Barron Cornelius Housel

EXPRESS: a data EXtraction, Processing, and Restructuring System

EXPRESS is an experimental prototype data translation system which can access a wide variety of data and restructure it for new uses. The system is driven by two very high level nonprocedural languages: DEFINE for data description and CONVERT for data restructuring. Program generation and cooperating process techniques are used to achieve efficient operation. This paper describes the design and implementation of EXPRESS. DEFINE and CONVERT are summarized and the implementation architecture presented. The DEFINE description is compiled into a customized PL/1 program for accessing source data. The restructuring specified in CONVERT is compiled into a set of customized PL/1 procedures to derive multiple target files from multiple input files. Job steps and job control statements are generated automatically. During execution, the generated procedures run under control of a process supervisor, which coordinates buffer management and handles file allocation, deallocation, and all input/output requests. The architecture of EXPRESS allows efficiency in execution by avoiding unnecessary secondary storage references while at the same time allowing the individual procedures to be independent of each other. Its modular structure permits the system to be extended or transferred to another environment easily.

WebExpress: a client/intercept based system for optimizing Web browsing in a wireless environment

This paper describes an application model and software technology that makes it possible to run World Wide Web applications in wide area wireless networks. Web technology in conjunction with todays mobile devices (e.g., laptops, notebooks, personal digital assistants) and the emerging wireless technologies (e.g., digital cellular, packet radio, CDPD) offer the potential for unprecedented access to data and applications by mobile workers. Yet, the limited bandwidth, high latency, high cost, and poor reliability of todays wireless wide-area networks greatly inhibits (to the point of infeasibility) supporting such applications over wireless networks. This paper presents the Client/Intercept computational model that makes it possible to run such distributed applications efficiently in wide area wireless networks. Furthermore, it presents WebExpress, a client/intercept based system for optimizing Web browsing, that reduces data volume and latency of wireless communications by intercepting the HTTP data stream and performing various optimizations including: file caching, forms differencing, protocol reduction, and the elimination of redundant HTTP header transmission. This paper describes these optimizations and presents some experimental results.

Mobile Web access using eNetwork Web Express

The mobile computing environment poses severe problems for Web browsing and Web-based applications. Mobile communication links are typically slow, expensive, and unreliable. This is especially true of wide-area wireless networks, which are becoming increasingly popular. Furthermore, both voluntary and involuntary disconnections from servers are common in the mobile environment, and the standard browsing model provides no support for disconnected operation. In addition, the usual request/response model of browsing is synchronous, which means that congestion in the network and Web servers cannot be masked from users. This article describes eNetwork Web Express, a software system that addresses these issues. Paired proxies are used to optimize communication in low-bandwidth networks and to enable a browsing model in which both disconnected and asynchronous operations are supported. The resulting environment allows Web-based applications to be used effectively in a mobile setting.

A general methodology for data conversion and restructuring

This paper presents a methodology and a model for data conversion or translation. The model assumes that both source and target systems are available and that conversion interfaces may be required to interact between these systems and the conversion system. To achieve data conversion or translation using this approach, two languages are needed: 1) a language to describe the data structures, and 2) a language to specify the mapping between source and target data. This paper describes these two languages, DEFINE and CONVERT and gives numerous examples to show the capabilities of these languages and how they can be used in data conversion and restructuring. Both languages are high level and nonprocedural and have the power to deal with most situations encountered in data conversion processes. In addition, the paper also describes some of the facilities in the languages specifically designed for data checking in a data conversion process.

A high-level data manipulation language for hierarchical data structures

In this paper we assert that the hierarchical view of data will continue to be popular for a broad class of applications and users. In particular, some of these applications require complex data manipulation which, heretofore, has been dealt with procedurally. In this light, a nonprocedural language, CONVERT, is proposed as a high-level DBMS interface. CONVERT is meant to provide users with a tool for performing complex data manipulation and query of hierarchical data abstractions, called “Forms”. Included in the paper are a description of the Form data abstraction and the CONVERT language, as well as a complete illustrative sample application.

Architecture to an interactive migration system (AIMS)

Growth in the computer industry produces a need to convert data and/or programs from one system to another from time to time. While this process has been going on for years, the techniques used to execute this task have been ad hoc and expensive. Very few aids exist on the market today to help this process. Examination into the conversion scenario reveals that the structure of a system to aid conversion should have the following features: (1) ability to extract pertinent information from high level source application programs and source systems environment. (2) interactive facility where users and the conversion aid system can work together to make the decisions. (3) ability to carry out the translation process automatically after directions are given from a high level language. This paper describes the architecture of such a system and gives the motivations which lead to such conclusions.

Emulator express: a system for optimizing emulator performance for wireless networks

IBM eNetworkTM Emulator Express is an IBM program product that optimizes the operation of Telnet 3270 and 5250 emulation over extremely low-bandwidth networks. These optimizations enable mobile workers using laptops, notebooks, or other mobile devices to access legacy host applications effectively over wide-area wireless networks as well as low-bandwidth wireline modem connections. This paper describes how the Emulator Express system intercepts the data stream and optimizes it transparently to both the client emulator and the Telnet server. The optimizations include a new data stream caching technology, a new optimized protocol that reduces the number of Telnet negotiation flows, and traditional compression. The data stream caching technology is particularly significant because it may be applied to other distributed application domains. The results of several performance experiments are reported that illustrate the improvements in data transport volume and response time when using Emulator Express.

Pipelining: a technique for implementing data restructurers

In the past several years much attention has been given to the problem of data translation. The focus has been mainly on methodologies and specification languages for accomplishing this task. Recently, several prototype systems have emerged, and now the issues of implementation and performance must be addressed. In general, a data restructuring specification may contain multiple source and target files. This specification can be viewed as a “process graph” which is a network of restructuring operations subject to precedence constraints. One technique used to achieve good performance is that of pipelining data in the process graph. In this paper we address a number of issues pertinent to a pipelining architecture. Specifically, we give algorithms for resolving deadlock situations which can arise, and partitioning the process graph to achieve an optimal schedule for executing the restructuring steps. In addition, we discuss how pipelining has influenced the design of the restructuring operations and the file structures used in an actual system.