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A Warnier-Orr diagram (also known as a logical
construction of a program/system) is a kind of hierarchical
flowchart that allows the description of the organization of
data and procedures.
 They were initially developed in France by Jean-Dominique
Warnier and in the United States by Kenneth Orr.
 This method aids the design of program structures by
identifying the output and processing results and then
.

 The simple graphic method used in Warnier/Orr
diagrams makes the levels in the
Warnier/Orr diagrams show the processes and
sequences in which they are performed. Each
process is defined in a hierarchical manner i.e. it
consists of sets of sub processes that define it. At
each level, the process is shown in bracket that
groups its components.

UsingWarnier/Orr Diagrams
 To develop a Warnier/Orr diagram, the analyst works
backwards, starting with and using output
oriented analysis.
 On paper, the development moves from right to left. First,
the intended output or results of the processing are
defined.
 At the next level, shown by inclusion with a bracket, the
. Each step
in turn is further defined.
the result on the next level.

Advantages of Warnier/Orr diagram
According to Experts:
 They are
. Yet they are powerful design tools.
that
must be passed from level to level.
 In addition, the sequence of working backwards
. This
method is useful for both data and process
definition.

Basic Constructs in
Warnier-Orr diagram
There are four basic constructs used on
Warnier/Orr diagrams:
.
 There are also two slightly more advanced
concepts that are occasionally needed:
concurrency and recursion.

Constructs in Warnier-Orr Diagrams
Hierarchy
Hierarchy is the most fundamental of all of the Warnier-
Orr constructs. It is simply a nested group of sets and
subsets shown as a set of nested brackets.
Each bracket on the diagram (depending on how you
represent it, the character is usually more like a brace
"{" than a bracket "[", but we call them "brackets")
represents one level of hierarchy.

Sequence
 Sequence
Within one level of hierarchy,
the features listed are shown in the order in which they
occur.
 In other words, the step listed first is the first that will
be executed (if the diagram reflects a process), while
the step listed last is the last that will be executed.
 Similarly with data, the data field listed first is the first
that is encountered when looking at the data, the data
field listed last is the final one encountered.

Repetition
Repetition is the representation of a classic
"loop" in programming terms.
 It occurs whenever the same set of data occurs
over and over again ( ) or
whenever the same group of actions is to occur
over and over again ( ).
Repetition is
beneath the
repeating set.

Alternation
Alternation, or selection, is the traditional
"decision" process whereby a determination is
made to execute one process or another.
This diagram indicates that an Employee is either
one
Employee cannot be both.
 It is also permissible to use a "negation bar"
above an alternative in a manner similar to
engineering notation.

Concurrency
Concurrency is one of the two advanced
constructs used in the methodology.
It is used whenever sequence is unimportant.
For instance, years and weeks operate
concurrently (or at the same time) within our
calendar.

Recursion
Recursion is the least used of the constructs. It is
used to indicate that a set contains an earlier or a
less ordered version of itself.
 In the classic "bill of materials" problem
components contain parts and other sub-components.
Sub-components also contain sub-sub-components,
and so on. The doubled bracket
indicates that the set is recursive. Data structures
that are truly recursive are rather rare

 A Nassi–Shneiderman diagram (NSD) in
computer programming is a graphical
design representation for structured
programming .
 This type of diagram was developed in 1972
by who were
both graduate students at SUNY-Stony Brook.

 Nassi–Shneiderman diagrams are (almost)
isomorphic with flowcharts.
 Everything you can represent with a
 For flowcharts of programs, almost everything
you can represent with a flowchart you can also
represent with a Nassi–Shneiderman diagram.

Process
A process describes a program function as
pseudocode. You can stack processes on top of each
other to illustrate a sequence.

Parallel Process
Place processes that are executed at the same time
inside a trapezium created by drawing two diagonal lines in
the upper and lower border of the table.

Repeated Process (Loop)
 Use loop notations when processes are repeated until a
certain condition is met.

Decision
 The selection symbol is a rectangle divided into three parts
by diagonal lines.
 Write the condition or decision in the uppermost triangle
and place the two possible outcomes on either side of the
decision. The two outcomes don't need to be the same
size.

Case statement
List multiple cases next to each other in a
table format.

 A decision tree is a decision support tool
that uses a tree-like graph or model of
decisions and their possible
consequences, including chance event
outcomes, resource costs, and utility.

 It is a table of possibilities for defining a problem and the
actions to be taken
 It is a single representation of the relationships
between conditions and actions
 It consists of two parts: stub and entry
 The stub part is divided into called
the and a lower quadrant called the action
stub
 The entry part is also divided into an upper quadrant,
called the condition entry and a lower quadrant called
the action entry

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