The SEDRIS Data Representation Model
APPENDIX A - Classes
Relative Time

Class Name: Relative Time

Superclass - <Time Point>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class specifies a date and time relative to either a specified GMT (<Absolute Time>); or if an <Absolute Time> instance is not specified, relative to the simulation start time.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

This class appears on only one page of the DRM class diagram.

Example

  1. The date / time is a astronomical Julian day of 2449143.77083 (June 5, 1993 0630Z). Astronomical Julian dates are referenced to 1 January 4712 BCE at 12Z. Since the fractional days shall be converted to hours, minutes and seconds, the fields in the <Relative Time> instance are as follows.

    delta_days 2449143
    delta_hours 18
    delta_minutes 30
    delta_seconds 0.0

    The fields in the component <Absolute Time> are as follows.

    time_value. configuration SE_TIME_CFG_DATE_YMD_AND_TIME_H
    time_value. value.ymd_h. year -4712
    time_value. value.ymd_h. month SE_MONTH_JANUARY
    time_value. value.ymd_h. day_of_month 1
    time_value. value.ymd_h. hour 12

  2. The time is 6 hours 25 minutes and 30 seconds after the start of the simulation. The fields of the <Relative Time> instance are set as follows.

    delta_days 0
    delta_hours 6
    delta_minutes 25
    delta_seconds 30.0

  3. An object becomes active 20 minutes after the simulation starts. That is, its activation time is expressed in simulation time (relative to the start of the simulation), so the activation time would be specified using <Relative Time>. The time_significance field would be set to SE_TIME_SIGNIF_OCCURRENCE.

FAQs

What is the purpose of this class?

This class provides a means to specify a time relative to another time. It can be used in the same manner as <Absolute Time>.

How can a data provider indicate the Julian day of the year?

Specify a component <Absolute Time> to indicate the reference date/time as 0Z 1 January of the appropriate year. If year = -1, the date applies to any year. See example 1.

Can a data provider specify times relative to date / times other than January 1?

Yes. See example 2.

How can a data provider indicate a time relative to start of the simulation?

If a <Relative Time> does not have an <Absolute Time> component, the time is relative to the start of the simulation. See example 3.

Constraints

Composed of (two-way)

Component of (two-way) (inherited)

Inherited Field Elements

SE_Time_Significance time_significance; (notes)

Field Elements

SE_Integer delta_days; (notes)
SE_Byte_Unsigned delta_hours; (notes)
SE_Byte_Unsigned delta_minutes; (notes)
SE_Long_Float delta_seconds; (notes)

Notes

Fields Notes


time_significance

 The time_significance field specifies the significance of
 the time information.

delta_days

 The delta_days field specifies the number of days relative to
 the specified time.

delta_hours

 The delta_hours field specifies the number of hours relative
 to the specified time, after delta_days has been taken into
 account.

delta_minutes

 The delta_minutes field specifies the number of minutes relative
 to the specified time, after delta_days and delta_hours have been
 taken into account.

delta_seconds

 Fractions of the delta_seconds field value provide higher accuracy
 if needed, such as milliseconds.
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Last updated: July 16, 2004 Copyright © 2004 SEDRIS™