CLiX Language and XML Schema

Definition of XML Schema and CliX

CLiX which is a markup language, stands for Constraint Language in XML which is in use to constrain the content of XML documents. It is based on first order logic and XPath.
The goal of CLiX is to enable users and developers to express business properties and complex constraints that cannot be handled in traditional schema languages.
And its purpose is to enable the specification of constraints on the structure and content of XML documents. CLiX constraints can be used both to constraint documents internally and to execute inter-document checks between a number of documents.

Why is CLiX important?

XML needs a strong validation rule language. Validation is one piece of the overall task of bringing business rules to XML. Themarkup Language CLiX is clear, well encapsulated and sufficient defined. It is the best choice for semantic validation. Since it is already published as an open specification, it could be integrated into standards work.

More Details on Clix:

    XML schema    

      XML schema is a language also referred to as the XML schema definition (XSD) and it is used for expressing restriction regarding XML documents hence it describes the structure of XML documents. These schema utilizes languages such as the Document Type Definitions (DTD) Schematron also referred to as CLiX, Relax-NG among others.  Below is an explanation of the purpose of XML schema and Constraint Language in XML(CLiX) used in Search Engine Optimization (SEO).CLiXMarkupLanguage

       XML schema has several purposes which include provision of a list of elements and attributes that can appear in a document and describing them, defining data for elements and attributes, availing documentation that can be processed by machine and is human readable and restriction of where attributes and elements should appear and what should be inside them.

            Due to insufficiency in XML schema to do a thorough expression of all semantic constraints over XML files a validation rule language such as CLiX was adopted. Constraint Language in XML(CLiX) is a language based on first order logic and it deals with constraints or validation rules that define the validity of XML files or documents. According to Nentwich,C (n.d)  CLiX also referred to as Schematron is highly recommended due to its ability to be easily integrated to the standards framework hence it is used in many application domains.

            The Constraint Language in XML is a language that includes a small number of properly defined logical operators such as the predicates (“forall” and “exists”), predicates (equals or Less) and the Boolean connectives. It is mostly used in Software Engineering, Bioinformatics, Chemical Engineering, Financial services to validate trade feeds and other software applications.

            In Conclusion the Constraint Language in XML improves the functionality of XML Schemas and since the Extensible Markup Language is widely used for the transportation and storage of data, this technology optimizes the Search Engine by making sure it is fast and easy to access data on the web.


Nentwich, C. (n.d.). “CLiX - A Validation Rule Language for XML”. Retrieved June 13, 2016, from

Dominik Jungo "CLiXML Schema Validator" from

PDF File
by Christian Nentwich: Validating FPML
 Christian Nentwich was part of a FpML Validation Working Group, which is specifying standard validation rules for the Financial Products Markup Language (FpML).  This Group looked at the two reference implementation languages, Schematron and CLIX, that they used to formally express the validation rules.
And some of the requirements they needed:  validation of the documents against external data sources like relational databases, expressiveness requirements and complex data type support.

Article :

"Let’s take a look at the most notable new features and some resources for learning more or getting started right away with XML Schema 1.1.

Web traffic

Learn What’s New in XML Schema 1.1

There’s a comprehensive explanation of the new and enhanced features in XML Schema 1.1 in our free, online XML Schema training course, which you can access at any time and complete at your own pace. If you’re an experienced schema developer and simply want to learn about what’s new and enhanced in XSD 1.1, skip ahead to Chapter 9. This course is a great way to learn about XML Schema 1.1 and quickly adapt your schemas to take advantage of the new features. ..." for more go to here.


Jules Jager SEO

Share this article

Leave a comment

Your email address will not be published. Required fields are marked *