1. SOFTWARE DESIGN DESCRIPTION (SDD)

2. IDENTIFICATION NUMBER

DI-IPSC-81435

3.1 The Software Design Description (SDD) describes the design
of a Computer Software Configuration Item (CSCI). It describes
the CSCI-wide design decisions, the CSCI architectural design,
and the detailed design needed to implement the software. The
SDD may be supplemented by Interface Design Descriptions (IDDs)
(DI-IPSC-81436) and Database Design Descriptions (DBDDs) (DI-IPSC-81437)
as described in Block 7 below.

3.2 The SDD, with its associated IDDs and DBDDs, is used as the
basis for implementing the software. It provides the acquirer
visibility into the design and provides information needed for
software support.

4. APPROVAL DATE (YYMMDD)

941205

5. OFFICE OF PRIMARY RESPONSIBILITY

EC

6a. DTIC APPLICABLE

6b. GIDEP APPLICABLE

7.1 This Data Item Description (DID) contains the format and content
preparation instructions for the data product generated by specific
and discrete task requirements as delineated in the contract.

7.2 This DID is used when the developer is tasked to define and
record the design of a CSCI.

7.3 Design pertaining to interfaces may be presented in the SDD
or in IDDs. Design pertaining to databases may be presented in
the SDD or in DBDDs.

7.4 The Contract Data Requirements List (CDRL) (DD 1423) should
specify whether deliverable data are to be delivered on paper
or electronic media; are to be in a given electronic form (such
as ASCII, CALS, or compatible with a specified word processor
or other support software); may be delivered in developer format
rather than in the format specified herein; and may reside in
a computer-aided software engineering (CASE) or other automated
tool rather than in the form of a traditional document.

7.5 This DID supersedes DI-MCCR-80012A, DI-IPSC-80691, DI-MCCR-80304,
and DI-MCCR-80306.

8. APPROVAL LIMITATION

Limited Approval from 12/5/94 through 12/5/96

9a. APPLICABLE FORMS

9b. AMSC NUMBER

N7078

10. PREPARATION INSTRUCTIONS

10.1 General instructions.

a. Automated techniques. Use of automated techniques is
encouraged. The term “document” in this DID means a
collection of data regardless of its medium.

b. Alternate presentation styles. Diagrams, tables, matrices,
and other presentation styles are acceptable substitutes for text
when data required by this DID can be made more readable using
these styles.

c. Title page or identifier. The document shall include
a title page containing, as applicable: document number; volume
number; version/revision indicator; security markings or other
restrictions on the handling of the document; date; document title;
name, abbreviation, and any other identifier for the system, subsystem,
or item to which the document applies; contract number; CDRL item
number; organization for which the document has been prepared;
name and address of the preparing organization; and distribution
statement. For data in a database or other alternative form, this
information shall be included on external and internal labels
or by equivalent identification methods.

d. Table of contents. The document shall contain a table
of contents providing the number, title, and page number of each
titled paragraph, figure, table, and appendix. For data in a database
or other alternative form, this information shall consist of an
internal or external table of contents containing pointers to,
or instructions for accessing, each paragraph, figure, table,
and appendix or their equivalents.

e. Page numbering/labeling. Each page shall contain a unique
page number and display the document number, including version,
volume, and date, as applicable. For data in a database or other
alternative form, files, screens, or other entities shall be assigned
names or numbers in such a way that desired data can be indexed
and accessed.

f. Response to tailoring instructions. If a paragraph is
tailored out of this DID, the resulting document shall contain
the corresponding paragraph number and title, followed by “This
paragraph has been tailored out.” For data in a database
or other alternative form, this representation need occur only
in the table of contents or equivalent.

g. Multiple paragraphs and subparagraphs. Any section,
paragraph, or subparagraph in this DID may be written as multiple
paragraphs or subparagraphs to enhance readability.

h. Standard data descriptions. If a data description required
by this DID has been published in a standard data element dictionary
specified in the contract, reference to an entry in that dictionary
is preferred over including the description itself.

i. Substitution of existing documents. Commercial or other
existing documents may be substituted for all or part of the document
if they contain the required data.

10.2 Content requirements.

Content requirements begin on the following page. The numbers
shown designate the paragraph numbers to be used in the document.
Each such number is understood to have the prefix “10.2”
within this DID. For example, the paragraph numbered 1.1 is understood
to be paragraph 10.2.1.1 within this DID.

This section shall be divided into the following paragraphs.

1.1 Identification.

This paragraph shall contain a full identification of the system
and the software to which this document applies, including, as
applicable, identification number(s), title(s), abbreviation(s),
version number(s), and release number(s).

1.2 System overview.

This paragraph shall briefly state the purpose of the system and
the software to which this document applies. It shall describe
the general nature of the system and software; summarize the history
of system development, operation, and maintenance; identify the
project sponsor, acquirer, user, developer, and support agencies;
identify current and planned operating sites; and list other relevant
documents.

1.3 Document overview.

This paragraph shall summarize the purpose and contents of this
document and shall describe any security or privacy considerations
associated with its use.

2. Referenced documents.

This section shall list the number, title, revision, and date
of all documents referenced in this document. This section shall
also identify the source for all documents not available through
normal Government stocking activities.

3. CSCI-wide design decisions.

This section shall be divided into paragraphs as needed to present
CSCI-wide design decisions, that is, decisions about the CSCI’s
behavioral design (how it will behave, from a user’s point of
view, in meeting its requirements, ignoring internal implementation)
and other decisions affecting the selection and design of the
software units that make up the CSCI. If all such decisions are
explicit in the CSCI requirements or are deferred to the design
of the CSCI’s software units, this section shall so state. Design
decisions that respond to requirements designated critical, such
as those for safety, security, or privacy, shall be placed in
separate subparagraphs. If a design decision depends upon system
states or modes, this dependency shall be indicated. Design conventions
needed to understand the design shall be presented or referenced.
Examples of CSCI-wide design decisions are the following:

a. Design decisions regarding inputs the CSCI will accept and
outputs it will produce, including interfaces with other systems,
HWCIs, CSCIs, and users (4.3.x of this DID identifies topics to
be considered in this description). If part or all of this information
is given in Interface Design Descriptions (IDDs), they may be
referenced.

b. Design decisions on CSCI behavior in response to each input
or condition, including actions the CSCI will perform, response
times and other performance characteristics, description of physical
systems modeled, selected equations/algorithms/rules, and handling
of unallowed inputs or conditions.

c. Design decisions on how databases/data files will appear to
the user (4.3.x of this DID identifies topics to be considered
in this description). If part or all of this information is given
in Database Design Descriptions (DBDDs), they may be referenced.

d. Selected approach to meeting safety, security, and privacy
requirements.

e. Other CSCI-wide design decisions made in response to requirements,
such as selected approach to providing required flexibility, availability,
and maintainability.

4. CSCI architectural design.

This section shall be divided into the following paragraphs to
describe the CSCI architectural design. If part or all of the
design depends upon system states or modes, this dependency shall
be indicated. If design information falls into more than one paragraph,
it may be presented once and referenced from the other paragraphs.
Design conventions needed to understand the design shall be presented
or referenced.

4.1 CSCI components.

This paragraph shall:

a. Identify the software units that make up the CSCI. Each software
unit shall be assigned a project-unique identifier.

Note: A software unit is an element in the design of a CSCI; for
example, a major subdivision of a CSCI, a component of that subdivision,
a class, object, module, function, routine, or database. Software
units may occur at different levels of a hierarchy and may consist
of other software units. Software units in the design may or may
not have a one-to-one relationship with the code and data entities
(routines, procedures, databases, data files, etc.) that implement
them or with the computer files containing those entities. A database
may be treated as a CSCI or as a software unit. The SDD may refer
to software units by any name(s) consistent with the design methodology
being used.

b. Show the static (such as “consists of”) relationship(s)
of the software units. Multiple relationships may be presented,
depending on the selected software design methodology (for example,
in an object-oriented design, this paragraph may present the class
and object structures as well as the module and process architectures
of the CSCI).

c. State the purpose of each software unit and identify the CSCI
requirements and CSCI-wide design decisions allocated to it. (Alternatively,
the allocation of requirements may be provided in 6.a.)

d. Identify each software unit’s development status/type (such
as new development, existing design or software to be reused as
is, existing design or software to be reengineered, software to
be developed for reuse, software planned for Build N, etc.) For
existing design or software, the description shall provide identifying
information, such as name, version, documentation references,
library, etc.

e. Describe the CSCI’s (and as applicable, each software unit’s)
planned utilization of computer hardware resources (such as processor
capacity, memory capacity, input/output device capacity, auxiliary
storage capacity, and communications/network equipment capacity).
The description shall cover all computer hardware resources included
in resource utilization requirements for the CSCI, in system-level
resource allocations affecting the CSCI, and in resource utilization
measurement planning in the Software Development Plan. If all
utilization data for a given computer hardware resource are presented
in a single location, such as in one SDD, this paragraph may reference
that source. Included for each computer hardware resource shall
be:

• 1) The CSCI requirements or system-level resource allocations
  being satisfied
• 2) The assumptions and conditions on which the utilization
  data are based (for example, typical usage, worst-case usage,
  assumption of certain events)
• 3) Any special considerations affecting the utilization (such
  as use of virtual memory, overlays, or multiprocessors or the
  impacts of operating system overhead, library software, or other
  implementation overhead)
• 4) The units of measure used (such as percentage of processor
  capacity, cycles per second, bytes of memory, kilobytes per second)
• 5) The level(s) at which the estimates or measures will be
  made (such as software unit, CSCI, or executable program) f. Identify
  the program library in which the software that implements each
  software unit is to be placed

4.2 Concept of execution.

This paragraph shall describe the concept of execution among the
software units. It shall include diagrams and descriptions showing
the dynamic relationship of the software units, that is, how they
will interact during CSCI operation, including, as applicable,
flow of execution control, data flow, dynamically controlled sequencing,
state transition diagrams, timing diagrams, priorities among units,
handling of interrupts, timing/sequencing relationships, exception
handling, concurrent execution, dynamic allocation/deallocation,
dynamic creation/deletion of objects, processes, tasks, and other
aspects of dynamic behavior.

4.3 Interface design.

This paragraph shall be divided into the following subparagraphs
to describe the interface characteristics of the software units.
It shall include both interfaces among the software units and
their interfaces with external entities such as systems, configuration
items, and users. If part or all of this information is contained
in Interface Design Descriptions (IDDs), in section 5 of the SDD,
or elsewhere, these sources may be referenced.

4.3.1 Interface identification and diagrams.

This paragraph shall state the project-unique identifier assigned
to each interface and shall identify the interfacing entities
(software units, systems, configuration items, users, etc.) by
name, number, version, and documentation references, as applicable.
The identification shall state which entities have fixed interface
characteristics (and therefore impose interface requirements on
interfacing entities) and which are being developed or modified
(thus having interface requirements imposed on them). One or more
interface diagrams shall be provided, as appropriate, to depict
the interfaces.

4.3.x (Project-unique identifier of interface).

This paragraph (beginning with 4.3.2) shall identify an interface
by project-unique identifier, shall briefly identify the interfacing
entities, and shall be divided into subparagraphs as needed to
describe the interface characteristics of one or both of the interfacing
entities. If a given interfacing entity is not covered by this
SDD (for example, an external system) but its interface characteristics
need to be mentioned to describe interfacing entities that are,
these characteristics shall be stated as assumptions or as “When
[the entity not covered] does this, [the entity that is covered]
will ….” This paragraph may reference other documents (such
as data dictionaries, standards for protocols, and standards for
user interfaces) in place of stating the information here. The
design description shall include the following, as applicable,
presented in any order suited to the information to be provided,
and shall note any differences in these characteristics from the
point of view of the interfacing entities (such as different expectations
about the size, frequency, or other characteristics of data elements):

a. Priority assigned to the interface by the interfacing entity(ies)

b. Type of interface (such as real-time data transfer, storage-and-retrieval
of data, etc.) to be implemented

c. Characteristics of individual data elements that the interfacing
entity(ies) will provide, store, send, access, receive, etc.,
such as:

• 1) Names/identifiers
  • a) Project-unique identifier
  • b) Non-technical (natural-language) name
  • c) DoD standard data element name
  • d) Technical name (e.g., variable or field name in code or
    database)
  • e) Abbreviation or synonymous names
• 2) Data type (alphanumeric, integer, etc.)
• 3) Size and format (such as length and punctuation of a character
  string)
• 4) Units of measurement (such as meters, dollars, nanoseconds)
• 5) Range or enumeration of possible values (such as 0-99)
• 6) Accuracy (how correct) and precision (number of significant
  digits)
• 7) Priority, timing, frequency, volume, sequencing, and other
  constraints, such as whether the data element may be updated and
  whether business rules apply
• 8) Security and privacy constraints
• 9) Sources (setting/sending entities) and recipients (using/receiving
  entities)

d. Characteristics of data element assemblies (records, messages,
files, arrays, displays, reports, etc.) that the interfacing entity(ies)
will provide, store, send, access, receive, etc., such as:

• 1) Names/identifiers
  • a) Project-unique identifier
  • b) Non-technical (natural language) name
  • c) Technical name (e.g., record or data structure name in
    code or database)
  • d) Abbreviations or synonymous names
• 2) Data elements in the assembly and their structure (number,
  order, grouping)
• 3) Medium (such as disk) and structure of data elements/assemblies
  on the medium
• 4) Visual and auditory characteristics of displays and other
  outputs (such as colors, layouts, fonts, icons and other display
  elements, beeps, lights)
• 5) Relationships among assemblies, such as sorting/access
  characteristics
• 6) Priority, timing, frequency, volume, sequencing, and other
  constraints, such as whether the assembly may be updated and whether
  business rules apply
• 7) Security and privacy constraints
• 8) Sources (setting/sending entities) and recipients (using/receiving
  entities)

e. Characteristics of communication methods that the interfacing
entity(ies) will use for the interface, such as:

• 1) Project-unique identifier(s)
• 2) Communication links/bands/frequencies/media and their characteristics
• 3) Message formatting
• 4) Flow control (such as sequence numbering and buffer allocation)
• 5) Data transfer rate, whether periodic/aperiodic, and interval
  between transfers
• 6) Routing, addressing, and naming conventions
• 7) Transmission services, including priority and grade
• 8) Safety/security/privacy considerations, such as encryption,
  user authentication, compartmentalization, and auditing

f. Characteristics of protocols that the interfacing entity(ies)
will use for the interface, such as:

• 1) Project-unique identifier(s)
• 2) Priority/layer of the protocol
• 3) Packeting, including fragmentation and reassembly, routing,
  and addressing
• 4) Legality checks, error control, and recovery procedures
• 5) Synchronization, including connection establishment, maintenance,
  termination
• 6) Status, identification, and any other reporting features

g. Other characteristics, such as physical compatibility of the
interfacing entity(ies) (dimensions, tolerances, loads, voltages,
plug compatibility, etc.)

5. CSCI detailed design.

This section shall be divided into the following paragraphs to
describe each software unit of the CSCI. If part of all of the
design depends upon system states or modes, this dependency shall
be indicated. If design information falls into more than one paragraph,
it may be presented once and referenced from the other paragraphs.
Design conventions needed to understand the design shall be presented
or referenced. Interface characteristics of software units may
be described here, in Section 4, or in Interface Design Descriptions
(IDDs). Software units that are databases, or that are used to
access or manipulate databases, may be described here or in Database
Design Descriptions (DBDDs).

5.x (Project-unique identifier of a software unit, or designator
of a group of software units).

This paragraph shall identify a software unit by project-unique
identifier and shall describe the unit. The description shall
include the following information, as applicable. Alternatively,
this paragraph may designate a group of software units and identify
and describe the software units in subparagraphs. Software units
that contain other software units may reference the descriptions
of those units rather than repeating information.

a. Unit design decisions, if any, such as algorithms to be used,
if not previously selected

b. Any constraints, limitations, or unusual features in the design
of the software unit

c. The programming language to be used and rationale for its use
if other than the specified CSCI language

d. If the software unit consists of or contains procedural commands
(such as menu selections in a database management system (DBMS)
for defining forms and reports, on-line DBMS queries for database
access and manipulation, input to a graphical user interface (GUI)
builder for automated code generation, commands to the operating
system, or shell scripts), a list of the procedural commands and
reference to user manuals or other documents that explain them

e. If the software unit contains, receives, or outputs data, a
description of its inputs, outputs, and other data elements and
data element assemblies, as applicable. Paragraph 4.3.x of this
DID provides a list of topics to be covered, as applicable. Data
local to the software unit shall be described separately from
data input to or output from the software unit. If the software
unit is a database, a corresponding Database Design Description
(DBDD) shall be referenced; interface characteristics may be provided
here or by referencing section 4 or the corresponding Interface
Design Description(s).

f. If the software unit contains logic, the logic to be used by
the software unit, including, as applicable:

• 1) Conditions in effect within the software unit when its
  execution is initiated
• 2) Conditions under which control is passed to other software
  units
• 3) Response and response time to each input, including data
  conversion, renaming, and data transfer operations
• 4) Sequence of operations and dynamically controlled sequencing
  during the software unit’s operation, including:
  • a) The method for sequence control
  • b) The logic and input conditions of that method, such as
    timing variations, priority assignments
  • c) Data transfer in and out of memory
  • d) The sensing of discrete input signals, and timing relationships
    between interrupt operations within the software unit
• 5) Exception and error handling

6. Requirements traceability.

This section shall contain:

a. Traceability from each software unit identified in this SDD
to the CSCI requirements allocated to it. (Alternatively, this
traceability may be provided in 4.1.)

b. Traceability from each CSCI requirement to the software units

to which it is allocated.

7. Notes.

This section shall contain any general information that aids in
understanding this document (e.g., background information, glossary,
rationale). This section shall include an alphabetical listing
of all acronyms, abbreviations, and their meanings as used in
this document and a list of any terms and definitions needed to
understand this document.

A. Appendixes.

Appendixes may be used to provide information published separately
for convenience in document maintenance (e.g., charts, classified
data). As applicable, each appendix shall be referenced in the
main body of the document where the data would normally have been
provided. Appendixes may be bound as separate documents for ease
in handling. Appendixes shall be lettered alphabetically (A, B,
etc.).

Translator: Simon Wright [email protected]
Last updated: 22.iii.99