STRUCTURING SYSTEM REQUIREMENTS

LOGIC MODEL MAKING
Previously, we have studied how the change process  data into information is a vital part of the system information. The best possible data flow diagram or DFD identify processes, DFD is not good enough to show logic contained in a process. In fact, at the level DFD primitive does not show the processing steps fundamental. What happens in the process? how the data input is converted into output information? Since the DFD is designed not to show the detailed processing logic, you must create a logic model of the process using other techniques. this discussion talk about the techniques you use to make logic model process. First, you will be
introduced to Structured English, English version that has been modified naturally beneficial in representing logic in the process of information systems. you can use English structured to represent three basic statement required in structured programming, namely: choice, repetition, and sequence. Logic Modeling In the previous section, you learned how to system requirements for collected information. analysts making the needs of information structure into the diagram DFD data flow or data flow modeling the entrance, flows  and finally came out of a process in information systems. Although, DFD, is useful and good technique, DFD is not enough sufficient to demonstrate all of the complexity of the system  information. Although decomposition enables you represent process up to the level of detail, the name itself does not process adequately describe what processes are doing and how do it. With the above reasons you should represent the logic contained in a process symbols in DFD with other engineering models. Modeling Logic with Structured English You have to understand more than just the incoming flow, flows, and out of the system information. You also have to understand what is done by each process identified and how each process is doing. Structured English, for short hereinafter BIT, is a modified form of the English Language used to define the contents of the black box in the process a DFD. He is different from English general in the sense that the BIT to use some English vocabulary for statesin the process of information systems. The verb used for the name of the process in a DFD, also can beused in the BIT. This verb them, read, write, print, sort, move, merge, add, subtract, multiply, and divide.

BIT also using noun phrases to describe the data structure such as customer name and address-customer. Unlike natural English, BIT does not use adjectives and adverbs. The main intent is to explain the use of BIT process briefly, namely that users and programmers can more easy to read and understand. Because there is no standard version then each BIT analysts use their own dialect.  Bits can represent three processes are generally present in structured programming, namely: sequence, conditional statements, and looping. Sequence but does not require any special structure represented by a series of statements followed other statements. Conditional statements can be represented by
structure as follows:
BEGIN IF
IF Quantity-Stock = ªKuantitas-Message-Minimum
THEN Generate-new orders
ELSE not-do-anything
ENDIF
Another type of conditional statement is a statement of case in which
There are many different actions that can follow the program, but only
one is selected. Case statement can be represented as
the following:
READ Quantity-Stock
SELECT CASE
1 CASE (Quantity-Stock> Quantity-Minimum-Message)
DO-any non-lalukan
CASE 2 (Quantity-Stock = Quantity-Minimum-Message)
DO not-do-anything
CASE 3 (Quantity-Stock <-Message-Minimum Quantity)
-Generate new orders
CASE 4 (Out of stock)
Initiate regular-order-emergency
AND CASE
Repetition can take the form of Do-Until loop or Do-While loop. Do-Until
loop can be shaped as follows:
DO
READ record Inventory
BEGIN IF
IF Quantity-Stock <-Message-Minimum Quantity
THEN Generate-new orders
ELSE DO not-do-anything
END IF
UNTIL End-of-file
Do-While loops can be represented as follows:
READ record Inventory
WHILE NOT End-of-file DO
BEGIN IF
IF Quantity-Stock <-Message-Minimum Quantity
THEN Generate-new orders
ELSE DO-any non-lalukan
END IF
END DO