8,915 research outputs found
Concurrent Computing with Shared Replicated Memory
The behavioural theory of concurrent systems states that any concurrent
system can be captured by a behaviourally equivalent concurrent Abstract State
Machine (cASM). While the theory in general assumes shared locations, it
remains valid, if different agents can only interact via messages, i.e. sharing
is restricted to mailboxes. There may even be a strict separation between
memory managing agents and other agents that can only access the shared memory
by sending query and update requests to the memory agents. This article is
dedicated to an investigation of replicated data that is maintained by a memory
management subsystem, whereas the replication neither appears in the requests
nor in the corresponding answers. We show how the behaviour of a concurrent
system with such a memory management can be specified using concurrent
communicating ASMs. We provide several refinements of a high-level ground model
addressing different replication policies and internal messaging between data
centres. For all these refinements we analyse their effects on the runs such
that decisions concerning the degree of consistency can be consciously made.Comment: 23 page
A Survey of Languages for Specifying Dynamics: A Knowledge Engineering Perspective
A number of formal specification languages for knowledge-based systems has been developed. Characteristics for knowledge-based systems are a complex knowledge base and an inference engine which uses this knowledge to solve a given problem. Specification languages for knowledge-based systems have to cover both aspects. They have to provide the means to specify a complex and large amount of knowledge and they have to provide the means to specify the dynamic reasoning behavior of a knowledge-based system. We focus on the second aspect. For this purpose, we survey existing approaches for specifying dynamic behavior in related areas of research. In fact, we have taken approaches for the specification of information systems (Language for Conceptual Modeling and TROLL), approaches for the specification of database updates and logic programming (Transaction Logic and Dynamic Database Logic) and the generic specification framework of abstract state machine
State-of-the-art on evolution and reactivity
This report starts by, in Chapter 1, outlining aspects of querying and updating resources on
the Web and on the Semantic Web, including the development of query and update languages
to be carried out within the Rewerse project.
From this outline, it becomes clear that several existing research areas and topics are of
interest for this work in Rewerse. In the remainder of this report we further present state of
the art surveys in a selection of such areas and topics. More precisely: in Chapter 2 we give
an overview of logics for reasoning about state change and updates; Chapter 3 is devoted to briefly describing existing update languages for the Web, and also for updating logic programs;
in Chapter 4 event-condition-action rules, both in the context of active database systems and
in the context of semistructured data, are surveyed; in Chapter 5 we give an overview of some relevant rule-based agents frameworks
As-built design specification for LACIE phase 3 automatic status and tracking system
There are no author-identified significant results in this report
Behavioural Theory of Reflective Algorithms I: Reflective Sequential Algorithms
We develop a behavioural theory of reflective sequential algorithms (RSAs),
i.e. sequential algorithms that can modify their own behaviour. The theory
comprises a set of language-independent postulates defining the class of RSAs,
an abstract machine model, and the proof that all RSAs are captured by this
machine model. As in Gurevich's behavioural theory for sequential algorithms
RSAs are sequential-time, bounded parallel algorithms, where the bound depends
on the algorithm only and not on the input. Different from the class of
sequential algorithms every state of an RSA includes a representation of the
algorithm in that state, thus enabling linguistic reflection. Bounded
exploration is preserved using terms as values. The model of reflective
sequential abstract state machines (rsASMs) extends sequential ASMs using
extended states that include an updatable representation of the main ASM rule
to be executed by the machine in that state. Updates to the representation of
ASM signatures and rules are realised by means of a sophisticated tree algebra.Comment: 32 page
NASTRAN general purpose interface requirements document
This NASTRAN (NASA STRuctural ANalysis) General Purpose Interface Requirements Document (IRD) defines standards for deliverables required of New Capability Contractors (NCCs) and relates these deliverables to the software development cycle. It also defines standards to be followed by NCCs for adding to and modifying the code in the NASTRAN software system and for adding to and modifying the four official NASTRAN manuals: The NASTRAN Theoretical Manual, the NASTRAN User's Manual, The NASTRAN Programmer's Manual, and The NASTRAN Demonstration Problem Manual. It is intended that this General Purpose IRD shall be incorporated by reference in all contracts for a new NASTRAN capability
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