The KPML documentation

Stratal organization
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Stratal organization
The context-embedded system of language as a whole is in SFL organized as a resource for making and
exchanging meanings. It is organized in such a way that it can construe the symbolic `gap' between
high-level communicative goals in the context of communication and expressions in speech or
writing; it construes this `gap' through organization into a series of stratified subsystems -- from the
most abstract stratum of semantics to the least abstract level of expression, the resources for
expressing the grammar's wordings in writing (graphology) or speech (phonology). Each stratal
subsystem is organized in such a way that it can relate to its immediate stratal environment: it is
organized as inter-related strategic options available to the next higher stratum. Thus, any given
stratum is contextualized by the immediately higher stratum -- the higher stratum provides the
functional motivation for the lower one; and the lower one provides the resources to realize the higher
stratum. This is crucial in the design of a multilingual system: languages may have a fair amount of
functional commonality at one stratum but diverge with respect to the realization at the stratum next
below.
So far three levels of abstraction in the resources that make up language have received extensive
computational treatments -- a higher level that supports processing global to a text, a lower level that
supports more local text processing, and an intermediate level that serves as an interface between the
former two. These three levels constitute three strata in a stratal theory of language in context such as
systemic functional theory or stratificational theory:
● the highest stratum -- the semantic environment: higher-level meanings that provide the
semantic environment for any text, and the principal means of relating to context;
● the intermediate stratum -- the semantic interface: the semantic interface resources for relating
these higher-level meanings to the grammar;
● the lowest stratum -- the lexicogrammar: the grammatical resources for wording the meanings,
for expressing them lexically and structurally.
We therefore prefer a rather more finely differentiated stratification than that typical in computational
linguistics and give full stratal status to the relations defined between semantics and grammar. This is
both linguistically necessary and practically useful. Emele et al. () demonstrate that the sheer diversity
of interactions between distinct kinds of linguistic information is guaranteed to defeat any staged
approach to generation/understanding that successively maps between levels of representation. A
highly differentiated scheme of stratification then simplifies inter-stratal mappings and provides
maximal support for the necessarily simultaneous resolution of constraints drawn from multiple levels
of representation. This becomes increasingly important the further one moves away from toy research
prototypes.
http://www.darmstadt.gmd.de/publish/komet/kpml-1-doc/node17.html (1 von 2) [11.12.2004 14:20:50]