Overview

You map the structure of your application in DataView with the aid of the entity relationship model (ERM). The ERM consists of logic model objects, that can be physically represented in the database in the form of tables. The tables will later store the user data. All model objects can be represented on the user interface in the form of default masks, so that you can work with test data in the tables already during model definition. After model definition you can use copies of the default masks as a starting point for the creation of complex masks.


Logical Model Objects in the ERM

The following model objects can be used for the development of an ERM:

Entity
In entities user data with similar features are logically combined.

Entity Type
In entity types (also called type instance of an entity) you form sub-objects for an entity, in order to be able to manage data elements with deviating additional features in one entity.

Relation
With relations you combine two sets of data elements, which are combined in entities and manage specific features of that relation. There are three kinds of relations - 1:1-, 1:n and n:m relation. The combination of the data elements is implemented via an intern number mechanism.

Link
With regard to the logical structure in the data model a link is a relation. As opposed to a relation it is not realized using the internal number mechanism, but via key fields which must be realized manually.

Example: Entity Relationship Model for the application of a small medical supply firm meditronic.

The meditronic-ERM contains all possible model objects and the most important model structures. Meditronic buys different medical devices (entity Item) from several suppliers (entity Supplier). The devices are of different kinds (type instances Endoscope and Instruments). All devices are stored (entity Warehouse) and described by different documents (entity Document). In order to model the interrelations of storage, buying and describing, the entities are combined with each other by relations and links.


Mapping of Model Objects in the Database

DataView maps each model object (with the exception of links) as two-dimensional table. These tables always contain all data elements (user data) in the form of records. The features of the data elements are described by attributes in the fields (columns) of the table. Which columns the table contains depends on the model object mapped:

Master Table
Each entity is mapped in a master table. It contains columns to store master attributes.

Type Table
Each type instance of an entity is mapped in a type table. It contains columns to store type-specific additional attributes.

Relation Table
Each relation between entities is mapped in a relation table. It contains columns to store relation attributes.

No Link Table
There is no database table for a link. The link is only a logical mode object in the data model.

You can additionally map entities as -> Views in the database. With the help of views you are able to set up different, task-specific user views on data already on modelling level.

Example: For the meditronic-ERM the following tables are created in the database.


Mapping Model Object on the Desktop (Default Masks)

You can create default masks for all model objects (with the exception links). The masks show table data (user data) on the user interface and allow the manipulation of these data with the aid of automatically installed standard functions (search, edit, delete, show dependent data...). With default masks you map the created data model in minimized form on the user interface. After this you can work with test data. Simultaneously the default masks are the starting point for creating complex masks and their integration into the interactive flow of the future application. Depending on model object, a default mask shows the object-specific attribute fields of one or several database tables:

Master List or -Form
For each entity a default master list or a default master form can be created. Both display the master attribute fields of the master table or view fields.

Type List or -Form
For each type instance of an entity a default type list or a default type form can be created. Both display the first master attribute field of the master table (significant field) and the type-specific additional attribute fields of the type table.

Refine and Aggregate List
For each relation a default list refine and a default aggregate list can be created. Both display the first master attribute field of the master table, that contains the child elements and the relation attribute fields of the relation table.

Link Mask
For links no default masks can be created. Masks with attribute fields of linked tables must be manually created. To do so, you will usually extend existing default masks of a model object by attribute fields of the linked model object. Masks that are created that way, will be subsequently called link masks.

Example: For the meditronic-ERM the following default masks could be immediately created and displayed on the desktop (selection).