> For the complete documentation index, see [llms.txt](https://docs.pentaho.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.pentaho.com/install/10.2-install/relational-data-modeling-in-pentaho/the-abstract-business-layer.md). # The Abstract Business Layer The abstract business layer is the heavy lifter in the metadata business model. The business model encompasses the abstract business layer and the business view. In the abstract business layer, you have business tables, business columns, and business relationships. You can create business tables for any physical table you have defined in the physical layer. You can also create more than one business table to reference the same physical table. The same rules apply for business columns. This can be useful in a multitude of scenarios, filtering security or even data at this level being one example. The business table keeps a reference to the physical table that it models, and this allows a metadata inheritance relationship between physical tables and business tables. If you define metadata on a physical table, the business table will inherit that metadata, unless and until the business table itself has overridden the inherited metadata. This concept operates on a metadata property to property basis, meaning that each property can be overridden individually. The same relationship exists between physical columns and business columns. If you define metadata on a physical column, the business column will inherit that metadata, unless and until the business column itself has overridden the inherited metadata. Then there are relationships. Do not confuse the term relationships here with the relationships described in the domain diagram. The relationships described here are not represented in that diagram. These relationships are mappings that you define to describe the relational (or other) bonds between your business tables. One example may be a one to many relationship between a customer table and an orders table. The strength in metadata relationships is that you can identify relationships between columns or tables in the abstract business layer that may not be obvious in the physical layer. An example would be to compare budget, actual and sales numbers, using a formula-derived business column that is specific to your business rules. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.pentaho.com/install/10.2-install/relational-data-modeling-in-pentaho/the-abstract-business-layer.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.