Synthetic Data:

Comparison of Model-based Generation Versus Rule-based Generation


Amin Chirazi, Managing Director at Automators

11 min readJul 10 2023

Synthetic (or fake) data refers to artificially generated data that mimics the properties, distributions, and patterns of real-world data. It is created using various techniques, including mathematical models, algorithms, and predefined rules, to simulate data points that closely resemble authentic observations. Synthetic data can encompass a wide range of formats, such as images, text, numerical values, or even complex multidimensional structures.

The purpose of this blogpost is to delve into two popular approaches for generating synthetic data: model-based generation and rule-based generation. Rule-based generation relies on predefined rules, heuristics, or logical constraints to create synthetic data that adheres to specific characteristics or conditions. Synthetic data generator is a useful tool to get it. On the other hand, model-based generation involves leveraging machine learning models to learn the underlying distribution of real data and generate synthetic samples.

By comparing these two approaches, we aim to provide insights into their strengths, limitations, and suitability for different use cases.



Model-based generation involves the use of machine learning models to generate synthetic data that closely resembles real-world data. These models are trained on existing real data to learn the underlying patterns, distributions, and relationships. Once trained, they can generate new data samples by sampling from the learned latent space or by decoding random inputs.

Advantages of Model-based Generation

1.Ability to capture complex relationships

Model-based generation techniques excel at capturing intricate relationships within the data. By learning from large and diverse datasets, these models can capture complex patterns, dependencies, and structures that may not be easily discernible by simple rule-based approaches. This enables the generation of synthetic data that closely mimics the characteristics and intricacies of the real data. On the other hand, this ability could be sometimes also a disadvantage, because the model may find relationships where there are none.

2.Flexibility to generate diverse data

The learned models can generate samples that span a wide range of variations, capturing the natural diversity present in the real data. This diversity can be especially beneficial for training machine learning models, as it exposes them to a broader spectrum of scenarios, leading to improved generalization and performance.

3.Potential for data that closely resembles the real data

Since model-based generation uses machine learning models, it has the potential to produce synthetic data that closely resembles real data. The models can learn and capture the statistical properties, distributions, and nuances of the real data. As a result, the generated data can exhibit similar statistical characteristics, making it more representative of the underlying population and more suitable for training robust and accurate models.

Limitations of Model-based Generation

1.Dependency on quality and size of training data

The most significant limitation of model-based generation is that its performance heavily relies on the quality and size of the training data. Insufficient or biased training data may result in models that fail to capture the true underlying distribution accurately. Therefore, obtaining a diverse and representative training dataset is crucial for achieving high-quality synthetic data generation. It is extremely important to put enough time and effort into careful and expert preparation of the data for the model to learn on.

2.Difficulty in capturing rare or outlier cases

Model-based generation approaches can struggle with accurately capturing rare or outlier cases present in the real data. The models tend to learn the dominant patterns and distributions, making it challenging to generate synthetic data that accurately represents the tail ends of the distribution. This limitation can be particularly relevant in applications where rare events or outliers are significant. Moreover, because of the way the data gets generated model-based approaches can also create outliers that are unexpected and did not appear in the original data.

3.High computational requirements

Model-based generation can be computationally demanding, especially when working with complex models and large datasets. Training deep learning models often requires significant computational resources, including powerful GPUs or specialized hardware. The training process may take a considerable amount of time, making it less feasible for applications with strict time constraints or limited computing capabilities.

Overall, model-based generation techniques offer the potential to generate high-quality and diverse synthetic data by leveraging complex machine learning models. However, they come with computational requirements and dependencies on training data quality, and they may struggle with capturing rare or outlier cases. Understanding these limitations is essential when considering the suitability of model-based generation for specific use cases.



Rule-based generation involves the creation of synthetic data by following predefined rules, heuristics, or logical constraints. These rules are designed to dictate the generation process, specifying the characteristics, relationships, and constraints that the synthetic data should adhere to. Rule-based generation can be implemented through scripting, deterministic algorithms, or expert knowledge to generate data that aligns with specific requirements.

Advantages of Rule-based Generation

1.Simplicity and interpretability

One of the major advantages of rule-based generation is its simplicity and interpretability. The rules used to generate synthetic data are typically explicit and understandable, making it easier to comprehend and control the data generation process. This transparency allows users to have a clear understanding of how the synthetic data is created and how different rules influence the resulting data.

2.Control over specific data characteristics

Rule-based generation offers precise control over specific data characteristics. By defining rules and constraints, users can generate synthetic data that exhibits desired properties or behaviors. This control is particularly valuable when specific scenarios or edge cases need to be simulated, enabling focused testing, analysis, or validation of models against known scenarios.

3.Low computational requirements

Compared to model-based generation, rule-based generation often requires fewer computational resources. The process typically involves executing deterministic algorithms or applying predefined rules, which are less computationally intensive than training complex machine learning models. This makes rule-based generation more accessible, particularly in situations with limited computational capabilities.

Limitations of Rule-based Generation

1.Limited ability to capture complex relationships

Rule-based generation approaches may struggle with capturing complex relationships present in real data. While the predefined rules provide control and simplicity, they may oversimplify the underlying patterns and dependencies. This limitation can hinder the generation of synthetic data that accurately represents the intricacies and complexities of the real data, making it less suitable for applications where capturing nuanced relationships is essential.

2.Limited diversity in generated data

Since rule-based generation relies on predefined rules, the diversity of the generated data is inherently limited to the range of scenarios covered by the rules. While it offers control over specific characteristics, it may struggle to produce synthetic data that encompasses the full spectrum of variations present in the real data. This can potentially restrict the generalization capabilities of machine learning models trained on synthetic data generated through rule-based approaches.

3.Challenges in defining accurate rules for all scenarios

Real-world datasets often contain diverse and complex patterns that may be difficult to capture with a predefined set of rules. Creating rules that encompass all possible scenarios and accurately mimic the complexities of the real data can be time-consuming, error-prone, and may require expert domain knowledge.

Despite its indisputable advantages, rule-based generation has limitations in capturing complex relationships, generating diverse data, and defining accurate rules for all scenarios. Understanding these limitations is crucial when considering the appropriateness of rule-based generation for specific use cases.



Data Quality

1.Accuracy and fidelity

Model-based generation techniques have the potential to produce synthetic data with higher accuracy and fidelity. While it can be more accurate in capturing the statistical properties and complexities of the original data, it is not without its challenges. If the model is inadequate or improperly trained, it may produce synthetic data that deviates significantly from the original dataset. One issue that can arise in model-based data generation is the generation of data points that are completely outside the parameters or range of the original data. This can happen when the model extrapolates beyond the observed data, resulting in synthetic samples that do not match the typical patterns or characteristics present in the real-world data. Rule-based generation, on the other hand, heavily relies on predefined rules, which may not capture the full complexity and intricacies of the real data.

2.Realism and representation of underlying distribution

Model-based generation approaches excel in generating synthetic data that represents the underlying distribution of the real data. The learned models can capture the statistical patterns and dependencies, leading to realistic synthetic data that aligns with the distribution of the real data. On the other hand, as the model needs a lot of data to be trained on, it could also take over biases that while, “correct” based on the data the model was trained on, might be something we would like to avoid. Rule-based generation, although capable of generating data with specific characteristics, may struggle to accurately represent the full range of variations present in the real data.

Flexibility and Diversity

1.Ability to capture complex patterns and variations

Model-based generation techniques offer flexibility in capturing complex patterns and variations present in the real data. The learning capacity of machine learning models allows them to capture intricate relationships and dependencies, making them well-suited for generating synthetic data that accurately represents complex data distributions. Rule-based generation may be limited in capturing such complexities due to the predefined nature of the rules.

2.Incorporation of noise and outliers

Model-based generation methods can incorporate noise and outliers in the synthetic data generation process. By introducing randomness or perturbations to the learned latent space, models can simulate variations, noise, or outlier cases, enhancing the diversity of the generated data. Rule-based generation approaches may struggle to capture these nuances as they typically rely on explicit rules without the inherent randomness of model-based methods. It is important to mention that while model-based data generation has the potential to produce accurate and representative synthetic data, it also carries the risk of generating nonsensical outliers and noise if not used carefully and controlled. When using models to generate synthetic data, especially complex and high-dimensional data, there is a possibility that the model may produce outliers or noise that do not align with the underlying data distribution.

Computational Requirements

1.Processing time and resource consumption

Model-based generation techniques often require significant computational resources and time for training complex machine learning models. The training process involves iterations and optimization steps, making it computationally expensive, especially for large datasets. Rule-based generation, being deterministic and rule-based, generally requires less computational time and resources.

2.Scalability and efficiency

Rule-based generation methods are often more scalable and efficient compared to model-based generation. Once the rules are defined, generating synthetic data can be a straightforward process that scales linearly with the desired sample size. Model-based generation, on the other hand, may face scalability challenges due to the computational requirements of training and generating data from complex models.

Understanding the Data Generation Process

Rule-based generation offers a high level of interpretability as the data generation process is governed by explicit rules or constraints. Users can easily understand how the synthetic data is generated based on the predefined rules, providing transparency and interpretability. Model-based generation techniques, while powerful, can be less interpretable as the generation process relies on complex machine learning models.

By comparing model-based and rule-based generation methods it becomes evident that each approach has its strengths and limitations. When choosing between model-based and rule-based generation, several considerations come into play. The nature of the data, the complexity of relationships, the desired level of control and the desired outcomes of the particular application should be taken into account. Model-based generation is suitable when complex patterns and variations are required.

Rule-based generation is more appropriate when specific scenarios or characteristics need to be simulated, or when simplicity and control are paramount. This makes it valuable for generating synthetic data to simulate specific scenarios for testing and validation purposes. Rule-based generation approaches can also be employed to generate privacy-preserving synthetic data. By defining rules that preserve the statistical properties of sensitive data while obscuring the actual values, synthetic data can be generated for sharing or analysis without compromising individual privacy.

Final Thoughts


Synthetic data generation is expected to play an increasingly crucial role in the future of machine learning and data-driven applications. Advances in model-based generation, such as the development of more sophisticated deep learning architectures and improved training techniques, will lead to higher-quality and more realistic synthetic data. Rule-based generation may also evolve with the integration of automated rule discovery techniques and the incorporation of machine learning for rule refinement.

Moreover, the combination of model-based and rule-based approaches could offer the benefits of both methods. Hybrid approaches that leverage the strengths of each approach may provide more accurate and diverse synthetic data while maintaining interpretability and control.

As the field progresses, addressing the limitations of both model-based and rule-based generation techniques will be crucial. Overcoming computational challenges, improving the capture of complex relationships, and enhancing diversity will contribute to more reliable and effective synthetic data generation.

In conclusion, synthetic data generation, whether through model-based or rule-based approaches, offers a powerful solution to address the challenges of acquiring large, diverse, and high-quality datasets. Understanding the trade-offs, considering specific use cases, and leveraging advancements in both techniques will enable researchers and practitioners to harness the full potential of synthetic data for machine learning and data analysis.

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