Database with Maintenance-Driven Approach

Building Database with MDA

A maintenance-driven approach is better than tools-driven approach; although with the tools-driven approach, it's easy to get the work done once you know how to make use of the tools also tools-driven approach is good for departmental application development. 

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In a nutshell, many applications are more scope beyond that of a departmental level where you will anticipate changes often-Enterprise level. Here you will learn how to use a maintenance driven approach to creating a database that could anticipate changes. Using this approach involves the logical separation of concerns, where the presentation, domain, and the persistence layers need to work together to get the work done.

Step1: Create a project-LocalDbMDA
Then rename this project to LocalDbMDA.Presentation, This layer present the end result of the application to the end user.
LocalDbMDA.Presentation
LocalDbMDA.Presentation Diagram
Step2: Adding New Projects to the Main Project
Ideally, It is good to make the Persistence and the Presentation layers depend on the Domain
Now we need to add the 2 other layers the domain and the persistence layers by selecting from the menu for each new project.  File > Add > New Projects. Moreover, right within the new project Dialogue, choose Class Library, and be sure that the selection for the solution is changed to 'Add to Solution' and not 'Create New Solution'.
 Then named the new file LocalDbMDA.Persistence. Repeat this step to create LocalDBMDA.Domain, right after this press Cltr+Shift+B which is the shortcut key to build a solution.

Step3: Set Dependencies through Add References
Ideally, you do not want your project to depend on each other, which is the main principle of SOC. But some level of dependency is going to be needed. A project taking dependency from another one simply means a project makes reference to another one in code. Now the Reference logic that we will use for this lesson looks like this:
                      Reference                 Reference
Presentation -------------->Domain--------------> Persistence

layer, which will keep the dependency chain central to the Domain layer, like this:

                      Reference                      Reference
Presentation ---------------->Domain<--------------Persistence

Re-create the Entity Model in the Persistence Layer and also add Data Transfer Object that each layer will reference. This DTO allows data transfers access within the other 3 layers.


Note:
In order to facilitate the development of a system in a piecemeal fashion and simplify making changes in the system, its decomposition into subsystems must follow the advice of patterns of assigning responsibilities (General Responsibility Assignment Software Patterns, GRASP) like Low Coupling and High Cohesion.

Low Coupling means in this context that a subsystem should not depend too much on other subsystems. It helps us to achieve low dependency of subsystems, low change impact of subsystems, and increased reuse of the artifacts that are created during the development of subsystems.

High Cohesion means in this context that the responsibilities of a subsystem must be strongly related in order to reduce the complexity of subsystems. 

These rules are applicable to creating of a database. 

Database is a set of true propositions (facts) about the real world.
Propositions contain representation of values (data) and their interpretation.
Examples of propositions.
A car manufacturer has a numeric identifier 1 and a textual name "Toyota".

A car manufacturer has a textual name "Mitsubishi", numeric id = 2 and its description is "Rarity".


You can also check out an environment for executing SQL statements based on different SQL DBMSs and a set of SQL puzzles
You can also check these catalogs of data models, that contain logical design models of SQL databases. These help us to understand databases domains and hence are an important source of information for the creation of conceptual data models.

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