BUS Matrix

A Bus Matrix is a critical tool used to connect and reconcile data across multiple systems during the data modelling process. This guide will walk you through the core concepts and step-by-step process for constructing and populating a Bus Matrix, addressing key challenges, and mastering your data integration.

Prerequisites

Before starting, ensure you have access to:

• A data warehouse with connected sources.
• A clear understanding of the entities and sub-entities within your system.

Example BUS Matrix during project delivery:

1. Understand the Core Concepts

1.1 Data Warehouse Structure

In a typical data warehouse, data is sourced from various third-party systems. These systems contain different types of information, which are then brought into the data warehouse through connectors and extracts.

Sources: External systems like CRM, payment systems, or analytics tools.
Raw Staging Area: This is where data from sources is initially landed in the warehouse for processing.

1.2 Entities and Sub-Entities

Entities: Unified concepts across all your data sources like Customer, Product, or Transaction.
Sub-Entities: These are entities as they exist within the context of a single system only. For example: the customer sub-entity from Salesforce must be combined with other systems customer sub-entities to give rise to the customer entity.

2. Setting Up the Bus Matrix

A Bus Matrix connects different sub-entities and systems by defining how data should be joined across sources.

2.1 What is a Bus Matrix?

The Bus Matrix is a table that shows:

Entities: Core objects (e.g., User, Customer, Product).
Systems: Different data sources (e.g., HubSpot, Stripe, Google Ads).
Primary Keys: Keys that allow you to join and connect data across these systems.

3. Step-by-Step Guide to Creating a Bus Matrix

3.1 Define Your Entities

Start by listing all the entities that need to be included in the matrix. These should represent key business objects in your data, such as customers, transactions, and products.

3.2 Identify Data Sources

For each entity, identify which systems contain relevant data. Examples include:

• HubSpot CRM
• MySQL Database
• Stripe Payment System

3.3 Determine Primary Keys

For each system, locate the primary key that uniquely identifies records for each entity. For example:

HubSpot: Contacts table with a user_id as the primary key.
Stripe: Customers table with a customer_id as the primary key.

3.4 Populate the Matrix

Your bus matrix will start empty, and your job is to populate it by mapping how each sub-entity in a system connects to the entity. If an entity spans multiple systems, you need to combine and reconcile the data.

Example:

Customer Entity:
HubSpot: contacts.user_id
Stripe: customers.customer_id
MySQL: companies.id

3.5 Reconciling Data Differences

Once data is mapped, identify discrepancies between systems. For instance:

Customer names might be spelled differently across systems.
IDs might use different formats (e.g., numeric vs. alphanumeric).
The reconciliation process helps create a unified, accurate view of the data.

4. Mastering the Data and Resolving Issues

4.1 Handling Data Discrepancies

During reconciliation, it is common to encounter issues such as:

Missing IDs: Some systems may not contain relevant data for an entity (e.g., HubSpot might lack subscription info).
Unjoinable Keys: Data may not have a shared primary key between systems, making it difficult to join.
Document these challenges in the matrix to keep track of issues, such as:

Unmatched records: Use techniques like fuzzy matching when data is incomplete or inaccurate.

5. Finalizing and Maintaining the Bus Matrix

5.1 Completing the Bus Matrix

Once the matrix is populated and reconciled, review it to ensure all entities are connected across systems. This completed matrix should serve as a system of record for how data is joined between different sources.

5.2 Ongoing Maintenance

The Bus Matrix is a living document. As data sources evolve or new discrepancies are found, update the matrix. Always document unresolved issues or challenges (e.g., different ID formats or data quality problems).

Conclusion

The Bus Matrix is a vital tool for mastering the entity reconciliation process during data modelling. By ensuring that you can connect and join data across different systems, you create a unified and reliable source of truth. Use this guide to efficiently build, populate, and maintain your Bus Matrix, ensuring smooth integration throughout your data project lifecycle.