Vijay-Shanker et al. (1987) note that many interesting linguistic formalisms can be thought of as having essentially context-free structure, but operating over objects richer than simple stringsâ€¦ (More)

Proceedings of the 19th Annual IEEE Symposium onâ€¦

2004

We introduce a new class of automata, which we call vector addition tree automata. These automata are a natural generalization of vector addition systems with states, which are themselves equivalentâ€¦ (More)

In this work we establish that the language MIX = {w âˆˆ {a; b; c}||w|a = |w|b = |w|c} and the language O2 = {w âˆˆ {a; a; b; b}||w|a = |w|a âˆ§ |w|b = |w|b} are 2-MCFLs. As 2-MCFLs form a class ofâ€¦ (More)

We propose a new approach to analysing higher-order recursive schemes. Many results in the literature use automata models generalising pushdown automata, most notably higher-order pushdown automataâ€¦ (More)

We consider simply-typed lambda calculus with fixpoint operators. Evaluation of a term gives as a result the BÃ¶hm tree of the term. We show that evaluation is compatible with monadic secondorderâ€¦ (More)

A non-deterministic recursion scheme recognizes a language of finite trees. This very expressive model can simulate, among others, higher-order pushdown automata with collapse. We show decidabilityâ€¦ (More)

We consider simply typed lambda-calculus with fixpoints as a non-interpreted functional programming language: the result of the execution of a program is its normal form that can be seen as aâ€¦ (More)

We define a new class of pushdown systems where the pushdown is a tree instead of a word. We allow a limited form of lookahead on the pushdown conforming to a certain ordering restriction, and weâ€¦ (More)