PPM::XML::ValidatingElement - XML Element with DTD-like validation rules

- NAME
- SYNOPSIS
- DESCRIPTION
- VALIDATION RULES
- METHODS
- LIMITATIONS
- AUTHORS
- HISTORY
- SEE ALSO

# NAME

PPM::XML::ValidatingElement - XML Element with DTD-like validation rules

# SYNOPSIS

     use PPM::XML::ValidatingElement;

     package PPM::XML::MyElement;
     @ISA = qw( PPM::XML::ValidatingElement );
     @oattrs = qw( BAR );       # Allow for both FOO and BAR attributes
     @rattrs = qw( FOO );
     @okids  = qw( BLEARGH );   # Allow for both BLEARGH and FOOBAR children
     @rkids  = qw( FOOBAR );

# DESCRIPTION

PPM::XML::ValidatingElement inherits from PPM::XML::Element. It extends this class to support methods for validation to allow for DTD-like restrictions to be places on documents read in with the XML::Parser module.

# VALIDATION RULES

In order to set up rules for validation of elements, each element should define four list values in it's own package namespace. When validating, this module will check to ensure that any parsed attributes or child elements are actually ones that are possible for this element, as well as checking to see that any required attributes/child elements are present.

Note that an attribute/child element only has to be present in either the optional or required list; when checking for possible attributes/children, these lists will be combined.

Validation lists:

@oattrs
  List of optional attributes.

@rattrs
  List of required attributes.

@opkids
  List of optional child elements.

@rkids
  List of required child elements.

# METHODS

validate( err_handler )
  Validates the current element. This method calls four other methods to validate all of requirements for the element. Returns non-zero on success and zero if any errors occurred.

rvalidate( err_handler )
  Validates the current element, and recursively validates all child elements. This method calls four other methods to validate all of the requirements for the element. Returns non-zero on success and zero if any errors occurred.

validate_possible_attrs( err_handler )
  Checks against the list of attributes possible for this element (taken from @oattr and @rattr) to ensure that all of the parsed attributes are valid. If any parsed attributes are not in the list of possible attributes for this element, err_handler will be called with a message stating the error. Returns non-zero on success and zero if any errors occurred.

validate_required_attrs( err_handler )
  Checks against the list of required attributes (taken from @rattr) to ensure that all of the required attributes are present and have been parsed. If any required attributes are missing, err_handler will be called with a message stating the error. Returns non-zero on success and zero if any errors occurred.

validate_possible_kids( err_handler )
  Checks against the list of child elements this element can contain (taken from @okids and @rkids) to ensure that any child elements that have been read in are valid. If any child elements have been parsed which are not in the list of possible children, err_handler will be called with a message stating the error. Returns non-zero on success and zero if any errors occurred.

validate_required_kids( err_handler )
  Checks against the lsit of required child elements (taken from @rkids) to ensure that all of the required child elements are present and have been parsed. If any of the required child elements are missing, err_handler will be called with a message stating the error. Returns non-zero on success and zero if any errors occurred.

# LIMITATIONS

The PPM::XML::ValidatingElement module only provides checks for determining whether or not the possible/required attributes/children are present. This module currently has no support for determining whether or not the values provided are actually valid (although I imagine it wouldn't be too hard to add this in somewhere). This also includes elements which have been declared in a DTD as being 'EMPTY' elements.

# AUTHORS

Graham TerMarsch <grahamt@activestate.com>

# HISTORY

v0.2 - Added failure return values to each of the methods.

v0.1 - Initial version

# SEE ALSO

the PPM::XML::Element manpage, the XML::Parser manpage

PPM::XML::ValidatingElement - XML Element with DTD-like validation rules