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L AB 6 D ATA A TTRIBUTE AND D ATA E NTITY D ISCOVERY DESIGING THE DATA OF AN INFORMATION SYSTEM The process of designing the data structure of an information system begins with identifying the data entities and data attributes that comprise the data. Attributes are the various pieces of data that have to be stored. For instance, an employee training information system would need to store data (attributes) for employee name, training class name, instructor, date of the class, etc. Attributes can be grouped into Entities . Each data entity stores data attributes related to a single kind of person , place , object , event , or concept . Generally you will have multiple data entities in an information system, with each entity storing many data attributes about a given class of persons, places, objects, events, or concepts. For instance, a college enrollment information system might have an entity for student data, another entity for course information, and another entity for professor data. Entities should be named with a singular noun or a short singular noun phrase, such as those discussed above. Entities correspond roughly to the tables in a relational database. Why use the terms entities and attributes instead of the terms tables and fields? Tables and fields are relational database terms. Though most information systems are implemented using relational databases, not all are. Some information systems use non- relational database systems. Some web-based information systems store data in XML, a non-relational data format. Jumping too soon into any kind of implementation decision is not a good idea. It limits how you think about the design and ultimately limits your choices. So for now, we'll use the implementation-neutral terms data entities and data attributes. Recognizing data entities and data attributes you need for your data is a skill that you will develop with practice. In the next three labs, we will give you the conceptual tools for designing basic data structures and implementing them in a database. In this lab, we will concentrate on identifying data attributes and data entities. In the next lab we'll learn how to correctly design the entity relationships. In the final data lab we will see how to implement a data design in a database. But, like learning to play the piano, the only way you will learn it is in actually working through data design on multiple systems. Page 1
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DETERMINING DATA ATTRIBUTES In performing data analysis, some people like to start by determining the data entities and then determining the attributes that belong to each of those entities. Other people like to start with the data attributes and then determining what data entities those attributes describe. As with object discovery, you can discover data attributes and data entities from use case narratives. Or, as we will do in this lab, you can discover data attributes and data entities from the forms and reports of the current system.
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