From Distributed Object Features to Architectural Styles

Distributed object oriented software is gaining interest. Nevertheless, developing distributed systems is inherently more difficult than creating single-machine applications. Middleware solutions and distributed object frameworks are intended to help developers in building distributed software. Deciding on which distributed technology to deploy, however, is not straightforward. In this paper, we will introduce three architectural styles to classify distributed OO software. The styles differ in the dimensions of data location and object migration. In addition to a description of the styles we will give examples, discuss guidelines for their usage, and indicate which technologies can be deployed to implement the styles. Thus, by classifying and cataloging distributed OO software in architectural styles and providing guidelines for their usage, we are trying to give some guidance for the development of distributed software

Dynamic and Mobile VRML Gadgets

VRML97 still falls short when it comes to support dynamic, interactive multi-user worlds and shared visualizations. In this paper, we will discuss the use of CORBA and mobile object technology for the realization of VRML gadgets and VRML display agents that allow for updates in response to server-push events. In particular, a user can share a VRML world with another user simply by sending a clone of a display agent. This technique also allows us to create a repository-server for fragments of dynamic VRML visualizations. We will briefly discuss an example where this technology is used to realize collaborative visualizations to support decisionmaking processes. CR Categories and Subject Descriptors: I.3.2 [Computer Graphics]: Graphics Systems - Distributed/network graphics; I.3.8 [Computer Graphics]: Applications; D.2.12 [Software Engineering]: Interoperability - Distributed objects Additional Keywords: VRML, Information Visualization, Virtual Worlds, CORBA, Mobile Object Technology, ..

3D Gadgets for Business Process Visualization - a case study

Business visualization is becoming increasingly important, since managers recognize the power of human visual intuition in information-rich decision tasks. Nevertheless, despite its promises, 3D visualizations are far less common than one would expect. In this paper, we describe a case study where we took a 2D visualization of a business process as a starting point, for which we subsequently provided a 3D visualization. We introduce a small set of 3D visualization gadgets and associated behaviors, implemented in Java3D, that proved to be relatively complete for our case. For each of these gadgets and behaviors, we will discuss requirements and design trade-offs. The case study, which concerns an actual business process of the largest social security provider in the Netherlands, illustrates the usability of our gadgets and their associated behaviors, which include brushing, grouping, and (drill down) manipulation. CR Categories and Subject Descriptors: I.3.2 [Computer Graphics]: Grap..

Animating the Web - an SGML-based approach

The DejaVu framework offers access to the Web as one of the facilities in a collection of software components for developing multimedia user interfaces and hypermedia applications. It provides a vehicle for experimenting with true hypermedia extensions to the Web. Our approach, which is essentially object-oriented, allows for integrating the Web in applications and vice versa, for composing a Web browser with support for sound synthesis, digital video, 3D graphics and virtual reality. On a software level this is realized by extending HTML to allow for embedded scripts, written in a script language that is extensible with application-defined functionality. However, in addition to this rather low-level provision for active documents, our Web browser component allows for SGML-defined document types capturing the syntax and semantics of multimedia extensions. This paper gives a brief overview of the various components constituting the DejaVu framework and discusses briefly the architectura..

Web applications and SGML

This article advocates the use of SGML technology for the creation, dissemination and display of Web documents. It presents a software architecture that allows for defining the operational interpretation of arbitrary document types by means of style sheets, written in a scripting language. Our approach has been motivated by a desire to extend the functionality of the Web with support for multimedia and active documents. Although growing in complexity, HTML is still lacking in functionality. We prefer a more flexible and generic approach, as enabled by the employment of SGML. After a brief introduction to SGML, we will illustrate how our approach accommodates (extensions of) HTML as well as arbitrary SGML documents containing multimedia data such as video and audio. We will then briefly sketch the software components used in the realization of our approach and discuss some topics for further research. KEY WORDS SGML WWW Style sheets Active documents

Components for Embedded Software - The PECOS Approach

components do not have a representation in the model as they do not contribute to the run--time behavior of field device software. They are merely a technique to simplify specification and to enable the reuse of designs. abstract component PecosControlLoop# role AbstractProcessApplication PecosPA; role AbstractControlDevice PecosCtrl; role AbstractFeedBackDevice PecosFdbck; connector setPoint(setPoint, PecosPA.setPoint); connector feedback1(PecosPA.actualPosition, PecosFdbck.actualPosition); connector feedback2(PecosPA.velocity, PecosFdbck.velocity); connector control(PecosPA.setFrequency, PecosCtrl.setFrequency); [...] component PositionValve is PecosControlLoop# ProcessApplication pa is PecosPA; ModBus mb is PecosCtrl; FQD fqd is PecosFdbck; Fig. 7. Using abstract components to specify system families Besides the elements known from normal components, abstract components can define so--called roles. Roles are typed variation points or holes in a (micro--)architecture. Fig. 7 shows the specification of an architectural style for control loops

PECOS in a Nutshell

COMPONENT identifier isList hasPropertySets abstractComponentBody componentType : PASSIVE | ACTIVE | EVENT | isList : (IS abstractComponentNames | ) hasPropertySets : (HAS propertySetNames | ) 71 componentBody : { (propertySettings | ) (portDecl | instance | connector | ;)* } abstractComponentBody : { (propertySettings | ) (portDecl | instance | role | connector | ;)* } abstractComponentNames : abstractComponentName (COMMA abstractComponentName)* abstractComponentName : Identifier propertySettings returns : PROPERTIES { (propertyStatement | ;)* } componentName : Identifier portDecl : portOption portType dataType Identifier hasPropertySets portBody portOption : OPTIONAL | MANDATORY | portType : IN | OUT | INOUT dataType : (typeName | baseType) ([ Integer ])* portBody : { (propertyStatement)* } | ; propertyStatement : IF String propertyStatement | compoundPropStatement | propertyInList portAccess : (instName DOT | ) portName instName 73 por..