ACE (editor)

ACE

Company type	Free software
Industry	Software
Area served	Worldwide
Products	Collaborative real-time text editor

ACE (ACE – a collaborative editor) is a cross-platform, collaborative real-time editor designed to allow multiple users located in different places to simultaneously view and modify shared text documents.

Introduction

ACE is an easy-to-use text editor that offers basic features such as copy/paste and load/save, with support for handling several documents at once. It facilitates document sharing among various computers connected through communication networks (LAN, Internet) and automatically detects users and shared files on local networks by leveraging zero-configuration networking, eliminating the need for manual setup.

Participants who join a shared document can edit it together in real time, aided by awareness tools that highlight each user’s cursor position and selected text using unique colors to reduce editing conflicts.

At the heart of ACE lies a concurrency control mechanism based on operational transformation, which enables simultaneous, lock-free editing without restrictions. This method guarantees consistency by ensuring all collaborators see the same document state once all messages have been delivered.

Built upon open standards such as BEEP (RFC 3080) and zero-configuration networking, ACE employs a public protocol that supports interoperability with other compatible software.

ACE is compatible with major operating systems including Windows, Mac OS X, and Linux, and is available as free software under the GPL license.

Example use case

Imagine a collaborative editing scenario involving three users: Bill, Steve, and Scott. Sam, a fourth individual, does not take part. The shared document, Collaboration.txt, is owned and published by Scott. Steve and Bill work on Microsoft Windows, Scott uses Mac OS X, while Sam operates on Linux. Within the ACE interface, the local user's text appears in blue, with other participants’ contributions highlighted in their assigned colors in the GUI.

Usage

ACE serves various professional and educational purposes, including:

• Group brainstorming sessions
• Source code development (XP)
• Shared note-taking
• Collaborative composition of e-mails, letters, or journals
• Educational teamwork

In academic settings, small teams can co-author essays together, fostering improvements in language proficiency and computer skills through interactive collaboration.

Technology background

ACE supports multiple users simultaneously viewing and editing the same document across geographically dispersed locations connected via communication networks. Essential system characteristics include:

• Real-time: Rapid local responsiveness with minimal delay reflecting remote changes.
• Distributed: Users operate from different machines over networks exhibiting varying latency.
• Unconstrained: Any number of users may edit any part of the document concurrently to encourage natural collaboration.

Each participant runs an instance connected over the network. A key challenge is preserving consistency among replicated documents. Consistency entails:

• Convergence: All replicas become identical after applying all operations.
• Causality-preservation: Dependent operations are executed in the same sequence on every site.
• Intention-preservation: Operations consistently achieve their intended effects without disrupting independent actions.

These consistency requirements are typically met using Operational Transformation (OT) algorithms, which consist of:

• An integration algorithm responsible for receiving, broadcasting, and executing operations—this part is independent of the application.
• A transformation function that merges concurrent operations—this component is specific to the type of application (e.g., text editor versus whiteboard).

This theoretical framework originates from research within the domain of Computer Supported Cooperative Work (CSCW).

See also

• Collaborative real-time editor
• SubEthaEdit
• Computer Supported Cooperative Work