3.1 DEVELOP SYSTEM/SUBSYSTEM SPECIFICATIONS
The primary focus of this activity is to develop and describe the detailed
design of the system/subsystems. The development team analyzes the functions,
described during the Define System phase, and determines which functions
logically may be processed together to form a subsystem. The development
team documents the system/subsystem specifications that are used to partition
the system/subsystem and hierarchically decompose it to the lowest-level
functions. The system/subsystem specifications comprise the system detailed
design. The following activities are performed to develop the system/subsystem
specifications:
Table 3-3 defines the roles and responsibilities of key personnel for
acquiring and installing system components.
Table 3-3. Roles and Responsibilities for Developing
System/Subsystem Specifications
| Project Manager |
Coordinates development of system/subsystem specifications. |
| User |
Defines system/subsystem specifications. |
| Developer |
Defines and prepares system/subsystem specifications. |
| Project Data Administrator |
Analyzes data requirements. |
| Quality Assurance |
Reviews system/subsystem specifications for adherence to standards.
|
3.1.1 Analyze Functional Requirements and Data Requirements
The project development team performs a detailed study of the functional
and data requirements developed during the Define System phase to determine
which requirements and data logically may be processed together. The logical
groupings of requirements and data are subsystems.
3.1.2 Describe System/Subsystem Specifications
Develop a description of the system/subsystem specifications. If a prototype
was developed earlier in the lifecycle, include those specifications defined
with the prototype. For each system/subsystem, include such information
as timing requirements, equipment needs, communication environment, support
software, security, and input and output records. During the process of
describing the system/subsystem specifications, the project development
team performs the following actions:
- Partition the functional and data requirements into logical subsystems.
- Document the traceability between the functional and data requirements
and the defined subsystems.
- Characterize the features incorporated in the design of the system/subsystem
that meet the accuracy and validity requirements imposed on the system/subsystem
during the Define System phase.
- Determine the timing requirements imposed on the system/subsystem under
varying conditions.
- Determine the system/subsystem's capabilities for adapting to changing
requirements, and document how these capabilities are incorporated into
the system/subsystem's design. Identify those procedures and components
designed to support failure contingencies.
- Identify the equipment needed for the operation of the system/subsystem.
Include a description of the equipment that is currently available as well
as the characteristics of any new equipment requirements that may be necessary
for the system/subsystem to operate correctly.
- Identify the system/subsystem's data communications environment. Develop
detailed schematics of the portions of the communications environment that
directly relate to the system/subsystem.
- Identify the software with which the system/subsystem must interact.
Include both support software and test software, if needed. Provide the
correct name, description, and documentation references of each such software
system, subsystem, and program. Include a reference to the language (compiler,
assembler, program, query) and to the operating system to be used. If operation
of the computer programs to be developed is dependent on forthcoming changes
to other software, identify and discuss the nature, status, and anticipated
availability date of such changes.
- Outline the potential threats to the system/subsystem and the security
measures that have been incorporated to reduce or eliminate those threats.
An example would be the threat of unauthorized access being reduced by
incorporating into the design a password requirement at all system/subsystem
access points. List and describe all controls that have been incorporated
in the system/subsystem design; for example, batch controls on the entry
of financial data.
- Identify the input and output data and reports. For inputs, provide
information about the characteristics of each input to the system/subsystem,
such as file name, format and type of data, validation criteria, volume,
frequency, means of entry, source documents and their disposition, and
security and privacy considerations. For output, provide file names, report
formats, selection criteria for displays or outputs, types of output media,
and disposition of products.
3.1.3 Perform Walkthroughs
Arrange one or more review walkthroughs to educate the attendees on
the system/subsystem design and specifications. Include representatives
from 1) other development and maintenance teams whose programs interface
the system/subsystems being designed, 2) the system acceptance test team
staff, 3) and user and sponsor organizations. Choose a walkthrough moderator
to record action items and track them to completion. Incorporate feedback
from the attendees into the design and specifications.
3.1.4 Document System/Subsystem Specifications
Prepare the System/Subsystem Specifications document in accordance with
SBA SDM documentation standards .
Update the requirements traceability matrix to reflect the allocation
of system objectives to system/subsystem design components.
*Last Modified: 11-16-01
