Requirements Gathering

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Introduction

• Goal: Understand how to gather requirements and design data systems that meet stakeholder needs and business goals.
• Key Concepts:
  • Hierarchy of Needs: Business goals → Stakeholder needs → System requirements (functional and non-functional).
  • Requirements Gathering: Conversations with stakeholders to understand their needs and current systems.
  • Documentation: Clearly document functional and non-functional requirements.

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Hierarchy of Needs

1. Business Goals🚩:
   • High-level objectives (e.g., increase revenue, improve customer retention, expand to new markets).
   • Example: “The company aims to grow by launching new products and improving customer retention.”
2. Stakeholder Needs:
   • What stakeholders (e.g., marketing, data scientists) need to achieve business goals.
   • Example: “Marketing needs real-time dashboards to monitor product sales and a recommender system for personalized product recommendations.”
3. System Requirements:
   • Functional Requirements: What the system must do (e.g., serve data no more than one hour old).
   • Non-Functional Requirements: Characteristics of the system (e.g., scalability, reliability, latency).

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Requirements Gathering Process

1. Identify Stakeholders:
   • Talk to leadership (e.g., CTO, CEO) to understand business goals.
   • Engage with end users (e.g., marketing, data scientists) to understand their needs.
2. Understand Current Systems:
   • Learn about existing systems and their limitations.
   • Example: Marketing currently gets daily data files, but they need real-time data.
3. Ask Key Questions:
   • What actions will stakeholders take with the data?
   • What problems exist with the current system?
   • Who else should you talk to for more information?
4. Document Requirements:
   • Use a hierarchical format to connect business goals, stakeholder needs, and system requirements.

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Functional Requirements

• Analytics Dashboards:
  • Serve data no more than one hour old.
  • Example: “The system must provide real-time product sales data for marketing dashboards.”
• Recommender System:
  • Provide training data for the recommender model.
  • Ingest, transform, and serve user data to the model.
  • Return product recommendations to the sales platform.
  • Example: “The system must serve personalized product recommendations based on user behavior.”

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Non-Functional Requirements

• Analytics Dashboards:
  • Scalability: Handle peak user activity without slowing down.
  • Reliability: Perform data quality checks to ensure data conforms to the expected format.
  • Maintainability: Easily adapt to changes in data schema.
• Recommender System:
  • Latency: Serve recommendations in less than one second.
  • Scalability: Handle maximum concurrent users.
  • Reliability: Default to popular products if the recommender fails.

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Conversations with Stakeholders

1. Marketing Team:
   • Needs real-time dashboards to monitor product sales and react to demand spikes.
   • Wants a personalized recommender system for customers.
2. Data Scientists:
   • Currently work with daily data files but need real-time data for dashboards and recommender models.
3. Software Engineers:
   • Plan to set up a read replica database and API for continuous data access.
   • Will notify data engineers of schema changes and system outages.

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Trade-Offs in Requirements Gathering

• Iron Triangle 🔼:
  • Scope: Features and functionality of the system.
  • Timeline: How quickly the system needs to be built.
  • Cost: Budget constraints for the project.
• Key Insight: You can’t optimize all three simultaneously (e.g., fast and cheap may compromise quality).
• Solution:
  • Build loosely coupled systems for flexibility.
  • Make reversible decisions (two-way doors).
  • Deeply understand stakeholder needs to prioritize effectively.

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Sample Project: Recommender System

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Key Components of the Project

• Recommender System: A content-based recommender system is being developed to recommend products to users based on:
  • User features: Customer number, credit limit, city, postal code, country.
  • Product features: Product code, quantity in stock, buy price, MSRP, product line, product scale.
  • User interactions: Products browsed or added to the cart.
• Two Data Pipelines:
  1. Batch Data Pipeline: Delivers training data to the data scientist for model retraining.
  2. Streaming Data Pipeline: Provides real-time product recommendations to users based on their activity.

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Functional Requirements

• Batch Pipeline:
  • Deliver training data in tabular format.
  • Include user features, product features, and user ratings (1-5).
  • Support retraining the model periodically (weekly, monthly, or quarterly).
  • Handle modifications in data format (e.g., new user or product features).
• Streaming Pipeline:
  • Provide real-time recommendations with subsecond latency (1-2 seconds).
  • Handle up to 10,000 concurrent users, with potential for growth.
  • Use pre-trained recommender system to generate recommendations.
  • Save model outputs for later analysis.

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Non-Functional Requirements

• Latency: Recommendations must be generated in under 1 second to match page rendering times.
• Scalability: The system must handle spikes of up to 10,000 concurrent users and scale as the company grows.
• Flexibility: The system should accommodate changes in data format (e.g., new features).
• Operational Overhead: Minimize the effort required to deliver new batches of training data.

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Recommender System Details

• Content-Based Recommender:
  • Uses vector embeddings for users and products to find similarities.
  • Predicts user ratings for products based on embeddings.
  • Combines recommendations from:
    • User features (e.g., “Based on your profile, you may like…”).
    • Product interactions (e.g., “Based on your browsing history, you may like…”).
• Vector Database:
  • Stores precomputed product embeddings for faster similarity searches.
  • Organizes embeddings so similar products are close together, speeding up retrieval.

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Implementation Steps

1. Extract Requirements: Identify functional and non-functional requirements from the conversation.
2. Select Tools: Choose AWS tools and services that meet the requirements.
3. Lab Exercise:
   • Set up batch pipeline to deliver training data.
   • Use pre-trained recommender system for streaming pipeline.
   • Implement vector database for fast similarity searches.

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Key Takeaways

1. Stakeholder Engagement:
   • Talk to leadership, end users, and source system owners to understand needs and constraints.
2. Documentation:
   • Clearly document functional and non-functional requirements using a hierarchical format.
3. Trade-Offs:
   • Balance scope, timeline, and cost by applying principles like loose coupling and reversible decisions.
4. System Design:
   • Design systems that are scalable, reliable, and maintainable to meet stakeholder needs and business goals.