SSADM - Stage 6

Physical Design

 

Page Contents

Introduction

Step_610 Prepare for Physical Design

Step_620 Create Physical & Data Design

Step_630 Create Function Component Implementation Map (FCIM)

Step_640 Optimise Physical Data Design

Step_650 Complete Function Specification

Step_660 Consolidate Process Data Interface (PDI)

Step_670 Assemble Physical Design

 

 

 

Introduction

This is the final Stage of SSADM and involves the physical design of the required system from the logical design of stages 4 and 5. Once the detailed design work is accepted, the detail of the final system specification is created.


Step 610 Prepare for Physical Design

The target physical environment is known from a step in Stage 4. Further details may be known about this environment.

E.g. Through a procurement exercise.

The Physical environment specification contains precise details about the technical environment for further development work and operations of the proposed IS.

This specification is available through Project procedures.

It may be necessary to modify development standards within an organisation due to information held in the specification. This work is done in this step.

User manuals should be written.
 

Step 620 Create Physical and Data Design

There are two parts:

      1. Takes Logical Data Model (LDM) and creates a physical design by applying general transformations which are provided by physical data design technique. Design should minimize access time by placing data which is likely to be accessed together on the same physical block.

      2. Further transformation, but this time applying rules which are specific to the Database Management System (DBMS)

        1. group records with similar access patterns together

        2. implement relationships between physical groups together

 

 

Step 630 Create Function Component Implementation Map (FCIM)

 

There are two major activities to be undertaken:

      1. Ensure logical description of processing is complete.

        1. support design functions which contain multiple events and update process models

        2. requires checks to be made for common processing

      2. Determines how each component of the logical design will be built.

 

Step 640 Optimise Physical Data Design

 

This step calculates the size and timings of the IS. The user should be consulted in this step for any technical decisions to be made.

Any changes in the IS need to be documented. Discretion & Expertise are required in this step to decide how much effort should be used.



 

Step 650 Complete Function Specification

 

All functions that require its processing to be written in a procedural language are considered. Programs containing more than one function may need to be reworked.

There are two main activities for each function:
      1. Identify logical processing components in each function.
      2. Combine these components and their associated fragments in program specifications.

 

 

Step 660 Consolidate Process Data Interface (PDI)

The PDI links the physical data design and the processing, which is built on a logical view of the data model.

This step has two roles:
      1. Define the interfaces between the physical data, whose structure may well have changed as a result of Steps 620 and 640, and the processing units defined in Steps 630 and 650.
      2. Require that all validation routines or special processing modules are recorded. The purpose is to ensure that all routines that link the data and processing are recorded in a single place.

 

 

Step 670 Assemble Physical Design



In this stage all the outputs from previous steps and stages are assembled. They are brought together and given a final check of their quality. When everything has been checked for quality it is then time to publish the Requirement Specification.