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A Distributed Data Flow Model for Composing Software Services

David W. Liu
Ph.D. Thesis, Department of Electrical Engineering, Stanford University, 2003.
Last Updated: 6/10/2003

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Composition of Autonomous Services with Distributed Data Flows and Computations

David Liu, Jun Peng, Kincho H. Law, Gio Wiederhold, and Ram D. Sriram
Submitted to ACM Transactions on Internet Technology, 2003
Last Updated: 6/25/2003

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This paper presents a Flow-based Infrastructure for Composing Autonomous Services (FICAS) that supports a software composition paradigm, where software components are linked together through an integration framework to form composed software applications called megaservices. The software components are provided as processes managed by independent service providers; we call these components autonomous services. FICAS employs a distributed data-flow approach that differs from the centralized data-flow approach adopted by many current service integration frameworks, such as CORBA, J2EE and SOAP. The distributed data-flow approach allows direct data exchange among the autonomous services and consequently facilitates the distribution of computations. FICAS is implemented as a collection of software modules that support the construction of autonomous services, facilitate the functional composition of autonomous services into megaservices, and carry out the execution of megaservices. We have built a prototype for an information service environment based on FICAS that incorporates a variety of construction project scheduling software. The prototype demonstrates that the distributed data-flow approach is more efficient than the centralized approach when integrating large engineering software services.

An Engineering Information Service Infrastructure for Ubiquitous Computing

David Liu, Jinxing Cheng, Kincho H. Law, Gio Wiederhold, and Ram D. Sriram
Journal of Computing in Civil Engineering, October 2003.
Last Updated: 6/25/2003

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This paper describes a software framework for the development of a ubiquitous computing environment for distributed engineering information services. Two fundamental issues are addressed: universal accessibility from devices to information services, and collaboration among the parties accessing the information services. The first issue calls for the development of device-independent information services that have the flexibility to support wide range of client devices. We introduce a mediation-based framework that enables the information clients to calibrate the source information services to the clients' characteristics. The second issue requires effective integration of information services, for which we address in two ways: (1) we sketch an ontology standard and describe how such a standard can be applied effectively for exchanging scheduling information; (2) we illustrate an infrastructure that is particularly suitable for the integration of engineering services. A prototype for the ubiquitous computing environment has been developed that incorporates a variety of project management software as well as different devices ranging from PDA (personal digital assistant), web browsers, desktop computers, and servers.

Composition of Engineering Web Services

David W. Liu, Jim Cheng, James Peng, Kincho H. Law, and Gio Wiederhold
Last Updated: 4/10/2003

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Composition of Web Services

David W. Liu, Kincho H. Law, and Gio Wiederhold
Last Updated: 6/4/2002

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The presentation:

Identifies the key research areas in web service composition;
Outlines the research issues in each area;
Provides an overview of the contributions made to address the research issues.

Ubiquitous Computing Environment for Project Management Services

David Liu, Jinxing Chen, Kincho Law, and Gio Wiederhold
Civil Engineering Conference, Washington DC, 2002

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This paper describes a mediation based software framework for the development of a ubiquitous computing environment for distributed engineering services. Two fundamental issues are addressed: (1) universal accessibility from devices to services, and (2) coordination and interaction among the parties accessing the services. A prototype infrastructure has been developed and illustrated using a variety of project management application software as well as different devices ranging from PDA, web browsers and desktop computing.

An Engineering Data Access System for a Finite Element Program

Jun Peng, David Liu and Kincho H. Law
Journal of Advances in Engineering Software, 2002

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This paper describes a prototype implementation of an engineering data access system for a finite element analysis program. The system incorporates a commercial off-the-shelf (COTS) database as the backend to store selected analysis results; and the Internet is utilized as the communication channel to access the analysis results. The objective of using an engineering database is to provide the users the needed engineering information from readily accessible sources in a ready-to-use format for further manipulation. Three key issues regarding the engineering data access system are discussed, including data modeling, data representation, and data retrieval. The engineering data access system gives great flexibility and extendibility to the data management in finite element programs and can provide additional features to enhance the applicability of finite element analysis software.

Active Mediation Technology for Service Composition

David Liu, Neal Sample, Jun Peng, Kincho Law, and Gio Wiederhold
Submitted to International Symposium on Distributed Objects and Applications, Irvine, CA, 2002

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This paper discusses how active mediation allows information clients to modify the processing behavior of source information services to facilitate service composition. A new computing paradigm is enabled by incorporating active mediators into autonomous services to allow execution of mobile classes - dynamic information processing modules. We describe two key components of active mediation in the FICAS service composition infrastructure: (1) the programming language support for specifying mobile classes and using mobile classes in a composed service; and (2) the runtime support that enables the execution of mobile classes by the autonomous services. The power of active mediation is demonstrated by a few examples of mobile classes that conduct complex information processing for service composition. Finally, we discuss the performance issues in deploying active mediation. Specifically, we introduce an algorithm that determine the optimal placement of mobile classes on alternative autonomous services, and discuss the applicability of the algorithm using example mobile classes.

Data-flow Distribution in FICAS Service Composition Infrastructure

David Liu, Kincho Law, and Gio Wiederhold
15th International Conference on Parallel and Distributed Computing Systems, Louisville, KY, 2002

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This paper presents FICAS, a distributed data-flow infrastructure for composing software services into megaservices.  The purpose of using distributed data-flows is to promote scalability and performance without affecting how services are composed.  We discuss the basic features of FICAS that enable the distribution of data-flows within megaservices.  An autonomous service access protocol, ASAP, is defined to enforce the explicit separation of control-flows from data-flows of software services.  The protocol serves as the basis for enabling data-flow distribution.  We illustrate the procedure to construct and optimize megaservice execution plans that form distributed data-flows among collaborating services.  The megaservice performance under FICAS is evaluated and compared with that under the centralized data-flow infrastructures.  FICAS enhances the megaservice performance and is especially suitable for large-scale service composition.

Analysis of Integration Models for Service Composition

David Liu, Kincho Law, and Gio Wiederhold
Third International Workshop on Software and Performance, Rome, Italy, 2002

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This paper studies service integration infrastructures that support the execution of megaservices - large-scale applications that are composed of autonomous service modules. Integration infrastructures are classified according to their control-flow and data-flow structures. We analyze the effects of data-flows on the performances of the centralized and distributed data-flow models. A mathematical model is built to compare the performances of megaservices. Particularly, aggregated cost and response time metrics are defined and evaluated. We arrive at the conclusion that the distributed data-flow model is in general superior in performance. We also identify the key system parameters as well as system bottlenecks. The analysis provides recommendations for a few techniques to build high-performance and scalable service integration infrastructures based on the distribution of data-flows.

Composition of A/E/C Services

David Liu, Laurence Melloul, Kincho H. Law, Armando Fox, and Gio Wiederhold
CIFE Seed Proposal 2002

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This interdisciplinary, joint research project seeks to address the issues that will allow the composition of services based on isolated large-scale software applications commonly employed in the A/E/C industry.  We expect the following results from the proposed research:

A common data exchange model based on which information can be exchanged among collaborating software applications;
A scalable infrastructure in which autonomous services can be integrated;
Development of a high-level compositional language;
A megaservice control module for coordinating the execution of megaservices; and
Development of algorithms for distribution of megaservice data-flows.

We have successfully exchanged data among project management tools such as Vite, 4D modeling tool, Primavera and Microsoft Project. We plan to continue focusing on these software applications, which are to be adopted in the flagship project planned by CIFE. In addition, our plan also includes demonstrating the framework with supply chain management and on-line e-business applications.

CHAOS: An Active Security Mediation System

David Liu, Kincho Law, and Gio Wiederhold
International Conference on Advanced Information Systems Engineering, Stockholm, Sweden, 2000

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With the emergence of the Internet, collaborative computing has become more feasible than ever.  Organizations can share valuable information among each other.  However, certain users should only access certain portions of source data.  The CHAOS (Configurable Heterogeneous Active Object System) project addresses security issues that arise when information is shared among collaborating enterprises.  It provides a framework for integrating security policy specification with source data maintenance.  In CHAOS, security policies are incorporated into the data objects as active nodes to form active objects.  When active objects are queried, their active nodes are dynamically loaded by the active security mediator and executed.  The active nodes, based on the security policy incorporated, can locate and operate on all the elements within the active object, modifying the content as well as the structure of the object.  A set of APIís is provided to construct more complex security policies, which can be tailored for different enterprise settings.  This model moves the responsibility of security to the source data provider, rather than through a central authority.  The design provides enterprises with a flexible mechanism to protect sensitive information in a collaborative computing environment.