LIM, MARYLYN GRACE C.

OOA

            Book: Systems Analysis and Design: an Active Approach

            Author: George M. Marakas

            Reference No.: QA

                                    76.9

                                    S88

                                    M37

                                    2001

Chapter 9: Designing the Files and Databases

Quote: “The commercial world is a great reality check for new ideas.”

Review:

            This chapter focuses on physical file and database design. Database schema is the physical model of the new system. This also represents the technical implementation of the logical model. During this process, there are 2 primary goals that should be accomplished. 1.) Accurately translate the logical relations into a comprehensive technical specification for the files and database. 2.) Specify the storage and technologies needed for the data to be contained within the system.

            In designing and specifying fields, there are 2 things to be remembered. 1.) Field type. This is the principal database. 2.) Data type. This is the specification of how each field in the file represents the data contained within it. 3.) Field representation. This determines the characteristics about each field and records it in the data dictionary for the system. 4.) Date integrity. This focuses on processes and procedures that are intended to facilitate an atmosphere of trust. 5.) Key integrity. This insures that every file has a unique primary key. 6.) Domain integrity. This insures that no data element in a file on database takes on a value that is outside its range of legal. 7.) Referential integrity. This insures that the value of the field is limited to the range of existing values of another field in another file.

            In designing the physical record, there are 3 things to be remembered. 1.) Determine the arrangement of the fields contained in each record of the file. 2.) Make a decision on the recording length. 3.) Consider the information process, retrieval and display methods.

            In designing and specification files, there are 3 things to be remembered. 1.) File access methods. This contains the methods used to access a particular record in a file.  2.) Organization technologies. This focuses on physical arrangement of records within a file in the storage media. 3.) File volumetric. This addresses the question of exactly how much data the system needs to manage.

            Lastly, this chapter discusses about designing the database. Databases architecture determines the structure of the database system. There are 4 basic architectural approaches being used. 1.) Network database model. This approach tells us that in each file in the database may be associated with any number of subordinate or superior files. 2.) Hierarchical database model. This links the files within the database in the form of hierarchy. 3.) Relational database model. This represents a table in which each column represents a data field and the row represents a single record in that file. 4.) Object-oriented database model. This summarizes both the attributes associated with an object and the methods that operate on the objects in a structure known as object class.