ATMS-Based architecture for stylistics-aware text generation

This thesis is concerned with the effect of surface stylistic constraints (SSC) on syntactic and lexical choice within a unified generation architecture. Despite the fact that these issues have been investigated by researchers in the field, little work has been done with regard to system architectures that allow surface form constraints to influence earlier linguistic or even semantic decisions made throughout the NLG process. By SSC we mean those stylistic requirements that are known beforehand but cannot be tested until after the utterance or — in some lucky cases — until a proper linearised part of it has been generated. These include collocational constraints, text size limits, and poetic aspects such as rhyme and metre to name a few. This thesis introduces a new NLG architecture that can be sensitive to surface stylistic requirements. It brings together a well-founded linguistic theory that has been used in many successful NLG systems (Systemic Functional Linguistics, SFL) and an exist¬ ing AI search mechanism (the Assumption-based Truth Maintenance System, ATMS) which caches important search information and avoids work duplication. To this end, the thesis explores the logical relation between the grammar formalism and the search technique. It designs, based on that logical connection, an algorithm for the automatic translation of systemic grammar networks to ATMS dependency networks. The generator then uses the translated networks to generate natural language texts with a high paraphrasing power as a direct result of its ability to pursue multiple paths simultaneously. The thesis approaches the crucial notion of choice differently to previ¬ ous systems using SFL. It relaxes the choice process in that choosers are not obliged to deterministically choose a single alternative allowing SSC to influence the final lexical and syntactic decisions. The thesis also develops a situation-action framework for the specification of stylistic requirements independently of the micro-semantic input. The user or application can state what surface requirements they wish to impose and the ATMS-based generator then attempts to satisfy these constraints. Finally, a prototype ATMS-based generation system embodying the ideas presented in this thesis is implemented and evaluated. We examine the system's stylistic sensitivity by testing it on three different sets of stylistic requirements, namely: collocational, size, and poetic constraints

Extending Attribute Grammars to Support Programming-in-the-Large

Attribute grammars add specification of static semantic properties to context-free grammars, which in turn describe the syntactic structure of program units. However, context-free grammars cannot express programming-in-the-large features common in modern programming languages, including unordered collections of units, included units and sharing of included units. We present extensions to context-free grammars, and corresponding extensions to attribute grammars, suitable for defining such features. We explain how batch and incremental attribute evaluation algorithms can be adapted to support these extensions, resulting in a uniform approach to intra-unit and inter-unit static semantic analysis and translation of multi-unit programs

Exploiting the Layout Engine to Assess Diagram Completions

A practicable approach to diagram completion is to first compute model completions on the abstract syntax level. These can be translated to corresponding diagram changes by the layout engine afterwards. Normally, several different model completions are possible though. One way to deal with this issue is to let the user choose among them explicitly, which is already helpful. However, such a choice step is a quite time-consuming interruption of the editing process. We argue that users often are mainly interested in completions that preserve their original diagram as far as possible. This criterion cannot be checked on the abstract syntax level though. In fact, minimal model changes might still result in enormous changes of the original diagram. Therefore, we suggest to use the layout engine in advance for assessing all possible model completions with respect to the diagram changes they eventually cause

Natural language semantics and compiler technology

This paper recommends an approach to the implementation of semantic representation languages (SRLs) which exploits a parallelism between SRLs and programming languages (PLs). The design requirements of SRLs for natural language are similar to those of PLs in their goals. First, in both cases we seek modules in which both the surface representation (print form) and the underlying data structures are important. This requirement highlights the need for general tools allowing the printing and reading of expressions (data structures). Second, these modules need to cooperate with foreign modules, so that the importance of interface technology (compilation) is paramount; and third, both compilers and semantic modules need "inferential" facilities for transforming (simplifying) complex expressions in order to ease subsequent processing. But the most important parallel is the need in both fields for tools which are useful in combination with a variety of concrete languages -- general purpose parsers, printers, simplifiers (transformation facilities) and compilers. This arises in PL technology from (among other things) the need for experimentation in language design, which is again parallel to the case of SRLs. Using a compiler-based approach, we have implemented NLL, a public domain software package for computational natural language semantics. Several interfaces exist both for grammar modules and for applications, using a variety of interface technologies, including especially compilation. We review here a variety of NLL, applications, focusing on COSMA, an NL interface to a distributed appointment manager