18.104.22.168 Data Dictionary (DatD)
This product contains all information about the data used in SW Units (individual data and complex structures). It can be generated manually-but it is better with the help of a tool. The information is collected and administered in activity CM4.1 - Data Administration.
The input information for the Data Dictionary is delivered by the SW Architecture and SW Design. The Data Dictionary must contain the identifiers, the characteristics and attributes of the data structures and its elements (data description). Also important is information dependent on the implementation (data realization).
Such a product exists for each project.
1. General Information
2. Data Description
3. Data Realization
See schema 1. General Information.
The tabular description contains the following information:
The following information has to be given:
unique identifier of the data elements chosen in accordance with the conventions of the programming language and project rules for identification in the CM Plan
- long name
the long name describes the content and the use of the data elements
- relations within a data element
e. g. structuring into record-field-item, identifying key, etc.
- relations to other data elements
e. g. redundancy, dependencies with regard to contents or time
- physical unity and normalization
Decisive for processing a datum is its physical unity. Is a temperature given in Centigrade, Fahrenheit, or Kelvin? A distance given in kilometers or miles?
identifiers of data elements are given into which the (complex) data is structured
- defining SW Component/SW Module
A data element is only defined by a SW Component or SW Module. The identifier is given here.
- referencing SW Component/SW Module
All SW Components and SW Modules referencing (using) the data element are listed by giving its identifier and kind of reference:
- special characteristics and attributes
- data type and size
in the case of scalar data: e. g. integer, real, char, and number of digits,
in the case of composite data: e. g. record, array, and description of individual fields analogously to scalar data
- range and domain
- default setting
kind of access (e. g. sequential, indexed) and identifying key
- life time
generation times and frequencies
- memory space requirements
calculated from data type and format, while considering HW dimensioning
If memory has to be allocated statically the addresses are taken from the cross-reference listings of the compilers and/or linkers.
It is to list the start address; for parts of data elements the address relative to the beginning of the structure must be given. A note is required if a relative address is concerned.
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