January 16, 2012

Design justification file - E-7

Justify the technical solution selected and comply with the Technical Specification

A. Scope

The Justification File (DJD) contains all the information required to justify the definition of the product with respect to its specifications. It consists of a list, or in some cases a compilation, of all the justification documents of the product definition at a given moment in time. It clearly shows that the choices made for the definition of the product meet the expressed needs and requirements; it also records the reasons for these choices, throughout the duration of the project, and therefore provides the "history" of the product definition.

It must obviously be coherent with respect to the definition of the product at the time concerned: for this reason, any change in the definition requires the rationale to be updated.

The Justification File is therefore, by construction, modifiable and iterative. It is prepared progressively, in parallel with the definition.

B. Fundamentals

During phase B, the Justification File contains all the results of the theoretical preliminary design work and the resulting choices.

Throughout the preliminary definition of the product, this rationale can consist of analyses, calculations, simulations or tests on mock-ups.



C. Typical content

1. Scope

This Section shall contain the general information that defines the project to which the Justification File applies, the product it concerns and the definition it justifies.

2. Documentation

2.1 Applicable documents

These are all the documents whose applicability is mandatory for the definition of the product. They are the Tender Specification (see E 1) and/or the Technical Specification (see E 2), as well as applicable documents of the Tender specification or of the Technical specification that correspond to the definition to be justified and the associated Definition File.

These documents are usually issued by the customer of the product (CNES, ESA, NASA, etc.).

2.2 Reference documents

These constitute the bibliography that is necessary in order to prepare the Technical Specification.

2.3 Glossary

The terminology and acronyms used in the document shall be explained in this paragraph.

This consists in re-using the terminology and acronyms as listed in the Qualification/Verification matrix (see EF 5).

3. Contents of the justification file

In front of each requirement of the applicable documents (or amalgamation of requirements),the Justification File:

  • shows briefly that the choices made for the definition of the product meet the expressed needs and requirements, recall the method used to justify the definition (combination or not of simulation results, calculation results, Dependability analyses, test results, qualification results, appraisal reports, etc.), as well as main conclusions of these works,
  • details the references to the corresponding justification technical notes that show, the suitability of the product with respect to its specifications
  • recalls the main open works at the project stage where the justification file is prepared.


To make it easier to access the information, the various justification documents can be compiled into a single folder (or rendered accessible by hyperlinktext).

A definition justification table can also be prepared (see to EF 2).


RisksNon-obtainment of functional performance
Non-resistance to the environment
 RecommandationsDEFINE THE PRODUCT
Definition File
Status reports
Verification Matrix
Justification File
Assembly, Integration and Test drawing
Integration Procedure
Test Procedure and Report



Activities / documentation

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