UML

An Education in Notation {2}

by Brian B
The article I chose this week is entitled “Notation Usage in Data Modeling Education” by Michael Mannino. The article starts off by saying that there has never been a true standard of notation in the data modeling field. There have been attempts in the past, but none of them have ever gained wide usage throughout the industry.  He talks about the fact that there is a wide variety of notation styles which has been increased with the differences in textbooks and the CASE Tools used in the industry. The author believes that creating a standard now would be difficult because of the current “diversity” in modeling notation. The author says that students should be taught both ERD and UML, however they should be taught in separate classes. The article goes on to talk about ways to instruct students in subject matter such as design errors or advancing their knowledge in data modeling. He finishes the article off by saying that “These guidelines are just building blocks to develop data modeling skills. (Mannino, Spring 2006)” He then offers some ideas on how data modeling education can be advanced. One way he suggests is that students be given real world examples of data modeling to actually prepare them for what is in store for them in their field of work. read more...

ER or UML? {4}

by Andrew H
For this weeks blog I read an academic journal by James Suleiman and Monica Garfield called, “Conceptual Data Modeling in the Introductory Database Course: Is it Time for UML?.” The article talks about what type of data modeling schools are using for their introductory database courses. The answer has proven to be E-R modeling even though the article states that UML could possibly be the better style. The authors say, that a lot of programs use Object-Oriented (OO) methodology which embraces UML, therefore UML would be a good approach to teach as most students are already accustomed to it after a few programming courses. They believe as a result that there should be further discussion and teachers should press for teaching the UML way that way everything is more uniform and students can get a more comprehensive understanding of the material. read more...

UML Diagram for Rookie {1}

by Jamal A
A picture worth a thousand words, but it worth way more than that when creating a UML Diagram. UML is a graphical modeling language, and it represents a class as a rectangle with the class name inside. I usually think of it as a box full of stuff.  The author in this article, talks about how UML class diagrams are very good for interconnecting the overall structure of classes and the dependencies between them.  However, In a UML class diagram it is somewhat easier to see whether one class inherits from another class, or it just simply holds the reference to another class.  According to the article, “Diagrams make certain dependency structures visible. We can see dependency cycles, and determine how best to break them. We can see when abstract classes depend upon concrete classes, and determine a strategy for rerouting such dependencies”. Next, the authors Robert C. Martin talks about the associations between classes that are most often represent instance variables that hold references to other objects. read more...

Physical Data Warehouse Advantages with UML {Comments Off on Physical Data Warehouse Advantages with UML}

by Ermie C
This article is about how there are several approaches on how to create a data warehouse.  The specifics on which parts of a data warehouse is approached are the logical and conceptual modeling, the use  of something they call ETL(Extraction, Transformation, Loading), and unique customization of the schema of the database.  They conclude that when creating a DW, it needs many decisions to create a more efficient database.  So they started to used the design and implementation tools from UML.  UML stands for Unified Modeling Language and with this language it would “reduce the overall development time of a DW, such as replicating dimension tables, vertical and horizontal partitioning of a fact table, and the use of particular servers for certain ETL processes. (Mora)” read more...

ERD vs UML? what do employers want? {Comments Off on ERD vs UML? what do employers want?}

by Willen L
In this article the author talks about the employment demands of ERD vs. UML. Whether employers prefer one over the other and with the ever fast changing IT field it’s sometime difficult to gauge what skills are preferred in the profession but with all these job search tools online it’s possible to gauge where the demand is. The author analyzed data that he obtained from SkillPROOF since the beginning of 2004 and wrote this article 2 years later in 2006. The data was collected from 137 IT focused companies and the data was collected daily and there were a total of 35,932 jobs recorded. They did a keyword categorization according to history and a sampled content analysis for a week to dig deeper into the matter. They found that data modeling when searched without a specific methology is one of the required knowledge bases. That means a lot of jobs want data modeling but did not specify what type of modeling (ERD vs UML).  UML appears to be more on the application development side and are often listed as a critical skill. ERD tends to focus on database design and maintenance and is also often accompanied by skills in software such as ErWin, Visio and TOAD. read more...

The differences of UML and ER model {3}

by Polun L
The article, “How to Draw an Architectural Data Model in UML”, by David C. Hay, talks about the differences of UML model and ER model. At the beginning of the article, the author described the development of entity/relationship data model which was formalized in 1970’s. Two decades later, the Unified Modeling Language (UML) was officially released. However, programmers found out that UML model is very different from ER model because they have significantly different structure in relational database. Even though object oriented programmers attempted to save persistent object data in relational database, it still could not make UML and ER model to be consistent. Finally, programmers realized that UML was developed to support object oriented design while entity relationship modeling was designed to support the analysis of business structures. In the end of the article, the author listed a guideline for those who would like to draw a ER model using  a  UML diagramming tool. read more...

Wanted: Database Models {Comments Off on Wanted: Database Models}

by James C
Summary:

The topic of data modeling has always been hard for students to grasp. Even though the there are many techniques on data modeling, no one standardized method has been agreed on by educational institutions. In order for developers to understand the connections between entities and their relationships they first must study the entity relationship (ER) modeling technique. Despite the effectiveness of this technique, though, many developers, as seen through their work, are still having trouble using, learning, and integrating with it. To add to this dilemma, many developers are also having additional issues with combining the object-oriented approach with the entity relationship modeling technique. This article sheds some light on the subject of which modeling technique is more effective, the UML or ER modeling technique. The debate between the better of the two are is not answered, but rather explored. Both methods having similar issues, like dealing with multi-valued attributes, for example. One real issue that did arise in the end was that database designers and system analysts are in constant disagreement. Both systems analysts and database designers are both comfortable with different ideas. SA’s are at ease with object-oriented programming methods. Database designers are more structured and mathematically centered. read more...