C170 _ C175 Notes.docx - Data Modeling and Representation...

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Data Modeling and RepresentationLesson 1: Introduction to Databases, Information and DataFlat files:Files having no internal hierarchyHeap files:Files containing an unsorted set of records that are uniquelyidentified by a record id which allows them to be inserted or deleted using that id.Index files:Files that store a list of lookup field values from a data file – alongwith the location (address) in the data file of the corresponding record. Becausethe lookup field is much smaller than the entire record, the entire index willusually fit in main memory for quick look up. Once the address of the record isobtained from the index, the entire record can then be directly accessed from thedata file instead of reading in the entire data file – record by record, in order tolocate the desired one.Hashed files:Files are encrypted using hash functions that convert dataconsisting of various formats into numeric values. This allows for faster datalookup without the use of an index file.Dataconsists of raw facts.The wordrawindicates that the facts have not yet been processed to reveal theirmeaning.Informationis the result of processing raw data to reveal its meaning.Dataconstitutes the building blocks of information.Informationis produced by processing data.Informationis used to reveal the meaning of data.Accurate, relevant, and timelyinformation is the key to good decision making.Good decision makingis the key to organizational survival in a globalenvironment.Data managementis a discipline that focuses on the proper generation, storage,and retrieval of data.Adatabaseis a shared, integrated computer structure that stores a collection ofthe following:End-user data—that is, raw facts of interest to the end userMetadata, or data about data, through which the end-user data isintegrated and managedAdatabase management system (DBMS)is a collection of programs thatmanages the database structure and controls access to the data stored in thedatabase.In a sense, adatabaseresembles a very well-organized electronic filing cabinetin which powerful software (the DBMS) helps manage the cabinet's contents.In particular, aDBMSprovides these advantages:Improved data sharing.The DBMS helps create an environment inwhich end users have better access to more and better-managed data.Such access makes it possible for end users to respond quickly tochanges in their environment.Improved data security.The more users access the data, the greaterthe risks of data security breaches. Corporations invest considerableamounts of time, effort, and money to ensure that corporate data is usedproperly. A DBMS provides a framework for better enforcement of dataprivacy and security policies.

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Term
Fall
Professor
N/A
Tags
Data Management, Databases, Sort, Relational model

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