Assoc. Prof. Dr. Ahmet Turan ÖZCERİT

 The concept of Data, Information and Knowledge  The fundamental terms:  Database and database system  Database Management System  Database architectures  File Systems  Data models You will learn: 2

He/She can explain the fundamental terms of database systems 3

4 Data... data is raw. It simply exists and has no significance beyond its existence (in and of itself). It can exist in any form, usable or not. It does not have meaning of itself Information... information is data that has been given meaning by way of relational connection. This "meaning" can be useful, but does not have to be. Knowledge... knowledge is the appropriate collection of information, such that it's intent is to be useful. Knowledge is a deterministic process. When someone "memorizes" information (as less-aspiring test-bound students often do), then they have amassed knowledge. This knowledge has useful meaning to them, but it does not provide for, in and of itself, an integration such as would infer further knowledge. For example, elementary school children memorize, or amass knowledge of, the "times table". They can tell you that "2 x 2 = 4" because they have amassed that knowledge (it being included in the times table). But when asked what is "1267 x 300", they can not respond correctly because that entry is not in their times table. To correctly answer such a question requires a true cognitive and analytical ability that is only encompassed in the next level... understanding

He/She can explain the fundamental terms of database systems 5 Phase-1 Requirements and Analysis Phase-1 Requirements and Analysis Phase-2 Conceptual Modeling Phase-2 Conceptual Modeling Phase-3 Logical Modeling Phase-3 Logical Modeling Phase-4 Physical Modeling Phase-4 Physical Modeling Functional Analysis Application Design Application Design Application Programs Application Programs Functional RequirementsUser Requirements Data Requirements

He/She can explain the fundamental terms of database systems 6 A database is an organized collection of data which can be manageable, portable, updatable. It is the collection of schemes, tables, queries, reports, views and other objects that computer applications can manipulate them. The data is typically organized to model aspects of reality A database management system (DBMS) is a computer software application that interacts with the user, other applications, and the database itself to capture and analyze data. A general-purpose DBMS is designed to allow the definition, creation, querying, update, and administration of databases. Well-known DBMSs include MySQL, PostgreSQL, Microsoft SQL Server, Oracle, Sybase and IBM DB2. A database is not generally portable across different DBMSs, but different DBMS can interoperate by using standards such as SQL and ODBC or JDBC to allow a single application to work with more than one DBMS

He/She can explain the fundamental terms of database systems 7 DBMS SOFTWARE Query Processing Software Data Accessing Software User Interfaces Application Software Queries User Interfaces Application Software Queries

He/She can explain the fundamental terms of database systems Actors on the Scene Database Administrator Database Developers Database Programmers Users Actors on the Scene Database Administrator Database Developers Database Programmers Users Actors on the Back DBMS Developers Tool Developers Operators Maintenance and Repair Personal Actors on the Back DBMS Developers Tool Developers Operators Maintenance and Repair Personal

He/She can explain the fundamental terms of database systems History 1960s Network Model (CODASYL) Hierarchical Model (IMS by IBM) 1970sRelational Model 1976 Entity-Relationship 1980s SQL, standard query language 1990 Object-Relational 1993 Object Oriented Data Model History 1960s Network Model (CODASYL) Hierarchical Model (IMS by IBM) 1970sRelational Model 1976 Entity-Relationship 1980s SQL, standard query language 1990 Object-Relational 1993 Object Oriented Data Model

He/She can explain the fundamental terms of database systems 1- Central System Architecture User tools, DBMS and data are located on a server Client DBMS Database

He/She can explain the fundamental terms of database systems 2- Two-Layered Client/Server System Architecture Client DBMS Database Network Client More than one user act as client. Clients access the database through network First layer: Client layer Second layer: Database server

He/She can explain the fundamental terms of database systems 3- Three-Layered Client/Server System Architecture Application Software Application Software Database Network Client More than one user act as client. Clients access the database through network First layer: Client layer Second layer: Database server DBMS Database

He/She can explain the fundamental terms of database systems 4- N-Layered Client/Server System Architecture Web Software Web Software Web Server Network Client Application Software Application Software Application Server Client DBMS Database

He/She can explain the fundamental terms of database systems 5- Distributed Database System Architecture Database Network Client DBMS Database Server 1 Server 2

He/She can explain the fundamental terms of database systems A computer file is a resource for storing information, which is available to a computer program and is usually based on some kind of durable storage. A file is "durable" in the sense that it remains available for other programs to use after the program that created it has finished executing. Computer files can be considered as the modern counterpart of paper documents which traditionally are kept in office and library files, and this is the source of the term.

He/She can explain the fundamental terms of database systems Sequential Files: A sequential file is one in which the individual records can only be accessed sequentially, that is, in the same order as they were originally written to the file. New records are always added to the end of the file. Indexed Files: An indexed file is a file in which each record includes a primary key. To distinguish one record from another, the value of the primary key must be unique for each record. Records can then be accessed randomly by specifying the value of the record's primary key. Indexed file records can also be accessed sequentially. As well as a primary key, indexed files can contain one or more additional keys known as alternate keys. The value of a record's alternate key(s) does not have to be unique. Hashed Files: Hash files are commonly used as a method of verifying file size. This process is called check-sum verification. When a file is sent over a network, it must be broken into small pieces and reassembled after it reaches its destination. In this situation the hash number represents the size of the data in a file. The hash can then be used as a tool for validating the entire file was successfully transmitted over the network.

He/She can explain the fundamental terms of database systems Advantages of DBMS :  No redundant data  Data consistency and integrity  Data security  Easy access  Easy recovery  Flexibility What about disadvantages?  Cost  Complexity  Performance loss

He/She can explain the fundamental terms of database systems  There are three different types of data models produced while progressing from requirements to the actual database to be used for the information system. The data requirements are initially recorded as a conceptual data model which is essentially a set of technology independent specifications about the data and is used to discuss initial requirements with the business stakeholders. The conceptual model is then translated into a logical data model, which documents structures of the data that can be implemented in databases. Implementation of one conceptual data model may require multiple logical data models. The last step in data modeling is transforming the logical data model to a physical data model that organizes the data into tables, and accounts for access, performance and storage details. Data modeling defines not just data elements, but also their structures and the relationships between them.

He/She can explain the fundamental terms of database systems  Step-1: Requirement analysis describes to determine data types, data groups, data related rules and processes operating on data. It also describes the functionalities of the system, the data to be stored in the system, relationship between data and user’s operations.  Step-2: Conceptual model describes the semantics of a domain (the scope of the model). For example, it may be a model of the interest area of an organization or of an industry. This consists of entity classes, representing kinds of things of significance in the domain, and relationships assertions about associations between pairs of entity classes. A conceptual schema specifies the kinds of facts or propositions that can be expressed using the model. In that sense, it defines the allowed expressions in an artificial "language" with a scope that is limited by the scope of the model. Simply described, a conceptual schema is the first step in organizing the data requirements.

He/She can explain the fundamental terms of database systems  Step-3: Logical model describes the structure of some domain of information. This consists of descriptions of (for example) tables, columns, object-oriented classes, and XML tags. The logical schema and conceptual schema are sometimes implemented as one and the same  Step-4: Physical model describes the physical means used to store data. This is concerned with partitions, CPUs, tablespaces, and the like.

He/She can explain the component of the data modeling The components of conceptual data modeling Entity: Existing and distinguishable object Array of Entities

He/She can explain the component of the data modeling Example: Entity-Relation Sets E 1 = { John, Alice} E 2 = { Math, ICE} The relationship between E 1 and E 2 is students and their course E 1 x E 2 = { (John, Math), (John, ICE), (Alice, Math), (Alice, ICE)} Then we can describe three relation sets below: R 1 ={(John,Math)} R 2 ={(John,ICE)} R 3 ={(John,ICE), (Alice, Math)} So, all R n relation sets are subsets of E 1 x E 2

He/She can explain the component of the data modeling Attributes and Domains (set of valid values)

He/She can explain the component of the data modeling Derived Attributes

He/She can explain the component of the data modeling Multi-valued Attributes

He/She can explain the component of the data modeling Composite Attributes More than one attributes can be grouped as one attribute

He/She can explain the component of the data modeling Entity Roles

He/She can explain the component of the data modeling Relation of Entities

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