Design Tools
Name the common Tools for System Design
1.Funtional Flow Block Diagram.
2.Flow Charts.
3.Nassi–Shneiderman chart.
4.Structured English.
1.Functional Flow Block Diagram.
FFBDs are one of the classic business process modeling.The FFBD
notation was developed in the 1950s, and is widely used in classical systems
Development.They are also refered as Functional Block Diagrams or Functional
Flow diagram.Functional Flow Block Diagrams (FFBD) usually define the detailed,
step-by-step operational and support sequences for systems.
In the FFBD method, the functions are organized and depicted by
their logical order of execution. Each function is shown with respect to its
logical relationship to the execution and completion of other functions. A node
labeled with the function name depicts each function. Arrows from left to right
show the order of execution of the functions. Logic symbols represent
sequential or parallel execution of functions.
FFBDs depict the time sequence of functional events. That is,
each function (represented by a block) occurs following the preceding function.
Some functions may be performed in parallel, or alternate paths may be taken.
The duration of the function and the time between functions is not shown, and
may vary from a fraction of a second to many weeks. The FFBDs are function
oriented, not equipment oriented. In other words, they identify "what" must
happen and do not assume a particular answer to "how" a function will be
performed.
A key concept in modeling functional flow is that for a function
to begin, the preceding function or functions within the “control” flow must
have finished.The logical sequence of functions (i.e., the functional flow)
describes the “control” environment of the functional model. In addition to a
function being enabled, it may also need to be triggered with an input
2.Flow Charts.
Flowcharts are a modeling technique introduced in the 1940/50s
and popularized for structured development in the 1970s (Gane and Sarson 1979)
as well as business modeling.There are three basic symbols on this flowchart:
Squares which represent activities or tasks, diamonds which represent decision
points, and arrows which represent flow of control. Flowcharts support other
types of symbols, such as off page connectors (for when your diagrams get too
big) and input/output symbols to represent printed reports and data storage
options.
Unlike DFDs which are used to describe data flow within a system,
flow charts are typically used to describe the detailed logic of a business
process or business rule
Each flow chart is concerned with one particular process or
system. It begins with the input of data or materials into the system and
traces all the procedures needed to convert the input into its final output
form. Specialized flow chart symbols show the processes that take place, the
actions that are performed in each step, and the relationship between various
steps. Flow charts can include different levels of detail as needed, from a
high-level overview of an entire system to a detailed diagram of one component
process within a larger system. In any case, the flow chart shows the overall
structure of the process or system, traces the flow of information and work
through it, and highlights key processing and decision points.
Flow charts are an important tool for the improvement of
processes. By providing a graphical representation, they help project teams to
identify the different elements of a process and understand the
interrelationships among the various steps. Flow charts may also be used to
gather information and data about a process as an aid to decision making or
performance evaluation.
Flow charts typically utilize specialized symbols. Some of the
main symbols that are used to construct flow charts include:
1.A round-edged rectangle to represent starting and ending
activities, which are sometimes referred to as terminal activities.
2.A rectangle to represent an activity or step. Each step or
activity within a process is indicated by a single rectangle, which is known as
an activity or process symbol.
3.A diamond to signify a decision point. The question to be
answered or decision to be made is written inside the diamond, which is known
as a decision symbol.
4.The answer determines the path that will be taken as a next
step. Flow lines show the progression or transition from one step to another.
3.Nassi–Shneiderman chart (NS chart).
Nassi–Shneiderman chart (NS chart) A kind of diagram (devised
1973–74) for representing the sequence of execution in a program. The diagram
takes the form of a rectangle divided mainly into smaller rectangles with the
sequence of execution going from top to bottom of the diagram. There are
various standard constructs, including NS sequence structures, NS repetition
structures, and NS selection structures.
Nassi-Shneiderman charts were developed by Nassi and Shneiderman
as an alternative to traditional logic flowcharts. Their intent was to provide
a structured, hierarchical, graphical view of the flow of logic through a
program, a routine, a module, or a process. Nassi-Shneiderman charts are used
to document, plan, and design detailed program logic. A Nassi-Shneiderman chart
describes within a single rectangular box the flow of logic through a module or
a routine. Control enters at the top, drops through the box, and exits at the
bottom, yielding a single entry point and a single exit point. No branch
instructions are permitted.
4. Structured English.
Structured English is the use of the English language with the
syntax of structured programming.
Structured English is useful for planning or designing program routines,
modules, and manualprocedures. It resembles a programming language, so
programmers find it easy to understand. Thebase for structured English
is,English, so users find it easy to follow, too.
Structured English is excellent for describing an algorithm, particularly when
user communication is essential. Structured English is not a good choice for
describing a high-level control structure or an algorithm in which numerous
decisions must be made; logic flowcharts, decision tables, and decision trees
are better for such tasks.
Structured English consists of the following elements:
1.Operation statements written as English phrases executed from the top down
2.Conditional blocks indicated by keywords such as IF, THEN, and ELSE
3.Repetition blocks indicated by keywords such as DO, WHILE, and UNTIL
A good structured English statement reads like a short imperative sentence. By
convention, only key words such as IF, THEN, SO, REPEAT, UNTIL, DO, and so on
are capitalized; data names and the general English needed to complete a
sentence or a phrase are lower case.
Read More Strctured
English
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