Data Item Description

1 Title.

2 Identification Number.

3 Description/Purpose.

3.1

3.2

3.3

1. present the preliminary design at the Preliminary Design Review(s),
2. present the detailed design at the Critical Design Review(s), and
3. use the design information as the basis for coding each CSU.

3.4

4 Approval Date.

5 Office of Primary Responsibility.

6.1 DTIC Applicable.

6.2 GIDEP Applicable.

7 Application/Interrelationship.

7.1

7.2

7.3

1. Sections 1>, 2, 3, 7, and 8 are produced during preliminary design and are presented at Preliminary Design Review (PDR).
2. Sections 4, 5, and 6 are produced during detailed design and all other sections are updated, as applicable. The complete SDD is presented at Critical Design Review (CDR).

7.4

7.5

8 Approval Limitation.

9.1 Applicable Forms.

9.2 AMSC Number.

10 Preparation Instructions.

10.1 Content and format instructions.

1. Response to tailoring instructions. In the event that a paragraph or subparagraph has been tailored out, a statement to that effect shall be added directly following the heading of each such (sub)paragraph. If a paragraph and all of its subparagraphs are tailored out, only the highest level paragraph heading need be included.
2. Use of alternate presentation styles. Charts, tables, matrices, or other presentation styles are acceptable when the information required by the paragraphs and subparagraphs of this DID can be made more readable.
3. Page numbering. Each page prior to Section 1 shall be numbered in lower-case roman numerals beginning with page ii for the Table of Contents. Each page starting from Section 1 to the beginning of the appendixes shall be consecutively numbered in arabic numerals. If the document is divided into volumes, each such volume shall restart the page numbering sequence.
4. Document control numbers. For hardcopy formats, this document may be printed on one or both sides of each page (single-sided/double-sided). All printed pages shall contain the document control number and the date of the document centered at the top of the page. Document control numbers shall include revision and volume identification as applicable.
5. Multiple subparagraphs. All paragraphs and subparagraphs starting with the phrase "This (sub)paragraph shall..." may be written as multiple subparagraphs to enhance readability. These subparagraphs shall be numbered sequentially.
6. Identifiers. The letters "X" and "Y" serve as identifiers for a series of descriptions. For example, the paragraphs and subparagraphs described by 10.1.6.1 shall be structured as follows:

       4.1 (Name and identifier of the first CSC)
         4.1.1 (Name and identifier of the first CSU)
         4.1.2 (Name and identifier of the second CSU)
         4.1.3 etc.
       4.2 (Name and identifier of the second CSC)
         4.2.1 etc.
   

7. Document Structure. This document shall consist of the following:
   1. Cover
   2. Title page
   3. Table of contents
   4. Scope
   5. Referenced documents
   6. Preliminary design
   7. Detailed design
   8. CSCI data
   9. CSCI data files
   10. Requirements traceability
   11. Notes
   12. Appendixes.

10.1.1 Title Page.

10.1.2 Table of Contents.

10.1.3 Scope.

10.1.3.1 Identification.

10.1.3.2 System overview.

10.1.3.3 Document overview.

10.1.4 Referenced documents.

10.1.5 Preliminary design.

10.1.5.1 CSCI Overview.

10.1.5.1.1 CSCI architecture.

10.1.5.1.2 System states and modes.

10.1.5.1.3 Memory and processing time allocation.

10.1.5.2 CSCI design description.

10.1.5.2.1 (CSC name and project unique identifier).

1. Identify the requirements allocated to the CSC from the applicable requirements specification(s). If the CSC is composed of sub-level CSCs, some or all of this information may be referenced and provided by the sub-level CSC description.
2. Describe the preliminary design of the CSC in terms of execution control and data flow. If a CSC is composed of sublevel CSCs, this description shall identify each CSCI internal interface documented in the Software Requirements Specification, that is to be addressed by the CSC and its sub-level CSCs, as applicable. This information may be referenced rather than duplicated for each sub-level CSC.
3. Identify the derived design requirements for the CSC and any design constraints imposed on or by the CSC. If the CSC is composed of sub-level CSCs, some or all of this information may be referenced and provided by the sub-level CSC description.

10.1.5.2.1.1 (Sub-level CSC name and project unique identifier).

10.1.6 Detailed Design.

10.1.6.1 (CSC name and project unique identifier).

10.1.6.1.2 (CSU name and project unique identifier).

10.1.6.1.2.1 (CSU name) Design specification/constraints.

10.1.6.1.2.2 (CSU name) Design.

1. Input/output data elements. Identify and state the purpose of each input and output data element to the CSU. The design information for data elements shall be provided in section 5.
2. Local data elements. Identify and state the purpose of each data element that originates in the CSU and is not used by any other CSU. Each data element shall be describe in terms of name, brief description, data type, data representation, size, units of measure, limit/range, accuracy, precision/resolution, and any other attributes of the data. This information may be provided in a CSU local data definition table.
3. Interrupts and signals. Identify and describe the interrupts and signals handled by the CSU. Identify for each interrupt and signal, as appropriate, its source, purpose, priority, expected response and response time, and minimum, maximum, and probable frequency of occurrence.
4. Algorithms. Identify, state the purpose, and describe in detail the algorithms to be incorporated into the execution of the CSU. The algorithms shall be describe in terms of the manipulation and input and local data elements and the generation of output data elements.
5. Error handling. Identify and describe the error detection and recovery features of the CSU, including handling of erroneous input data and other conditions that affect the execution of the CSU.
6. Data conversion. Identify and describe any data conversion operations performed in order to implement the CSU's interfaces.
7. Use of other elements. Describe the use of other elements that are used by the CSU including, but not limited to:
   1. Other CSU's (e.g., calls for library functions, calls for I/O services for access to databases, mass storage devices, and real-time I/O channels).
   2. Shared data stored in a global memory, (e.g., databases or data files, tables, compool, datapool, etc.).
   3. Input and output buffers, including message buffers.
8. Logic flow. Describe the logic flow of the CSU in terms of the above items. Describe the conditions under which CSU execution is initiated and, if applicable, communication interface features are invoked, and the conditions under which control is passed to other CSUs, as applicable. If sequencing is dynamically controlled during the CSCI's operations, the method for sequence control and the logic and input conditions of that method shall be describe, such as timing variations, priority assignments, internal operations such as data transfer in and out of internal memory, sensing of discrete input signals, and timing relationships between operations with the CSCI.
9. Data structures. Describe the local data structures implemented by the CSU and any shared data structures used by the CSU. Shared data structures shall be describe under one CSU and referenced thereafter by the sharing CSUs.
10. Local data files or database. If a data file(s) or a database are part of the local data of a CSU, state the purpose of each file or database, the structure of each file or database in terms of records, fields, etc., and describe the access procedures, such as sequential or random.
11. Limitations. Describe any limitations or unusual features that restrict the performance of the CSU.

10.1.7 CSCI data.

1. For data elements internal to the CSCI:
   1. Name of the data element
   2. A brief description
   3. The units of measure, such as knots, seconds, meters, feet, etc.
   4. The limit/range of values required for the data element (for constants provide the actual value)
   5. The accuracy required for the data element
   6. The precision/resolution in terms of significant digits
   7. For real time systems, the frequency at which the data is calculated or refreshed, such as 10 KHz, 50 Msec, etc.
   8. Legality checks performed on the data element
   9. The data type, such as integer, ASCII, fixed, real, enumeration, etc.
   10. The data representation/format
   11. The CSU project unique identifier where the data element is set or calculated
   12. The CSU project unique identifier(s) where the data element is used
   13. The data source from which the data is supplied, such as database or data file, global common, local common, compool, datapool, parameter, etc. When applicable, each source shall be identified by its project unique identifier.
2. For data elements of the CSCI's external interfaces:
   1. Identify the data element
   2. Identify the interface by name and project unique identifier
   3. Reference the Interface Design Document (IDD) in which the external interface is described.

10.1.8 CSCI data files.

10.1.8.1 Data file to CSC/CSU cross reference.

10.1.8.2 (Data file name and project unique identifier).

10.1.9 Requirements traceability.

10.1.10 Notes.

10.1.11 Appendixes.

11 Distribution Statement.