# XPath

> query language for selecting nodes from an XML document

**Wikidata**: [Q16340](https://www.wikidata.org/wiki/Q16340)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/XPath)  
**Source**: https://4ort.xyz/entity/xpath

## Summary
XPath (XML Path Language) is a query language designed for selecting nodes from an XML document. Developed by the World Wide Web Consortium (W3C), it serves as a sub-language within XQuery, XSLT, and XSL. In addition to XML, version 3.1 expanded its capabilities to support JSON data.

## Key Facts
- **Full Name:** XML Path Language.
- **Developer:** World Wide Web Consortium (W3C).
- **Initial Release:** 1999 (XPath 1.0).
- **Latest Version:** XPath 3.1 (W3C Recommendation released on March 21, 2017).
- **Primary Function:** Query language for selecting nodes from XML documents.
- **Secondary Function:** Programming language for communicating instructions to a machine.
- **Supported Formats:** XML and JSON (support for JSON added in version 3.1).
- **Parent Standards:** It is a part of XSLT, XQuery, and XSL.
- **Official Resource:** Specifications are available at `https://www.w3.org/TR/xpath/`.

## FAQs
### Q: What is the difference between XPath and XQuery?
A: XPath is a query language specifically for selecting nodes and is a subset of XQuery. XQuery is a full functional programming and query language for XML that utilizes XPath for its navigation logic.

### Q: Does XPath work with JSON?
A: Yes, as of version 3.1 (released in 2017), XPath supports JSON as a readable file format in addition to XML.

### Q: Who maintains the XPath standard?
A: XPath is developed and maintained by the World Wide Web Consortium (W3C), which issues recommendations for the language.

### Q: When was XPath first introduced?
A: The first version, XPath 1.0, was published as a W3C Recommendation on November 16, 1999.

## Why It Matters
XPath is a fundamental technology in the field of data processing and web development, serving as the standard syntax for navigating XML document structures. Its significance lies in its widespread integration; it is not just a standalone tool but a core component required by other major W3C standards including XSLT (for transforming XML), XQuery (for querying XML), and XSL (for styling XML). By providing a path-based syntax to address specific parts of an XML hierarchy, it allows developers and systems to precisely locate and manipulate data elements.

The language has demonstrated adaptability over decades. Since its inception in 1999, it has evolved through four major versions, expanding from simple node selection to a robust language capable of complex computations. The inclusion of JSON support in version 3.1 highlights its continued relevance, bridging the gap between the traditional XML ecosystem and modern web data formats. This longevity and versatility make it an essential skill for backend processing, data extraction, and configuration management.

## Notable For
- **Dual Classification:** It is distinctively classified as both a **query language** and a **programming language**, capable of more than just data retrieval.
- **JSON Evolution:** It distinguishes itself from earlier XML-only tools by adding native support for **JSON** in version 3.1.
- **Standardization:** It is one of the few languages formally governed by the W3C as a **Recommendation**, ensuring strict interoperability across different software platforms.
- **Integration:** It is unique in being a mandatory sub-component of **XQuery**, **XSLT**, and **XSL**, making it omnipresent in XML processing.

## Body

### Definition and Purpose
XPath, short for XML Path Language, is a language designed primarily for addressing parts of an XML document. It operates by modeling an XML document as a tree of nodes, allowing users to select nodes based on various criteria such as name, value, or relationship to other nodes. While its primary use case is querying, it also functions as a programming language for communicating instructions to a machine.

### Version History and Timeline
The development of XPath has been marked by four major W3C Recommendations:

- **XPath 1.0:** Released on November 16, 1999. This established the foundational syntax for path expressions.
- **XPath 2.0:** Released on December 14, 2010. This version introduced a more expressive language with a type system based on XML Schema.
- **XPath 3.0:** Released on April 8, 2014. This update added support for higher-order functions and improved the handling of data types.
- **XPath 3.1:** Released on March 21, 2017. The most significant update in this version was the addition of support for JSON and maps/arrays, extending its utility beyond XML.

### Ecosystem and Relationships
XPath does not exist in isolation; it is a central pillar of the XML technology stack.
- **Parent Technologies:** It is defined as a part of **XSL** (Extensible Stylesheet Language), **XSLT** (XSL Transformations), and **XQuery**.
- **XQuery:** XQuery, a functional programming language for XML (incepted in 2007), relies on XPath for its path expressions.
- **Key Figures:** The related knowledge base entry for Michael Howard Kay, a British computer scientist born in 1951, is linked to this domain, indicating his association with these technologies.

### Technical Identifiers
The entity is indexed under various technical and academic identifiers:
- **GND ID:** 4613223-5
- **Library of Congress Authority ID:** sh2002000754
- **ACM Classification Code (2012):** 10003312

## Schema Markup
```json
{
  "@context": "https://schema.org",
  "@type": "Thing",
  "name": "XPath",
  "description": "Query language for selecting nodes from an XML document",
  "url": "https://www.w3.org/TR/xpath/",
  "sameAs": [
    "https://en.wikipedia.org/wiki/XPath",
    "https://stackoverflow.com/tags/xpath"
  ],
  "additionalType": "ProgrammingLanguage"
}

## References

1. [Source](http://www.w3.org/TR/xpath-20)
2. [Source](http://www.w3.org/TR/xpath-10)
3. [Source](https://www.w3.org/TR/xpath-30/)
4. [Source](https://www.w3.org/TR/xpath-31/)
5. Freebase Data Dumps. 2013
6. Quora
7. National Library of Israel Names and Subjects Authority File
8. KBpedia
9. [OpenAlex](https://docs.openalex.org/download-snapshot/snapshot-data-format)