SIENTIAPDE-1253: Update README.md to include documentation for the Train Model workflow and renumber the Minimal Retrain workflow. (+101, -1)

README.md

@@ -17,7 +17,8 @@ A comprehensive AI model management platform for the complete machine learning l
   - [Predictions Batch Workflow](#1-predictions-batch-workflow-predictions_batchpy)
   - [Prediction Process Workflow](#2-prediction-process-workflow-prediction_processpy)
   - [Format and Export Prediction Workflow](#3-format-and-export-prediction-workflow-format_and_export_predictionpy)
-  - [Minimal Retrain Workflow](#4-minimal-retrain-workflow-minimal_retrainpy)
+  - [Train Model Workflow](#4-train-model-workflow-train_modelpy)
+  - [Minimal Retrain Workflow](#5-minimal-retrain-workflow-minimal_retrainpy)
 - [Installation & Setup](#installation--setup)
   - [Prerequisites](#prerequisites)
   - [Environment Setup](#environment-setup)
@@ -379,7 +380,99 @@ flowchart LR
     C -.-> Prometheus[Prometheus]
 ```
 
-### 4. Minimal Retrain Workflow (`minimal_retrain.py`)
+### 4. Train Model Workflow (`train_model.py`)
+
+The **TrainModel** workflow orchestrates the complete ML model training pipeline from parameter validation through model saving and cleanup.
+
+#### Purpose
+- **Model Training**: Complete ML model training pipeline
+- **Parameter Validation**: Defense-in-depth validation with business rules
+- **Resource Management**: Automatic cleanup of temporary resources
+- **Status Tracking**: Comprehensive experiment tracking in database
+- **Error Handling**: Robust error handling with detailed context logging
+
+#### Execution Flow
+1. **Validate Experiment Run ID**: Critical validation before any DB updates
+2. **Validate Training Parameters**: Type checking + business rules validation
+3. **Download Training Data**: Fetch file from MinIO storage
+4. **Train Model**: Execute ML model training with validated parameters
+5. **Save to MLFlow**: Save trained model and artifacts to MLFlow
+6. **Cleanup Resources**: Delete temporary files and MinIO data
+
+#### Key Features
+- **Granular Retry Policies**: Different strategies for network, training, MLFlow, database, and filesystem operations
+- **Configurable Timeouts**: Environment variable-based timeouts supporting files up to 200MB
+- **Idempotent Cleanup**: Safe replay with Temporal workflow replay mechanism
+- **Structured Logging**: Rich context in error messages for debugging
+- **Business Validation**: 10 business rules including range checks, consistency validation, and data integrity
+
+#### Input Parameters
+```json
+{
+  "experiment_run_id": 123,
+  "target_variable": "price",
+  "variable_columns": ["feature1", "feature2", "price"],
+  "train_size": 80,
+  "shuffle": true,
+  "use_scaler": true,
+  "include_ar": false,
+  "bucket_name": "ml-data",
+  "file_name": "training_data.csv",
+  "line_separator": "\n",
+  "decimal_separator": ".",
+  "lag_train": 5,
+  "lag_val": 3,
+  "rem_static_win": false,
+  "low_lim": {"feature1": 0.0, "feature2": 0.0, "price": 0.0},
+  "upp_lim": {"feature1": 100.0, "feature2": 100.0, "price": 1000.0},
+  "window": 10,
+  "experiment_name": "production_model_v1",
+  "removed_intervals": []
+}
+```
+
+#### Architecture Diagram
+```mermaid
+flowchart TD
+    A[1. validate_experiment_run_id] --> B[2. validate_train_params]
+    B --> C[3. fetch_file_from_minio]
+    C --> D[4. train_model]
+    D --> E[5. save_model]
+    E --> F[6. cleanup_run_directory]
+    F --> G[7. delete_file_from_minio]
+    
+    B -.-> DB[(PostgreSQL)]
+    C -.-> MinIO[MinIO Storage]
+    D -.-> Training[ML Training]
+    E -.-> MLFlow[MLFlow]
+    F -.-> FS[Filesystem]
+    G -.-> MinIO
+```
+
+#### Retry Strategies
+
+The workflow implements 5 different retry policies optimized for each operation type:
+
+| Operation Type | Initial Interval | Max Interval | Backoff | Max Attempts | Use Case |
+|---------------|------------------|--------------|---------|--------------|----------|
+| **Network** | 1s | 10s | 2.0x | 5 | MinIO operations (transient network errors) |
+| **No Retry** | - | - | - | 1 | Training/Validation (permanent data errors) |
+| **MLFlow** | 5s | 30s | 2.0x | 3 | MLFlow operations (API timeouts) |
+| **Database** | 2s | 20s | 2.0x | 5 | PostgreSQL updates (lock contention) |
+| **Filesystem** | 2s | 10s | 1.5x | 3 | Cleanup operations (busy resources) |
+
+#### Business Validation Rules
+
+The workflow validates 10 business rules beyond type checking:
+
+1. **train_size**: Must be between 1-99%
+2. **variable_columns**: Cannot be empty
+3. **lag_train, lag_val, window**: Must be positive integers
+4. **low_lim/upp_lim**: Must have same keys and low < upp for each variable
+5. **target_variable**: Must be in variable_columns
+6. **bucket_name, file_name, experiment_name**: Cannot be empty or whitespace
+
+### 5. Minimal Retrain Workflow (`minimal_retrain.py`)
 
 The **MinimalRetrain** workflow handles automated model retraining and production model updates.