《现代数据库管理(英文版)》课件—01
合集下载
现代数据库时态数据库PPT课件
（2）有效时间 有效时间（Valid Time）是指一个对象（事件）在现实世界中发生并保持的那段时间，或者该对象在现实世
界中为真的时间。既可以反映过去和现在的时间，还可以反映将来的时间。有效时间的含义依赖于具体应用， 取值是否有效视具体应用场合而定，对应于实际应用的需要或现实世界变化的历史，比如身份证，教师的职称 等。和用户定义的时间不同，当查询语句被检测到有时态语义的时候，有效时间是由数据库系统解释的。而且 有效时间可以被更新，有效时间的提供和更新也是由用户来完成的。
姓名 李小山
张又宝
出生年 月
196009
职称 讲师
196411
副教授 教授
工资
有效时间
1000 1300
1700 2100
(199809，199903) (199904，now)
(199803，200003) (200004，now）
姓名 李小山
张又宝
出生年月 196009
职称
讲师 副教授
196411
第6页/共53页
• 3、目前时态数据库研究取得了相当的进展，但是大多 研究局限在数据库的时态属性，而忽视了其他信息的时 态属性。时态数据技术目前还停留在“数据”处理上， 关于时态逻辑和推理方面的研究，主要优点是符号演算 和推理能力强，但是信息处理能力弱，与时态数据库和 时态信息处理研究相脱离。关于时态知识与逻辑方面主 要包括时间区间逻辑运算的扩充等，没有涉及时态知识 数据库模型。
有效时间维 Now
Now
事务时间维
第14页/共53页
6.6.2 回滚数据库
•
回滚数据库(Rollback Database)支持事务时间，它按事务时间进行编址，
保存了过去每次事务提交，状态演变之前的状态，是数据库事务变化的时间轴。
界中为真的时间。既可以反映过去和现在的时间，还可以反映将来的时间。有效时间的含义依赖于具体应用， 取值是否有效视具体应用场合而定，对应于实际应用的需要或现实世界变化的历史，比如身份证，教师的职称 等。和用户定义的时间不同，当查询语句被检测到有时态语义的时候，有效时间是由数据库系统解释的。而且 有效时间可以被更新，有效时间的提供和更新也是由用户来完成的。
姓名 李小山
张又宝
出生年 月
196009
职称 讲师
196411
副教授 教授
工资
有效时间
1000 1300
1700 2100
(199809，199903) (199904，now)
(199803，200003) (200004，now）
姓名 李小山
张又宝
出生年月 196009
职称
讲师 副教授
196411
第6页/共53页
• 3、目前时态数据库研究取得了相当的进展，但是大多 研究局限在数据库的时态属性，而忽视了其他信息的时 态属性。时态数据技术目前还停留在“数据”处理上， 关于时态逻辑和推理方面的研究，主要优点是符号演算 和推理能力强，但是信息处理能力弱，与时态数据库和 时态信息处理研究相脱离。关于时态知识与逻辑方面主 要包括时间区间逻辑运算的扩充等，没有涉及时态知识 数据库模型。
有效时间维 Now
Now
事务时间维
第14页/共53页
6.6.2 回滚数据库
•
回滚数据库(Rollback Database)支持事务时间，它按事务时间进行编址，
保存了过去每次事务提交，状态演变之前的状态，是数据库事务变化的时间轴。
《现代数据库管理(英文版)》课件—14
Chapter 13 (Online): Object-Oriented Data
Modeling
Modern Database Management 10th Edition
1
Objectives
Define terms Describe phases of object-oriented development life
Class Object Association Inheritance of
attributes
Inheritance of behavior
EER
Entity type Entity instance Relationship Inheritance of
attributes
No representation of behavior
3
Figure 13-1 Phases of object-oriented systems development cycle
Progressive and iterative development process
4
OO vs. EER Data Modeling
Object Oriented
Behavior is expressed through operations that can be performed on it
Identity: every object has a unique identity, even if all of its attribute values are the same
composition Specify types of business rules in a class diagram
Modeling
Modern Database Management 10th Edition
1
Objectives
Define terms Describe phases of object-oriented development life
Class Object Association Inheritance of
attributes
Inheritance of behavior
EER
Entity type Entity instance Relationship Inheritance of
attributes
No representation of behavior
3
Figure 13-1 Phases of object-oriented systems development cycle
Progressive and iterative development process
4
OO vs. EER Data Modeling
Object Oriented
Behavior is expressed through operations that can be performed on it
Identity: every object has a unique identity, even if all of its attribute values are the same
composition Specify types of business rules in a class diagram
《现代数据库管理(英文版)》课件—11
2
Traditional Administration Definitions
Data Administration: A high-level function
that is responsible for the overall management of data resources in an organization, including maintaining corporate-wide definitions and standards
Integrity Controls
Protect data from unauthorized use Domains–set allowable values Assertions–enforce database conditions Triggers – prevent inappropriate actions, invoke
10
Figure 11-3 Establishing Internet Security
11
Web Security
Static HTML files are easy to secure
Standard database access controls Place Web files in protected directories on server
Database Administration: A technical
function that is responsible for physical database design and for dealing with technical issues such as security enforcement, database performance, and backup and recovery
Traditional Administration Definitions
Data Administration: A high-level function
that is responsible for the overall management of data resources in an organization, including maintaining corporate-wide definitions and standards
Integrity Controls
Protect data from unauthorized use Domains–set allowable values Assertions–enforce database conditions Triggers – prevent inappropriate actions, invoke
10
Figure 11-3 Establishing Internet Security
11
Web Security
Static HTML files are easy to secure
Standard database access controls Place Web files in protected directories on server
Database Administration: A technical
function that is responsible for physical database design and for dealing with technical issues such as security enforcement, database performance, and backup and recovery
数据库系统原理英文PPT课件
file system: file’s logical structures and access methods
I/O system : drivers
memory controllers (i.e. disk controller),
on the basis of secondary storage’s physical structures, such as storage structures, access method
February 2011
7
第7页/共70页
§1.2 Purpose of Database Systems (cont.)
• Data management on the basis of file systems
• Example
— customer_record=<c_name, c_id, street, city> in Customer_File
February 2011
1
第1页/共70页
§1.0 DB, DBMS, DBS
• Definitions in the textbook • Database (DB) — a collection of interrelated data, stored in systems as files • Database management system (DBMS) — DB, or a collection of interrelated data — set of programs to access the data in DB
• Databases and DBS touch all aspects of our lives • Banking: all transactions • Airlines: reservations, schedules • Universities: registration, grades • Sales: customers, products, purchases • Manufacturing: production, inventory, orders, supply chain • Human resources: employee records, salaries, tax deductions
I/O system : drivers
memory controllers (i.e. disk controller),
on the basis of secondary storage’s physical structures, such as storage structures, access method
February 2011
7
第7页/共70页
§1.2 Purpose of Database Systems (cont.)
• Data management on the basis of file systems
• Example
— customer_record=<c_name, c_id, street, city> in Customer_File
February 2011
1
第1页/共70页
§1.0 DB, DBMS, DBS
• Definitions in the textbook • Database (DB) — a collection of interrelated data, stored in systems as files • Database management system (DBMS) — DB, or a collection of interrelated data — set of programs to access the data in DB
• Databases and DBS touch all aspects of our lives • Banking: all transactions • Airlines: reservations, schedules • Universities: registration, grades • Sales: customers, products, purchases • Manufacturing: production, inventory, orders, supply chain • Human resources: employee records, salaries, tax deductions
数据库英文PPT课件
8
第8页/共45页
Example: Deletion
• Delete from relation StarsIn the fact that Sydney GreenStreet was a star in The Maltese Falcon:
DELETE FROM StarsIn WHERE movieTitle = ‘The Maltese Falcon’ AND
value, the value that is placed in a component if no other value is known.
23
第23页/共45页
Example
• We might wish to use the character ‘?’ as the default for an unknown gender, and we might also wish to use the earliest possible date, DATE ‘0000-00-00’ for an unknown birthdate.
22
第22页/共45页
Default values
• When we create or modify tuples, we sometimes don’t have values for all components.
• To address this problem, SQL provides the NULL value. • However, there are times when we would prefer to use default
1. Insert a tuple or tuples.
2. Delete a tuple or tuples.
第8页/共45页
Example: Deletion
• Delete from relation StarsIn the fact that Sydney GreenStreet was a star in The Maltese Falcon:
DELETE FROM StarsIn WHERE movieTitle = ‘The Maltese Falcon’ AND
value, the value that is placed in a component if no other value is known.
23
第23页/共45页
Example
• We might wish to use the character ‘?’ as the default for an unknown gender, and we might also wish to use the earliest possible date, DATE ‘0000-00-00’ for an unknown birthdate.
22
第22页/共45页
Default values
• When we create or modify tuples, we sometimes don’t have values for all components.
• To address this problem, SQL provides the NULL value. • However, there are times when we would prefer to use default
1. Insert a tuple or tuples.
2. Delete a tuple or tuples.
《mysqll教程》课件
论坛系统
如phpBB使用MySQL作为其数据库存储解决方案。
博客平台
如WooCommerce使用MySQL作为其商品和订单数据的存储。
02 MySQL基础
安装和配置MySQL
总结词
安装步骤、配置选项
详细描述
提供详细的MySQL安装步骤，包括下载安装包、运行安装程序、选择安装组件等。同时介绍常见的配置选项， 如端口号、字符集、时区等。
1995年发布第一个版本，2000年 MySQL AB公司被Sun Microsystems公司收购，2008年被 甲骨文公司（Oracle Corporation） 收购。
03
里程碑
随着版本的更新，MySQL不断优化和 改进，成为世界上最流行的关系型数 据库管理系统之一。
MySQL的特点和优势
特点
数据仓库
建立数据仓库，对大数据进行多维分 析和报表生成。
数据可视化
使用工具如Tableau或Power BI，将 数据分析结果进行可视化展示。
06 MySQL的未来发展
MySQL的新特性和发展方向
分布式数据库
MySQL将进一步支持分布式数据 库功能，实现更高效的数据存储 和处理。
人工智能与机器学
系统架构
02 设计新闻发布系统的整体架构
，包括前后端分离、数据库设 计等。
数据库优化
03 对数据库表进行优化，如索引
、分区等，以提高查询效率。
缓存技术
04 使用缓存技术如Redis，减少
对数据库的访问次数。
异步处理
05 使用消息队列如Kafka，实现
异步处理，提高系统响应速度 。
安全措施
06 对用户输入进行校验和过滤，
高效数据库的需求。
如phpBB使用MySQL作为其数据库存储解决方案。
博客平台
如WooCommerce使用MySQL作为其商品和订单数据的存储。
02 MySQL基础
安装和配置MySQL
总结词
安装步骤、配置选项
详细描述
提供详细的MySQL安装步骤，包括下载安装包、运行安装程序、选择安装组件等。同时介绍常见的配置选项， 如端口号、字符集、时区等。
1995年发布第一个版本，2000年 MySQL AB公司被Sun Microsystems公司收购，2008年被 甲骨文公司（Oracle Corporation） 收购。
03
里程碑
随着版本的更新，MySQL不断优化和 改进，成为世界上最流行的关系型数 据库管理系统之一。
MySQL的特点和优势
特点
数据仓库
建立数据仓库，对大数据进行多维分 析和报表生成。
数据可视化
使用工具如Tableau或Power BI，将 数据分析结果进行可视化展示。
06 MySQL的未来发展
MySQL的新特性和发展方向
分布式数据库
MySQL将进一步支持分布式数据 库功能，实现更高效的数据存储 和处理。
人工智能与机器学
系统架构
02 设计新闻发布系统的整体架构
，包括前后端分离、数据库设 计等。
数据库优化
03 对数据库表进行优化，如索引
、分区等，以提高查询效率。
缓存技术
04 使用缓存技术如Redis，减少
对数据库的访问次数。
异步处理
05 使用消息队列如Kafka，实现
异步处理，提高系统响应速度 。
安全措施
06 对用户输入进行校验和过滤，
高效数据库的需求。
《现代数据库管理(英文版)》课件—02
This attribute is both
multivalued and
composite
17
More on Relationships
Relationship Types vs. Relationship Instances
The relationship type is modeled as lines between entity types…the instance is between specific entity instances
Derived from date employed and current date
ቤተ መጻሕፍቲ ባይዱ15
Figure 2-9 Simple and composite identifier attributes
The identifier is boldfaced and underlined
16
Figure 2-19 Simple example of time-stamping
An object that will be composed of multiple attributes
An object that we are trying to model
SHOULD NOT BE:
A user of the database system An output of the database system (e.g., a
Classifications of attributes:
Required versus Optional Attributes Simple versus Composite Attribute Single-Valued versus Multivalued Attribute Stored versus Derived Attributes Identifier Attributes
multivalued and
composite
17
More on Relationships
Relationship Types vs. Relationship Instances
The relationship type is modeled as lines between entity types…the instance is between specific entity instances
Derived from date employed and current date
ቤተ መጻሕፍቲ ባይዱ15
Figure 2-9 Simple and composite identifier attributes
The identifier is boldfaced and underlined
16
Figure 2-19 Simple example of time-stamping
An object that will be composed of multiple attributes
An object that we are trying to model
SHOULD NOT BE:
A user of the database system An output of the database system (e.g., a
Classifications of attributes:
Required versus Optional Attributes Simple versus Composite Attribute Single-Valued versus Multivalued Attribute Stored versus Derived Attributes Identifier Attributes
数据库英文课件1PPT教学课件
Chapter 7 System Aspects of SQL
SQL in a Programming Environment Transactions Authorization
2020/12/10
1
7.1 SQL in a Programming Environment
Host Languages:
2020/12/10
7
7.1.2 Dynamic SQL
Most applications use specific queries and modification statements in their interaction with the database.
Thus, we can compile the EXEC SQL … statements into specific procedure calls and produce an ordinary host-language program that uses a library.
Any conventional language can be a host language, that is, a language in which SQL calls are embedded.
The use of a host/SQL combination allows us to do anything computable, yet still get the very-high-level SQL interface to the database.
EXEC SQL INSERT INTO Studio(name,address)
VALUES(:studioName, :studioAddr);
SQL in a Programming Environment Transactions Authorization
2020/12/10
1
7.1 SQL in a Programming Environment
Host Languages:
2020/12/10
7
7.1.2 Dynamic SQL
Most applications use specific queries and modification statements in their interaction with the database.
Thus, we can compile the EXEC SQL … statements into specific procedure calls and produce an ordinary host-language program that uses a library.
Any conventional language can be a host language, that is, a language in which SQL calls are embedded.
The use of a host/SQL combination allows us to do anything computable, yet still get the very-high-level SQL interface to the database.
EXEC SQL INSERT INTO Studio(name,address)
VALUES(:studioName, :studioAddr);
数据库系统原理(英文)1PPT课件
Database System Concepts- Chapter1 Introduction - 3
§1.0 DB, DBMS, DBS(cont.)
DBMS provides an environment that is both convenient and efficient for store and retrieve information definition of structures for storage of information data manipulation mechanisms data safety mechanisms
Definitions in some other textbooks Fig. 1.0.1 Database(DB) — a collection of interrelated data , stored in systems as files
February 2007
Database System Concepts- Chapter1 Introduction - 4
February 2007
Database System Concepts- Chapter1 Introduction - 7
§1.2 Purpose of Database Systems
In the early days, database applications were built on top of file systems
Chapter 1 Introduction
Main Parts in This Chapter
Database System Applications
Purpose of Database Systems
数据库管理系统[]PPT课件
![数据库管理系统[]PPT课件](https://img.taocdn.com/s3/m/d717d55fbfd5b9f3f90f76c66137ee06eff94e3d.png)
14.10.2024
精品课件
21
3 MySQL
MySQL是最流行的开发源码SQL数 据库管理系统，他是有MySQL AB公 司开发、发布并支持。
开放源码：意味着任何人都能使用和改 变软件；任何人都能从INTERNER下载 软件，无需支付任何费用。
14.10.2024
精品课件
22
4 Microsoft SQL Server
目前， Visual FoxPro已经成为高等学 校、各类培训非信息系统专业学生数据 库技术介绍的首选软件。
14.10.2024
精品课件
24
6 Microsoft Access
Microsoft Access作为Microsoft office 组件之一，是在windows环 境下非常流行的桌面型数据库管 理系统。
14.10.2024
精品课件
15
4 结构清晰
数据库管理系统是一个复杂的系统软件， 涉及面广，包括向上与用户接口，向下与 操作系统、软件硬件资源的接口。
因此，应该使数据库管理系统内部结构清 晰，层次分明，便于自身设计、开发和维 护，以及支持外层开发环境的构造。
14.10.2024
精品课件
16
5 开放性
系 教研室
学生
老师
14.10.2024
精品课件
6
网状模型
学生
课程
选课
14.10.2024
精品课件
7
关系模型
第一个基于关系模型的商业产品时 1980年左右Oracle公司和IBM公司出 品的Oracle和DB2。
第一个成功的微机数据库产品是运行 于CP/M,PC-DOS,MS-DOS操作系统 上的dBASE。
英文数据库课件
1.2
Chapter 1 Introduction
1.1 Evolution of Database Management Systems 1.2 Levels of Abstraction 1.3 Data Models 1.4 Components of Database Management Systems
Degree
Credit Academic Division
Adress
Property Division
1.11
2) Database Systems
Advantages of using a DBMS to manage data:
Data independence
Provide an abstract view of data to hide the details of
1.4.1 Data Definition Language 1.4.2 Data Manipulation Language
1.4.3 Database Users
1.4.4 Database Administrator
1.4.5 Transaction Management
1.4.6 Storage Management
File Systems
Database Systems
1.5
1）File Systems
program 1
data 1
program 2
file systems
data 2
program n
data n
1.6
Example
Treasury
Sno Sname Department Allowance
《现代数据库管理(英文版)》课件—15
connects to a class
Multiplicity:
How many objects participate in an association. Lower-bound…Upper-bound (cardinality)
9
Figure 13-3 Examples of association relationships of different degrees
Behavior is expressed through operations that can be performed on it
Identity: every object has a unique identity, even if all of its attribute values are identical to another object’s
5
Figure 13-2 UML class and object diagram a) Class diagram showing two classes
Class diagram shows the static structure of an objectoriented model: object classes, internal structure, relationships
Tangible: person, place or thing Concept or Event: department, performance,
marriage, registration Artifact of the Design Process: user interface,
controller, scheduler
Multiplicity:
How many objects participate in an association. Lower-bound…Upper-bound (cardinality)
9
Figure 13-3 Examples of association relationships of different degrees
Behavior is expressed through operations that can be performed on it
Identity: every object has a unique identity, even if all of its attribute values are identical to another object’s
5
Figure 13-2 UML class and object diagram a) Class diagram showing two classes
Class diagram shows the static structure of an objectoriented model: object classes, internal structure, relationships
Tangible: person, place or thing Concept or Event: department, performance,
marriage, registration Artifact of the Design Process: user interface,
controller, scheduler
《现代数据库管理(英文版)》课件—03
Generalization: The process of
defining a more general entity type from a set of more specialized entity types. BOTTOM-UP
Specialization: The process of defining
Note: no subtype for motorcycle, since it has no unique attributes
11
Figure 3-5 Example of specialization a) Entity type PART
Only applies to manufactured parts Applies only to purchased parts
21
Figure 3-9 Subtype discriminator (overlap rule)
22
Figure 3-10 Example of supertype/subtype hierarchy
23
Entity Clusters
EER diagrams are difficult to read when there are too many entities and relationships
Total Specialization Rule: Yes (double line) Partial Specialization Rule: No (single line)
14
Figure 3-6 Examples of completeness constraints a) Total specialization rule
defining a more general entity type from a set of more specialized entity types. BOTTOM-UP
Specialization: The process of defining
Note: no subtype for motorcycle, since it has no unique attributes
11
Figure 3-5 Example of specialization a) Entity type PART
Only applies to manufactured parts Applies only to purchased parts
21
Figure 3-9 Subtype discriminator (overlap rule)
22
Figure 3-10 Example of supertype/subtype hierarchy
23
Entity Clusters
EER diagrams are difficult to read when there are too many entities and relationships
Total Specialization Rule: Yes (double line) Partial Specialization Rule: No (single line)
14
Figure 3-6 Examples of completeness constraints a) Total specialization rule
数据库系统概念原书第5版(英文)第一章ppt
Database designers: design database ―schema‖ to model aspects of the real world Database application developers: build applications that interface with databases Database administrators (a.k.a. DBA‘s): load, back up, and restore data, fine-tune databases for performance DBMS implementors: develop the DBMS or specialized data management software, implement new techniques for query processing and optimization inside DBMS
August 15, 2013
Dept. of Comp. Sci. & Tech., Tongji Uni.
4
What is a database?
A very large, integrated collection of data
The amount of data is very large The data is structured and interrelated The data is integrated Entities (e.g., students, courses) Relationships (e.g., Li is taking Database and Knowledge) More recently, also includes active components (e.g. “business logic”)
August 15, 2013
Dept. of Comp. Sci. & Tech., Tongji Uni.
4
What is a database?
A very large, integrated collection of data
The amount of data is very large The data is structured and interrelated The data is integrated Entities (e.g., students, courses) Relationships (e.g., Li is taking Database and Knowledge) More recently, also includes active components (e.g. “business logic”)
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form
Requires a Database Management System (DBMS)
11
Database Management System
A software system that is used to create, maintain, and provide controlled access to user databases
Each application program must have its own processing routines for reading, inserting, updating, and deleting data
Lack of coordination and central control Non-standard file formats
Compromises in data integrity
10
SOLUTION: The DATABASE Approach
Central repository of shared data Data is managed by a controlling
agent Stored in a standardized, convenient
Order Filing System
8
Duplicate Data
9
Problems with Data Redundancy
Waste of space to have duplicate data Causes more maintenance headaches The biggest problem:
Data changes in one file could cause inconsistencies
2
Definitions
Database: organized collection of logically related data
Data: stored representations of meaningful objects and events
Structured: numbers, text, dates Unstructured: images, video, documents
Limited Data Sharing
No centralized control of data
Lengthy Development Times
Programmers must design their own file formats
Excessive Program Maintenance
Figure 1-1a Data in context
Context helps users understand data
4
Figure 1-1b Summarized data
Graphical displays turn data into useful information that managers can use for
Information: data processed to increase knowledge in the person using the data
Metadata: data that describes the properties and context of user data
3
decision making and interpretation
5
Descriptions of the properties or characteristics of the data, including data types, field sizes, allowable values, and data context
Chapter 1: The Database Environment and Development Process
Modern Database Management 10th Edition
1
Objectives
Define terms Name limitations of conventional file processing Explain advantages of databases Identify costs and risks of databases List components of database environment Identify categories of database applications Describe database system development life cycle Explain prototyping and agile development approaches Explain roles of individuals Explain the three-schema architecture for databases
6
Disadvantages of File Processing
Program-Data Dependence
All programs maintain metadata for each file they use
Duplication of Data
Different systems/programs have separate copies of the same data
80% of information systems budget
7
Problems with Data Dependency
Each appΒιβλιοθήκη ication programmer must maintain his/her own data
Each application program needs to include code for the metadata of each file
Requires a Database Management System (DBMS)
11
Database Management System
A software system that is used to create, maintain, and provide controlled access to user databases
Each application program must have its own processing routines for reading, inserting, updating, and deleting data
Lack of coordination and central control Non-standard file formats
Compromises in data integrity
10
SOLUTION: The DATABASE Approach
Central repository of shared data Data is managed by a controlling
agent Stored in a standardized, convenient
Order Filing System
8
Duplicate Data
9
Problems with Data Redundancy
Waste of space to have duplicate data Causes more maintenance headaches The biggest problem:
Data changes in one file could cause inconsistencies
2
Definitions
Database: organized collection of logically related data
Data: stored representations of meaningful objects and events
Structured: numbers, text, dates Unstructured: images, video, documents
Limited Data Sharing
No centralized control of data
Lengthy Development Times
Programmers must design their own file formats
Excessive Program Maintenance
Figure 1-1a Data in context
Context helps users understand data
4
Figure 1-1b Summarized data
Graphical displays turn data into useful information that managers can use for
Information: data processed to increase knowledge in the person using the data
Metadata: data that describes the properties and context of user data
3
decision making and interpretation
5
Descriptions of the properties or characteristics of the data, including data types, field sizes, allowable values, and data context
Chapter 1: The Database Environment and Development Process
Modern Database Management 10th Edition
1
Objectives
Define terms Name limitations of conventional file processing Explain advantages of databases Identify costs and risks of databases List components of database environment Identify categories of database applications Describe database system development life cycle Explain prototyping and agile development approaches Explain roles of individuals Explain the three-schema architecture for databases
6
Disadvantages of File Processing
Program-Data Dependence
All programs maintain metadata for each file they use
Duplication of Data
Different systems/programs have separate copies of the same data
80% of information systems budget
7
Problems with Data Dependency
Each appΒιβλιοθήκη ication programmer must maintain his/her own data
Each application program needs to include code for the metadata of each file