Description of database models
Creating a database model is done through the project's explorer in the "Data Models section. (data models). To do this, call the context menu of this section (right mouse button) and select the item "New Logical Data Model (in the case of creating a logical model of the database). In addition to the logical model, through this context menu the developer can create a physical database model, define a glossary of names for use in object names (entities, attributes), a domain model (user-defined data types), a logical and physical model for multivariate analysis (data warehouse), configure transformation (transformation) of models of different levels during the transition from one level to another.
Creating a logical model begins with the definition of the basic template of the model (Figure 3.42), which can be generated by the user and used to create new models, or made earlier by the developers of the tool. The project for which the model is created is also defined. In the case of creating a new model through the mechanism of the context menu of the open source project model (Data Models) - the name of the project - the model owner is determined automatically, but the developer can change this binding. The model name is also defined within the project, which should give an opportunity to unambiguously understand the essence of the data presented in the model and the relation to the domain.
Fig. 3.42. Fixing the location and name of the logical model of the database
One of the features of the IBM InfoSphere Data Architect tool is the fact that developers can create several models within a single project, dividing them according to a functional feature related to the selection of subject areas or the content of the database for which a logical model is created. Usually, when a database is projected, the developer, based on the analysis of the subject area and the specifics of the implementation of information security requirements, understands which separate databases the information component of the projected system should be divided into. This allows you to define the set of models that you need to create when modeling a database.
Creating a database model, the developer specifies it, defining the basic characteristics (Figure 3.43) and a description of the model being created using the following properties:
• Name - the exact name of the database model defined in the analysis of the subject area, highlighting the information essence of the data stored in it;
• Location - the physical location of the database model repository file that has the extension "*. ldm & quot ;;
• Size - the actual size of the database model repository on the hard disk;
• Compress diagrams - a sign of the need to compress, in order to reduce the size of the repository file, create graphical diagrams of the database model;
• Last Modified - the date of the last correction of the database model;
• Editable is a fixed sign of the ability to edit a database model.
Fig. 3.43. Description of the basic properties of a logical model
The specified properties, except the "Compress diagrams" property, are predefined, some of which are specified at the time the database model was created. The Compress diagrams can be changed, which will lead to its application and changing the size of the database model database repository according to the specified solution: the selected box shortens the file size, compressing the graphical image of the diagrams, the absence of the check box selects a larger file size without compression of the diagrams.
In addition to the basic properties, the developer is able to specify in the section "Intellectual Property Information"; (Information about intellectual properties) information about the author and the owner of the model (Figure 3.44):
- Author (author) - indicates the person or persons who participate in the development of the database model being created;
- Company (organization) - indicates the organization where the database model is being developed;
- Version - specifies the version of the logical database model;
- Copyright (copyright) - indicates the organization, person or persons who own the database model.
Fig. 3.44. Additional properties of the logical model of the database
Of particular note is the property "Copyright" (copyright), since the right to own a model may be owned by individuals or organizations that are not developers. This is explained by the fact that the development of an information system can be carried out at the request of the contracting authority and then the right to the database model will belong to it, and not to the development organization. At the same time, if the development organization creates a unique mechanism for working with data that is implemented in the solution for the customer, the right to the model of the implemented mechanism can belong to the developer organization. Given that it is necessary to create documentation for each model and for each stage of development of the information system, the correct indication of copyright will avoid many of the difficulties associated with resolving ownership disputes and the possibility of using and distributing elements, including models, of an information system.
In the Data Model Documentation (documenting the data model), the developer gives a meaningful description of the database model being formed.
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