type ref t = id:N{witnessed (has_a_t id t)} let has (id:N) (H h _) = match h id with Used _ _ (Untyped _)→⊤ | _→⊥ abstract type uref = id:N{witnessed (has id)}type uref = id:N{witnessed (has id)} To enforce these invariants on state-manipulating operations, we define a preorder rel on heap, that constrains the heap evolution. It states that every Used identifier remains Used; every Typed refere...

The former method starts by numerically estimating the adequacy and the inadequacy (with respect to the initial data) ofeach statement "the alternative i appears in on aggregate hierarchy on the j-th place* and constructs a preorder which maximizes the ratio of total sum of adequacy values by the total sum of inadequacy values for the associated hierarchy. The latter method involves usual conco...

A preorder on the line-of-sight (LOS) matrices in coherent multipleinput multiple-output (MIMO) Ricean fading channels is introduced. It is demonstrated that under this preorder, the information rate corresponding to zero-mean multivariate circularly symmetric Gaussian inputs of arbitrary covariance matrices is monotonic in the LOS matrix. This result implies the monotonicity of the information...

We present an extension of the classical testing semantics for the case when nondeterminism is unbounded. We deene the corresponding may and must preorders in the new framework. As in the bounded setting the may preorder can be characterized by using the set of nite traces of processes. On the contrary, in order to characterize the must preorder is necessary to record some additional informatio...

In this paper we show results on the combinatorial properties of shifted simplicial complexes. We prove two intrinsic characterization theorems for this class. The first theorem is in terms of a generalized vicinal preorder. It is shown that a complex is shifted if and only if the preorder is total. Building on this we characterize obstructions to shiftedness and prove there are finitely many i...

The parametric lambda calculus subsumes different existing λ-calculi, in particular the classical λβ-calculus and the λβv-calculus of Plotkin. Previously established results on the parametric calculus, such as as confluence and standardization, are primarily syntactical. In this paper our attention is mainly addressed to semantics, although we start again from a syntactical point of view. We pr...

In this paper, we present a general way of giving denotational semantics to a class of languages equipped with an operational semantics that fits the GSOS format of Bloom, Istrail and Meyer. The canonical model used for this purpose will be Abramsky’s domain of synchronization trees, and the denotational semantics automatically generated by our methods will be guaranteed to be fully abstract wi...

We define a language for Web services contracts as a parallelfree fragment of ccs and we study a natural notion of compliance between clients and services in terms of their corresponding contracts. The induced contract preorder turns out to be valuable in searching and querying registries of Web services, it shows interesting connections with the must preorder, and it exhibits good precongruenc...

We study the behavioural theory of πP, a π-calculus featuring restriction as the only binder. In contrast with calculi such as Fusions and Chi, reduction in πP generates a preorder on names rather than an equivalence relation. We present two characterisations of barbed congruence in πP: the first is based on a compositional LTS, and the second is an axiomatisation. The results in this paper bri...

It is well known that the vertices of any graph can be put in a linear preorder so that for random walk on the graph vertices appearing earlier in the preorder are “easier to reach but more difficult to get out of”. We exhibit further such preorders corresponding to various functions related to random walk and study their relationships. These preorders coincide when the graph is a tree, but not...