Information Systems Analysis and Design [Part-5]

Database and entity relationship diagram

The definition of database

Database can be definition by collection of data which stored in magnetic disk, optical disk or other secondary storage. In other word database is collection of data which is linked one to other of an enterprise (factory, governmental institution, or private section). For example is in manufacture company, the database include production planning data, actual production data, data ordering material. And in hospital database include of data of patient, doctor, nurse, etc.

Database management system (DBMS)

Database management System is database collection with software application in based of database. This application programs is use for accessing and maintaining the database. The first aim of DBMS is to preparing an easy and efficient environment for using, collecting and storing data and information.

Definition of bit, byte, field

>> Bit: is the smaller part of data, which contain of value 1 or 0

>> Byte: collection of bits that of a kind

>> filed: collection of byte that of a kind, which in database is called "attribute".


Attribute or field

Attribute or field is a characteristic of entity, which preparing detailed explanation about that's entity. A relation also could have attributed.

Example of attribute:

- Attribute of motor cycle is number plate, color, kind, etc.

- Attribute of book is title, kind, total page, author, etc.


Type of attribute

1. Single vs. multivalued

Single: only can fill by one value

multivalued: can fill with more one value with the same of kind

2. Atomic vs. composition

Atomic: can not divided into smaller attribute

Composition: boundless from some smaller attribute

3. Derived attribute

Derived attribute is an attribute which its value can be produced from other attribute

4. Null value attribute

Null value attribute is an attribute with no value for a record

5. Mandatory value attribute is an attribute which must have value


Record or Tuple

Record is a line of data in a relationship. It does consist of collection attribute, where the attributes is related one to other to give detailed information of the entity or relation.


Entity or file

File is a collection of record that of a kind and having same element, same attribute however different in their data value.

Type of file:

In processing application, file can be categorized such as:

- Parented file

- Transaction file

- Report file

- History file

- Protector file

- Work file


Domain

Domain is collection of values which enabled to stay in one or more attribute. Every attribute in a relational database is defined as a domain

Key of element data

Key is the element of record which used to find the record when accessing or can also used to identify every entity / record / row.

Kind of key:

* Super key is one or more attribute from a table which can be used for identifying entity / record from table uniquely

* Candidate key is super key with minimum attribute. Candidate key may not contain attribute of other table so that the candidate is super key, but not the contrary

* Primary key

One of the attribute of candidate key can be selected / determined into primary key with 3 criteria:

- The key is more natural for use as reference

- The key is simpler

- The key is unique

* Alternate key

Alternate key is attribute of candidate key which is not chosen become primary key

* Foreign key

Foreign key is any attribute subjecting to primary key at other tables. Foreign key will be happened in a relation which have one to many cardinality or many to many cardinality. Foreign key usually put at the table which direct to many cardinality.

* External key

External key is lexical attribute or collection of lexical attribute which values always identify one object instance


ERD (entity relationship diagram)

ERD is a network model that uses word order is stored in the system of abstract

The different between DFD and ERD:

- DFD is a network functions model that will be implemented by the system

- ERD is a network data model that emphasizes the on the structure and relationship data


Elements in ERD

Elements in ERD include:

* 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

In the ER diagram, the relationship can be described with a rhomb. Relationship is a natural relation that occurs between entities. In a general way given by name by vocabulary so that making it easier to do the reading of relation.

* Relationship degree

Relationship degree is the number of entities which participating in a relationship. Degree is unit which is often used in the ERD.

* Attribute

Attribute is the nature or characteristics of each entity and relationship

* Cardinality

Cardinality indicates the maximum number of record/tuple that can be relation with the entity on the other entity


Degree of relationship

* Unary relationship is the relationship model between the entity originating from the same entity set.

* Binary relationship is the relationship model between 2 entities

* Ternary relationship is a relationship between the instances of 3 types of entities is unilateral


Cardinality

There are three of cardinality relationship, which is:

* One to one

Level one to one relationship stated with one event in the first entity, only had one relationship with one event in the second entities and conversely.

Example:



*One to many or many to one

Level one to many relationship is the same as the many to one depending on the direction from which the relationship have to seen. For an event on the first entity, it can have many relationships with the event on the second entity, if conversely the event in second entities only gets a relationship with one event on the first entity.

Example:



* Many to many

happening if each event on one entities has a many relationship with event on another entities.

Example:


Notation in ER-Diagram

The notation symbol of ER-Diagram is:


• Length square declare for entities gathering

• Circle declares for attribute

• Rhomb declares for relationship gathering

• Lining as connecting among relationship gathering with entities gathering and Entities Gathering with its attribute

References:
1. Agus Sanjaya ER, S.Kom, M.Kom, slide presentation : Database and ER-Diagram

BRISINGR

Ini novel yang baru aja selesai ku baca setelah bergumul dengan tugas-tugas kuliah yang numplek akhirnya bisa menikmati baca niy novel ;P!

Brisingr adalah buku ketiga dari trilogi Warisan yang ditulis oleh Christopher Paolini, buku pertamanya adalah ERAGON kemudian ELDEST (Tapi ternyata gw salah!!! Setelah tak baca sampai akhir masih ada lanjutannya, berarti niy novel bukan trilogi toh???)

Dalam novelnya yang ketiga ini masih menceritakan tentang perjuangan eragon si penunggang naga dengan naganya yang bernama Saphira. masih juga tentang perlawanan kaum varden yang menentang kekuasaan raja kejam bernama Galbatorix.

Dalam novel ini diceritakan Eragon bersama Roran pergi mencari Katrina yang ditawan oleh para Ra'zackemudian ia menikahkan Roran dan Katrina. Eragon juga menepati janjinya untuk menghapuskan kutukan pada elva namun tidak sepenuhnya berhasil. Kemudian ia mengikuti pemilihan raja kurcaci karena raja sebelumnya yaitu Hrothgar telah tewas dalam pertempuran di daratan membara, ia bersama saphira memperbaiki Ishdar Mitrim di Farthen dur saat penobatan Orik menjadi raja kurcaci ke 44.

Setelah ritual penobatan raja kurcaci, eragon dan saphira balik ke Elesmera untuk bertemu dengan gurunya yang juga penunggang naga yaitu Oromis si cacat yang utuh. Oromis memberitahukan bahwa ayah Eragon bukanlah Morzan, melainkan Brom. Setelah Zar'oc diambil oleh saudara tiri Eragon yaitu Murtagh ia berniat membuat pedang baru yang sesuai dengan dirinya untuk itu ia mencoba untuk bertemu Rhunon si pandai besi elf. Eragon tidak mempunyai pedang yang layak untuk seorang penunggang. Maka ia teringat nasehat Solembum (kucing jadi-jadian) bahwa ketika ia membutuhkan senjata ia dapat mencarinya dibawah akar pohon Menoa. Setelah sempat bersitegang dengan penunggu pohon akhirnya eragon mendapatan brightsteel yang digunakan sebagai bahan membuat pedang tersebut, Rhunon-elda membantunya membuat pedang penunggang yang kemudian diberi nama BRISINGR. Pedang ini menyala setiap Eragon menyebut namanya. Hari terakhir Glaedr memberitahukan kelemahan Golbatorix dan rahasia tentang eldunari yaitu jantungnya jantung naga. Eldunari milik Glaedr diserahkan kepada Saphirauntuk membantu mereka melawan galbatorix. Oromis pun memutuskan untuk memperlihatkan diri di depan Golbatorix dan ikut berperang melawannya secara langsung.

Oromis dan Glaedr melawan Murtagh bersama naganya Thorn di Gil'ead, tiba-tiba Galbatorix menampakan diri melalui Murtagh dan membunuh Oromis. Eragon yang saat itu bertarung bersama Arya melawan Shade melihat pembunuhan itu dalam benaknya. Akhirnya Eragon dan Saphira menjadi penunggang terakhir dan sendirian yang harus melawan Golbatorik.

Novel ini masih berlanjut ke bukunya yang ke-empat...
Duwh.. jadi penasaran...

...buku yang membuat saya rela bergadang.
----The Washington Post

Penuh dengan adegan pertempuran seru yang mengombinasikan sihir dan ilmu perang tradisional...
----Children's Literature

Judul: Brisingr
Pengarang : Christopher Paolini
Penerbit edisi Bahasa Indonesia: Gramedia Pustaka Utama

Information Systems Analysis and Design [Part 4]

DATA FLOW DIAGRAM (DFD)

Data flow diagram also called Data Flow Diagram (DFD). Data flow diagram is use to figuring system division into smaller module. DFD can facilitate user that insufficiently understand computer's area for understanding system who will be worked.

CONTEXT DIAGRAM

Context diagram is consisting of one process and figures scope of a system. That is supreme level from DFD that figuring all input goes to system and output of system. In context diagram, stored (storage) is not available.

ZERO DIAGRAMS

Zero diagrams are use to figuring process from DFD. The diagram can giving views thoroughly concerning handled system, show function or aught main process, data flow and external entity. On this level is enabled to marks sense data storage. For a process that don't elaborated again on succeeding level then was enhanced symbol ‘*’ or ‘p’ by the end of process numbers. Balancing of input and output among zero diagram and context diagram must be maintained.

DETAILS DIAGRAM

Details diagram that describes the process what’s aught on zero diagram or level on it.

Numbering level on DFD:

Level’s name	Diagram’s name	Process number
0	Context
1	Diagram 0	1.0, 2.0, 3.0, ...
2	Diagram 1.0	1.1, 1.2, 1.3, ...
3	Diagram 1.1	1.1.1, 1.1.2, ...

In one level it is better to have no more than 7 processes and maximal 9 process, if more than that, and then should to be done decomposition.

SPECIFICATION PROCESSES

Each process on DFD shall have process specification. On top level method that is utilized to figure the process can by use of descriptive sentence. At more level detailed that is at lowermost process (primitive functional) requiring the specification of more structure. Specification of processes will be guidance for programmer in making program (coding). Method that is utilized in specification processes are breakdown of process in shaped story, decision table and decision tree.

EXTERNAL ENTITY

An external entity is a source or destination of a data flow which is outside the area of study or something that beyond system, but it gives data into system or gives data from system. Only those entities which originate or receive data are represented on a business process diagram. External entity is symbol with notation box. External entity is excluding part of system.

Rules for Naming:

- Terminal name as noun

- Terminal can not have a same name but the object is really same

DATA FLOW

A data flow shows the flow of information from its source to its destination. A data flow is represented by a line, with arrowheads showing the direction of flow. Information always flows to or from a process and may be written, verbal or electronic. Each data flow may be referenced by the processes or data stores at its head and tail, or by a description of its contents.

Dataflow notations:

Guideline to naming:

1. Name of Data's flow which consisting of several word's flow connected by interlocking lines

2. No data's flow which its have same name, and naming shall reflect its content

3. Data flow that consisting of several element gets to be declared with element group

4. Avoid of using word ‘ data ’ and ‘ information ’ to naming on data flow

5. As much as can the name of data flow is written completed

other rule:

· name of Data flow which turn in at a process may not same by the name of secretory data flow of that process.

· data flow that ingoing goes to or out from data storage not necessarily been given name if:

o Simple data flow and perspicuous

o Data flow figures all item's data

· there is no data flow from terminal to data storage or on the contrary because the terminal is not part of system, terminal relationship with data storage shall pass through process

PROCESS

The process is also often called bubble. Process is what does be worked by system. A process transforms incoming data flow into outgoing data flow. A process shows a transformation or manipulation of data flows within the system. Each process has one or many entries and resulting one or many outputs.

Guideline to naming processes:

* Name processes consisting of verb and noun that reflect that process function

* Don't utilize the word 'process' as part of name a bubble

* there is no many process that have same name

* Process shall be numbered. Number thread as much as can following the flow or process thread, but such number thread doesn't mean absolutely representing process thread chronologically

Process Notations

DATA STORAGE

Data storages are repositories of data in the system. They are sometimes also referred to as files. It is represented by a pair of parallel lines or two lines with one of the side open. Process can take data from or gives data to database

Guideline to naming:

· Name shall reflect data storage

· If its name more than one word then has to be hyphened

SYMBOLS USED ON DFD

DATA DICTIONARY

Data dictionary is also called with a system data dictionary is a catalog of facts and data information needs of an information system. In function to help system agent to interpreting application in detail and organization all of data element that utilized by system exactly so user and system analyst have same understanding basic about entry, output, storage and process. On analysis’s phase, data dictionary is utilized as communication device among system analyst with user. On system design phase, data dictionary is utilized to design input, reporting and database. Data flow on DFD has global character; the more detail information can be seen on data dictionary.

Data dictionary load things as follows:

· Name of data flow: must note that readers that require more explanation about a data flow can look for it squashy.

· Alias: alias or other name of data can written if available

· Data form: utilized to agglomerate data dictionary into its usage when designing of system

· Data flow: show that from where data flow and where data wend.

· Explanation: giving explanation about meaning of data flow

BALANCING IN DFD

· Data flow which it’s in and out from one process has to equal with data flow which it’s in and out from details of process on level under it.

· name of data flow which its in and out from one process must be same with the name of data flow which its in and out from details of that process

· Total and name of external entity of a process has to equal with total and name of external entity of details of that process

· Things that must be noticed on DFD who has more than one level:

o input and output balance must be available among one level and next level

o Balance among level 0 and level 1 is seen on input / output of data flow goes to or from terminal on level 0, meanwhile balance among level 1 and level 2 are seen on input / output of data flow goes to / from process that pertinent

o name of data flow, data storage and terminal on every level must be same if its object is same

PROHIBITION IN DFD

· Data flow may not from external entity directly to wend another external entity without passing a process.

· Data flow may not from data storage directly goes to external entity without passing a process

· Data flow may not of direct data storage wend to another data storage without passing a process

· Data flow from one process directly to wend another process without passing an data storage is advisable/can be avoided

DIAGRAM CASH INVESTMENT DATA

There are 2 forms of DFD:

1. Physical Data Flow Diagram (PDFD), more appropriately used to describe the existing system (old system). The emphasis is how the processes of the system is applied, including manual processes.

2. Logical Data Flow Diagram (LDFD), more appropriately used to describe the system that will be proposed (new system), with no emphasis on how the system implemented, but the emphasis only on the logic of the demand system, that is what the process logic needed by the system.

GUIDELINES TO DRAWING DFD

1. Identify the first unit outside of all involved in the system. For example, sales for the system have involved external entity such as customer, credit manager, warehouse division and delivery division.

2. Identification all of input and output that involved in union with the outside.

3. Draw the context diagram (context diagram) first. DFD is a tool for structured analysis. The structure of this system to try to describe the first time the outline (called by top level) and split them into the more detailed (called by lower level) is called overview diagram (level 0). Each overview will be drawn more detailed again called level 1, and each process in level 1 will be drawn back with a detailed level with a 2 and so on until each of these processes can not be drawn again.

4. Draw the hierarchy chart for all process that is in the system first. Tiered chart (hierarchy chart) used to prepare the DFD drawing to more levels down again.

5. Draw the sketch of DFD for overview diagram (level 0) based on process on the tiered chart.

6. Draw the DFD for next level which is level-1 and so on.

7. After all of level in DFD is drawn, next is draw the DFD for management reporting which its drawn separately.

8. after all of level in DFD is drawn, and then all of this DFD can combine in one diagram.

Reference:

1. ER Ngurah Agus Sanjaya. Slide Part 4 - DATA FLOW DIAGRAM.
2. HM, Jogiyanto. 2007. Analisis & Desain Sistem Informasi. Yogyakarta: ANDI.