Question { Accenture, 144118 }

Explain about HLD and LLD ?

Answer

For people who have been involved in software projects, they
will constantly hear the terms, High Level Design (HLD) and
Low Level Design (LLD). So what are the differences between
these 2 design stages and when are they respectively used ?

High – level Design gives the overall System Design in terms
of Functional Architecture and Database design. It designs
the over all architecture of the entire system from main
module to all sub module. This is very useful for the
developers to understand the flow of the system. In this
phase design team, review team (testers) and customers plays
a major role. For this the entry criteria are the
requirement document that is SRS. And the exit criteria will
be HLD, projects standards, the functional design documents,
and the database design document. Further, High level deign
gives the overview of the development of product. In other
words how the program is going to be divided into functions,
modules, subdivision etc.

Low – Level Design (LLD): During the detailed phase, the
view of the application developed during the high level
design is broken down into modules and programs. Logic
design is done for every program and then documented as
program specifications. For every program, a unit test plan
is created. The entry criteria for this will be the HLD
document. And the exit criteria will the program
specification and unit test plan (LLD).
The Low Level Design Document gives the design of the actual
program code which is designed based on the High Level
Design Document. It defines Internal logic of corresponding
submodule designers are preparing and mapping individual
LLD’s to Every module. A good Low Level Design Document
developed will make the program very easy to be developed by
developers because if proper analysis is made and the Low
Level Design Document is prepared then the code can be
developed by developers directly from Low Level Design
Document with minimal effort of debugging and testing.