The SEDRIS Data Representation Model
APPENDIX A - Classes
Relative Time Point

Class Name: Relative Time Point

Superclass - <Time Point>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class is used to specify a date and time relative to either a specified GMT (<Absolute Time Point>); or if an <Absolute Time Point> 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 Julian day of the year is 64 of 1997 and the time is 0630 GMT. The fields of the <Relative Time Point> instance are:
    delta_days 64
    delta_hours 30
    delta_minutes 30
    delta_seconds 0

    and this instance has an < Absolute Time Point> with the following field values:
    year 1997
    month SE_MONTH_USE_DAY_OF_YEAR
    day 0
    hour 0
    minutes 0
    seconds 0

    If year = -1, then the date can be applied to any year.

  2. 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 Point> instance are:
    delta_days 2449143
    delta_hours 18
    delta_minutes 30
    delta_seconds 0.0

    and the fields in the associated < Absolute Time Point> are:
    year -4712
    month SE_MONTH_JANUARY
    day 1
    hour 12
    minutes 0
    seconds 0

  3. The time is 6 hours 25 minutes and 30 seconds after the start of the simulation. The fields of the < Relative Time Point> instance are:
    delta_days 0
    delta_hours 6
    delta_minutes 25
    delta_seconds 30.0

  4. 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 Point>. The time_significance field would be set to SE_TIME_SIGNIFICANCE_CONTEXT_DETERMINED.

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 Point>.

How do I indicate the Julian day of the year?
Use an association with an <Absolute Time Point> to indicate the reference date/time as 0Z 1 January of the appropriate year. If year = -1 then the date applies to any year. See example 1.

Can I specify times relative to date/times other than January 1?
Yes. See example 2.

How do I indicate a time relative to start of the simulation?
If a <Relative Time Point> does not have an <Absolute Time Point> component, then 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;
SE_Byte_Unsigned delta_hours; (notes)
SE_Byte_Unsigned delta_minutes; (notes)
SE_Long_Float delta_seconds; (notes)

Notes

Fields Notes


time_significance

 This indicates the significance of the time information.

delta_hours

 Shall be between 0 and 23

delta_minutes

 Shall be between 0 and 59

delta_seconds

 Shall be between 0.0 and 59.0
 fractions provide higher accuracy if needed, e.g. milliseconds
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Last updated: October 1, 2002 Copyright © 2002 SEDRIS™