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Matrikulasi Basis Data. Teguh Bharata Adji. Model E-R. Model E-R mudah dimengerti karena dikembangkan sesuai dengan kondisi dunia nyata, yang selalu melihat segala hal berdasarkan obyek. Komponen-komponen dari Model E-R yang utama adalah: Entitas Atribut Relasi
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Matrikulasi Basis Data Teguh Bharata Adji
Model E-R • Model E-R mudah dimengerti karena dikembangkan sesuai dengan kondisi dunia nyata, yang selalu melihat segala hal berdasarkan obyek. • Komponen-komponen dari Model E-R yang utama adalah: • Entitas • Atribut • Relasi • Model E-R digambarkan dengan Diagram E-R, suatu diagram yang menggunakan simbol-simbol seperti pada Gb. • Entitas diwakili persegi panjang, atribut diwakili elips dan relasi diwakili diamond.
Inter-module Communications • There are 2 places of internal interaction between 3 sub-systems: • Front End ↔ Back End. • Back End ↔ SCADA Engine. • There are 2 points of external interaction with the 3 sub-systems: • User ↔ Front End. • SCADA Engine ↔ Attached Peripheral.
Inter-module Communications Schema Figure 3:
Front End ↔ Back End • A text based TCP protocol called “Front end listener” will be develop as a module in the back end dedicated to communicate with the front end. • The communication protocol is based on plain, line based ASCII, using a server socket which waits for connections. The front end is always the initiator of a conversation. • Requests which can be made by the front end via this channel: • find out SCADA Engine status. • send a message to SCADA Engine. • Plain ASCII is used such that it is easy to work with and debug the system. • The text is transferred in XML format as it gives the benefit of uniformity, scalability, and ease of use of other developer.
Back End ↔ SCADA Engine • This communication has 2 interfaces, the data channel and the control channel. Both are TCP connections. • Control Channel: • ?. • Data Channel: • SCADA Engine connects to the Back End on the port specified during initial conversation. • Messages are sent back and forth through data channel at the request of the user. • A message is defined as a sequence of ASCII characters terminated by a line-feed(\n) character, because of the easy testing.
User ↔ Front End • It is implemented using a web interface.
SCADA Engine ↔ Peripheral • It will be dependent on the particular peripheral attached. • Many peripherals will use basic digital/analogue IO, or RS-232 (with help from the compiler’s RS-232 library) together with the available DB-9 serial port.
4. Implementation • Equipment: • SCADA Engine board, which can be purchased. • PIC programmer. • DB-25 printer cables to connect the computer to the PIC programmer. • GPRS or CDMA data packet capable mobile phone or modem and an account with a mobile network service provider. • A PC: • must be connected to the Internet and have a globally accessible IP address (non private). • having some software (1) for development of this project, and (2) installed on the PC when used as a server (see Table).
5. Degree of Success • The system achieves the basic goals: • simple to use. • simple to maintain. • adaptable. • more real time than the previous project (Mayer, 2002). • more robust solution than the previous system. • The system can be used in a real life situation.