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46 APPENDIX E Template to Generate Data Dictionary and Download Specification for erwin Data - Item Preview
Data Modeling With Erwin Book Pdf Download.21 Data Modeling Tools to Design Database for Free ()
To choose the notation for a data model, from the Model menu, choose Model Properties and click the Notation tab. The cursor changes shape for each task so that you know what action will be performed. Alignment, Spacing, And Grouping Tools The appearance of your data model is important to you and the others who use it.
ERwin has many features that help you enhance the appearance of your model. The tools on the Alignment Toolbar speed the process of graphically arranging and grouping model objects. You can select multiple diagram objects, and space them to your preference. Similarly, the Group tool lets you group multiple diagram objects for easy manipulation. Drawing Tools The Drawing Objects toolbar includes a set of drawing tools that you can use to add text and objects to enhance the meaning of your data model.
The tools work like many other popular point-and-click drawing applications. Just click on a tool, click in the diagram window and drag the mouse until the object is the right size. After you add a drawing object, you can use the font and color toolbar to add color to the objects. Format menu, choose Default Fonts and Colors. Click the Drawing Objects tab on the Default Fonts and Colors editor to select the default setting for drawing objects. You have just skimmed the surface of ERwin's capabilities.
But now that you are becoming acquainted with ERwin's features, you are ready for an in-depth exploration. The following chapter explains how to take advantage of the latest modeling techniques that help optimize your data models while managing the impact of design changes throughout your organization.
In this chapter you will be creating and editing ERwin data models. Before you begin exploring the workspace, youll learn about the basic data modeling concepts and objects such as entities, attributes, and relationships. As its name implies, an Entity-Relationship data model, uses entities and relationships to represent the logical structures that will eventually become the physical tables in a database. ERwin uses a box with a horizontal line to depict an entity and solid or dashed connecting lines to depict a relationship between two entities.
What Is An Entity? An entity is a person, place, or thing about which an organization maintains information. In the logical model, an entity usually corresponds to a table in the physical model. For example, an independent entity is an entity whose instances can be uniquely identified without determining its relationship to another entity.
It is represented as a box with square corners. A dependent entity is an entity whose instances cannot be uniquely identified without determining its relationship to another entity or entities. It is represented as a box with rounded corners. What Is An Attribute? Once you have discovered the people, places, and events that define the entities in your model, you can begin to define the attributes for each entity.
In the physical model, attributes equate to columns in a table. Working With Data Models The area above the horizontal line is known as the key area because that is where the entitys primary key resides.
The primary key may be comprised of one or more attributes that uniquely identify the entity. The area below the horizontal line is known as the non-key area because that is where all other attributes reside.
When you add an entity, ERwin determines the entity type based on the relationship in which it is involved. For example, when you initially place an entity in a model, it is represented as an independent entity. When you connect the entity to another entity using a relationship, ERwin determines if the entity is independent or dependent based on the relationship type. What Is A Relationship? In an ERwin data model, a relationship shows an association between two entities or tables.
ERwin represents a relationship as a line connecting two entities or two tables. Depending on the notation you choose, the symbols at either end of the line may change. What Is A Foreign Key? When you create a relationship between entities, ERwin automatically migrates the primary key attribute s of the parent entity, to the child entity.
The designator FK indicates the name of the migrated key attribute, also known as a foreign key. This migration occurs automatically in the physical model. In an identifying relationship, the FK migrates above the line and becomes part of the primary key of the child entity. In a non-identifying relationship, the foreign key migrates below the line and becomes a non-key attribute in the child entity. In ERwin, a dashed line represents a non-identifying relationship.
Buddy Tip If you want a non-key to migrate instead of the primary key, you can use the alternate key migration option. Other Relationship Types In addition to identifying and non-identifying relationships, you can also create other relationships in ERwin, as shown below:.
The following dialog appears:. Locate the ERwin toolbox and click on the Entity tool. Then click anywhere in the Diagram Window to place the first entity. At this point, you should save your data model. From the File menu, choose Save As. ERwin adds. Click Save to return to the Diagram Window. Your data model should look like this:. The following procedure uses both methods: 1.
Click once on the entitys name, wait briefly, and then click again. An edit box appears around the name. When youre done, your diagram should look like this:. We will try both methods in the following exercise. An edit box appears below the entity name with the default name, Attribute Name.
To add the first attribute, which is the primary key, type Number directly over the default name. Then click the mouse outside of the edit box.
NOTE: To add another primary key, press Enter and the edit box will appear above the line in the entity. To add a non-key, press Tab and the edit box will appear below the line in the entity. Right-click on Attributes and choose New from the context menu. A New Attribute edit box appears under Number. Type Name in the edit box and when youre done click the mouse once outside of the edit box.
Buddy Tip To designate an attribute as a primary key, in the Model Explorer, doubleclick on the attributes name to open the Attributes editor. In the General tab, select check the Primary Key box. You can also assign other properties to the attribute such as datatype and domain. Your model should look similar to this:. Enhance Your Data Model You can add drawing objects to a data model to enhance it or to provide meaningful annotations.
In the following exercise, you will add a blue rectangle, a yellow circle, and some text. With My ERwin Model. Click the Text Properties tab and select any dark color for the text. Click OK to close the dialog and see the text in the circle. This is just an example of how you can use drawing objects to enhance your data model.
From the File menu, open the emovies. When the split model process completes, ERwin prompts you to save first the logical model, then the physical model. Save the logical model as emovies-L1. Save the physical model as emovies-P1. After you save the models, close all other models except emovies-P1.
With emovies-P1. In the Target Database list, choose Oracle version 8x. Click Next. You have created a new physical model.
Save the new model as emoviesP2. Forward Engineering When you have a physical data model, ERwin automatically generates the schema for the target server as you build the model. Forward Engineering is the process that ERwin uses to transfer the schema from the data model to the target server. When you forward engineer a data model, you can choose to generate a script file, which you can use to update the database using a database administration tool or you can forward engineer by directly connecting to the database catalog.
Either way, ERwin does the majority of work for you by generating the script for your target server. Before you forward engineer, you can view the schema, which is a text-based representation of the database objects that will be created in the database from the script. ERwin uses the data definition language DDL for the target database to write the script. Each time you add an object or property to your data model, ERwin automatically updates the script file to reflect the change to the data model.
When My ERwin Model. When the Oracle Schema Generation dialog appears, click the Preview button at the bottom of the dialog.
The Oracle Schema Generation Preview dialog appears. When you are finished previewing the schema, click the Close button to return to the Oracle Schema Generation dialog. To change the target server, with a physical data model open, go to the Database menu and select Choose Database. Click the button next to the target server and select the version from the list.
In the Oracle Schema Generation dialog, click the Report button at the bottom of the dialog. From the File menu, choose Close. When the Close dialog appears, choose the Save As. ER1 file option and then click OK. By this time you have a better idea of the basic features that ERwin offers, and how they interact. The next chapter takes you to a new level of achievement: you will perform reverse engineering and compare the changes between a script file and a data model.
In this chapter, we will explore how to create a data model by reverse engineering, which is a process that takes advantage of an existing database to speed the design of a new data model and the subsequent delivery of new systems. Reverse Engineering When you have an existing database from which you want to create a data model, ERwin lets you reverse engineer the database schema, which is converted by ERwin into a graphical representation of the database structures.
The process of reverse engineering saves considerable time because ERwin does the work of creating the data model directly from the database. For the purpose of this exercise, accept the default options in the remaining areas of the dialog and then click Next. You will see a small dialog with text that describes the database structures that ERwin is reverse engineering. When the process ends, a new data model appears in the Diagram Window.
When asked if you want to replace the existing file, click Yes. This trademark technology helps you easily compare and synchronize changes between a data model and its related database or another data model. If you prefer, you can use a SQL script file generated from the database or connect directly to the database catalog. Using a step-by-step approach, ERwin guides you into selecting the objects and properties that you want to compare and filters out those that you do not want to see.
Then, it presents the differences in a side-by-side workspace in which you can selectively import or export changes. Its that simple to keep your data model and database synchronized. The section that follows describes how to use Complete Compare to import and export changes between the data model and the database script file. In the Model Explorer, click the plus sign to expand Tables. From the Tools menu, choose Complete Compare.
The Complete Compare Set Options dialog appears:. On the Object Filter Options page, accept the default selection and click Next. At this point, ERwin begins to process the Script File. On the Resolve Differences page, two trees appear next to each other. They represent the differences that ERwin finds between the current model and the script file.
The next chapter describes the ERwin Report Template Builder and explains how you can use this tool to quickly create reports about your model. For instance, if you choose the RTF format, the report output will automatically invoke your local word processing software.
If you choose the HTML format, the report output will automatically launch your locally installed web browser. If you choose Text format, the report output will automatically launch Microsoft Excel.
You can view and save your reports to share with others using a web browser. Open eMovies. Go to the Tools menu, choose Report Builder. Until the first template is saved in the Reports folder, you may see a message indicating that the folder is empty. Or you may see a message indicating that you need to click the Browse button on the next dialog and select a folder where you want to save your reports.
Select your ERP report from the list, or click Browse to search for the file. Be sure to place a space at the end of the title before performing the next step. In the Report Template Builder, in the left Available Sections pane, select Picture, and click the right arrow to add this section to the Report Layout pane.
In Available Sections pane, select Entity in Logical Section , and click the right arrow to add this section to the Report Layout pane. In Report Layout pane, double-click Entity section to open the Properties dialog and specify the report details for this section. Click the plus sign to expand Attribute, check Name, and close the window to return to the Report Template Builder. To run an HTML report: 1. With emovies. When you run the report, the Report Template Builder launches your web browser with the report displayed.
In the left frame of the browser, locate the links to the Report Components. Click the links in the Picture and Entity sections to review each section. Click Run to launch your local word processor and display the report in the document window. For example, a logical model may represent business requirements and rules. From that model, a generic physical model may be derived, in which physical constructs are designed for a generic database. Once the generic physical model is considered stable, you can derive from it multiple database specific models.
In this way, the generic physical model becomes the standards model. A variety of ERwin features are necessary to support the separation of model types and to keep related models linked and in sync. A brief discussion about these features follows in this chapter. What Is A Design Layer? A design layer is a single data model or set of data models used for a particular purpose in the application development processes.
Each design layer is part of a hierarchy of two or more design layers. In the simplest view of design layer hierarchy, the first design layer is a logical data model that captures the business requirements for an application. Then in a second design layer, those business requirements are transformed into database implementation rules in a physical data model. A generic physical model may be created using generic ODBC as the target database.
A third design layer may represent different physical implementations of the same data model, but on different target server platforms. Logical Model. Generally, it is unfeasible to use the same model to accommodate all phases of the design process. Instead, you must be able to develop and link related models in different design layers. Within each design layer, you must be able to make and record design decisions that transform the structure from one layer to another.
Finally, you must be able to maintain the links between the models in different design layers and to synchronize changes made in different layers while maintaining the appropriate structures in each. In ERwin, the combination of linking models in different design layers via model sources and applying transforms within a model provide this capability. The Second Design Layer: The Generic Physical Model This is where you establish the structure of the tables and columns and generic naming needed to represent the business application.
But, in the physical generic data model, the objects and properties are independent of a database. Other database-specific data models can be derived from a generic physical data model.
The Third Design Layer: Database-specific Physical Models Now you can use ERwin to translate this expertise into database implementation by creating a database-specific physical design layer. Each application can run on several database platforms; a final design layer is needed for database-specific data models.
Other Design Layer Hierarchies Enterprise Model Hierarchy In a similar example, the conceptual data model may instead be an enterprise-level data model, which establishes the standards for all applications across the organization. The enterprise-level data model may be Logical and include all of the approved standards for entities and attributes that the organization supports.
The next design layer may have multiple Logical data models for multiple business applications, such as an Order Entry application and a Sales Commission application. The enterprise-level model may include both of these entities along with others that may not be selected for either of these application-specific models.
In this hierarchy, the next design layer may be a generic Physical model for each application. As in the previous example, if each application runs on several database platforms, a final design layer is needed for database-specific data models.
Enterprise Model Logical. Data Warehouse Hierarchy A data warehouse requires additional layers for models of the entire warehouse and data marts. ERwin provides options in the physical model for dimensional notation and for features related to data movement data source information, data transformation rules that allow you to optimize for warehouse models.
Warehouse Model. If you want to separate that model into two models a logical-only and a physical-only you can use the Split Model option, which is on the Tools menu. When you split a model, ERwin prompts you to save the separate logical and physical data models with different names. When you save the new models, the logical model becomes the source of the physical model, which is necessary for synchronizing changes between the two model types. Rather than copying objects from one model to another or starting from scratch, the Derive New Model wizard takes a step-by-step approach to help you derive a new model from a model source.
ERwin links the original model as the source of the new model. Then you and others can work on the separate models knowing that changes to each model can be synchronized at any time.
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Erwin is a data modeling tool which is used to create logical, physical, and conceptual data models. It is one of the best data modelling tools that helps you to create the actual database from the physical model. Moon Modeler is a data modeling tool for MongoDB and relational databases. Visit Moon Modeler. Archi is a cost-effective solution to enterprise architects and modelers.
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It has a centralized repository model which enable easy and simultaneously models collaboration. Visible Analyst software enables you to design e-business applications, develop a data warehouse, or integrate legacy systems with new enterprise applications.
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