Conceptual Schema (ER)

Conceptual schema is created in the entity relationship notation. You create a normalized model without redundancies to your business data.

Use the following model elements when modeling the conceptual schema:

• Entity Relationship Diagram

  An ER diagram graphically displays a partial model of the conceptual schema. Entities are shown as nodes and relationships are shown as edges. The user can choose the notation they want in Options in the application menu.

  Innovator supports the following diagram notations:

  • James Martin (crow's foot)

  • Chen (min,max)

  • Data Structure Analysis (DSA)

  • Unified Modeling Language (UML)

  • Structured Entity Relationship Model (SERM)

  The main difference between these notations is how they display relationships, whose cardinalities are illustrated with various different graphic icons or formal texts in different places.

  Views can also be displayed as nodes and their From clauses as edges.

• Entity

  Is the set of entities of the same type of the business world to be modeled. Entity set describes this well but the term instance is common place when talking about an entity in this set.

• Entity Relationship

  Relationships are modeled between entities. A relationship is a complex element that always contains two roles which link entities which are related to each other.

  A relationship can be hierarchical. In this case, an instance in the dependent element is related to another instance in another entity which is not modified throughout its entire lifecycle. This is normally achieved by the relationship's foreign keys being part of the dependent entity's primary key. This is why you normally speak about identifying relationships and call their dependent entities weak.

• An Entity Relationship's Role

  A relationship's role shows which role the entity has when it takes part in the relationship. An important characteristic of a role is how often the entity can have such a relationship. You can enter how many relationships an instance has to have (minimum) and can have (maximum).

• Generalization Relationship

  The generalization relationship (generalization for short) is certain type of relationship which links two entities in the sense of super and sub type. You can also talk about subordinate and superordinate entities.

• Generalization Set

  A generalization set combines various generalization relationships of a super entity with various sub entities. This is otherwise known as categorizing. The generalization set dictates whether the combined generalization relationships map a categorization with precisely one sub instance (is one), with an optional sub instance (partial) or with possible instances in various sub entities of theirs (overlapping). Each generalization relationship of the ER model needs to be assigned to precisely one generalization set in Innovator.

• Entity Attribute

  An entity's attributes describe an instance's properties.

• An Entity's Key

  A key is a subset which can uniquely identify attributes of its entity using their instance. If the key attributes' value remains forcibly unchanged throughout the whole lifecycle, this is a so-called key candidate. The primary key which is best suited for implementing a relationship using a foreign key is chosen from the key candidates. If an entity in the real world does not have any key candidates, an artificial key which contains an integer attribute especially modeled for this is normally defined.

• An Entity's Foreign Key

  A foreign key in the ER model implements a relationship. A foreign key is created in the dependent entity for each key attribute of the referenced key. The referenced key cannot merely reference a primary key; it can also reference an alternative key of the relationship entity.

• Value Verification

  A value verification constrains the possible values of attributes. It is the pendant to an SQL check constraint from the DB model.

• View

  A view combines the attributes of one or more entities in a table. This may mean that a view's rows contain redundant data.

  We will use the term attribute set as an umbrella term for an entity or view throughout this help.

• A View's Attribute

  The values of view attributes are obtained from values of the attributes used. This means that it is also possible for calculation expressions with functions to be used.

• From Clause

  A view contains one or more From clauses which determine which attribute set the view's content is taken from. The attributes of these attribute sets are used for calculating the view attribute's value.