WELD Infrastructure for a Distributed Design Environment

Introduction

The continuing advances in computer processing power, storage and network transmission capacity, as well as the ever-increasing amount of information and services available on the Internet indicate that future CAD environments will heavily leverage wide-area networks. And as design complexity continues to grow exponentially, so also do the needs, opportunities and potential advantages of network collaboration and design environments.

In the future, advances in computer and networking technologies will enable the rise of ubiquitous computing, applications that dynamically adapt to different hardware capabilities, and an increase in the number of network tools and services. Moreover, emerging technologies will enable data migration, agent/application migration, and network data access. In this environment, it will be imperative that distributed applications be scaleable and extensible. In addition, the rise of such distributed design systems will require advanced server features like consistency, fault tolerance, security, and intelligent resource location mechanisms.

On the client side, users of the system should be able to access and execute tools on the fly with minimal hardware and software in place (e.g. Java-enabled network browser). Furthermore, the working environment should allow remote tool invocation according to the user's access criteria and permission. Open frameworks could be achieved by users' flexible configuration of data formats and tools from different sources.

Motivation

The development of the Internet, networking and data processing technologies, such as HTTP, Java and OODBMS, together with the increase in complexity of the data and process of electronic design has provided many needs and opportunities for wide-area collaboration in the design of complex systems.

The benefits of a distributed design system at the system-level include:

Platform Independence - All that a user needs to access the system and available resources is a Java-enabled browser, such as Netscape and Internet Explorer.
Support of Wide Range of Computing Resources - Server technology allows local computing power to be coupled with applications and data processing on network servers. Such an environment supports a wide range of computing platforms, from high-end workstations to mobile PDAs.
Leverage of Existing Software, Systems and Toolkits - Java, network protocols and server technology can encapsulate existing tools and software resources regardless of their programming language, operating system base, and development environment (commercial, academia, etc.).
Implicit Parallelism - Operations can be distributed over the network to different servers, allowing low-cost parallel processing.
Scalability - Scalable addition for both users and tools.

Benefits at the user-level include:

Large User Base - The large number of Internet users both creates needs for and provides opportunities for innovation and wide-area collaboration.
High Availability - Networked tools provide users with on-demand access and ubiquitous computing.
Consistent, Intuitive User Interfaces - Consistent user interfaces across different computing platforms can help reduce engineers' start-up and training time.
Flexible Tool Configuration - An environment which allows users to custom design and configure tools and workflow to meet application-specific needs.

Architecture

WELD system architecture diagram.

The WELD architecture is a three-tier architecture consisting of:

Clients - Users/programs who access the network resources of the system.
Remote Servers - Tools or services that are made available for network access.
Network Services - Services existing in the network that assist various client/server activities.

The mechanism that enables these network entities to communicate with each other are:

Client-Server Communication Protocol
Client-Database Communication Protocol

Components Description

Clients

Java Network Clients - Java client programs which utilize the capabilities of the Java-Client Package can gain access to the system (database and remote servers) via a Java-enabled browser.
Stand-Alone Clients - Clients, developed in Java, C, C++, PERL, etc., that support network socket operations and the client protocol(s) can also connect with tools and services in the system.

Remote Servers

Legacy Tool Servers - Both new and legacy tools can be wrapped with server wrappers that allow them to be integrated with the distributed system and executed via network clients.
Integrated Servers - Servers, developed in Java, C, C++, etc., that have built-in support for socket connections and the client-server protocol can be seamlessly integrated into the WELD system. Such integrated network capabilities and protocol extension may also enable them to play a larger role (beyond simple program execution and data processing) in the system.

Network Services

Examples of network services include:

Distributed Data Manager

A database system that manages the data residing in the network, as opposed to on client machines or servers.

Functionality of the data manager include:

Saving and loading of data.
Query and search.
Versioning of data/objects/programs.
Incremental update mechanism.
Fine-grained granularity of object/data-locking
Transaction mechanism.
Directory/Registry service.
HTTP support (may be used also as a web server).

Proxies

A software program residing in the network that acts "intelligently" and transparently as an agent between clients, network servers and other proxies.

Functionality of proxies include:

When co-located with Web servers, proxies extend the Netscape-Java security model and enable Java applets/clients to communicate with available network resources.

Caching of (frequently accessed) data.
Automatic translation between data formats as needed for tools.
Data "distillation" [ref] according to application needs and network links.
Security/Access control.
Dynamic search for servers (in case of failures).
- Queuing, batch processing, and scheduling/locking for servers.
- Plug-in architecture that allows the extension of proxy capability to meet application-specific needs.

Registry Service

A table, which may be co-located with a data server, that maintains information on the availability of network resources.

Tools and services register with the system to inform the registry of their existence and availability, as well as any restriction that is placed upon access of the resources.
User applications can query the registry for availability and possible selection of tools.

Client/Server Communication Protocol

The client/server communication protocol enables communication between client-server and proxy-server. It was designed to:

Be able to flexibly handle server parameter type and values.
Allow for stand-alone, as well as recursive command structure.
Be extensible by users/application developers.

Client/Database Communication Protocol

The client/database communication protocol enables clients/client objects to communication with a network database. The protocol:

Allows client objects to be translated and mirrored in the database.
Allows the linking of objects in a completely arbitrary manner.
Enables clients to take advantage of built-in database capabilities, such as save, load, query, versioning, etc..

WELD Group Infrastructure

The development efforts of the WELD group have brought to fruition many of the software components mentioned above. While not all the capabilities have been implemented yet, the components and their features are rich enough to enable a prototype web-based design environment.

The components we (will) have in place (by June 1997) are:

Data Server - The current data server consists of a transaction manager on top of an object-oriented database. It allows any client object to be stored and mirrored as a database object through the use of a generic "connection" mechanism. Clients of the data server can store, retrieve (through our protocol or HTTP), query and traverse objects, as well as use the server for versioning purposes.

Server Wrapper - The server wrapper enables any legacy or new tools to be incorporated into the WELD system by enabling them to:

communicate with other network components
register with the registry service
be remotely invoked by networked users/programs

Client Package - A Java Client Persistent Object Management Package has been implemented that enables any Java objects/applications to communicate with and utilize the capabilities offered by the data server.

(Plans have also been made to port the package to C++ to support legacy tools.)

A Java client program has also been developed to allow any Java application to invoke network tools.

Communication Protocol - The two main communication protocols are the

client-server communication protocol and the client-database communication protocol. These mechanisms enable different network components to communicate with each other.

Proxy - The proxy mechanism extends the Java security model by allowing any Java applet to connect to available network resources.

Registry Service - The registry service receives registration information from network servers and serves the queries/requests of clients/tool flow managers.

Distributed Tool Flow Manager - The tool flow manager allows any user to configure the flow of network tools and data.

Modified: April 30, 1997
Feedback: (fchan@eecs.berkeley.edu)