Does anyone know if it's possible to generate a UML Class Model from a Database Relational Model? How?
edit:
To clarify what I consider to be a UML Class Model (UCM) and a Database Relational Model (DRM).
The UCM is a higher abstraction than DRM. On the UCM we don't talk about table but rather about entities. In UCM we model the properties of an entities and the relationships with which other.
In the DRM it is the opposite, we don't talk about entities, we talk about tables. Typically, if not every time, the DRM will have more tables than the number of entities in the UML.
I hope I have made myself clear now.
P.S: I am using SparxSystems Enterprise Arquitecht.
Thanks.
A database relational model in [Enterprise Architect][1] is just a stereotyped Class diagram where the Class elements are tables and the attributes are the columns.
So to answer your question, Yes it is possible to generate the relational model into a class model simply by using the Model Driven Architecture (MDA) transforms of Enterprise Architect to transform it directly to a class model.
To do this:
In the Project Browser of Enterprise Architect right on the DRM package then select Transform current package (Crtl+Shift+H)
Select an appropriate language.
Click "Do Transform" - and follow the promps to save the new class elements in the project browser.
Once this is done you can tweek exactly how you want the UCM to look (more/less entities etc). Hopefully this will get you 99% of the way there.
Related
I am at beginner stage of OOP. Got an academic project, need to make a UML Class Diagram of C# Code.
I am developing a project which will use database, I am confused about 1 thing. In UML we use inheritance like department and student, we create 2 classes and put department ID in student class.
Coming to my confusion, I will make some classes like department, student and teacher, and also a database with same tables. How can I use classes, because I know that on user request I can process data on database (on runtime), Like adding teacher or student to department, getting all students, etc. I am supposed to get all data from database when program loads? and save data in variables and put it in database when required? Simplifying my confusion, How to use classes when we use database to get data dynamically?
What you are talking about is a transition, which is not inheritance. At least not really. Once you have developed a class model you will think about persistence. The persistence can be designed in many ways (in most cases you will derive just one persistence scheme, though). Now what you do is to "copy" your classes from your design model to a new package for the persistence. Thereby <<trace>> from the persistence back to the design class. Now you almost independently optimize your persistence towards your desired schema. You will introduce primary and foreign keys, redundancy and things like that. Anyhow, your persistence model only remembers where it came from (via the <<trace>>) but it now has a living on his own.
Note that some UML tools offer automated transition from design models to various derivates.
I have doubt regarding design model.Does every class in the design model have to be present in the domain model?
Object modeling is best done as an iterative process, so start with whatever (simple) design you think meets your current requirements and build upon it as you learn more about your domain.
The question is not well explained even if the subject is important.
UML is an object approach like Java codding while domain modelling is related to databases structure. UML is not therefore the same as domain modelling.
Having said that JD5 and later allows ORM annotations in the code. It means that at object level you can also think about databases using Hibernate annotations directly in your java code. EclipseUML is lived synchronized with the Java code but also with ORM annotations. It means that all ORM annotations written in the code are updated in the class diagram as well as in the model and each class diagram annotations change is updated in the code.
It means that UML and domain modelling are now unified using standard ORM annotation.
Sorry if the question sounds too vague. I will improve based on your feedback.
I have managed to prepare a UML model of a problem domain. This is essentially a class diagram describing class attributes and aggregation relationships amongst classes. Intention now is to fill data.
For example, class-A aggregates N instances of Class-B. I would like to create a data model that has data for one instance Class-A and 5 instances of Class-B.
Basically, data pertaining to this meta model is available in a document (e.g. xls, framemaker) and it should be possible to read the source and populate the data model.
Are there tools that will let me create this data model? Please advise.
You have two options to creates your database model from our UML model.
You can use the UML model and then add a code generator to generate the database then finally reverse it with a database modeling tool such as erwin.
Another approach is to use the database modeling profile inside your UML model. It means that ypu model and add database stereotype related to java ORM.
Both works pretty well.
I have homework and I'm supposed to draw a class diagram AND data model. I wrote the class diagram. I don't know what to do about the data model. What are the differences?
According to texts on the Internet they seems to me, ie: class diagrams and data models are the same thing.
What is the difference between class diagrams and data models.
Unified Modelling Language, as you may already know, is a means of describing systems with diagrams. They don't just relate to software, but can also relate to hardware, economics, everyday items, in fact anything, although they are more generally used with software systems.
A class diagram details how you have split your system into discrete objects, how those objects relate to each other and any know interfaces that they may have. Each class in a class diagram can hold both data and function.
For example a Car class has an Engine, a Steering Wheel class and multiple Wheel, Door, Seat and Pedal classes linked to it. In all of this a class diagram is static.
I'm not exactly sure what you mean by data model.
I've seen class diagrams used to model database tables, usually these are without any functional element and just show how the data tables relate to each other.
There are those that argue that there needs to be an addition to the UML standard for Data Diagrams, but as yet none have been ratified.
This is because persistence of data, key relationships and constraints between tables can be difficult to model with a standard class diagram and most UML tools implement tweaks to the standard in order to allow this.
Then there are dataflow diagrams which are really Activity diagrams, used to show the flow of data between processes within a system.
Now if we go back to class diagrams and assume that a data diagram is used to model a database then you'll notice that there a few differences that may be overlooked.
A class on a class diagram can have data properties (code variables etc) and functional properties (methods, procedures, functions etc.) but these elements of a class can also have access properties (private, public etc.). A class diagram can also show inheritence e.g. a Volkswagon is a Car, so is a Ford, both will inherit from Car and this can be shown.
A data diagram in the database sense will show data items (columns/fields in database tables) but the idea of access properties (public, private etc.) or the idea of inheritence has no meaning and thus can't be shown.
This is because it isn't modelling discrete objects that have both data and function but the data associated with those objects. For example a Car table may have a relational link to a Manufacturers table in which is stored the values Volkswagon and Ford. It may have a Wheels column, but this will only show the number of wheels. Stored procedures for the database exist at a level labstracted from the data - they utilise the data, but are not governed or owned by the data tables that they get the data from.
I've probably not explained myself very well, but I hope that I've helped.
Here's a useful site
And here's another and on that site data modelling specifically.
Generally data models define how the database is implemented. Those diagrams are entity diagrams. A class model is the functional relationships between objects in your system. A class has data but it isn't the data model. A design has both a class model and a data model. As a simple example, a data model exists for a customer. That data model was the design for our customer database. A class model design exists to implement how to process a customer order. The data model is what the database designer uses. The class model is what the software designer uses to implement a ordering business function. Both the data model and class model have diagrams. They use different symbols and rules. Class diagram vs Entity diagram. Two different kinds of diagrams.
Datamodeling is not UML which is focused on object approach.
Having said that you can model inside a class diagram at object level and create your database using Hibernate annotations in the Java code.
I mean that you create your code and add persistence annotation at the same time. This would create your database at deployment.
UML which is not supposed to be datamodeling can also create data at deployment level if you use the Omondo Persistence profile. It means that you can model at object level and also create your database. Very powerful approach because the data creation stage is now joined with the object
This is still an initiative but it could become a standard if bigger companies adopt this approach which is for me one of the best practices when codding in Java that I would recommend.
I have read several tutorials on what a UML model should contain and what not. As a developer I always think in terms of a relational data model where you could never have a many to many relationship between tables. Now with a UML class model, I've read that if they don't provide added value, you could just skip the linktables.
However I've also read a tutorial where examples where given using data inside tables and was strongly suggesting to picture each class as a simple table while modeling your class model.
I am confused, what is it now?!
The "relational link table" is an implementation technique for a Many-to-Many relationship.
The relationship exists irrespective of how it's implemented.
In an object model, you have many choices for how to implement many-to-many, which may (or may not) involve an additional persistent table. It could be done lots of different ways.
The point of UML is to be able to describe the essential features of what the model really is.
You can also describe the implementation. They're separate diagrams with separate purposes. You can easily show the relational implementation with the link table. You can also show the essential model without the link table.
Here's the essential relationship
Here's the implementation of the relationship
Both are valid UML. The real question is "what do you need to show other people?" Essential truth or one particular implementation?
Model it as an M:N relationship. Same as in a relationship model there will be an associate class (or link class) of some kind in code. No need to put that on the diagram unless it has attributes on top of the join attributes (much like you would generally omit a join entity from an ERD unless it had attributes that weren't foreign keys in the related entities). The link class is typically drawn as a class connected to the relationship by a dashed line.
The Enrolment join entity is a good example of this in UML 2 Class Diagrams.