Data Base Definition
A database is a structured collection of records or data that is stored in a computer system. The structure is achieved by organizing the data according to a database model. The model in most common use today is the relational model. Other models such as the hierarchical model and the network model use a more explicit representation of relationships.
Database Management System (DBMS)
A database management system (DBMS) is computer software that manages databases. DBMSes may use any of a variety of database models, such as the network model or relational model. In large systems, a DBMS allows users and other software to store and retrieve data in a structured way.
Bit
A bit is a binary digit, taking a value of either 0 or 1. Binary digits are a basic unit of information storage and communication in digital computing and digital information theory. Information theory also often uses the natural digit, called either a nit or a nat. Quantum computing also uses qubits, a single piece of information with a probability of being true.
Byte
byte is a basic unit of measurement of information storage in computer science. In many computer architectures it is a unit of memory addressing. There is no standard but a byte most often consists of eight bits.
Field
Field is a group of same byte, in database used by attribute.
Attribute
Attribute or Field is a characteristic from entity, which preparing detailed explanation about that's entity.
ATRIBUTE TYPES
Single Vs multi value
Single >> can only fill at most one value
Multi value >> can fill my more than one value with same type
Atomic Vs composition
Atomic >> indiscrete into smaller attribute
Composition >> representing alliance of some smaller attribute
Record
Record represent a data line in a relationship
Record consist of a corps of attributes which is interacted to give information about entity / relationship completely
Entity / File
File is a group of same record and have same element, same attribute but different of each data value.
In application process, file can be categorized as :
Main file
Transaction file
Report file
History file
Protector file
Activity file
DOMAIN
Domain represents corps of values which is enabled to stay in one or more attribute. Each attribute in a relational data bases defined as a domain
KEY OF DATA ELEMENT
Key is element of record which is used to find the record when accessing or also can used to identify each entity / record / Line
TYPES OF KEY
Super key represent one or more attribute from a tables which is able to be used to identify entity / record of tables uniquely ( not all of attribute can become super key)
Candidate Key is super key with minimum attribute. Candidate Key may not contain attribute of other tables so that candidate key beyond super key but of course not yet on contrary.
Primary Key is one of the attribute of candidate key can be selected /determined to become primary key with three criterions:
1.The Key more natural to be used as reference
2.The Key more simple
3.The unique of Key have to guaranteed.
Alternate Key is attribute of candidate key which is not chosen become primary key.
Foreign Key represent any attribute subjecting to primary key at other tables. Foreign Key will happened in relationship which is has cardinality one to many or many to many. Foreign Key usually is always put down at tables which is flange to many.
External Key represent a lexical attribute ( or gathering of lexical attribute) which is its values always identify one instance object.
ERD(ENTITY RELATIONAL DIAGRAM)
ERD is a model of a network that uses word order is stored in the abstract system.
The difference among DFD and ERD :
DFD is a model of network functions that will be implemented by the system
ERD is a model that emphasizes the network data on the structure and relationship data
Elements Of ERD
Entity
In the ER Diagram Entity is described with the form of a rectangle. Entity is something that exists in the real system and the abstract where the data stored or where there are data.
Relationship
A relationship is some association between entities. In this section we shall concentrate on binary relationships. That is, associations between two entities. In section 16.4 we shall introduce other N-ary relationships. That is, relationships between one, three, four or N entities. In the E–R approach, more than one relationship can exist between any two entities.
Relationship Degree
Are total entity who participated in one relationship. Degree that frequent being used on ERD
Attribute
Are character or characteristic of every entity and also relationship.
Cardinality
Pointing out record optimum that relations can with entity on entity another one.
CARDINALITY
There are 3 relationship cardinality that is
One to One :Level of Relation one to one expressed with one occurrence at first entity, only having one relation with one occurrence at second entity.
One To Many or Many to One :Level of Relation one to many is equal to many to one .For one occurrence at first entity can have many relation with occurrence at second entity, if on the contrary one occurrence at second entity only can has relation with one occurrence at first entities.
Many To Many : happened if each occurrence at an entity has many relation with occurrence at other entity
ERD(ENTITY RELATIONAL DIAGRAM)
In software engineering, an Entity-Relationship Model (ERM) is an abstract and conceptual representation of data. Entity-relationship modeling is a database modeling method, used to produce a type of conceptual schema or semantic data model of a system, often a relational database, and its requirements in a top-down fashion.
Diagrams created using this process are called entity-relationship diagrams, or ER diagrams or ERDs for short.
Sunday, April 19, 2009
Thursday, April 9, 2009
DFD quiz
Data Flow Diagram
Figuring system division into smaller module
Facilitate user that insufficiently understand about computer area to understands system that will be worked
Context Diagram
- Consist of one process and figures scope of a system.
- Constituting supreme level from DFD that figure all of input and output of system.
- System limited by boundary (figured by dotted line)
- Stored is may not there
Zero Diagram
Zero diagram describes the process of the DFD. It's provides a view of the overall system, showing the main function or process that is, and the showing the flow of data and external entity. At this level, the data storage is possible. The process is no longer detailed on the next level then added the symbol '*' or 'P' at the end of the process. The input and output balance between zero diagram and context diagram should be maintained.
Detailed Diagram
Detailed Diagram is diagrams that decompose a process that is in the diagram zero level or above
Numbering level in the DFD.
In one level there should be no more than 7 units and the maximum of 9, when more should be done in the decomposition
1. External Entity
Each system has certain boundaries that separate a system with the environment outside the system. The system will receive input and produce output to the outside environment. External entity is an entity in environment outside the system that can be a human being, organization, or the other system. Most external entity is one of the following:
1. An office, department or division in the company but outside the system that is being developed.
2. Person or a group of people in the organization but outside of that system is being developed.
3. An organization or a person outside the organization such as customer and supplier.
4. Other information systems outside the system that is being developed.
5. Original source of a transaction.
6. Recipient of a final report produced by the system.
2. Data Flow
Data flow is a place of information flow. Data flow depicted with a straight line connecting the components of the system. Data flow is shown with the direction arrows and the name on the flow of data that flows. The data flow is pour between processes, storage data, and its indicates that the form of data input for the system.
Here are some examples of data flow:
a. Forms or documents used in the company.
b. Printed reports generated by the system.
c. Display or output on a computer screen generated by the system.
d. Input to the computer.
e. Speech communication.
f. Letter or memo.
g. Data is read or recorded to a file.
h. A field note book on the agenda.
i. Transmitting data from one computer to another.
Flow data should be given the name and have a clear meaning. The name of the data flow in addition to the written its arrow.
Guidelines for naming:
1. The flow of data flow consists of several words associated with the line speed
2. No data flow of the same name and should reflect the contents
3. Flow of data that consists of several elements can be expressed with the group element
4. Avoid using the word 'data' and 'information' to give a name to the flow of data
5. Wherever possible the complete flow of data is writte
3. Process
A process is an activity or work done by the person, machine or a computer from the result of data flow into the process for generated data that will flow out of the process. The process is what is done by the system and then can process data flows or data entry into the flow of data out. The transform function of one or more of data input into one or more of the output data in accordance with the desired specifications so each process has one or more inputs and produce one or more output. The process is also called bubble.
A process can be indicated with a circle symbol or rectangle with straight corners blunt.
Each process must be given a full explanation include the following.
1. Identification process. This included the identification of a number that indicates the number of reference and the process is written at the top of the symbol in the process.
2. Name of the process. The name indicates that the process is done by the process. Name of the process must be clear and complete.
3. Processor. The processor may not be listed.
Guidelines naming of the process:
1. The process consists of a verb and noun, which reflects the function of the process.
2. Do not use the process as part of the name of a bubble.
3. There may be some process that has the same name.
4. The process must be given a number. Order number wherever possible to follow the flow of the process or sequence, but the sequence number does not mean that the absolute is a process in chronological order.
4. Data Store
Data storage is a storage place for data that exists in the system.
Symbolized with a pair of parallel lines or two lines with one side open side. The process can retrieve data from or provide data to the database.
Guidelines for naming:
1. The name should reflect the data storage.
2. When its name more than one word must be marked with the number.
Data store can be as follows:
a. A file or database in the computer system.
b. An archive or records manual.
c. A box of data.
d. A table reference manual.
e. Agenda or a book.
Type of Data Flow Diagram
There are 2 forms of DFD, the physical data flow diagram and logical data flow diagram. Physical data flow diagram more emphasis on how the process of the system is applied while
logical data flow diagram is to emphasize the process of what is found in the system.
1. Physical Data Flow Diagram, more appropriately used to describe the existing system. The emphasis on this diagram is how the processes of the system is applied. PDFP must include the following:
1. Manual processes are also described.
2. Name of the flow data must indicate the number of such application form and the medium.
3. Savings data can show savings of non-computer.
4. The name of saving the data type of application must show, whether manual or computerized.
5. The process must show the name of the processor, the man, ministry, computer system or computer program to access the process.
2. Logical Data Flow Diagram, more appropriately used to describe the system that will be proposed. LDFD does not emphasize on how the system implemented, but the emphasis only on the logic of the needs of the system.
For computerized systems, drawing LDFD that shows only the needs of the proposed logic of system, usually the processes described is only the computer proces only.
Data Dictionary
Data dictionary is to help the system to interpret the application in detail and organize all elements of the data used in the system precisely so that the system analyst have a basic understanding of the same input, output, storage and process.
At analysis step, the data dictionary is used as a means of communication between the systems analyst with the user, and at the design stage of the system, the data dictionary is used to design input, reports and databases. Load the data dictionary as follows:
1. The flow of data: should be noted that readers who need further explanation about a flow of data can find it easily.
2. Alias: alias or other name of the data can be written when it is existence.
3. The form of data: used to segment the data dictionary to use when designing the system.
4. Data flow: indicates from which data flows and where the data goes.
5. Description: provides an explanation about the meaning of the data flow.
Balancing in DFD
Balancing in DFD means flow of data into and out of a process must be the same as the flow of data into and out of the details of the process on the level/levels below. Besides then the flow of data into and out of the process must match the name of the flow of data into and out of the details of the process. The number and name of an entity outside the process must be equal to the number of names and entities outside of the details of the process.
There are some issues that must be considered in the DFD which have more than one level:
1. Must be balance between input and output of one level and next level.
2. Balance between level 0 and level 1 at the input / output of stream data to or from the terminal on level 0, while the balance between level 1 and level 2 is seen on the input / output of stream data to / from the process concerned.
3. The flow of data, the data storage and the terminals at each level must be the same if its the same object.
Prohibition in DFD
1. Flow data may not be from outside the entity directly to other outside entities without going through a process.
2. Flow data may not be from the savings directly to the data to outside entities without going through a process.
3. Flow data may not be saving the data directly from the other savings data without going through a process.
4. Flow of data from one process directly to the other without going through the process of saving data should or be avoided as much as possible.
Figuring system division into smaller module
Facilitate user that insufficiently understand about computer area to understands system that will be worked
Context Diagram
- Consist of one process and figures scope of a system.
- Constituting supreme level from DFD that figure all of input and output of system.
- System limited by boundary (figured by dotted line)
- Stored is may not there
Zero Diagram
Zero diagram describes the process of the DFD. It's provides a view of the overall system, showing the main function or process that is, and the showing the flow of data and external entity. At this level, the data storage is possible. The process is no longer detailed on the next level then added the symbol '*' or 'P' at the end of the process. The input and output balance between zero diagram and context diagram should be maintained.
Detailed Diagram
Detailed Diagram is diagrams that decompose a process that is in the diagram zero level or above
Numbering level in the DFD.
In one level there should be no more than 7 units and the maximum of 9, when more should be done in the decomposition
1. External Entity
Each system has certain boundaries that separate a system with the environment outside the system. The system will receive input and produce output to the outside environment. External entity is an entity in environment outside the system that can be a human being, organization, or the other system. Most external entity is one of the following:
1. An office, department or division in the company but outside the system that is being developed.
2. Person or a group of people in the organization but outside of that system is being developed.
3. An organization or a person outside the organization such as customer and supplier.
4. Other information systems outside the system that is being developed.
5. Original source of a transaction.
6. Recipient of a final report produced by the system.
2. Data Flow
Data flow is a place of information flow. Data flow depicted with a straight line connecting the components of the system. Data flow is shown with the direction arrows and the name on the flow of data that flows. The data flow is pour between processes, storage data, and its indicates that the form of data input for the system.
Here are some examples of data flow:
a. Forms or documents used in the company.
b. Printed reports generated by the system.
c. Display or output on a computer screen generated by the system.
d. Input to the computer.
e. Speech communication.
f. Letter or memo.
g. Data is read or recorded to a file.
h. A field note book on the agenda.
i. Transmitting data from one computer to another.
Flow data should be given the name and have a clear meaning. The name of the data flow in addition to the written its arrow.
Guidelines for naming:
1. The flow of data flow consists of several words associated with the line speed
2. No data flow of the same name and should reflect the contents
3. Flow of data that consists of several elements can be expressed with the group element
4. Avoid using the word 'data' and 'information' to give a name to the flow of data
5. Wherever possible the complete flow of data is writte
3. Process
A process is an activity or work done by the person, machine or a computer from the result of data flow into the process for generated data that will flow out of the process. The process is what is done by the system and then can process data flows or data entry into the flow of data out. The transform function of one or more of data input into one or more of the output data in accordance with the desired specifications so each process has one or more inputs and produce one or more output. The process is also called bubble.
A process can be indicated with a circle symbol or rectangle with straight corners blunt.
Each process must be given a full explanation include the following.
1. Identification process. This included the identification of a number that indicates the number of reference and the process is written at the top of the symbol in the process.
2. Name of the process. The name indicates that the process is done by the process. Name of the process must be clear and complete.
3. Processor. The processor may not be listed.
Guidelines naming of the process:
1. The process consists of a verb and noun, which reflects the function of the process.
2. Do not use the process as part of the name of a bubble.
3. There may be some process that has the same name.
4. The process must be given a number. Order number wherever possible to follow the flow of the process or sequence, but the sequence number does not mean that the absolute is a process in chronological order.
4. Data Store
Data storage is a storage place for data that exists in the system.
Symbolized with a pair of parallel lines or two lines with one side open side. The process can retrieve data from or provide data to the database.
Guidelines for naming:
1. The name should reflect the data storage.
2. When its name more than one word must be marked with the number.
Data store can be as follows:
a. A file or database in the computer system.
b. An archive or records manual.
c. A box of data.
d. A table reference manual.
e. Agenda or a book.
Type of Data Flow Diagram
There are 2 forms of DFD, the physical data flow diagram and logical data flow diagram. Physical data flow diagram more emphasis on how the process of the system is applied while
logical data flow diagram is to emphasize the process of what is found in the system.
1. Physical Data Flow Diagram, more appropriately used to describe the existing system. The emphasis on this diagram is how the processes of the system is applied. PDFP must include the following:
1. Manual processes are also described.
2. Name of the flow data must indicate the number of such application form and the medium.
3. Savings data can show savings of non-computer.
4. The name of saving the data type of application must show, whether manual or computerized.
5. The process must show the name of the processor, the man, ministry, computer system or computer program to access the process.
2. Logical Data Flow Diagram, more appropriately used to describe the system that will be proposed. LDFD does not emphasize on how the system implemented, but the emphasis only on the logic of the needs of the system.
For computerized systems, drawing LDFD that shows only the needs of the proposed logic of system, usually the processes described is only the computer proces only.
Data Dictionary
Data dictionary is to help the system to interpret the application in detail and organize all elements of the data used in the system precisely so that the system analyst have a basic understanding of the same input, output, storage and process.
At analysis step, the data dictionary is used as a means of communication between the systems analyst with the user, and at the design stage of the system, the data dictionary is used to design input, reports and databases. Load the data dictionary as follows:
1. The flow of data: should be noted that readers who need further explanation about a flow of data can find it easily.
2. Alias: alias or other name of the data can be written when it is existence.
3. The form of data: used to segment the data dictionary to use when designing the system.
4. Data flow: indicates from which data flows and where the data goes.
5. Description: provides an explanation about the meaning of the data flow.
Balancing in DFD
Balancing in DFD means flow of data into and out of a process must be the same as the flow of data into and out of the details of the process on the level/levels below. Besides then the flow of data into and out of the process must match the name of the flow of data into and out of the details of the process. The number and name of an entity outside the process must be equal to the number of names and entities outside of the details of the process.
There are some issues that must be considered in the DFD which have more than one level:
1. Must be balance between input and output of one level and next level.
2. Balance between level 0 and level 1 at the input / output of stream data to or from the terminal on level 0, while the balance between level 1 and level 2 is seen on the input / output of stream data to / from the process concerned.
3. The flow of data, the data storage and the terminals at each level must be the same if its the same object.
Prohibition in DFD
1. Flow data may not be from outside the entity directly to other outside entities without going through a process.
2. Flow data may not be from the savings directly to the data to outside entities without going through a process.
3. Flow data may not be saving the data directly from the other savings data without going through a process.
4. Flow of data from one process directly to the other without going through the process of saving data should or be avoided as much as possible.
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