Display methods are basically main and important methods that are employed by software inspection process simply to ensure and confirm correctness of code and also to validate formal models.
In this method, display is a precise document i.e., accurate and correct document in which program is simply presented in a way that its correctness might be determined and identified without examining any other displays. A Display usually consists of three parts as given below :
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P1 :
Represents specification for the program that is presented in this display. -
P2 :
Represents program itself. Program name might appear in this text, so we can say that all of these programs are invoked in this display. -
P3 :
Represents specification of all programs that are invoked in P2 but are now known. A known program is a program that does not even require any specification. Semantic of known programs are simply considered to be easily understood. Therefore, each and every project should contain a list of programs that are assumed to be known.
Concept of Display Method :
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Lexicon –
Lexicon is basically a dictionary that contains several definitions of any mathematical functions, types, program constants, etc. that are required and used in more than one display. -
Index –
Index is basically a list containing all variables and programs indicating where all those items appear in displays. If some of names are used with more than one meaning, then we also explain category of each and every name. -
Completeness and Correctness –
Each of display might be reviewed without any reference to other displays. Its correctness can also be verified without even looking at the implementation of programs invoked in that display or either program invoke programs that it describes. -
Correctness –
A display is considered to be correct if program in P2 will completely satisfy specification that is given in P1, simply provided that programs that are invoked in P2 completely satisfy specifications that are given in P3. -
Completeness –
A set of displays is considered to be complete if, for each specification of a program that is present and found in P3 of a display, there exits another display in which this specification is found in P1. A set of displays is correct only if set of displays is complete and all displays are correct.
Role of Mathematical notation and Mathematical methods in Display Method :
Display method is generally based on a mathematical model of programs. It uses some mathematical notations simply to provide an accurate and correct description of programs. In software engineering, use of mathematical methods focuses more on program development or program verification.
Notation is very essential and important in the documentation. Documents are generally to be read by experts from different fields and must be understood in an easy and simple way. Therefore, while designing notation, we should apply principle “divide and conquer”.
Role of Tables and Tabular notation :
Tabular notation generally decreases complexity of expression. It decreases complexity in three ways as given below :
- Table usually parses expression i.e., to breakdown expression to make it easy for the reader to understand.
- Table also eliminates many of repetitions of sub-expressions that might appear in the headings of column.
- Each entry in the table only applies to a small part of function’s domain, therefore expression in that entry can be simplified.
Advantages :
- Makes program documentation much more useful when a program is very lengthy
- Represents a program simply as a set of displays along with property that each of display might be examined and verified without looking at any other displays.
- Used to ensure the correctness of the code.