{"id":34,"date":"2013-12-12T00:09:50","date_gmt":"2013-12-12T00:09:50","guid":{"rendered":"http:\/\/opentextbc.ca\/dbdesign01\/?post_type=chapter&#038;p=34"},"modified":"2019-06-11T15:55:18","modified_gmt":"2019-06-11T15:55:18","slug":"chapter-4-types-of-database-models","status":"publish","type":"chapter","link":"https:\/\/opentextbc.ca\/dbdesign01\/chapter\/chapter-4-types-of-database-models\/","title":{"raw":"Chapter 4 Types of Data Models","rendered":"Chapter 4 Types of Data Models"},"content":{"raw":"<h2>High-level Conceptual <span style=\"color: #000000;\">Data<\/span> Models<\/h2>\r\nHigh-level conceptual data models provide concepts for presenting data in ways that are close to the way people perceive data. A typical example is the entity relationship model, which uses main concepts like entities, attributes and relationships. An entity represents a real-world object such as an employee or a project. The\u00a0entity has attributes that\u00a0represent properties such as an employee\u2019s name, address and birthdate. A relationship represents an association among entities; for example, an employee works on many projects. A\u00a0relationship exists between the employee and each project.\r\n<h2>Record-based Logical<span style=\"color: #000000;\"> Data<\/span> Models<\/h2>\r\nRecord-based logical data models provide concepts users\u00a0can\u00a0understand\u00a0but are not too far from the way data is stored in the computer. Three well-known <span style=\"color: #000000;\">data<\/span> models of this type are relational <span style=\"color: #000000;\">data<\/span> models, network data models and hierarchical data models.\r\n<ul>\r\n \t<li><span style=\"color: #333333;\">The<em> relational model<\/em><\/span> represents data as<span><em> relations<\/em>, or<\/span>\u00a0tables. For example, in the membership system at Science World, each membership has many members (see Figure 2.2 in Chapter 2). The membership identifier, expiry date and address information are fields in the membership. The members are individuals such as Mickey, Minnie, Mighty, Door, Tom, King, Man and Moose. Each record is said to be an <em>instance<\/em> of the membership table.<\/li>\r\n<\/ul>\r\n<ul>\r\n \t<li><span style=\"color: #333333;\">The <em>network model<\/em> represents data as record types. This model also represents a limited type of one to many relationship called a <em>set type<\/em>, as shown in Figure 4.1.<\/span><\/li>\r\n<\/ul>\r\n[caption id=\"attachment_53\" align=\"aligncenter\" width=\"300\"]<a href=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Unary-Relationships-300x168.jpg\"><img class=\"wp-image-53\" alt=\"Diagram displaying 8 rectangular boxes and arrows crossing between them. The boxes contain labels such as EMPS and SUPPLIERS. Labels are also outside of these rectangles.\" src=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Network-data-model-300x244.jpg\" height=\"244\" width=\"300\" \/><\/a> Figure 4.1. Network model diagram.[\/caption]\r\n<ul>\r\n \t<li><span style=\"color: #333333;\">The<em> hierarchical model<\/em> represents data <span>as<\/span> a hierarchical tree structure. Each <span>branch of the<\/span> hierarchy represents a number of related records. Figure 4.2 shows this schema in hierarchical model notation.<\/span><\/li>\r\n<\/ul>\r\n[caption id=\"attachment_48\" align=\"aligncenter\" width=\"300\"]<a href=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Multivalued-Attribute-300x131.jpg\"><img class=\"wp-image-48\" alt=\"Diagram with labels in capitals connected by lines.\" src=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Hierarchical-Data-Model-300x116.jpg\" height=\"116\" width=\"300\" \/><\/a> Figure 4.2. Hierarchical model diagram.[\/caption]\r\n<div class=\"textbox textbox--key-takeaways\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Key Terms<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n<strong>hierarchical model<\/strong>: <span style=\"color: #333333;\">represents data as a hierarchical tree structure<\/span>\r\n\r\n<strong>instance<\/strong>: <span>a record within a table<\/span>\r\n\r\n<strong>network model<\/strong>: <span style=\"color: #333333;\">represents data as record types<\/span>\r\n\r\n<strong>relation<\/strong>: another term for table\r\n\r\n<strong>relational model<\/strong>: represents data as relations or tables\r\n\r\n<strong>set type<\/strong>: <span>a limited type of one to many relationship\u00a0<\/span>\r\n\r\n<\/div><\/div>\r\n<div class=\"textbox textbox--exercises\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Exercises<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\n<ol>\r\n \t<li>What is a data model?<\/li>\r\n \t<li>What is a high-level conceptual data model?<\/li>\r\n \t<li>What is an entity? An attribute? A relationship?<\/li>\r\n \t<li>List and briefly describe the common record-based logical data models.<\/li>\r\n<\/ol><\/div>\r\n<\/div>\r\n<h2>Attribution<\/h2>\r\nThis chapter of\u00a0<em>Database Design<\/em>\u00a0is a derivative copy of\u00a0<a href=\"http:\/\/cnx.org\/contents\/b57b8760-6898-469d-a0f7-06e0537f6817@1\">Database System Concepts<\/a>\u00a0by\u00a0Nguyen Kim Anh\u00a0licensed under\u00a0<a href=\"http:\/\/creativecommons.org\/licenses\/by\/3.0\/\">Creative Commons Attribution License 3.0 license<\/a>\r\n\r\nThe following material was written by Adrienne Watt:\r\n<ol>\r\n \t<li>Key Terms<\/li>\r\n \t<li>Exercises<\/li>\r\n<\/ol>\r\n&nbsp;","rendered":"<h2>High-level Conceptual <span style=\"color: #000000;\">Data<\/span> Models<\/h2>\n<p>High-level conceptual data models provide concepts for presenting data in ways that are close to the way people perceive data. A typical example is the entity relationship model, which uses main concepts like entities, attributes and relationships. An entity represents a real-world object such as an employee or a project. The\u00a0entity has attributes that\u00a0represent properties such as an employee\u2019s name, address and birthdate. A relationship represents an association among entities; for example, an employee works on many projects. A\u00a0relationship exists between the employee and each project.<\/p>\n<h2>Record-based Logical<span style=\"color: #000000;\"> Data<\/span> Models<\/h2>\n<p>Record-based logical data models provide concepts users\u00a0can\u00a0understand\u00a0but are not too far from the way data is stored in the computer. Three well-known <span style=\"color: #000000;\">data<\/span> models of this type are relational <span style=\"color: #000000;\">data<\/span> models, network data models and hierarchical data models.<\/p>\n<ul>\n<li><span style=\"color: #333333;\">The<em> relational model<\/em><\/span> represents data as<span><em> relations<\/em>, or<\/span>\u00a0tables. For example, in the membership system at Science World, each membership has many members (see Figure 2.2 in Chapter 2). The membership identifier, expiry date and address information are fields in the membership. The members are individuals such as Mickey, Minnie, Mighty, Door, Tom, King, Man and Moose. Each record is said to be an <em>instance<\/em> of the membership table.<\/li>\n<\/ul>\n<ul>\n<li><span style=\"color: #333333;\">The <em>network model<\/em> represents data as record types. This model also represents a limited type of one to many relationship called a <em>set type<\/em>, as shown in Figure 4.1.<\/span><\/li>\n<\/ul>\n<figure id=\"attachment_53\" aria-describedby=\"caption-attachment-53\" style=\"width: 300px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Unary-Relationships-300x168.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-53\" alt=\"Diagram displaying 8 rectangular boxes and arrows crossing between them. The boxes contain labels such as EMPS and SUPPLIERS. Labels are also outside of these rectangles.\" src=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Network-data-model-300x244.jpg\" height=\"244\" width=\"300\" \/><\/a><figcaption id=\"caption-attachment-53\" class=\"wp-caption-text\">Figure 4.1. Network model diagram.<\/figcaption><\/figure>\n<ul>\n<li><span style=\"color: #333333;\">The<em> hierarchical model<\/em> represents data <span>as<\/span> a hierarchical tree structure. Each <span>branch of the<\/span> hierarchy represents a number of related records. Figure 4.2 shows this schema in hierarchical model notation.<\/span><\/li>\n<\/ul>\n<figure id=\"attachment_48\" aria-describedby=\"caption-attachment-48\" style=\"width: 300px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Multivalued-Attribute-300x131.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-48\" alt=\"Diagram with labels in capitals connected by lines.\" src=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Hierarchical-Data-Model-300x116.jpg\" height=\"116\" width=\"300\" \/><\/a><figcaption id=\"caption-attachment-48\" class=\"wp-caption-text\">Figure 4.2. Hierarchical model diagram.<\/figcaption><\/figure>\n<div class=\"textbox textbox--key-takeaways\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Key Terms<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<strong>hierarchical model<\/strong>: <span style=\"color: #333333;\">represents data as a hierarchical tree structure<\/span><\/p>\n<p><strong>instance<\/strong>: <span>a record within a table<\/span><\/p>\n<p><strong>network model<\/strong>: <span style=\"color: #333333;\">represents data as record types<\/span><\/p>\n<p><strong>relation<\/strong>: another term for table<\/p>\n<p><strong>relational model<\/strong>: represents data as relations or tables<\/p>\n<p><strong>set type<\/strong>: <span>a limited type of one to many relationship\u00a0<\/span><\/p>\n<\/div>\n<\/div>\n<div class=\"textbox textbox--exercises\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Exercises<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<ol>\n<li>What is a data model?<\/li>\n<li>What is a high-level conceptual data model?<\/li>\n<li>What is an entity? An attribute? A relationship?<\/li>\n<li>List and briefly describe the common record-based logical data models.<\/li>\n<\/ol>\n<\/div>\n<\/div>\n<h2>Attribution<\/h2>\n<p>This chapter of\u00a0<em>Database Design<\/em>\u00a0is a derivative copy of\u00a0<a href=\"http:\/\/cnx.org\/contents\/b57b8760-6898-469d-a0f7-06e0537f6817@1\">Database System Concepts<\/a>\u00a0by\u00a0Nguyen Kim Anh\u00a0licensed under\u00a0<a href=\"http:\/\/creativecommons.org\/licenses\/by\/3.0\/\">Creative Commons Attribution License 3.0 license<\/a><\/p>\n<p>The following material was written by Adrienne Watt:<\/p>\n<ol>\n<li>Key Terms<\/li>\n<li>Exercises<\/li>\n<\/ol>\n<p>&nbsp;<\/p>\n","protected":false},"author":1,"menu_order":4,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["adrienne-watt-nelson-eng"],"pb_section_license":""},"chapter-type":[],"contributor":[48],"license":[],"class_list":["post-34","chapter","type-chapter","status-publish","hentry","contributor-adrienne-watt-nelson-eng"],"part":3,"_links":{"self":[{"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/pressbooks\/v2\/chapters\/34","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/wp\/v2\/users\/1"}],"version-history":[{"count":29,"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/pressbooks\/v2\/chapters\/34\/revisions"}],"predecessor-version":[{"id":1141,"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/pressbooks\/v2\/chapters\/34\/revisions\/1141"}],"part":[{"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/pressbooks\/v2\/parts\/3"}],"metadata":[{"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/pressbooks\/v2\/chapters\/34\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/wp\/v2\/media?parent=34"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/pressbooks\/v2\/chapter-type?post=34"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/wp\/v2\/contributor?post=34"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/wp\/v2\/license?post=34"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}