# Study on Effective Temporal Data Retrieval Leveraging Complex Indexed Architecture
## 5 Data Retrieval
### Proposed Select Statement Definition
Epsilon_definition can be used for both the time and positional data:  
**Epsilon_definition (time_value [_Epsilon_value [_window_frame_]])**  
**Epsilon_definition (_position_value [_Epsilon_value [_window_frame_]])**  
* **Monitored_data_set** Extending the Select statement with the Monitored_data_set clause allows you to define columns or synchronization groups in which changes need to be monitored and are relevant for further processing. The defined list does not have to be identical with the first part of the Select statement; in principle, it is possible to name any number of temporal attributes or groups of the given table, joined tables, or views, respectively. This part, unlike the first part of the Select statement definition, cannot contain non-temporal columns or function calls. Any change on the defined element forces the system to point state to the result set. Such property can be, however, too strict, resulting in providing a huge amount of data. Therefore, it is possible to extend the definition of the access approach for each element determined by the column itself, or composed from the group definition. As stated, by default, any change detection fires a new state to the output. Optional parameter extending each element determines the firing principles. The second parameter specifies the minimum number of attributes in the associated set that must change their values for such a changed state to be considered significant. This variable is specified for each element separately, if the value is not defined, the default used value representation is 1. The parameter can take any positive value, even greater than the number of attributes in the element. In this case, the entire set must be changed for the state to be considered important and directed to the output set of the Select statement. The syntax of the proposed solution is following. It is not necessary to differentiate the group and attribute itself, whereas each attribute can be considered as one element group set. **Monitored_data_set (group1 [limit _amount1, group2 [limit _amount2_]... )**  
The magnitude of the change may not always be an appropriate tool for representing the importance of change, relevance, or suitability. In the spatio-temporal environment, it may be appropriate to define a \"trigger\" by which the resulting change will be assessed. In the Monitored_data_set clause, we propose a clause extension, allowing you to specify a condition that must result in a bivalent value representing the status. Multiple conditions can be presently interconnected by the AND and OR evaluation. **Monitored_data_set (trigger_condition1 [AND trigger_condition2, OR trigger_condition3]... )**  
* **Type_of_granularity**  
The Type_of_granularity clause is placed in the proposed syntax extension after the Having clause, it is a way of formatting the result set. It defines the sensitivity and detail of displaying changes. It can take four values: OBJECT--defines granularity at the object level, it displays objects that have been changed in a defined time period. Thus, a projection of the times in which the complex state of the object has been changed is obtained--the value of at least one temporal attribute was changed. The changed values of temporal attributes of objects are obtained by setting the processing level to the type COLUMN, respectively GROUP. The difference is that the GROUP option allows you to aggregate multiple attributes into a common evaluation. In principle, the solution using the COLUMN option is a subset of the GROUP type--each attribute is a one-element set of the GROUP type. The CHANGES_MONITORING access mode displays comprehensive information about the change--a specific attribute (A\({}_{1}\)) as well as the original value (HA\({}_{11}\)) and the new value (HA\({}_{12}\))--Figure 17.  
* **NULL_category**  
Previous section deals with the undefined value categorization present in the index structure. It is modeled by the memory structure, to which individual segments of the index point.