The data access model defines the processes that create, update, and delete the data in the system. This model identifies processes that can be re-used and ensures that the data in the system is maintained in a consistent manner (i.e., ensures data integrity by applying the same rules when adding, changing, and deleting the data). Data access processes are low-level processes that can be re-used by higher level processes (i.e., that describe business transactions) on the data flow diagram.
The data access model is entirely dependent on the data model. Therefore, a normalized data model is required before the data access model can be completed.
Data Access Model Components
The data access model contains two components.
LIST OF DATA PROCESSES
The list of data processes identifies an initial set of data access processes. Once most of the fundamental entities (i.e., real-world, tangible objects) have been identified, the data access process list can be created. These processes can then be used by higher-level processes.
The list of data access processes is presented in a tabular format and contains the following columns:
· Process Name -- Names the data access process.
· Description -- Describes why the process exists and how it is related to other processes.
The data access list should be brief and should not describe the entities and attributes affected by the data access processes.
The list should be created early in the analysis process so that higher level business processes can re-use the data access processes.
List of Data Access Processes Example
DATA ACCESS DIAGRAMS
Data access diagrams identify which entities a data access process uses and describes how the entities are updated. It also identifies which attributes are read or updated. Once the data model is stable (i.e., in third normal form), the data access diagrams can be created.
Data access diagrams promote re-use, which ensure that the data in the system is maintained in a consistent manner.
The data access diagram is a data flow diagram.
Entities accessed by the data access process are modelled as data stores.
Data flows among the data stores and processes represent the attributes that are created, read, updated, and deleted by the data access process.
Data flows into and out of the data access diagram represent the information necessary to initiate the data access process and the result of the data access process.
Data Access Diagram Example