摘要:

AbstractMany Smalltalk implementations store objects in a large file called a virtual image. Each user must have a copy of the virtual image to execute. Since the image can exceed a megabyte in size, considerable disk space is required to support such a system in a multi‐user environment. In this paper, a method is described which can reduce storage requirements for systems which use generation scavenging as a memory reclamation technique. This method also improves the performance of the checkpoint operation and offline garbage‐collect

ISSN:0038-0644    

DOI:10.1002/spe.4380230302

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractWe consider the accuracy of linear interpolation in predicting which subsegment contains a random key, given that the key is contained in a particular segment consisting of a fixed number of subsegments. We assume that keys are stored in a file in sorted order, that the file is divided into fixed‐size segments, and that the first key in the segment containing the desired key is known, as is the first key of the next segment. We present empirical results for real files in which keys are social security numbers, names and telephone numbers, and for files of keys generated randomly from the uniform and from the exponential distributions. We present a theoretical analysis of the average success rate for the case in which keys are uniformly distributed. We show that the success rate depends on the number of subsegments in a segment, the size of a subsegment, and the distribution of keys, and that it is much higher than for random guessing. We describe practical applications in which this technique can be efficiently use

ISSN:0038-0644    

DOI:10.1002/spe.4380230303

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractCreating new applications by integrating user interface and application components is a relatively new idea which is currently of wide interest. A significant part of this problem is clearly defining the separation between user interface and application components. This paper proposes a new design methodology based on the concept of an abstract data view (ADV), a structuring method which cleanly defines this separation. A number of examples of composite interactive documents, ones which could contain several different user interfaces with entities such as text, calculations, drawings and possibly even multi‐media presentations, illustrate the ADV concept. These examples lead naturally to the introduction of the concept ofhole, a user interface area in a composite interactive document which is managed by an external program, and uses ADVs. Prototypes of a number of systems supporting ADVs and holes are currently running in our laborator

ISSN:0038-0644    

DOI:10.1002/spe.4380230304

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper shows how trees can be stored in a very compact form, called ‘Bonsai’, using hash tables. A method is described that is suitable for large trees that grow monotonically within a predefined maximum size limit. Using it, pointers in any tree can be represented within 6 + [log2n] bitsper nodewherenis the maximum number of children a node can have. We first describe a general way of storing trees in hash tables, and then introduce the idea of compact hashing which underlies the Bonsai structure. These two techniques are combined to give a compact representation of trees, and a practical methodology is set out to permit the design of these structures. The new representation is compared with two conventional tree implementations in terms of the storage required per node. Examples of programs that must store large trees within a strict maximum size include those that operate on trie structures derived from natural language text. We describe how the Bonsai technique has been applied to the trees that arise in text compression and adaptive prediction, and include a discussion of the design parameters that work well in pract

ISSN:0038-0644    

DOI:10.1002/spe.4380230305

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractDefinition of a software process to be analyzed is normally top‐down. Analysis starts with a rough description and evolves into finer granularity as more performance and functional requirements become available. This process involves different performance models at each stage. The relationship between these models forms a hierarchy of performance models. Performance parameters propagate bottom‐up and the analysis of these models is very complex, so that it is essential to develop computer aided performance evaluation (CAPE) tools to support the evaluation process. In this work, we developed a graphical interface for CAPE environments called the GRAphical Performance Evaluation (GRAPE) system. GRAPE supports the structural design of five different performance models: queueing, state, computation structure, data flow and statistical models. These models can be used to design parallel/distributed real‐time software systems at different levels of granularity. GRAPE is the front‐end tool for a CAPE environment that will allow the user to integrate the relationships between different performance metrics at different levels of analysis. These metrics propagate between the modeling hierarchy to arrive at a final quantitative or symbolic measure of its perf

ISSN:0038-0644    

DOI:10.1002/spe.4380230306

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractIn recent years, several attempts have been made to define query languages characterized by both high expressive power and easy query formulation. Several issues concern graphical applications, based on the diagrammatic representation of a semantic model and visual interaction. This paper describes the architecture and the implementation of a graphical query system, based on the diagrammatic representation of entity relationship schemata. The query language underlying the system allows the formulation of recursive queries; moreover, user interaction in both managing diagrams and expressing queries is simplified by the presence of a fully visual environment and a rich set of interaction strategies.

ISSN:0038-0644    

DOI:10.1002/spe.4380230307

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractCompilation time can be improved by precompiling interfaces so that the compiler can avoid processing unreferenced declarations. However, in C‐based languages precompiling a header is difficult because a header can have several meanings depending on the context in which it is included. We present anad hocsolution to this problem, and give the results of our precompilation strategy, which improved compile times by 25 to 65 per cent over compilation without precompiled header

ISSN:0038-0644    

DOI:10.1002/spe.4380230308

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:0038-0644    

DOI:10.1002/spe.4380230301

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY