Validate or at least check your XML!
[November 12, 2001] Validator for XML Schema (XSV). REC (2001-05-02) version. See also the announcement and XSU - Upgrade for XML Schema documents [20000922 to PR 2001031]. From Henry S. Thompson (HCRC Language Technology Group, University of Edinburgh). Version 1.4 of 2001-11-12 introduced support for constraints on derivation by restriction for complex type definitions.
Earlier reference for '20000922' version: XSV: W3C/HCRC Language Technology Group XML Schema Validator. XSV (XML Schema Validator) "is an open source (GPLed) work-in-progress attempt at a conformant schema-aware processor"; from Henry S. Thompson and Richard Tobin of the Language Technology Group, University of Edinburgh. Corresponds to the 2000-09-22 'Pre-CR' XML Schema release and namespace URI http://www.w3.org/2000/10/XMLSchema. See the development status report for binaries and Python sources; see also the original announcement of 2000-05-05.
W3C HTML Validation Service. Updated 2002-11-26. "It checks HTML documents for conformance to W3C HTML and XHTML Recommendations and other HTML standards. (1) Support for MathML; (2) Support for application/xhtml+xml; (3) Support for XHTML+MathML and XHTML+MathML+SVG; (4) Support for SVG and image/svg+xml; (5) Support for XHTML 1.0 Second Edition and XHTML 1.1.
Microsoft GotDotNet XSD Schema Validator. "allows you to validate an XML documents against an W3C XML Schema (XSD) or an XML Data-Reduced (XDR) schema, verify the schemas are valid, or simply check the well-formedness of XML documents. Different actions are taken depends on the submitted information." Files for validation must be located on the user's local file system (no validation of documents by URI). 2002-10.
DecisionSoft XML Schema Validator. This simple [W3C XML] Schema Validator (2002-11-21) "will take a single schema plus an instance document and list any errors found whilst validating the document against the schema. If you specify a schema file on the HTML form, it will use Xerces-J 2 for validation via the AS Builder class. If you do not supply a schema, it will use Xerces-J 1.4.3; it will fetch referenced schemas from the internet. This requires that the instance document specifies the location for the schema document using a schemaLocation attribute..." Contact: Paul Warren.
STG XML Validation Form. Validates XML in addition to checking well-formedness. With FAQ and documentation. Provides warnings about ambiguous content models; has experimental support for XML namespaces.
XML well-formedness checker and validator. From Richard Tobin. Based upon the RXP XML parser. Has a 'validate' option. If the document is well-formed, the parser outputs the corresponding canonical XML. Has namespace support. Available also with MSDOS/Windows32 binaries.
DOMit XML Validation Servlet." From IBM. "If the document passes the parser test, DOMit displays the XML document in your browser window. It creates an HTML tree view of the Document Object Model (DOM).
Check or validate an XML document using IBM's XML4J Parser. From a tutorial by Ralf I. Pfeiffer. [experimental]
Microsoft XML Well-Formedness Checking and Validation Tool. "This web page allows you to enter in the URL of an XML document and both parse and validate that document; the demo utilizes the new validation support (XML schemas, validateOnParse property, etc.). Requires Microsoft Internet Explorer 5 or greater on Win32 or Unix platforms."
RUWF. XML well-formedness checker from the XML.com Web site.
Architag International Real-Time XML Editor. The editor provides visual ("real-time") feedback about document well-formedness and validity. Requires MSIE 5.x.
XML Syntax Checker. From Frontier 5. Use blox or the Frontier 5.1.3 built-in XML parser to check well-formedness of an XML document.
Techno 2000 Project XML validation service. Part of a Korean XML site.
WebTechs' Validation Service. It now supports 'XML' - possibly using James Clark's SP xmlwf code.