Kernkonzepte
This work provides a formal syntax and denotational semantics for a large subset of the jq language, a widely used tool for manipulating JSON data. The most significant contribution is a new interpretation of updates that allows for more predictable and performant execution.
Zusammenfassung
The content provides a formal specification of the jq language, which is a widely used tool for manipulating JSON data. The key points are:
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Introduction to jq:
- jq provides a programming language to define filters and an interpreter to execute them.
- jq filters operate on streams of JSON values, allowing compact manipulation of JSON data.
- The semantics of the jq language are only informally specified, leading to inconsistencies between the documentation and the implementation.
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Syntax:
- The content defines a high-level intermediate representation (HIR) and a mid-level intermediate representation (MIR) for a subset of the jq language.
- It shows how to lower HIR filters to semantically equivalent MIR filters, simplifying the semantics definition.
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Values and Operations:
- The content defines JSON values, errors, exceptions, and streams, as well as functions and operations on these values.
- It defines arithmetic operations, object construction and merging, and other basic value manipulations.
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Semantics:
- The content defines the semantics for evaluating jq filters on input values, focusing on a new interpretation of updates that is simpler and more performant than the existing jq implementation.
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Equational Reasoning:
- The content shows how to prove properties of jq programs using equational reasoning.
The formal specification aims to provide a clear and consistent definition of the jq language semantics, addressing the issues with the existing informal specification.