Temporal Collection

overview

A temporal collection is a simple way to implement a Temporal Property or a Temporal Object.
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A temporal instance (either a Temporal Property or Temporal Object), when going through a series of amendments, the property itself or the properties the object references change over time. Each version of the temporal instance captures the state of the instance that will last for some period of time until the instance changes again with another amendment.​

Temporal Property vs. Temporal Object

If your underlying implementation tracks the changes of an instance at the property level but not at the object level, the implementation is Temporal Property. On the other hand, if the changes are tracked with snapshots at the object level, the implementation is Temporal Object.

When a class has a few properties that has temporal behavior and you want access to those temporal values, use Temporal Property. Whereas, if most of the properties of the class are temporal, use Temporal Object.

implementation

Temporal Collection

The basic representation and interface for a temporal collection provides get and put operations that use a date as an index:

TemporalCollection Interface

Single Temporal Collection

​The temporal collection implementation can use a Map<K,V> to keep track of the changes.

A Single Temporal Collection is an implementation of Temporal Collection. A Single Temporal Collection keeps track of changes of an instance over time - over a single kind of time. That is, the updated time which is also the effective time.

SingleTemporalCollection Class

[1] Temporal Collection is backed by a private HashMap<K,V>. This HashMap contains the values indexed by the effective date (the date of when they become effective).
​[2] milestones() returns keys (effective dates) of the MashMap in reverse order.
​[3] get() works through these milestones to find the right key (effective date). This algorithm works best when you are more likely to ask for the most recent value.
[4] Sorts the specified list into reverse order. All elements in the list must implement the Comparable interface.

Bi-Temporal Collection

A Bi-Temporal Collection is also an implementation of Temporal Collection. A Bi-Temporal Collection keeps track of changes of an instance over time. Two kinds of time are involved. That is, the updated time and the effective time of the change, both times can be different.

BiTemporalCollection Class

examples

Let's use the written Single Temporal Collection toward a Temporal Property (Addresses) of a Customer class:

Code Editor

[1] Addresses is a Single Temporal Property

references

• Temporal Object
• Temporal Property​
• Java – Collections sort() method
• Jetbrains / MPS​​