Types of DBMS Models. Data Model redefined 19/09/2013. Downloaded from Examples of DBMS. Types of DBMS Model. Lecture 2: LSG 2102

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1 Types of DBMS Models Lecture 2: LSG 2102 Types of DBMS Model 1. Hierarchical 2. Network 3. Relational - RDBMS 4. Object-oriented - OODBMS 5. Object-relational - ORDBMS Examples of DBMS Microsoft Access Oracle IBM DB2 PostgreSQL IBM Informix Microsoft SQL Server Data Model redefined A data model is a formal language that allows us to define the type of data and data processing that occurs in a database application. It supports o Definition of data structures for storage o Definition of rules that the stored data have to obey o Definition of operations on the data, such that changes to represented things in the real world can be accounted for Data Model redefined A data model is a collection of concepts for describing data and their operations A database schema is a description of a particular collection of data, using the given data model. the organization of data to create a blueprint of how a database will be constructed (divided into database tables) Schema for health insurance company 1. Hierarchical Database Management A hierarchical database model - data is organized into a tree - like structure. The structure allows representing information using parent/child relationships Each parent can have many children, but each child has only one parent (also known as a 1-tomany relationship). A DBMS is said to be hierarchical if the relationships among data in the database are established in such a way that one data item is present as the subordinate of another one. 1

Hierarchical Database Management Subordinate means that items have 'parentchild' relationships among them. Direct relationships exist between any two records that are stored consecutively.

Conceptual diagram (schema) showing a hierarchical structure Example of a Hierarchical Data Model 2.

2 Hierarchical Database Management Subordinate means that items have 'parentchild' relationships among them. Direct relationships exist between any two records that are stored consecutively. The data structure "tree" is followed by the DBMS to structure the database. No backward movement is possible/allowed in the hierarchical database. Conceptual diagram (schema) showing a hierarchical structure Example of a Hierarchical Data Model 2. Relational Database Management RDBMS Most popular type of DBMS (over 95%) RDBMS store data in tables (relations) that are two dimensional (list, array) (rows, columns). rows (tuples, records or ) and columns (object states, properties, fields or attributes). Data items at an intersection of a row and a column are called a cell and consist of attribute values. Data stored is simple data such as integers, real numbers, text, or string values. Multiple values may not be stored in one cell. Relational database tables are "normalized" so data is not repeated more often than necessary. Relational Data Models (RM) Provides: A tabular representation of data Simple intuition currently the most widely used Powerful and natural query language Data stored in records or rows called tuples A group of rows (a table ) is a relation all the tuples are related to each other The number of rows is called the cardinality Tuples can not be complete duplicates (normalization) Columns contain the attributes Number of columns is the degree The relational data model - terms Relation: a table with rows and columns defined by relation instance (cardinality and degree) Every relation has a schema which describes the attributes (columns or fields) Each column has a header called attribute name. A row or tuple represents a fact in the real world that we want to record As the real world changes over time, we will want to o Add facts (insert tuples) o Remove facts (delete tuples), or o Change facts edit (update tuples) 2

What is a relational database? Relational database: A collection of relations Each relation stores facts of a certain type A relation has 2 parts: 1.

3 What is a relational database? Relational database: A collection of relations Each relation stores facts of a certain type A relation has 2 parts: 1. the relation schema, formed by the relation name, and a list of attributes and their domains 2. the relation instance, which is a table of rows and columns, holding the data. A row = a tuple ; represents a fact. Rows are distinct (normalisation) Key terms illustrated. Example of a Relational Database Example of a Relational Database Student Example of a relation Sid Name Login age Gpa Jones Jones@ab Smith Smith@pp Jenkins Jenkins@math Relation instance, has cardinality 3, degree 5 Five attributes; their names suggest the meaning Relation schema: Student (Sid: Char(5), name: text, login: varchar (15), age: integer, gpa: real) Relations terms defined Domain = (in)finite set of atomic values. The RM supports various domains (real, integer, boolean, char(n), varchar (N), data/time, ) the set of values of the independent variable for which a function is defined Attribute = name that suggests the meaning that a domain plays in the relation; each attribute A has an associated domain dom (A) Relation schema = relation name plus bracketed list of attributes with their domains. R (A 1 : dom (A 1 ),, A n : dom (A n )) Tuple of Relation R = ordered list of values for each A i <v 1,, v n >, such that for all i: v i dom (A i ) 3

4 Relations terms defined Relation Instance r(r) of relation R = (the current) set of tuples of R Also known as a relation state Consequences: A relation instance cannot have duplicate elements: it is a set! Likewise, the tuples are not considered to be ordered: it is a set. Database Schema = collection of relation schemas (no duplicate relation names) DBS = {R 1,, R m } if there are m relations Database instance d for a database schema DBS = collection of relation instances, one for each relation in DBS: d(dbs)= {r 1 (R 1 ),, r m (R m )} Also known as database state 3. Object Oriented Database management OODBMS Supports the modeling and creation of data as Able to handle many new data types (complex), including graphics, photographs, audio, and video hence the term object-oriented Derived and leveraged by object oriented programming languages Each object consists of 2 elements 1. A piece of data (e.g. video, text, sound) 2. The instructions or software programs called methods for what to do with the data OODM OO Model sees the world as inter related Object is dynamic and has its own lifespan Deals with dynamic nature of real world Objects with similar behaviour are organised into types, a semantic concept Object class = data structure + Methods, an implementation construct Object Oriented Database management Includes some kind of support for classes of and the inheritance of class properties and methods for subclasses and their. There is currently no widely agreed-upon standard for what constitutes an OODBMS OODBMS products are considered to be still in their infancy More costly to develop OODBMS The object model captures the static structure of a system by showing the in the system, relationships between the, and the attributes and operations that characterize each Communication between is realized using a message passing system A message is a request sent from one object to another in order to execute one of the methods. Advantages of OODMS Real-world phenomena can be modelled closer to reality with more complex compared to defined structures Object models could be structured around conceptual rather than geometrical properties. Geometry can be modelled like other information Explicit storage of spatial information which is required in GIS can be realized without redundancy. For example geographical can be defined using methods it is possible to generate user-defined types 4

Role of DBMS 19/09/2013 Encapsulation Encapsulation means notion that all of the object's data is contained and hidden in the object and access to it restricted to members of that class bundling of

5 Role of DBMS 19/09/2013 Encapsulation Encapsulation means notion that all of the object's data is contained and hidden in the object and access to it restricted to members of that class bundling of data with the methods (or other functions) operating on that data Encapsulation concept permits possibilities such as; Integration of different abstraction levels for one Designing spatial, non-spatial and methods in one Expressing business rules as methods belonging to the Object Relational Database Management Object-oriented database concepts can be superimposed on relational databases hence ORDBMS This system simply puts an object oriented front end on a relational database (RDBMS). When applications interface to this type of database, it will normally interface as though the data is stored as. However the system will convert the object information into data tables with rows and columns and handle the data the same as a relational database. Likewise, when the data is retrieved, it must be reassembled from simple data into complex. This enables the usage of ADT s (Abstract Data Types) very customised. How is a SDBMS different from a GIS? GIS is a software to visualize and analyze spatial data using spatial analysis functions such as Search Thematic search, search by region, (re-)classification Location analysis Buffer, corridor, overlay Terrain analysis Slope/aspect, catchment, drainage network Flow analysis Connectivity, shortest path Distribution Change detection, proximity, nearest neighbor Spatial analysis/statistics Pattern, centrality, autocorrelation, indices of similarity, topology: hole description Measurements Distance, perimeter, shape, adjacency, direction GIS uses SDBMS to store, search, query, share large spatial data sets Difference between GIS and DBMS Type of Data Amount of Data to analyse and to maintain Type of analysis function Number of concurrent access Transaction control mechanism included Access mechanism to protect data against non-authorised access Embedded mechanism to protect against system failure Occurrences (variety and type) of distributed system architectures Embedded Standards (what type of standards?) Typical value of system within an enterprise (enterprise critical? Nice to have a system?) Type of user interfaces GIS DBMS Reflection Compare and contrast the different database models. 5

The Relational Model. Why Study the Relational Model? Relational Database: Definitions

The Relational Model. Why Study the Relational Model? Relational Database: Definitions The Relational Model Database Management Systems, R. Ramakrishnan and J. Gehrke 1 Why Study the Relational Model? Most widely used model. Vendors: IBM, Microsoft, Oracle, Sybase, etc. Legacy systems in