Maintain Date Alias Instances (of a particular date alias) - CALF0511

Purpose

To allow the creation, display, modification and deletion of date alias instances of a selected date alias.

Note that whereas in this form the context is a date alias record, in CALF0512 the context record is a calendar instance. Both forms allow for the display and maintenance of date alias instances.

Subsystem

Calendar

Structure

Three Blocks

Date Alias

Date Alias Instance

Date Alias Instance Offset

Date Alias Instance Pair

 

Navigation Buttons invoke

Date Alias Instance Pair overlay

Maintain Date Alias Instance Offset Constraint form

Image

 

Date Alias

Explanation

Date alias instances are the specific occurrences of a date alias, generally defined by having a date and being attached to a calendar instance.

This context block displays the date alias for which existing date alias instances can be displayed, modified or deleted or new ones created in the block below. Only one date alias is displayed and this is brought forward from the Maintain Date Aliases form. To display another date alias it is necessary to return to the Maintain Date Aliases form and query the new date alias.

Data in this block is protected and cannot be updated.

Example

A date alias CENSUS may represent the data collection dates of statistics required by government. One occurrence of this date alias assigned to a calendar instance for semester 1, 1996 (SEM-1, 1/1/96, 30/6/96) represents the census date for first semester 1996 on 31/3/96.

Date Alias Instance

Explanation

The assigning of a calendar instance and a date to the date alias has created a date alias instance. One exception is that where a date alias is assigned to a calendar instance with a system status of PLANNED, a date of occurrence is not required immediately but must be added before the calendar instance is made 'active'.

A date alias can have many instances.

This block displays the existing date alias instances, and the calendar instance to which they belong, for the context date alias. It allows the creation, deletion and modification of date alias instances.

Example

 

To add an instance of the context date alias to a calendar instance, using the Maintain Date Alias Instances form:

  1. Select any record in the Date Alias Instance block.
  2. Enter Insert mode.
  3. Select the desired calendar instance from the list of values in the Calendar Type field.
  4. Enter an absolute value, i.e. the date of occurrence of this instance OR
  5. Enter a date alias instance offset (see Date Alias Instance Offset )
  6. Save

Rules:

  • On entering an absolute value date for a date alias instance which already has a date derived by offset, the absolute value will override the derived offset value.

To modify an instance of the context date alias, using the Maintain Date Alias Instances form:

  1. Select the Absolute Value field to be modified.
  2. Enter the new date.
  3. Save.

Rules:

To delete an instance of the context date alias from a calendar instance, using the Maintain Date Alias Instances form:

  1. Select the record to be deleted.
  2. Delete record.
  3. Save.

Rules:

  • A date alias instance cannot be deleted if another instance is offset from it.

Date Alias Instance Offset

Explanation

The Date Alias Instance Offset block is used for defining the date value of a date alias instance in terms of its relationship to another date alias instance. It is possible to ensure that no matter what date is assigned to the offset date alias, the subject date alias instance will not fall on specified days. This is achieved by specifying Offset Constraints in CALF0520, accessed via the navigation button in this form.

Example

A date alias instance for the end of semester 1 examinations could be defined as occurring 3 weeks after the date alias instance for the commencement of semester 1 examinations.

To create a date alias instance offset for the selected date alias instance, using the Maintain Date Alias Instances form:

  1. Select the Offset Date Alias field in the Date Alias Instance Offset block.
  2. From the list of values in the Offset Date Alias field select the date alias instance from which the current date alias instance will be offset.
  3. Enter the offset duration in any combination of days, weeks, months and/or years. Values may be positive or negative. Notice that the offset alias value (i.e. the date from which the new date alias instance will be offset) is displayed.
  4. Save.

Rules:

  • If an absolute value for a date alias instance already exists, the creation of an offset will not override it.

To modify a date alias instance offset using the Maintain Date Alias Instances form:

  1. Select the date alias instance offset record to be modified.
  2. Change the offset duration to the new values.
  3. Save.

Rules:

  • Only the offset duration can be modified. To specify an offset from a different date alias instance the current date alias instance offset must be deleted and a new offset created.

To delete a date alias instance offset using the Maintain Date Alias Instances form:

  1. Enter an absolute value for the date alias instance in the Date Alias Instance block.
  2. Select the date alias instance offset record to be deleted.
  3. Delete record.
  4. Save.

Rules:

  • An absolute value for the date of occurrence of the date alias instance must be entered in the Date Alias Instance block prior to deleting the offset record.

Date Alias Instance Pair

Explanation

The pairing of date alias instances indicates that the two dates plus every day between the two dates are represented by the relationship. When a date alias instance pair is created using alias instances in calendars of category HOLIDAY, it effectively defines an institution break, one of the System Date Offset Constraint Types.

A pair relationship can also be defined at the date alias level in CALF0420.

Example

A date alias instance ST-BREAK, 15/05/1999 is created in a calendar of category HOLIDAY, and it is paired with the date alias instance END-BREAK, 30/05/1999, also in a holiday calendar, the System recognises the period 15/05/99 - 30/05/99 inclusive as an institution break.

To create a date alias instance pair, using the Maintain Date Alias Instances form:

  1. With the date alias instance to be paired selected in CALF0511, select the Date Alias Instance Pair navigation button. The Date Alias Instance Pair overlay is displayed.
  2. Select the other half of the pair in the Related Date Alias field. Tabbing or saving causes the Related Alias value to display.
  3. Save.
 

Changes within this form will have the following notable effects:

  • Altering the date of a date alias instance will also alter the date of any date alias instances which are offset from it.
  • Altering the offset duration of a date alias will also alter the date of any further date aliases which are offset from it.