...Chapter 2 - Database System Concepts and Architecture Data Models, Schemas and Instances A characteristic of the database approach is that it provides a level of data abstraction, by hiding details of data storage that are not needed by most users. A data model is a collection of concepts that can be used to describe the structure of a database. The model provides the necessary means to achieve the abstraction. The structure of a database is characterized by data types, relationships, and constraints that hold for the data. Models also include a set of operations for specifying retrievals and updates. Data models are changing to include concepts to specify the behaviour of the database application. This allows designers to specify a set of user defined operations that are allowed. Categories of Data Models Data models can be categorized in multiple ways. • High level/conceptual data models – provide concepts close to the way users perceive the data. • Physical data models – provide concepts that describe the details of how data is stored in the computer. These concepts are generally meant for the specialist, and not the end user. • Representational data models – provide concepts that may be understood by the end user but not far removed from the way data is organized. Conceptual data models use concepts such as entities, attributes and relationships. • Entity – represents a real world object or concept • Attribute - represents...
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...system buses, and Boolean operators to communicate programs and perform functions. Computer Architecture- Von Neumann Architecture Explained A computer is an electronic device that operates under the control of instructions that are stored in memory. The concept of storing memory or instructions within the computer came from John Von Neumann. Von Neumann architecture can be best described as a stored program design. A stored programmed design means that the program that operates the computer and the instructions that carry out the program are stored on the computer in one location, memory. By having a stored program design, the computer doesn’t have to go through a rigorous process to be reprogrammed, or to perform multiple functions. The basic design of today’s computers is founded on the architecture of Von Neumann, which can be referred to as the “fetch-execute cycle”. The Von Neumann model consists of five major components that work together to make the computer perform. There is an area for memory to be held and processed; today we know this as RAM or Random Access Memory. There is a control unit, which manages the process of moving data and program into and out of the memory, and also executes the programs instructions, one by one. There is an input and output which is the computers connection to the user. The arithmetic logic unit is responsible for carrying out calculations or instructions. Another important concept of the...
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...Overall System Structure 1.1 Silberschatz, Korth and Sudarshan c 1997 Database Systems Concepts Database Management System (DBMS) • Collection of interrelated data • Set of programs to access the data • DBMS contains information about a particular enterprise • DBMS provides an environment that it both convenient and efficient to use Database Systems Concepts 1.2 Silberschatz, Korth and Sudarshan c 1997 ' & ' & Purpose of Database Systems $ $ Database management systems were developed to handle the following difficulties of typical file-processing systems supported by conventional operating systems. • Data redundancy and inconsistency • Difficulty in accessing data • Data isolation – multiple files and formats • Integrity problems • Atomicity of updates • Concurrent access by multiple users • Security problems Database Systems Concepts 1.3 Silberschatz, Korth and Sudarshan c 1997 View of Data An architecture for a database system view level view 1 view 2 … view n logical level physical level Database Systems Concepts 1.4 Silberschatz, Korth and Sudarshan c 1997 ' & ' & Levels of Abstraction $ $ • Physical level: describes how a record (e.g., customer) is stored. • Logical level: describes data stored in database, and the relationships among the data. type customer = record name : string; street : string; city : integer; end; • View level: application programs hide details of data types. Views can also hide information (e.g. salary) for security...
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...Chapter 2 - Database System Concepts and Architecture Data Models, Schemas and Instances A characteristic of the database approach is that it provides a level of data abstraction, by hiding details of data storage that are not needed by most users. A data model is a collection of concepts that can be used to describe the structure of a database. The model provides the necessary means to achieve the abstraction. The structure of a database is characterized by data types, relationships, and constraints that hold for the data. Models also include a set of operations for specifying retrievals and updates. Data models are changing to include concepts to specify the behaviour of the database application. This allows designers to specify a set of user defined operations that are allowed. Categories of Data Models Data models can be categorized in multiple ways. • High level/conceptual data models – provide concepts close to the way users perceive the data. • Physical data models – provide concepts that describe the details of how data is stored in the computer. These concepts are generally meant for the specialist, and not the end user. • Representational data models – provide concepts that may be understood by the end user but not far removed from the way data is organized. Conceptual data models use concepts such as entities, attributes and relationships. • Entity – represents a real world object or concept • Attribute - represents...
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...Stored procedures Stored procedures can help improve application performance and reduce database access traffic. All database access must go across the network, which, in some cases, can result in poor performance. For each SQL statement, a database manager application must initiate a separate communication with DB2. To improve application performance, you can create stored procedures that run on your database server. A client application can then simply call the stored procedures to obtain results of the SQL statements that are contained in the procedure. Because the stored procedure runs the SQL statement on the server for you, database performance is improved. In addition, stored procedures can help to centralize business logic. If you make changes to a stored procedure, the changes are immediately available to all client applications that use it. Stored procedures are programs that have the following characteristics: • Contain procedural constructs with SQL statements • Are stored in databases and run on DB2 servers • Can be called by name by an application that is using SQL • Allow an application program to run in two parts: the application on the client and the stored procedure on the server The following figures show how two client applications access a database located on a database server. A client application that does not use stored procedures to access a database can require more network traffic. A client application that takes advantage of a...
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...Simulated Assembler-Objects and a Glass Bottom Computer (a polytechnic approach) William G. Verbrugge wgverbrugge@csupomona.edu California State Polytechnic University, Pomona 3801 West Temple Avenue Pomona, CA 91768 Abstract Integrated Development Environments are excellent production tools for intermediate and advanced programming students and even beginners after they have learned the core concepts (stored data, stored programs, computer instructions, and the anatomy of the computer). Most authors of introduction to programming books recognize this by their inclusion of one to twenty pages on this topic. This paper presents how using a simulated assembler (a tool for learning) with a simple assembly language can introduce the beginning student to the core concepts without having to be concerned with all the exceptions and rigor of a full assembler language. The Simulated Assembler with a full viewable Computer Machine (Glass Bottom Computer) and the easy procedures for using it in a first programming course are illustrated. Using the assembler tool described here should provide an increase in learning via a polytechnic (learn by doing) approach. A comparative analysis of using the assembler in an introduction to object programming course is provided. Keywords: assembler, simple machine, software tools, language, programming, object oriented, machine language 1. INTRODUCTION The growth in hardware technology has allowed the theories of modern...
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...are interested. DBMS - is a collection of programs that enables users to create and maintain a database. database system – it is a combination of database and DBMS software. program – data independence – The structure of data files is stored in the DBMS catalog separately from the access programs. user view - – includes a number of external schemas that describes the part of the database that a particular user group is interested in and hides the rest of the database from that user group. DBA – is an IT professional that is responsible for Installation, Configuration, Upgrade, Administration, Monitoring, Maintenance and Securing of databases in an organization. The chief administrator of the database. end user - are the people whose jobs require access to the database for querying, updating, and generating reports; the database primarily exists for their use. data model - a collection of concepts that can be used to describe the structure of a database-provides the necessary means to achieve this abstraction. database schema - of a database system is its structure described in a formal language supported by the database management system (DBMS) and refers to the organization of data as a blueprint of how a database is constructed. Internal schema - uses a physical data model and describes the complete details of data storage and access paths for the database. conceptual schema - or conceptual data model is a map of concepts and their relationships used...
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...Student Name: ID: TOTAL MARKS REQUIREMENT ANALYSIS | Fail | Marginal Fail | Pass | Credit | Distinction | | 0-3 | 4 | 5-6 | 7 | 8-10 | USE CASE DIAGRAM WITH DESCRIPTION (10%) | Incorrect overview use case, detail use cases with scenarios (where applicable) and use case descriptions OR incorrect user case notations OR illogical functional design | Inappropriate overview use case, detail use cases with scenarios (where applicable) and use case descriptions. | The use cases are well presented (generalization) with no major mistake in logic and notation, and described all flows in use case descriptions. | Appropriate labelling and no mistake in logic and notation and clear description for normal flow, subflow and alternative flow in use case descriptions. | Comprehensive provision of the required - overview use case; - detail use case diagrams with scenarios (where applicable: generalization, extends, includes);- use case descriptions for each use case / scenario and no mistake in logic and notation and appropriateness. | | | | | | | ACTIVITY DIAGRAMWITH DESCRIPTION(10%) | The business-level activity diagram(s) is without swimlanes and not logical in an overall cases. | The business-level activity diagram(s) is without swimlanes and logical partially. | The business-level activity diagram(s) provided are complete, with swimlanes, logical and with no major errors. ...
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...1 1.1. Define the following terms: data, database, DBMS, database system, database catalog, program-data independence, user view, DBA, end user, canned transaction, deductive database system, persistent object, meta-data, and transaction-processing application. • Data – known facts that can be recorded and that have implicit meaning. • Database – a collection of related data with an implicit meaning. • DBMS – a collection of programs that enables users to create and maintain a database • Database system – not only contains the database itself bit also a complete definition or description of the database structure and constrains. • Database catalog – the information about the database structure is stored in the Database Catalog which contains the structure of each file, the type and storage format of each data item, and various constrains of the data. • Program-Data Independence – DBMS access programs do not require changes in all programs due to the change in the structure of a file because the structure of data files is stored in the DBMS catalog separately from the access programs. • User View – a database typically has many users, and each of whom may require a different perspective or view of the database. A view may be a subset of the database or it may contain virtual data the is derived from the database files but is not explicitly stored. • DBA – a database administrator (short form DBA) is a person responsible for the installation...
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...1) Different of DBMS and IR (30%) DATABASE MANAGEMENT SYSTEM (DBMS) | INFORMATION RETRIEVAL(IR) | A database management system (DBMS) is a collection of programs that enables you to store, modify, and extract information from a database. There are many different types of DBMSs, ranging from small systems that run on personal computers to huge systems that run on mainframes.Also known as a database program which the software that allows you to create, manage and access database. Available for many sizes and types of computersSoftware package with computer programs that control the creation, maintenance, and use of a database. It allows organizations to conveniently develop databases for various applications by database administrators (DBAs) and other specialists. Data independence which application programs should be as independent as possible from details of data representation and storage. The DBMS can provide an abstract view of the data to insulate application code from such details. Utilizes a variety of sophisticated techniques to store and retrieve data efficiently. This feature is especially important if the data is stored on external storage devices. Data always accessed through the DBMS, the DBMS can enforce integrity constraints on the data. For example, before inserting salary information for an employee, the DBMS can check that the department budget is not exceeded. Also, the DBMS can enforce access controls that govern what data is visible to different classes...
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...and also noted that when it went awry it did so obviously, unlike methods which could be subtly incorrect. While consulting for the Moore School of Electrical Engineering at the University of Pennsylvania on the EDVAC project, von Neumann wrote an incomplete First Draft of a Report on the EDVAC. The paper, whose public distribution nullified the patent claims of EDVAC designers J. Presper Eckert and John William Mauchly, described a computer architecture in which the data and the program are both stored in the computer's memory in the same address space.[50] John von Neumann also consulted for the ENIAC project, when ENIAC was being modified to contain a stored program. Since the modified ENIAC was fully functional by 1948 and the EDVAC wasn't delivered to Ballistics Research Laboratory until 1949, one could argue that ENIAC was the first computer to use a stored program. John von Neumann also designed the instruction set for the modified ENIAC, and he should be given credit for this. The stored program version of ENIAC ran 6 times slower, but it was still entirely I/O bound, and...
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...was in written form, due to the lake of education, due to the in-familiarity with new techniques, lake of computer knowledge so all the data required would be stored in a file or files owned by the programs. Discuss the disadvantages of this approach. Different programs could be written in different languages, and would not be able to access another program's files. This would be true even for those programs written in the same language, because a program needs to know the file structure before it can access it. 1.4 Describe the main characteristics of the database approach and contrast it with the file-based approach. Focus is now on the data first, and then the applications. The structure of the data is now kept separate from the programs that operate on the data. This is held in the system catalog or data dictionary. Programs can now share data, which is no longer fragmented. There is also a reduction in redundancy, and achievement of program-data independence. 1.5 Describe the five components of the DBMS environment and discuss how they relate to each other. (1) Hardware: The computer system(s) that the DBMS and the application programs run on. This can range from a single PC, to a single mainframe, to a network of computers. (2) Software: The DBMS software and the application programs, together with the operating system, including network software if the DBMS is being used over a network. (3) Data: The data acts as a bridge between the...
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...Sequential Data Files 8 In this chapter, we will introduce the important concept of a data file and discuss the use of sequential files for data input. We will also describe how to manipulate the records in these files in several ways. After reading this chapter, you will be able to do the following: Identify the types of data files [Section 8.1] Identify records and fields within a data file [Section 8.1] Create, write data to, and read data from a sequential file [Section 8.1] Delete, modify, and insert records in a sequential file [Section 8.2] Use arrays for file maintenance [Section 8.2] Merge two data files so that their records stay in order [Section 8.3] Use the control break processing technique in certain programming situations [Section 8.4] Combine many techniques learned so far—data files, arrays, searching, and sorting—to create a longer program [Section 8.5] ISBN 1-256-14455-X 405 Prelude to Programming: Concepts and Design, Fifth Edition, by Stewart Venit and Elizabeth Drake. Published by Addison-Wesley. Copyright © 2011 by Pearson Education, Inc. 406 Chapter 8 Sequential Data Files In the Everyday World Data Files You probably write information you need to remember on little scraps of paper all the time, and that’s good enough for a lot of things. But if you try to run a business that way, you’ll find yourself in trouble because you’ll have a difficult time locating the data you need to pay bills, employees, and suppliers. If you...
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...second function:- MOVING DATA FROM ONE MEMORY LOCATION TO ANOTHER:- After applying the ALU to the data, the data will now be stored in the primary storage, before being processed. There are two main types of the Primary Storage:- 1-ROM (read only memory) permanent memory. 2-RAM (random access memory) temporary memory. 1- ROM:- Rom holds all the data and the instructions which are permanent or fixed at the time of production and that data cannot be changed by the operator of the computer nor even by the computer. It is the permanent memory which only allows to “see” or read the data and does not allow to change or write something else in that data. The software which is usually stored in ROM is firmware, as its name firm tells us that the...
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...In the late 1940's, John Von Neumann, developer of the stored program concept, authored a treatise, "Theory and Organization of Complicate Automata", in which he described the theory of what came to be called, the computer virus. He proposed the theory that software can multiply like a biological virus. Several scientists pursued this theory in a few journals, even though most everyone else dismissed the idea. About 10 years later, this radical theory, was brought to life at the highly respected Bell Labs. One of the programmers responsible for this amazing feat was Robert Morris, Sr., the father of the infamous, Robert Morris, Jr., who created the worst infection in the history of the Internet. These programmers, realizing that both programs and data are stored in the same computer memory, proved that programs could be created and destroyed just like data. They created a computer game, in which the programs replicated themselves and destroyed the opposing programs. Because computer memory at that time was referred to as core, this game was later called Core Wars in a Scientific American article. Although news of this experiment soon spread to researchers at MIT and Xerox, apparently the programmers were able to keep this information from most of the computer community for several years. They were well aware of the disastrous effects this concept could have on a network. As an experiment, Xerox demonstrated how rapidly it could spread through a network, and shut down...
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