and layers of function or responsiblity in the system, then it looks like a layer diagram. Those columns look like layers: presentation, business logic, data...
Ok now I see the problem after a good sleep :-)
It seems it is a powerpoint and not a class diagram because you can not have straight line in a class diagram. I mean you can not have 3 separators like Presentation/ objectos .......etc
This powerpoint tried to use class diagram and have added titles in order to separate 3 layers. The problem is that the class diagram is incorrect and it is not because you present it with 3 layer that it would become correct !! This is a bad understanding of what means JPA stereotypes inside a class diagram.
It looks like a Class Diagram that uses "swimlanes" on the background to facilitate some kind of MVC.
This class diagram is not correct because there is confusion between Java EE stereotypes and class names!
What are the << class module>> , << module>> stereotypes and Session, Session persistence names should be Java EE stereotypes. If it persists in the database then it is an entity! Persistence etc...can be written on attributes.
This diagram doesn't make sense!
The main advantage of scheme in this diagram is that if you use a code generator such as AndroMDA, MIA software or Blue Age, then you can then generate your database directly from the model. These tools look at stereotypes during code generation.
If you don't want to generate code from a model but prefer to let hibernate mapping do the job, then the "entity" stereotype can be written as an annotation in your java code. Then thanks to live code and model synchronization, hibernate can take the annotation and produce a mapping.
This is why stereotyping is really very important and using the wrong stereotype can be a very serious mistake!
Related
I had been doing some UML class diagram examples from the recent exams for my software design course, and I found one where it says:"Design a class model for a specific problem, by using MVC and STATE pattern, but no need to include getters and setters." Is this the same thing as the regular class diagram? I've been googling and I found nothing UML based by searching for class MODEL.
The model is abstract. A diagram is a view on the model. UML offers a number of different diagrams. There are mainly two categories: static and behavioral. Class diagrams fall under the static category and they show how the classes in the model are related to each other. You can create multiple class diagrams like one with all classes (assuming that you have a rather limited number of classes) and/or one per class with that in focus. Or you have sub-domains with related classes placed in one diagram. The behavioral diagrams shed light on how class instances communicate with each other at run time.
As a side note you can think of it in terms of Platon's Cave Allegory. The diagrams are the shadows of the real world projected by a fire to the wall you can see from you chained position.
"Design a class model" means: "Create one or more class diagrams that together form a consistent model".
A model in computer science is a graphical representation of (a piece of) software or of (a part of) the business domain in order to help people know or understand the subject the model represents (see wikipedia). This graphical representation may consist of one or more diagrams.
In a UML diagram where one class is comprised by another class, is there an implicit association table, or does it need to be shown?
For example, if I have Chapters that are composition of Paragraphs, is this alone enough:
Or does the association class to be explicitly shown like so:
I've never seen it done like that latter example, so I'm assuming it's implied. Or maybe I haven't normalized the data properly (considering chapter both appears in the Chapter class and the Paragraph class).
Simply, there is no implication. If you need an association class, you need to define it. However, UML is not about diagraming, it's about modeling. You can omit your association class in a diagram if you want to. The association class will still exist in your model, though.
No, it is not implied.
The reason why you haven't seen this is that in most cases it simply doesn't make sense. In the association class the class part additionally describes the properties of the association. In your example you create an artificial object that actually brings little or nothing. This kind of approach can be useful for many-to-many relationships which are impossible for composition (each part can have at most one whole). Even if you wanted to show Foreign Key it would simply be on one of the classes. But that's implied by the association itself. According to UML specification an inline attribute is equivalent to an association.
Moreover on UML you can depict many to many relationship simply but applying appropriate multiplicities on association ends. You may want to show the class depicting that only when modelling on the code level.
No, it is not implied.
UML is not about tables, but about classes. The author of the class diagram should tell the audience how a class should be interpreted. Some UML diagrams model the real world, others model a piece of application functionality and yet others depict a physical implementation.
Apparently, reading your question, you are modeling a relational database, where a class is a physical table. In that case, I would expect that every table is explicitly modeled as a UML class.
The UML standard does not demand this.
By the way, the notation (PK) and (FK) is not in accordance with the UML standard.
I have an assignment that states the following criteria:
For this view you may use a truncated version of
your Design Class Diagram (DCD) including
only the architecturally significant classes.
For context, this is for the Logical View of a 4 + 1 Architectural View. How does a design class diagram (DCD) differ from a regular class diagram? Is it the UML diagram without the functions or variables included (i.e. just the names of the classes and their interactions with each other)?
Most of the time, people model their code. That's good! In that case, class diagram modeling is used to graphically represent the structure of (object-oriented) classes: class, method, attribute, annotations with stereotypes. Imagine all the JPA, Spring, whatever annotations in the class diagram of a JPA-J2EE based architecture...
As it's said above, the "design class diagram" should only design your domain model, from an architecture level. What are the basic entities your structural system rely on?
No details about the programming language, no "dto", "dao" or technical stuff like that.
Here's a good example I use: online shopping cart domain model. It only contains the architecturally significant classes.
HTH, Tom
Still its amibigous to understand. The main difference between analysis class diagrams and design class diagram is the analysis phase focus on designing a class diagram without concerning about the implementation detail. where as, desgin modelling concern with the implementaion and architechture since, it the high-level static view of the system.
can somebody please explains what is a high level class diagram. As far as I know class diagram shows the association between the classes but what about high level class diagram??
Ok, I knew what this means, a Class Diagram contains many details. A high-level class diagram is a simple class diagram reflecting only initial domain knowledge
What's the context? Class diagrams in themselves are pretty "high-level", in that they only show classes and methods rather than algorithms and other implementation details. It might just be an adjective. Or, you might be looking for something more like a block-level diagram which shows components of a system and how they interact.
I often use the term "high-level", or more usually, "top-level" diagram for the very highest level class diagram I make for a system. Usually this will show as many of the most important packages as will reasonably fit, along with some classes that give the best idea of what functionality the classes in that package provide. From there I can do class diagrams of each package, and so on.
Depending on the type of system and what your supervisor want to see, you may be better off creating a component diagram.
If I create a conceptual class diagram such that each class captures 'name' and 'attributes' but not 'operations', have I not basically created what would be otherwise considered an ERD? I'm trying to gain an understanding of what the differences are between creating a conceptual class diagram as I have described versus calling it a ERD? If these are still two different animals, can somebody please explain what the differences are?
The class diagram contains just the classes in your object model with eventual links/relationships connecting diagram elements. However those links don't necessarily correspond to physical relationships like in an ERD diagram, but instead they represent logical connections.
The class diagram is just the object model of your application and does not contain any persistence-specific information. When you think about the class diagram forget about the database or any other storage you may use.
The ERD diagram on the other side, is a persistence-specific diagram which display the entities (tables) existing in a (most often) relational database. It also displays the physical relations (and cardinalities) between those tables and all other database-specific information. The ERD diagram can sometimes look similar to the class diagram, but that doesn't mean is the same as a class diagram.
There´s little difference in the expressiveness of both (if we just focus on the attributes, classes and associations part) if you use Extended Entity Relationship diagrams (the most common case nowadays)
True, they look very different at the graphical level since they use different symbols for the elements but the "semantics" are quite similar. They both allow inheritance (again, I´m talking about EER), n-ary associations, association classes, ...
The ER diagrams I've seen (most frequently ERWin IE notation) have focused on the design for a database. They are concerned with primary keys, foreign keys, have unnamed relationships, and usually have no generalization / specialization.
A good UML conceptual class diagram, on the other hand, is not concerned with keys, reflects the problem domain, and has association-end properties that at least hint at the semantics of why things are related. This helps communicate the domain down to more junior developers so they don't have to guess.
It depends on the situation where you may not like to do the ER-D. But imagine if you have a seperate data layer where the data logic is handled. In this case many details of data shall not be shared with the application layer. And you class diagram shall not go beyond the application layer. I must stress that both the diagrams are not equal. And there are situations where you need to do both, mainly in multi-tier architecture, and there are situations where you may be able to just use class diagram; e.g. single-tier application.
I strongly advocate the view that class diagram doesn't abrogate the E-R diagram.
Design class diagrams are made from conceptual model and collaboration diagrams.
Design class diagrams include:
Classes, associations and attributes
Methods
Types of attributes
Navigability
Dependencies
IMO In Simple terms
Class diagram depicts the details of how will the system work.
ER diagram depicts how the system persists 'state' as a blue print.
Goal:
Detail out state and behavior of the components(classes) of the system.
Design 'efficient', flexile system(less coupling and more cohesion) using Solid principles.
Goal:
Design a blue print of how to 'efficiently' persist the state of the system.
Consider what kind of queries will be made (read vs write), are there any joins required
consequently figure out the columns for indexing
Use Normalization, ACID properties.
PS: notice the both the diagram tries to efficiently do thing in their on respect.