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Introduction

The foundation of scheduling is the availability of information about those periods when an attendee or resource is available to be scheduled and when that attendee or resource is not available to be scheduled. This information is referred to in calendaring and scheduling as “Freebusy” time, and is most commonly expressed as an IETF RFC 2445 VFREEBUSY object, which can be a request for Freebusy time, a response to a request, or a published set of busy time.

Calendaring standards, such as IETF RFC 2445, IETF RFC 2446, IETF RFC 2447, IETF RFC 4791, and the draft CalDAV Scheduling (http://tools.ietf.org/html/draftdesruisseaux- caldav-sched.txt) provide mechanisms for publishing, retrieving, and interrogating Freebusy status.

Outside these specifications, another mechanism for sharing Freebusy information is widely used — Freebusy URL. Freebusy URL typically allows for the publication and/or retrieval of Freebusy information via HTTP. The exact form of the URL, the specifics of the data actually returned (such as the period, format, etc), and error handling are all proprietary to each product or server. In most instances, a URL is stored, most often in an addressbook of some kind. This does not accommodate requests for Freebusy information across specific periods of time.

Freebusy URL is a weak form of calendar sharing which does not provide for interoperability across the range of calendaring products and services, but it is a very useful form of sharing, nonetheless:

  • It is simple (in many respects)

  • It is relatively easy to implement Freebusy URL

  • It facilitates scheduling in the non-enterprise, standalone calendaring client scenario.

  • Microsoft Outlook supports a form of Freebusy URL in the “Internet Free/Busy” feature

The objective of this specification is to preserve the simplicity, ease of implementation, and compatibility with Outlook, while providing additional benefits and functionality:

  • Standardize and normalize parameters, using a template approach.

  • Provide greater flexibility and functionality through the use of optional parameters

  • Standardize error handling

  • Allow for strong, weak, and no authentication

  • Standardize formats for returned Freebusy data

Freebusy URL potentially bridges the divide between enterprise calendaring and calendar/scheduling augmentation/aggregation sites, and standalone calendaring clients (no server).

This document deals only with the Freebusy Read URL, used to retrieve Freebusy information from servers. Other documents will describe publishing of Freebusy information and discovery issues.