This document represents a draft microformat specification. Although drafts are somewhat mature in the development process, the stability of this document cannot be guaranteed, and implementers should be prepared to keep abreast of future developments and changes. Watch this wiki page, or follow discussions on the microformats-new mailing list to stay up-to-date.
hReview-aggregate is a format for embedding review information (of products, services, businesses, etc). Whereas hReview is intended for an individual review, hReview-aggregate is meant for summary information about a collection of user or critic reviews about an item. hReview-aggregate is one of several microformats open standards suitable for embedding in HTML, XHTML, Atom, RSS, and arbitrary XML.
Microformats Draft Specification 2009-11-10
- Kavi Goel, Google
- Authors/Contributers (alphabetical)
- Tantek Çelik
- Othar Hansson, Google
- Jay Myers, Best Buy, Co., Inc.
Many websites publish reviews using a variety of organization schemes. hReview-aggregate and the similar microformat hReview were designed to enable sharing of review information.
hReview, created in 2006, is well suited to mark up reviews done by individuals on their own websites or for editor's reviews for a new product or service. However, in recent years, there has been an increasing number of sites who aggregate user reviews, either by accepting reviews submitted to their website or by collecting those user reviews from across the web. In these cases, it is often valuable to share not just the individual reviews shown on the webpage, but the consensus opinion derived from those individual reviews.
hReview-aggregate was created to address this need. hReview-aggregate is a standard that can be used to share the number of reviews, average rating, and consensus opinion for a particular product or service. It is meant to complement hReview and reuses hReview properties wherever appropriate. Research and discussion that fed into the design of hReview-aggregate can be found on the aggregate review brainstorming wiki page.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.
Collections of reviews consistently share several common aspects. Where possible hReview-aggregate has been based on this common subset.
Out of scope
Portions of reviews that are specific to particular kinds of items have been omitted from hReview-aggregate.
The hReview-aggregate schema consists of the following:
- hReview-aggregate (
photo) | hCard (for person or business) | hCalendar (for event) | hProduct (for product)
rating. required. fixed point integer [1.0-5.0], with optional alternate
best(default:5.0), also fixed point integers, and explicit
count. optional. non-negative integer.
votes. optional. non-negative integer. Note that while
votesare both marked optional, at least one of the two fields must be specified.
summary. optional. text.
Details of the hReview-aggregate properties:
item:: This required property MUST have at a minimum the name of the entity being reviewed (using the subproperty "fn"), or alternatively have an encapsulated microformat (i.e. hCard for a business or person, hProduct for a product, or hCalendar for an event). If an encapsulated microformat is not used, a URI ("url") for the item and a photo or depiction ("photo") MAY also be provided. Non-URL unique item IDs (e.g. ISBNs, UPCs) MAY be represented as a URN ("url") for the item. Encapsulated microformats must be set on the item itself (e.g. class="item vcard"). However, when using item info subproperties ("fn", "url", "photo"), they must be nested inside the item element.
rating:: The rating is a fixed point integer (one decimal point of precision) from 1.0 to 5.0 inclusive indicating the average rating for the item across all reviews, higher indicating a better rating by default. Optionally a different integral "worst" value and/or "best" value may be specified to indicate a different range (e.g. 6 from 0-10).
count:: This property is used to specify the total number of reviews for the product or service.
votes:: This property is used to specify the total number of users who have rated the product or service, contributing to the average rating. For some sites, the number of votes is equal to the number of reviews, so
count may be used and this property omitted.
summary:: This optional property can be the title for the review collection or a very short summary of the consensus opinion from the collection.
summary properties are reused from hReview.
Here is an example showing aggregate review information for a restaurant:
<div> <h3> <span>Mediterranean Wraps</span> </h3> <span>Customers flock to this small restaurant for their tasty falafel and shawerma wraps and welcoming staff.</span> <span>4.5 out of 5 based on 17 reviews</span> </div>
Adding hReview-aggregate markup to this is straightforward:
<div class="hreview-aggregate"> <h3 class="item"> <span class="fn">Mediterranean Wraps</span> </h3> <span class="summary">Customers flock to this small restaurant for their tasty falafel and shawerma wraps and welcoming staff.</span> <span><span class="rating">4.5</span> out of 5 based on <span class="count">17</span> reviews</span> </div>
Embedded microformat, 10-point rating scale
Often, there is more information available on a page about the item being reviewed than the title. Here is another example of a restaurant review, but with address information present.
<div> <div> <h3>Mediterranean Wraps</h3> <span>433 S California Ave</span> <span>Palo Alto, CA <span>(650) 321-8189</span> </div> <span>Customers flock to this small restaurant for their tasty falafel and shawerma wraps and welcoming staff.</span> <span>9.2 out of 10 based on 17 reviews</span> </div>
And here it is with hReview-aggregate markup, along with an embedded hCard to describe the address and phone information for the restaurant:
<div class="hreview-aggregate"> <div class="item vcard"> <h3 class="fn">Mediterranean Wraps</h3> <span class="adr"> <span class="street-address">433 S California Ave</span> <span><span class="locality">Palo Alto</span>, <span class="region">CA</span></span> <span class="tel">(650) 321-8189</span> </span> </div> <span class="summary">Customers flock to this small restaurant for their tasty falafel and shawerma wraps and welcoming staff.</span> <span class="rating"><span class="average">9.2</span> out of <span class="best">10</span> based on <span class="count">17</span> reviews</span> </div>
Note that the
vcard are put next to each other in the same class attribute in order to show that the item being reviewed is described by the embedded hCard.
Count vs votes
In the examples so far, the
count property has been used but not
votes is useful when users have rated an item without writing full corresponding reviews. Their vote contributed toward the average rating but not towards the number of reviews available.
Consider this example:
<div> <h3> <span>Mediterranean Wraps</span> </h3> <span>Customers flock to this small restaurant for their tasty falafel and shawerma wraps and welcoming staff.</span> <span>4.5 out of 5 based on 24 ratings.</span> <span>5 user reviews:</span> ... </div>
Here the example is again, with both
votes specified where appropriate.
<div class="hreview-aggregate"> <h3 class="item"> <span class="fn">Mediterranean Wraps</span> </h3> <span class="summary">Customers flock to this small restaurant for their tasty falafel and shawerma wraps and welcoming staff.</span> <span><span class="rating">4.5</span> out of 5 based on <span class="votes">24</span> ratings.</span> <span><span class="count">5</span> user reviews:</span> ... </div>
examples in the wild
This section is informative.
The following sites have implemented hReview-aggregate, and thus are a great place to start for anyone looking for examples "in the wild" to try parsing, indexing, organizing etc. If your site is marked up with hReview aggregate, feel free to add it to the top of this list. Once the list grows too big, we'll make a separate wiki page like hreview-aggregate-examples-in-wild.
- PetFoodTalk, a pet food review and coupon site, implements hreview-aggregate for its presentation of dog food user ratings and reviews and coupons e.g. Blue Buffalo coupons and reviews.
- DineHere is a restaurant review site that publishes hreview-aggregates of hCards e.g. Blue Edge Organic Cafe.
- urbanspoon is a restaurant review site that publishes hreview-aggregates e.g. 3 Friends Coffee House.
- Tickets Tour is a community news site about concerts where users can rate music events (also marked up with hCalender). Example: Westernhagen
- Golf Made Simple In Scotland uses hReview-aggregate for a page of golf tour testimonials written by clients. Example: Golf tour testimonials.
- the 'hreview-aggregate' element is unfortunately set to style="display:none" - Tantek 17:35, 10 October 2011 (UTC)
- ALA GAP Insurance use hReview-aggregate on their home page based on hProduct/hReviews used throughout the site
- Citysearch supports hReview-aggregate (e.g. Tulio Ristorante in Seattle and Four Barrel in SF) with a nested hCard for the venue.
- minor flaw: uses a capitalized form of the root class name:
hReview-aggregateTantek 01:37, 22 July 2011 (UTC)
- minor flaw: uses a capitalized form of the root class name:
- Giga Music is a community site where customers can rate different music and sport events (which are also marked up with hCalender). Example: David Garrett
- CABS Car hire South Africa Lists reviews submitted by customers on the customer testimonial page. Example: car rental reviews
- Trust a Friend Lists reviews of products and services submitted by users and external blogs. Example: J.George Plastering, Newent, Gloucestershire
- CustomerLink Reviews has implemented hReview-aggregate for reviews of local businesses. Example: Review of Auto Tech & Tire
- SuperStoreSearch.com is a shopping search engine and price comparison site and offers an interesting implementation of hReview-aggregate and hProduct, whereas typical e-commerce sites feature one store offer, this shopping search vertical site allows users to compare prices, therefore you can see an example of the 'price' class being utilized with nested tags that also features the 'pricerange' class - which can be seen on individual pages such as this comparison listing for the Apple iPod Touch 8GB. The product information pages that have hReview-aggregate markup, also incorporate hProduct classes. hProduct has also been used on category menu pages such as this guide on Washing Machines - where multiple instances of hProduct can be seen on a single page. In total, over 10+ million products and pages have been updated with hProduct and hReview-aggregate markup.
- theSUGGESTR.com has implemented hReview-aggregate for it's business ratings and reviews.
- Google has implemented support for hReview-aggregate via Rich Snippets.
- STV Local uses hreview-aggregate for business ratings, average prices and contact details with hcard
- Critiki publishes ratings and reviews of Tiki bars, and uses hReview aggregate for average ratings on their pages, e.g. overview of The Tonga Room. (as tweeted by humuhumu 2009-09-21)
- NAPLESPLUS is an example of a website that has implemented hreview-aggregate via Google specs.
- FriendsEAT is an example of a food website that has implemented hreview-aggregate for it's restaurant and recipe ratings/reviews, e.g. Review of Churrascaria Plataforma