  This work examines how much template instantiation can narrow down schema
validation for XML-documents. First, instantiation and validation are
formalised. Properties towards their practical meaning are probed, an
implementation is developed. Requirements for an unification are elaborated and
a comparison is taken out. The semantics are formulated in terms of
denotational semantics as well as rule-based referring to the data models
chosen. Formalisation makes it clearer instantiation is adequately represented.
Both semantics show, that the rules set for both, instantiation and validation,
cannot totally be unified. However, reuse of simplified code also simplifies
unification. Implementation allows unification of both processes on
document-level. The validity of all implementations is guaranteed by a
comprehensive test suite. Analysis shows the minimal XML template language has
got regular grammar properties, except macros. An explanation was given, why
filters and arrows are not best, especially towards a unified language to be
variable and extensive. Recommendations for future language design are
provided. Instantiation shows a universal gap in applications, for instance, as
seen by XSLT. Lack of expressibility of arbitrary functions in a schema is one
such example, expressibility of the command language is another basic
restriction. Useful unification constraints are found out to be handy, such as
typing each slot. In order to obtain most flexibility out of command languages
adaptations are required. An alternative to introducing constraints is the
effective construction of special NFAs. Comparison criteria are introduced
regarding mainly syntax and semantics. Comparisons is done accordingly. Despite
its huge syntax definitions XSD was found weaker than RelaxNG or XML template
language. As template language the latter is considered universal.
