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XPath Keywords and System Variables
/refguide8/xpath-keywords-and-system-variables/
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1 Overview

In XPath, several keywords and system variables can be called as a comparison.

2 Keywords

Either of these keywords can be used to check whether an attribute has a value (any value) or if it has been left empty:

  • NULL
  • empty

2.1 Example

This query returns all the customers whose name is not known to the system:

//Sales.Customer[Name = NULL]

These keywords can only be used in conjunction with attributes. The existence of associations cannot be confirmed in this manner. For more information on how to constrain on associations, see XPath Constraint Functions.

3 System Variables

System variables can be used to obtain system or date related values. The available tokens are described below.

3.1 Object-Related

Token Description
[%CurrentUser%] The GUID of the user currently logged in.
[%CurrentObject%] The GUID of the active object (in the context).

3.2 User Roles

These will be created for each user role in your app. Here is an example:

Token Description
[%UserRole_Administrator%] The Administrator user role.

Here is an example for retrieving that user role:

{{< figure src="/attachments/refguide8/modeling/xpath/xpath-constraints/xpath-keywords-and-system-variables/user-role.png" class="no-border" >}}

3.3 Time-Related {#time-related}

The following tokens can be used to obtain a date and time value:

Token Description
[%CurrentDateTime%] The current date and time.
[%BeginOfCurrentMinute%] The date and time at the beginning of the current minute.
[%BeginOfCurrentMinuteUTC%] The date and time at the beginning of the current minute in UTC.
[%EndOfCurrentMinute%] The date and time at the end of the current minute.
[%EndOfCurrentMinuteUTC%] The date and time at the end of the current minute in UTC.
[%BeginOfCurrentHour%] The date and time at the beginning of the current hour.
[%BeginOfCurrentHourUTC%] The date and time at the beginning of the current hour in UTC.
[%EndOfCurrentHour%] The date and time at the end of the current hour.
[%EndOfCurrentHourUTC%] The date and time at the end of the current hour in UTC.
[%BeginOfCurrentDay%] The date and time at the beginning of the current day.
[%BeginOfCurrentDayUTC%] The date and time at the beginning of the current day in UTC.
[%EndOfCurrentDay%] The date and time at the end of the current day.
[%EndOfCurrentDayUTC%] The date and time at the end of the current day in UTC.
[%BeginOfCurrentWeek%] The date and time at the beginning of the current week.
[%BeginOfCurrentWeekUTC%] The date and time at the beginning of the current week in UTC.
[%EndOfCurrentWeek%] The date and time at the end of the current week.
[%EndOfCurrentWeekUTC%] The date and time at the end of the current week in UTC.
[%BeginOfCurrentMonth%] The date and time at the beginning of the current month.
[%BeginOfCurrentMonthUTC%] The date and time at the beginning of the current month in UTC.
[%EndOfCurrentMonth%] The date and time at the end of the current month.
[%EndOfCurrentMonthUTC%] The date and time at the end of the current month in UTC.
[%BeginOfCurrentYear%] The date and time at the beginning of the current year.
[%BeginOfCurrentYearUTC%] The date and time at the beginning of the current year in UTC.
[%EndOfCurrentYear%] The date and time at the end of the current year.
[%EndOfCurrentYearUTC%] The date and time at the end of the current year in UTC.

The following tokens can be used to add or subtract a period of time from a date and time token value:

Token Description
[%DayLength%] The length of one day (24 hour).
[%HourLength%] The length of one hour.
[%MinuteLength%] The length of one minute.
[%SecondLength%] The length of one second.
[%WeekLength%] The length of one week (seven days).
[%MonthLength%] The length of one month.
[%YearLength%] The length of one year.

{{% alert color="info" %}} These variables must be used as string values and placed between two quotes. Time-related tokens combined with period-related tokens must be placed within one string. See example 3. {{% /alert %}}

3.3.1 Examples

This query returns only customers who have registered since the beginning of this week:

//Sales.Customer[DateRegistered >= '[%BeginOfCurrentWeek%]']

This query returns only customers who have registered this week:

//Sales.Customer[DateRegistered >= '[%BeginOfCurrentWeek%]' and DateRegistered < '[%EndOfCurrentWeek%]']

This query returns only customers who have registered in the past three years:

//Sales.Customer[DateRegistered > '[%BeginOfCurrentDay%] - 3 * [%YearLength%]']

This query returns users with the role "Administrator":

//System.User[System.UserRoles = '[%UserRole_Administrator%]']

{{% alert color="info" %}} Because system variables are written as a string (between quotes), it is not possible to use parentheses to group expressions. {{% /alert %}}