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Fusion of Symbolic and Subsymbolic AI: The Power of Integrating Transformers with Real-world Examples

Artificial Intelligence (AI) has witnessed remarkable progress through two main approaches: symbolic AI, characterised by explicit knowledge representation using rules and logic, and subsymbolic AI, represented by data-driven methods like neural networks. The fusion of these two paradigms holds the promise of creating more intelligent, interpretable, and versatile AI systems. In this article, we delve into the integration of Transformers, a cutting-edge subsymbolic AI architecture, with symbolic AI techniques, exploring real-world examples and code snippets to illustrate the potential of this fusion.

The Duality of Symbolic and Subsymbolic AI

Symbolic AI relies on explicit rules and logical reasoning, enabling interpretable decision-making. However, it faces challenges in handling uncertainty and learning from vast unstructured data. On the other hand, subsymbolic AI, such as Transformers, excels in learning patterns from data but may lack the explainability and reasoning capabilities of symbolic approaches.

Transformers: A Dominant Subsymbolic AI Paradigm

Transformers have risen to prominence as a leading subsymbolic AI architecture, particularly in natural language processing and beyond. The Transformer’s self-attention mechanism enables parallel processing and capturing long-range dependencies, making it ideal for sequential data analysis.

Example 1: Knowledge Graph Transformers

One promising integration of Transformers with symbolic AI is the concept of Knowledge Graph Transformers. Knowledge graphs offer structured representations of information in the form of nodes and edges, representing entities and their relationships. By combining Transformers with knowledge graph embeddings, we can create AI models capable of reasoning over explicit knowledge while leveraging subsymbolic learning capabilities.

Example Code Snippet:

# Import required libraries
import torch
import torch.nn as nn

# Define a Transformer-based encoder
class TransformerEncoder(nn.Module):
    def __init__(self, input_dim, hidden_dim, num_heads, num_layers):
        super(TransformerEncoder, self).__init__()
        self.transformer = nn.TransformerEncoder(
            nn.TransformerEncoderLayer(d_model=input_dim, nhead=num_heads),
        self.linear = nn.Linear(input_dim, hidden_dim)
    def forward(self, x):
        x = self.transformer(x)
        x = self.linear(x)
        return x

# Define a Knowledge Graph Transformer
class KnowledgeGraphTransformer(nn.Module):
    def __init__(self, num_entities, num_relations, hidden_dim, num_heads, num_layers):
        super(KnowledgeGraphTransformer, self).__init__()
        self.entity_embeddings = nn.Embedding(num_entities, hidden_dim)
        self.relation_embeddings = nn.Embedding(num_relations, hidden_dim)
        self.transformer_encoder = TransformerEncoder(

    def forward(self, entity_indices, relation_indices):
        entity_emb = self.entity_embeddings(entity_indices)
        relation_emb = self.relation_embeddings(relation_indices)
        input_emb = entity_emb + relation_emb
        output_emb = self.transformer_encoder(input_emb)
        return output_emb

In this example, we define a simple Knowledge Graph Transformer with an entity embedding and a relation embedding. The TransformerEncoder processes the embeddings, enabling reasoning over structured knowledge.

Example 2: Neural-Symbolic Reinforcement Learning

Another exciting application of the fusion of symbolic and subsymbolic AI is in neural-symbolic reinforcement learning. By combining the reasoning capabilities of symbolic AI with the learning and representation power of Transformers, we can create intelligent AI agents capable of reasoning over explicit rules while learning optimal policies from data.

Example Code Snippet:

# Import required libraries
import torch
import torch.nn as nn

# Define a symbolic rule-based policy
def symbolic_policy(state):
    if state['distance_to_goal'] < 5:
        return 'stop'
        return 'move_forward'

# Define a Transformer-based value function approximator
class ValueFunctionTransformer(nn.Module):
    def __init__(self, input_dim, hidden_dim, num_heads, num_layers):
        super(ValueFunctionTransformer, self).__init__()
        self.transformer = nn.TransformerEncoder(
            nn.TransformerEncoderLayer(d_model=input_dim, nhead=num_heads),
        self.linear = nn.Linear(input_dim, hidden_dim)
    def forward(self, x):
        x = self.transformer(x)
        x = self.linear(x)
        return x

# Example RL loop with symbolic reasoning and Transformer-based value function
def rl_loop():
    for step in range(max_steps):
        state = get_current_state()
        action = symbolic_policy(state)

        # Perform action and observe reward and next state
        reward, next_state = perform_action(action)

        # Use the next state to calculate value estimate
        next_state_emb = torch.tensor(next_state).unsqueeze(0)
        value_estimator = ValueFunctionTransformer(input_dim=state_dim, hidden_dim=32, num_heads=4, num_layers=2)
        value_estimate = value_estimator(next_state_emb)

        # Perform updates to improve the value function and policy
        # (not shown in the code snippet)

In this example, we combine a symbolic policy function with a Transformer-based value function approximator. The agent uses the symbolic policy for decision-making while learning an accurate value function using the Transformer.


The fusion of symbolic and subsymbolic AI, particularly in conjunction with Transformers, offers exciting possibilities for creating more powerful, interpretable, and adaptable AI systems. Through examples and code snippets, we have illustrated the integration of Transformers with symbolic reasoning, knowledge graphs, and reinforcement learning. As researchers and developers continue to explore this integration, we can expect groundbreaking advancements that push the boundaries of AI and pave the way for smarter, more capable AI systems with a deeper understanding of the world around us.

Let’s further expand on the topic of “Fusion of Symbolic and Subsymbolic AI” by exploring additional dimensions, challenges, and potential applications of integrating Transformers with symbolic AI techniques.

  • Hybrid Models and Compositional AI: The fusion of symbolic and subsymbolic AI opens up the possibility of creating hybrid models that combine the best of both worlds. Compositional AI, a form of hybrid modeling, leverages symbolic reasoning to decompose complex problems into simpler components, while subsymbolic models like Transformers learn to handle each component. This synergy can lead to more efficient problem-solving and generalization capabilities.
  • Meta-Reasoning and Learning to Learn: Integrating Transformers with symbolic meta-reasoning approaches allows AI systems to reason about their own reasoning processes. Meta-learning techniques can enable AI models to adapt rapidly to new tasks and learn from limited data, resulting in more agile and flexible AI systems.
  • Domain-Specific AI Transformers: Customizing Transformers with domain-specific knowledge enhances their performance on specialized tasks. For example, in the medical domain, incorporating medical ontologies and domain-specific embeddings in Transformers can lead to more accurate disease diagnosis and personalized treatment recommendations.
  • Reasoning over Time and Temporal Data: Combining Transformers with symbolic temporal reasoning enables AI to reason over time-series data and temporal relationships effectively. This has applications in forecasting, anomaly detection, and event prediction in various domains, including finance, climate science, and healthcare.
  • Cognitive Reasoning and Human-AI Collaboration: By integrating symbolic AI reasoning techniques with Transformers, AI systems can exhibit more cognitive-like reasoning abilities. This brings AI closer to human-like thinking, enabling more effective collaboration between humans and machines in tasks like decision-making, creativity, and problem-solving.
  • Scalability and Resource Efficiency: A significant challenge in integrating symbolic and subsymbolic AI is ensuring the fusion remains scalable and computationally efficient. Balancing the complexity of symbolic reasoning with the computational requirements of Transformers is crucial for real-world deployment.
  • Hybrid Language Models: Hybrid language models, combining symbolic grammar rules with the power of large-scale Transformers, can lead to more accurate and controlled language generation. Such models can be valuable in creative writing, code generation, and story generation.
  • Human-Robot Interaction and Explainable Robotics: The integration of symbolic reasoning with subsymbolic learning in robots can lead to more interpretable and explainable AI agents. This is vital for building trust and understanding between humans and robots, making AI more acceptable in our daily lives.
  • AI for Education: Integrating Transformers with symbolic reasoning can create intelligent tutoring systems capable of personalized and adaptive learning experiences. Such systems can understand a student’s knowledge gaps and tailor explanations accordingly, improving learning outcomes.
  • Privacy-Preserving AI: The fusion of symbolic and subsymbolic AI techniques can lead to novel approaches for privacy-preserving AI. By incorporating symbolic reasoning at various stages, AI models can make decisions without directly accessing sensitive data, ensuring data privacy.
  • AI Ethics and Bias Mitigation: The integration of symbolic reasoning can help AI systems identify and mitigate biases in data-driven models. By incorporating ethical rules and guidelines, AI can ensure fairness and inclusivity in decision-making processes.


The fusion of symbolic and subsymbolic AI, particularly with the integration of Transformers, represents a rich research area with diverse applications and challenges. As AI continues to evolve, harnessing the synergies between these two AI paradigms has the potential to create more powerful, versatile, and responsible AI systems that better understand and adapt to the complexities of the real world.

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