Cooperative Visitors for Expression Tree Rewriting
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Solution Overview
Problem
Existing data retrieval systems are limited in modifying expression trees due to their immutable nature, restricting the scope of modifications that can be made prior to or at runtime, especially in programming languages without multiple inheritance, leading to tightly coupled and less extensible expression rewrite processes.
Innovation Solution
The introduction of cooperative visitors that traverse and modify expression trees by extracting metadata from nodes, allowing for decentralized expression rewrite processes through a repository of cooperative visitors, enabling looser coupling and higher extensibility by utilizing reflective metadata for transformation and analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional visitors are used to modify expression trees, then the expression tree can be traversed and modified, but the system remains tightly coupled and lacks extensibility due to reliance on inheritance and polymorphism
Solution Approach 1:
The patent introduces metadata as an intermediary layer between the visitor and the expression tree nodes. This metadata contains information about which visitors should be applied to specific nodes, allowing the system to dynamically select and apply appropriate visitors without tight coupling through inheritance. The metadata acts as a decoupling mechanism that enables extensibility while reducing structural complexity.
2Reliability
If expression trees are made immutable, then thread safety and consistency are improved, but the ability to modify expressions prior to or at runtime is restricted
Solution Approach 1:
The patent applies visitors to modify expression trees in advance, before the expressions are executed or before runtime modifications are needed. By performing modifications preliminarily through the visitor pattern with metadata-driven selection, the system maintains immutability during execution while still allowing flexible modifications to be made beforehand, thus preserving both thread safety and adaptability.
3Ease of operation
If a centralized rewrite mechanism is used, then the process is simpler to manage, but the system lacks decentralized control and flexibility in applying different rewrite rules
Solution Approach 1:
The patent enables different parts of the expression tree to have different qualities by associating specific metadata with individual nodes. Each node can have its own metadata specifying which visitors should be applied, allowing localized rewrite rules to be applied to specific portions of the tree while maintaining overall system manageability. This local quality approach provides decentralized control without sacrificing ease of operation.
Data Source
AI summary
In non-limiting examples of the present disclosure, systems and methods for rewriting expressions utilizing cooperative visitors are provided. A data request may be received by a computing device, which may then be represented in a data structure, e.g., an expression tree, representative of the data request. A node within the data structure representative of the data request may be visited. Metadata associated with at least one cooperative visitor may be extracted from the node, and the node may then be transformed by applying the at least one cooperative visitor to the node.