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Interface Design Description (IDD)
The Interface Design Description (IDD) describes the interface characteristics of one or more systems, subsystems, Hardware Configuration Items (HWCIs), Computer Software Configuration Items (CSCIs), manual operations, or other system components. An IDD describes any number of interfaces.
The IDD is used to supplement the System/Subsystem Design Description (SSDD), Software Design Description (SDD), and Database Design Description (DBDD). The IDD and its companion Interface Requirements Specification (IRS) serve to communicate and control interface design decisions.
1. Scope
This section is divided into the following sub-sections.
1.1 Identification
This sub-section contains a full identification of the system(s), the interfacing entities, and interfaces 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 sub-section briefly states the purpose of the system(s) and software to which this document applies. It describes 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 sub-section summarizes the purpose and contents of this document and describes any security or privacy considerations associated with its use.
2. Referenced Documents
This section lists the number, title, revision, and date of all documents referenced in this document. This section also identifies the source for all documents not available through normal Government stocking activities.
3. Interface Design
This section is divided into the following sub-sections to describe the interface characteristics of one or more systems, subsystems, configuration items, manual operations, or other system components. If part or all of the design depends upon system states or modes, this dependency is indicated. If design information falls into more than one sub-section, it is presented once and referenced from the other sub-sections. If part or all of this information is documented elsewhere, it is referenced. Design conventions needed to understand the design are presented or referenced.
3.1 Interface Identification and Diagrams
For each interface identified in 1.1, this sub-section states the project-unique identifier assigned to the interface and identifies the interfacing entities (systems, configuration items, users, and so on.) by name, number, version, and documentation references, as applicable. The identification states 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 are provided, as appropriate, to depict the interfaces.
3.2 (Project Unique Identifier of Interface)
This sub-section (beginning with 3.2) identifies an interface by project unique identifier, briefly identifies the interfacing entities, and is divided into sub-sections 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 IDD (for example, an external system) but its interface characteristics need to be mentioned to describe interfacing entities that are, these characteristics are stated as assumptions or as “When [the entity not covered] does this, [the entity that is covered] will ….” This sub-section 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 includes 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, and so on) to be implemented
c. Characteristics of individual data elements that the interfacing entity(ies) will provide, store, send, access, receive, and so on such as:
1. Names/identifiers
a) Project-unique identifier
b) Non-technical (natural-language) name
c) DoD standard data element name
d) Technical name (for example, variable or field name in code or database)
e) Abbreviation or synonymous names
2. Data type (alphanumeric, integer, and so on)
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, and so on) that the interfacing entities will provide, store, send, access, receive, and so on, such as:
1. Names/identifiers
a) Project-unique identifier
b) Non-technical (natural language) name
c) Technical name (for example, 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 entities 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 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.)
4. Requirements Traceability
This sub-section contains:
a. Traceability from each interfacing entity covered by this IDD to the system or CSCI requirements addressed by the entity’s interface design.
b. Traceability from each system or CSCI requirement that affects an interface covered in this IDD to the interfacing entities that address it.
5. Notes
This section contains any general information that aids in understanding this document (for example, background information, glossary, rationale). This section includes 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.
6. Appendixes
Appendixes may be used to provide information published separately for convenience in document maintenance (for example, 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 are lettered alphabetically (A, B, and so on).
