Data Model

Logical vs. Physical Modeling {3}

by Kathy S
The two authors of this article start off by declaring that data modeling serves as a link between business needs and system requirements. They stress that if we are going to work with databases, it is important to understand the difference between logical and physical modeling, and how they relate to each other. First, Logical Modeling deals with gathering business requirements and converting those requirements into a model. Also, it involves gathering information about business processes, business entities, and organizational units. After, diagrams and reports are produced (entity relationship , business process, and process flow diagrams). According to the authors, it’s important to note that logical modeling affects the direction of database design and indirectly affects the performance and administration of an implemented database. More options become available when time is invested performing logical modeling. Next, the authors go into Physical modeling. Physical modeling involves the actual design of the database according to the requirements that were established during logical modeling. Physical modeling deals with the conversion of the logical, or business model, into a relational database model. During physical modeling, objects are created based on everything that was defined during logical modeling. Other objects like indexes and snapshots can be defined during physical modeling. Physical modeling is when all the pieces come together to complete the process of defining a database for a business. The authors conclude that the importance of understanding the difference between logical and physical modeling helps us to build better organized and more effective database systems. read more...

The Data Model Owner {2}

by Kathy S
The author (of the article I read) is a data modeling consultant and instructor, and he asked the question,”Who owns the data model?” He received over 100 responses.  It is known that an organization has a team of skilled developers, and these developers do the data modeling. When a developer from this organization asks,”Who owns the data model?” How does one respond? 37% say the business should own the model because “the modelers don’t ‘own’ the data model – they are only the caretakers of the model.”  22% say the development team because as the owners, they would keep all the members informed about changes while maintaining the ability for everyone to make changes to the model as needed. 15% say the individual developer because they have the skill and knowledge to manage the data model well. 11% say the application manager or database administrator because they are the ones who feel the pain when the application is not working properly and they are the ones who are contacted first if the application isn’t working as it should. 15% say no one owns the model simply because no one may have the big picture in mind. read more...

New Way to Model Data {3}

by Andrew M
The article I read this week was entitled “Software Tool for Automated Analysis of Conceptual Data Model” by Z. Kazi and B. Radulovic. This article goes over the idea that databases can be majorly improved if they are efficiently and correctly made from the get go. The authors point out that many times there are issues created because the admins who are creating the database either do not have the knowledge or the skill to create the initial data model correctly. The proposed solution is to use a few tools to help enable database admins to create better and more efficient databases. The first tool they suggest using is CASE. This software tool helps to create the actual data model itself in the correct form. Next, a tool named PROLOG is used which actually tests the model and gives back input. This program shows the relationships that the user has modeled and also how they relate to each other. PROLOG prints out a form in which it can show attributes of a certain entity and also the rules governing that specific entity. The authors feel that if these tools are used that databases can be created much more efficiently. read more...

Important Steps to Convert The Data Sucessfully {1}

by Jamal A
The article I read talks about the procedure that can successfully convert a logical data model into a physical  data model, particularly in a warehouse setting. The article describes some of the necessary steps that can   help convert the data successfully. The article talks about the rules that are necessary to follow when creating logical and physical data models. For Instance: “The business authorization to proceed is received, business requirements are gathered and represented in a logical data model, which will completely represent the business data requirements and will be non-redundant, the logical model is transformed into a first-cut physical model by applying several simple modifications, such as splitting a large table or combining entities in a 1:1 relationship, the logical model is then transformed into a second-cut physical model by iteratively  applying three levels of optimizations or compromises. The outcome from this is a physical database design, apply safe compromises to the model, such as splitting a table or combining two tables, apply aggressive  compromises to the model, such as adding redundant data, the physical database design is then converted to  a physical structure by generating or writing the DDL and installing the database”. In This article, The Information  Gathering Task is also described. I think gathering information is the most critical task when developing a data model. The article described three ways to approach data model development that is, “Top down, inside out, and bottom up”. read more...

The Importance of Learning to Identify Relationships and Entities. {1}

by Kevin Q
The peer-reviewed journal I read discussed reasons that students have trouble grasping and learning data modeling. The main reason being that students have a hard time identifying the relationships among the entities, and not so much in how to express the relationships. Students who do not learn how to identify relationships and thus create them in their data models will eventually run into problems due to poor data modeling.Typical mistakes that Dr. Watson has seen in his years of teaching include: “Not recognizing that an attribute is an entity, failing to generalize several entities as a single entity, not reading relationships both ways, and ignoring exception that result in a failure to represent reality.” Students who are good at identifying relationships are better off than student who can create diagram representations but unfortunately cannot interpret the relationships and entities. Watson then goes over on how he chooses a representation of data modeling. He bases it on two factors: something that is able to be quickly sketched on the front board in class, and something that students will be able to understand and emulate through SQL statements. Watson then goes on to his teaching method of “integrated spiral approach,” which means that he teaches data modeling and SQL side by side so that the students can make the connection and begin to see the connections between the two as opposed to the general teaching of data modeling followed by SQL. In the end, Watson says that its not how you represent the final data model, but that the data model grasps the true nature of the project. read more...

Data Modeling: What you need to know? {6}

by Jasmine C
What designing a data model, what is the most essential skill that you need to know? Well, according to an article I read, the most basic skill needed is not the representation of entities and relationships. What a person needs to know is how to identify entities and the correct relationship among them. Data modeling is more than just “drawing a diagram (Watson)”. It is being able to ” capture reality so that the database based on the data model can be used to answer questions about reality (Watson)”. If you have a model, what good is it if you cannot relate it to reality! When teaching  data modeling to students, they are going to make a lot of mistakes. However, once they are taught the correct way, modeling will come easy to them.  In the article, the writer suggests that integrating the teaching of data modeling and SQL provides for an enhanced learning experience for the student because they will be better equip to comprehend many of the key features of relational databases.  Students will be able to make a connection between their diagrams and SQL, effectively gaining a better understanding of SQL and data modeling. read more...

Automated Data Model Evaluation {1}

by Tuyen H

In the article “Software tool for automated analysis of conceptual data model,” the authors mention about how to automate evaluating a data model. Data modeling is very important to business because it strongly affects to quality of business database. The idea is using CASE Tool output to process data model evaluation based on transformation of XML form of conceptual data model. In data modeling, there are two main reasoning roles such as:
• Each strong type entity must have at least one or more attributes.
• Each entity must have an identifying attribute.

Data Modeling the First Step of Database Design {Comments Off on Data Modeling the First Step of Database Design}

by Tuyen H
In the Article “Why you want to be good at data modeling,” (Schumacher, 2011) Robin Schumacher writes about how important of Data Modeling in the design phase of Database. According to his article, many big projects cost many years to complete because of Data modeling and design are not taking serious in overall system development as they should be. Therefore, as database designers, the designers should take carefully first data modeling as the first step instead of physical design. He also recommends that if you carefully work on data modeling step, your physical design and implementation will much more easier. Moreover, a good data modeling will help you on the maintenance later. In conclusion, there are many data modeling tools to help us in data modeling such as Entity Relationship Model and MySQL Workbench, so choose your tools and take seriously on the first step of database design. read more...