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>Design and Implementation of a validating XML parser in Haskell: Master's thesis; 
			University of Applied Sciences Wedel
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>Chapter 4. Package hvalidator</H1
><P
>&#13;	This chapter describes the package <TT
CLASS="filename"
>hvalidator</TT
> which provides all functions for validating XML documents represented as <TT
CLASS="literal"
>XmlTree</TT
>. The validation process basically consists of three phases. First the DTD is validated, after this the document is validated. In the last step the document is transformed: missing default values are added and attribute values are normalized. Unlike other popular XML validation tools the validation functions return a list of errors instead of aborting after the first error was found.
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>&#13;	While the modules from package <TT
CLASS="filename"
>hparser</TT
> use a monadic approach, these modules are written purely functional. Validation is done by filter functions of type <TT
CLASS="literal"
>XmlFilter</TT
>. These filters return a list of errors or an empty list if no errors are detected.
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>4.1. Module hierarchy</H1
><P
>&#13;		The only public module for validating XML documents is the module <TT
CLASS="classname"
>Validation</TT
>. It exports all functions for validating and transforming XML documents. <TT
CLASS="classname"
>Validation</TT
> is basically a helper module, which combines the functionalities of the internal modules taking part at validation and transformation.
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>Internal modules</B
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><DT
><TT
CLASS="function"
>DTDValidation</TT
></DT
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>&#13;					Provides functions for validating the DTD of XML documents.
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><DT
><TT
CLASS="function"
>DocValidation</TT
></DT
><DD
><P
>&#13;					Provides functions for validating the elements and attributes of XML documents.
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></DD
><DT
><TT
CLASS="function"
>DocTransformation</TT
></DT
><DD
><P
>&#13;					Provides functions for transforming XML documents after they have been validated. The transformation phase is part of the validation process.
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></DD
><DT
><TT
CLASS="function"
>AttributeValueValidation</TT
></DT
><DD
><P
>&#13;					Provides functions to normalize attribute values and to check if the attribute value matches the lexical constraints of its type.
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></DD
><DT
><TT
CLASS="function"
>XmlRE</TT
> and <TT
CLASS="function"
>RE</TT
></DT
><DD
><P
>&#13;					Support <TT
CLASS="function"
>DocValidation</TT
> by validating the content model of an element. The algorithm used is based on derivatives of regular expressions.
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>&#13;        	<DIV
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><B
>Figure 4-1. Modules of package hvalidator</B
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