Contribution of CASE Tools to the System Development
By Richard Ngu
The entity is the basic construct of data modeling. An entity instance is one occurrence of an entity. Entities are described by attributes that hold data about entity instances. Attributes have domains that define the legal set of data values for the attributes. One or more attributes in every entity are used to uniquely identify each instance of the entity, which is known as a key. The instances of an entity may be divided into subsets based on the value of subsetting criteria. Relationships are natural business associations that exist between one or more entities.
Whereas, in object modeling the data or attributes represent characteristics of interest about an object. Objects can be categorized into classes. A class is a set of objects that share common attributes and behaviors. Objects may be grouped into multiple levels of classes. Objects and classes have relationships. A relationship is a natural business association that exists between one or more objects/classes. The degree, or multiplicity, of a relationship specifies the business rules governing the relationship.
When using System Architect to work on a project, one will find eight major pieces to work with.
1. Graphical Interface
The System Architect graphical interface consists of a large drawing window and ten general-purpose drop-down menus, which make available all the System Architect functions.
2. Data Dictionary Facility
The data dictionary stores the definitions of the components that make up a project. One can give some kind of information to each of the symbols on every diagram. Every graphic and non-graphic object in System Architect has at least the property "Description," in which one can enter some informative text about the reason that object is in the project.
3. Reporting System
Through the reporting system one can generate a variety of project monitoring and management reports. A number of predefined reports have been provided, the users can define their own. There's an extensive on-line help facility for using the reporting system.
4. Documentation Facility
The documentation facility takes the reporting system one step further and allows user to integrate any grouping of reports and diagrams into a single, cohesive document.
5. Rules Checkers and Balancers
The rules checkers and balancers examine diagrams and all related dictionary definitions for completeness and adherence to accepted rules, examine the data dictionary for data-structure completeness and correctness, and test for consistency within and between diagrams.
6. Schema Generator for Various Database Management Systems (DBMS)
The System Architect Schema Generator creates data definition language (DDL) statements for a wide variety of SQL and non-SQL DBMS products, or links directly to an existing database through ODBC drivers. It also creates data definitions for inclusion into COBOL and C-language programs.
7. Reverse Data Engineer for Various Database Management Systems (DBMS)
The System Architect Reverse Data Engineer reverse engineers from a wide variety of SQL schema and databases into existing or new System Architect encyclopedias, providing a relatively easy way to upgrade legacy systems. Output from RDE includes dictionary definitions and physical data models. It also creates diagrams from Windows-based .DLG and .MNU files.
8. Screen Painter
User can use the System Architect Screen Painter to create Windows-style graphical user interface (GUI) windows and menus. The Graphic Screen and Menu diagrams come with their own toolboxes that include standard Windows controls. One can also drag and drop previously defined objects, such as entities, classes, data elements, and data structures onto a Graphic Screen.
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About Richard Ngu
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