Trace time management

As a trace aims at representing an activity, time management is an important concept in the kTBS.

There are several areas where you manipulate timestamps, and we will focus at first on time management for the Stored trace.

Use ISO 8601 format for datetimes

When you want to specify a real datetime, you MUST use the ISO-8601 format and you should specify the timezone.

If you don’t specify anything the datetime string (1) will be considered as an UTC datetime as when the datetime string ends with “Z” character (2) because “Z” character is the zone designator for the zero UTC offset.

(1) "2016-01-06T08:15:00"
(2) "2016-01-06T08:15:00Z"

The timezone is specified as an UTC-time-offset, showing the difference in hours and minutes from Coordinated Universal Time (UTC), from the westernmost (−12:00) to the easternmost (+14:00).

Suppose that it is “09:15 am” in French local time on January 6th 2016, the UTC time is then “08:15 am”. To specify that your datetime string as a French datetime, you must use the UTC datetime and add the French UTC offset (+ 1 hour) at the end of the UTC datetime string (3).

(3) "2016-01-06T08:15:00+01:00"

See ISO-8601 time zones representation

Stored trace origin

Each stored trace must have an origin which should be either:

  • a datetime in ISO-8601 format, as specified above;
  • the special string now, which will be replaced by the current datetime;
  • any other string that can not be interpreted as a datetime, called an opaque origin.

If you do not configure the trace origin explicitly, an random opaque origin will be generated and associated to the stored trace.

Trace Model time-unit

The Trace time-unit is specified in the Trace Model.

The kTBS supports 3 time-units:

  • :millisecond which is the default unit
  • :second
  • :sequence

Obsels timestamps

For the sake of simplicity, we will only consider the “begin timestamp”.

When you create an Obsel in the kTBS, you may :

  • omit the “begin timestamp”
  • specify an integer “begin timestamp”
  • specify a datetime “begin timestamp”

No timestamp specified

If no timestamp is specified, the kTBS will compute the “begin timestamp”.

If the trace model unit is :second or :millisecond, the “begin timestamp” is the difference between the current datetime and the trace origin.


If the trace origin is opaque, an error will occur.

If the trace model unit is :sequence, an automatic integer numbering could be generated.


This is not yet implemented.

Integer begin timestamp

The integer value must be passed in the :hasBegin rdf parameter or in the "begin": parameter if passed in json format.

The kTBS keeps the integer as :hasBegin value.

Datetime begin timestamp

The datetime value must be passed in the :hasBeginDT rdf parameter or in the "beginDT": parameter if passed in json format.

The kTBS keeps the datetime as :hasBeginDT value and computes :hasBegin as the difference between the :hasBeginDT value and the trace origin using the trace model unit. Note that this only happens when the obsel is created. If after that the obsel is modified, and one of the timestamp (begin or beginDT), the other one will not be automatically updated.