Logs

An important feature of the system is its integrated record history. Before processing a data modification request (i.e. deletion or update) on a record, first a snapshot of the current record data is created together with all related entities. Then, the modification request is evaluated and the resulting final re-cord data is compared with the snapshot data to determine whether any changes have occurred or not. If changes are found, the snapshot data is compressed and stored in the database together with infor-mation on type, date and user of the request.

Data display functions of the system, which retrieve data from the database and generate output for presentation, are developed in such a way that they can work on both current and historical data. In other words, they can process historical data and create output as if they were processing recent data in the database. The system is capable of comparing output generated by the display functions and can automatically determine and mark differences between them.

Log records are used to store and visualize historical record data. Type and ID of the record, date and type of the action (insert, update and delete), name of the user who performed the action, and the pres-ence of a parent log are indicated in each log report. The record information is displayed in such a way that parts of a record that are added, changed or removed between two points in time are highlighted. Added or deleted information can be toggled on and off, so that only the initial or the final state of the record is obtained (Figure 1).

Logs can be listed by the type and date of action. The record type and record ID can also be specified. If needed, logs belonging to a certain user can be listed. Listed logs can be sorted by date, action, record type, and record ID (Figure 2).

Log records allow the administrators to follow the actions of the users and the data evolution stored in each record. In case improper actions are noticed, such as removal of valuable information or insertion of inappropriate data, they can be rolled-back using the historical data in the log records.