Contains abstract model for grammar-based schema and concrete verifier implementation for the abstract schema.

The model of the schema consists of two interfaces:

1. DocumentDeclaration, which corresponds to constraints over XML documents
2. ElementDeclaration, which corresponds to constraints over an XML element
3. Acceptor, which verifies XML content against the content model

Note that these definitions capture schema from verifier's point of view. ���؂ɑ΂��Ē����ȃX�L�[�}�̃I�u�W�F�N�g���f���ƁA���؂̃A���S���Y���ɓ��������A�_�v�^�Ƃ͕ʂɗp�ӂ���̂��]�܂����BThese definitions are for the latter, not for the former.