Bridge entity

A bridge entity is used to capture a many-to-many relationship that cannot be accommodated by the natural granularity of a single fact or dimension entity. A bridge entity serves to bridge between the fact and dimension entities to support many-valued dimension attributes. A bridge entity is also useful to support relationships between dimension entities, if business users want to be able to analyze those relationships without traversing fact entities. Bridge entities of the delivered DWM support this specific usage. In this context, the cardinality of the relationship does not matter and even one-to-many relationships between dimension entities may be supported by a bridge entity. Bridge entities are sometimes historically referred to as associative entities.

Note: Ragged hierarchies are supported by a special case of bridge entities: Hierarchy bridge entity

Properties

Name (mandatory)

A textual name that identifies the bridge entity in title case (all words start with a capital letter). This name is based on the name of the dimensions that are linked by the bridge entity. The name is suffixed with Bridge.

e.g. bridge entity Involved Party Contact Information Bridge
e.g. bridge entity Product Group Bridge

Dimensional type (mandatory)

The dimensional type is set to Bridge for all bridge entities.

Owning package (mandatory)

The owning package to which the bridge entity belongs. All bridge entities are grouped in the Bridges package.

e.g. package Bridges owns bridge entity Involved Party Contact Information Bridge
e.g. package Bridges owns bridge entity Product Group Bridge

Description (mandatory)

A complete and unambiguous description of the bridge entity. This description is as precise as possible. For example, the left or right parent of the bridge can support more than one specialized dimension entity, in which case the description mentions the scope of the bridge entity.

e.g. definition of bridge entity Involved Party Contact Information Bridge: Involved Party Contact Information Bridge supports many-to-many relationships between the Involved Party Dimension or any other type of Involved Party, such as Organization Dimension, Individual Dimension, Organization Unit Dimension, Corporate Customer Dimension, Employee Dimension and the Contact Information Dimension.
e.g. definition of bridge entity Product Group Bridge: Product Group Bridge supports many-to-many relationships between the Product Dimension or the Financial Market Instrument Dimension, and the Group Dimension or any other subtype dimension of Group.

Persistent (mandatory)

A flag that indicates whether the entity is persistent or not. All entities of the delivered model are set to persistent. When the persistent flag is enabled, the entity is included in the scope of the practitioner, project, or enterprise data model.

Note: A persistent entity is physically implemented when it transforms the logical data model into a physical data model. When harvesting the data model, special care must be taken in connection with the persistent flag. For example, project A can decide to include an entity, but project B can decide not to include it. When harvesting project A at the enterprise level, the entity is set to persistent, indicating that the entity is part of the enterprise data model. Afterward, when harvesting project B at the enterprise level, care must be taken to keep the entity as persistent, although project B does not include it.

Basic attributes (optional)

One or more basic attributes that describe the bridge entity. These basic attributes may be based on the business terms that they originate from and can depend on their corresponding attributes in the Atomic Warehouse Model (AWM). A specific basic attribute that is held by most bridge entities is the Nature Of Relationship attribute, which describes the type of relationship that links the left and right dimensions. This attribute is necessary only if multiple types of relationship are supported by the bridge entity.

e.g. attribute Solicitable Flag describes bridge entity Involved Party Contact Information Bridge
e.g. attribute Nature Of Relationship describes bridge entity Involved Party Contact Information Bridge

Unique identifier (mandatory)

An attribute that identifies uniquely and without business meaning the bridge entity. By convention, the name is the name of the bridge entity, which is suffixed with Id. This sole attribute defines the surrogate primary key of the bridge entity.

e.g. attribute Involved Party Contact Information Bridge Id is the unique identifier of bridge entity Involved Party Contact Information Bridge
e.g. attribute Product Group Bridge Id is the unique identifier of bridge entity Product Group Bridge

By convention, keys that identify the left and right parents of the bridge are designed as mandatory basic attributes and do not compose the unique identifier of the bridge entity. In order to limit the number of bridge entities, some of these may have parent dimensions that spread over multiple dimension entities. The identification of the parent dimensions follows two design templates:

When a parent dimension of the bridge refers to only one dimension entity, it is identified by the foreign key representing that dimension entity.
When a parent dimension of the bridge refers to more than one dimension entity, no explicit relationship can be created and the parent dimension is identified by:
1. The value of the surrogate primary key of the dimension that is the parent of the bridge.
2. A Type attribute, which identifies the name of the actual parent dimension entity. Combining this attribute with the value of the surrogate key allows the unique identification of the parent dimension.

e.g. Attributes Involved Party Dimension Id and Involved Party Type uniquely identify the left parent dimension of bridge entity Involved Party Contact Information Bridge. The parent dimension entities supported are the Involved Party Dimension entity itself and more specialized dimension entities, such as Organization Dimension, Individual Dimension, Organization Unit Dimension, Organization Customer Dimension, Individual Customer Dimension, Employee Dimension.
e.g. Attribute Contact Information Dimension Id identifies as a foreign key the right parent dimension of bridge entity Involved Party Contact Information Bridge

Primary key (mandatory)

The primary key uniquely identifies an instance of the bridge entity and is composed of the unique identifier attribute. By convention, the name of the primary key is the name of the bridge entity, which is suffixed with PK.

e.g. primary key Involved Party Contact Information Bridge PK is the primary key of bridge entity Involved Party Contact Information Bridge
e.g. primary key Product Group Bridge PK is the primary key of bridge entity Product Group Bridge

History Support attributes (optional)

Bridge History Support is an attribute group that holds all the technical attributes required to handle history management for bridge entities. Bridge History Support is used in all bridge entities.

Current Row Indicator

An attribute that indicates whether the version represents the current values in the business reality. It eases model consumability by allowing the business user to immediately identify, among all history versions of an instance, which row represents the current values in the business reality, without having to use a more complex condition on the Effective From Timestamp and Effective To Timestamp in their query. For example, this attribute is useful for current and ad hoc analysis on dimensions without traversing fact tables.

Although the Current Row Indicator is defined as a true/false Boolean attribute, two more explicit values, such as Current and Not current can also be used.

Note: Not current is a better value than Expired, because rows may be created with values that will only become true in the business reality in the future.

e.g. attribute Current Row Indicator in bridge entity Involved Party Contact Information Bridge

Business transaction timestamps

Business transaction timestamps indicate the period during which the values of all attributes of the bridge entity instance are true in the business reality:

Effective From Timestamp: the transaction time that represents the beginning of the time period during which the values of this recorded data are true in the business reality.
Effective To Timestamp: the transaction time that represents the end of the time period during which the values of this recorded data are true in the business reality.

These timestamps can be equivalent to the timestamps of the recording in the source system (system transaction timestamps) or can be different when the data is recorded before or after it is effective in the business reality.

System transaction timestamps

System transaction timestamps indicate the period during which the values of all attributes of the bridge entity are true in the source system:

Valid From Timestamp: the transaction time that represents the beginning of the time period during which the values of this recorded data are true in the source system.
Valid To Timestamp: the transaction time that represents the end of the time period during which the values of this recorded data are true in the source system.

No overlap exists between the periods of versions of the same bridge entity.

Population information attributes

Bridge Population Info is an attribute group that holds all the technical attributes regarding the population cycle of the bridge entity. Those attributes assure a proper traceability between each instance of a bridge entity and either the Atomic Warehouse element, or the source system element, from which it gets populated. Bridge Population Info is used in all bridge entities.

Population Timestamp: An attribute that holds the time of the population cycle.
Population Description: An attribute that provides textual information about the population cycle.
Source System Name: An attribute that holds the name of the application or source system from which the entity instance was populated.
Source System Code: An attribute that holds the code of the application or source system from which the entity instance was populated.
Source System Unique Id: An attribute that holds the source system's unique identifier of the information used to populate the entity instance.

Relationships (optional)

The relationships to other entities. The bridge entity is related to one or two dimension entities, which represent the two sides of the bridge, or to no dimension entity. When a parent identifier of a bridge entity may represent more than one dimension entity, then the relationship is implicit and the foreign key is replaced by a soft link.

e.g. dimension entity Contact Information Dimension is parent of relationship is parent of / has for parent with bridge entity Involved Party Contact Information Bridge
e.g. dimension entity Alternative Identification Dimension is parent of relationship is parent of / has for parent with bridge entity Involved Party Alternative Identification Bridge

Note: A bridge entity may also be attached directly to a fact entity.

Originating Atomic Warehouse Model elements (mandatory)

One or more dependencies to the AWM elements from which the bridge entity originates. This indicates from which AWM entity, the bridge entity is populated, in an environment where this model is deployed. By convention, the name of the dependency is AWM - Data Model Mapping and the dependency type is Data Model Mapping.

e.g. bridge entity Involved Party Alternative Identification Bridge has a population dependency to the target AWM entities Involved Party Alternative Identification and Involved Party Alternative Name
e.g. bridge entity Involved Party Contact Information Bridge has a population dependency to the target AWM entities Involved Party / Email Address Rltnp, Involved Party / Location Rltnp, Involved Party / Postal Address Rltnp, Involved Party / Telephonic Address Rltnp and Involved Party / Web Address Rltnp