Draft:Hub Star Modeling
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Hub Star Modeling is a database modeling method specialized for data integration. It simplifies the integration of reference data, master data, and transactional data in data warehouses and data lakehouses. This method was introduced by Shahram Salami in 2024 [1].
Main Components
Hub Star comprises two main components: hubs, which integrate entities from different data sources, and stars, which represent the data in relationships between these hubs.
Hubs
Hubs are classified into three types: domain hubs, reference hubs, and virtual hubs, which represent master data, reference data, and transactional data:
• Domain hubs abstractly define master data and transactional data by their business keys.
• Reference hubs define reference data with their business keys and descriptive attributes.
• Virtual hubs, including Time hub and Item hub, are not explicitly defined in the model but their keys are used in the star tables. The Time hub contains all timestamps, while the Item hub contains partial keys for week entities that lack independent business keys.
The following table represents the structure of domain and reference hubs:
| Attribute | Description | Applicable Hubs |
|---|---|---|
| LoadSoure | Metadata/ The loading source | Domain and Reference |
| ChangeTS | Metadata/ The record change/create timestamp in the source | Domain and Reference |
| LoadTS | Metadata/ The record load timestamp in the hub | Domain and Reference |
| Hub Key | A special simple (non-composite) surrogate key that can be generated by the system (as auto-increment) or be computed over business keys (using functions such as concatenation, hashes, or numeric casts) | Domain and Reference |
| Global/ Local Business Key | One of the entity natural keys, which is immutable, mandatory, and either unique globally or locally within each data source | Domain and Reference |
| Descriptives | Optional descriptive attributes including hub keys of other reference hubs | Reference |
Stars
Stars represent the data in relationship between hubs. Depending on the implementation, stars are classified as either mutable or append-only stars. Some metadata are only supported in mutable stars. Stars have the following structure:
| Attribute | Description | Applicable Stars |
|---|---|---|
| LoadSource | Metadata/ The loading source | All |
| ChangeTS | Metadata/ The source change/create timestamp of the record | All |
| LoadTS | Metadata/ The load timestamp of the record | All |
| IsDeleted | Metadata/ Has a true value if a delete operation expires the row | All |
| ChangeEndTS | Metadata/ The timestamp of expiring by the next change | Mutable |
| LoadEndTS | Metadata/ The timestamp of expiring by the next load | Mutable |
| Hub keys | Hub keys of participating hubs in the relationship including the virtual hubs | All |
| Descriptives | Attributes measured/observed in the relationship | All |
• A minimal subset of hub keys, optionally combined with LoadTS, forms the star composite primary key.
Modeling Example
These ER diagrams represent a sample source schema and the target Hub Star model. Reference hubs are prefixed with ‘Ref’, and domain hubs are prefixed with ‘Dom’. The following table shows the entity mapping between the source and target models:
| Data Class | Soure Table | Hub | Star |
|---|---|---|---|
| Reference Data | City | RefCity | - |
| Reference Data | Country | RefCountry | - |
| Master Data | Customer | DomCustomer | StarCustomer |
| Master Data | Product | DomProduct | - |
| Transactional Data | Order | DomOrder | StarOrder |
| Transactional Data | OrderDetail | - | StarOrderItem |
Hub Star Integration Matrix
The Hub Star Integration Matrix facilitates the incremental development of the target model. It shows the participation of hubs in stars at the intersections of rows and columns. For example, the following table represents the integration matrix for the previous example. (The sign × indicates that the hub key is also part of the star primary key):
| Star | DomCustomer | DomProduct | DomOrder | RefCity | RefCountry | Item | Time |
|---|---|---|---|---|---|---|---|
| StarCustomer | × | ○ | ○ | ||||
| StarOrder | ○ | × | ○ | ||||
| Example | ○ | × | × | ○ |
References[edit]
- ^ 1. Shahram Salami, “Hub Star Modelling for Data Integration,” Research Gate, May 2024. https://www.researchgate.net/publication/380910376_Hub_Star_Modelling_for_Data_Integration