Let’s look first at format, which can be one of the values listed in Table 4-1.

If format is not specified, Atom 1.0 is assumed. Note that RSS 2.0, RSS 1.0, and Atom 1.0 (along with RSS 0.92 and RSS 0.91) are included among the formats. I’ll present some samples of various formats later in this chapter, after I cover the rest of the URL language for Flickr feeds.

The second pervasive and optional parameter is lang, which represents the language you can use to query Flickr. Table 4-2 lists the values. The default language is en-us (English).

I’ll now list the feeds available. Remember that all the feed URLs can include the optional format and lang parameters.

Feeds for public photos in Flickr are available here:

http://api.flickr.com/services/feeds/photos_public.gne

with the following optional parameters:

For example, the following:

http://api.flickr.com/services/feeds/photos_public.gne?tags=flower%2CBerkeley&format=rss2&lang=fr-fr

returns a RSS 2.0 feed, annotated in French, of recent public photos tagged with both flower and Berkeley tags.

You can get a feed of recent photos of a user’s friends here:

http://api.flickr.com/services/feeds/photos_friends.gne?user_id={user-nsid}

where user-nsid is the NSID of the user whose friends’ photos you want to access. There are also optional parameters:

For example, the following:

http://api.flickr.com/services/feeds/photos_friends.gne?user_id=48600101146@N01&friends=0&display_all=0&lang=en-us&format=atom_1

is an Atom 1.0 feed of up to one photo each from my Flickr friends, family, and contacts.

You can get feeds of a group discussion here:

http://api.flickr.com/services/feeds/groups_discuss.gne?id={group-nsid}

Feeds for the group photo pools are accessible here:

http://api.flickr.com/services/feeds/groups_pool.gne?{group-nsid}

Discussion feeds from the Help forum (http://www.flickr.com/help/forum/en-us/) are here:

http://api.flickr.com/services/feeds/forums.gne

You can track recent activity on a user’s photos through feeds here:

http://api.flickr.com/services/feeds/activity.gne?user-id={user-nsid}

Feeds of recent comments made by a user are here:

http://api.flickr.com/services/feeds/photos_comments.gne?user-id={user-nsid}

You can track Flickr news bulletins here:

http://api.flickr.com/services/feeds/news.gne

Now that you know how to access the various feeds available in Flickr, you’ll look at some examples of feeds to understand how various formats are implemented, including the role of extensions. Consider the following excerpt of a sample RSS 2.0 feed of recent public photos with the tag tree:

            http://api.flickr.com/services/feeds/photos_public.gne?tags=tree&format=rss2
            <?xml version="1.0" encoding="utf-8"?>
            <rss version="2.0" xmlns:media="http://search.yahoo.com/mrss/"
                 xmlns:dc="http://purl.org/dc/elements/1.1/">
              <channel>
                <title>tree - Everyone's Tagged Photos</title>
                <link>http://www.flickr.com/photos/tags/tree/</link>
                <description>A feed of tree - Everyone's Tagged Photos</description>
                <pubDate>Mon, 29 Jan 2007 06:40:42 -0800</pubDate>
                <lastBuildDate>Mon, 29 Jan 2007 06:40:42 -0800</lastBuildDate>
                <generator>http://www.flickr.com/</generator>
                <image>
                  <url>http://www.flickr.com/images/buddyicon.jpg</url>
                  <title>tree - Everyone's Tagged Photos</title>
                  <link>http://www.flickr.com/photos/tags/tree/</link>
                </image>
                <item>
                  <title>Odd Tree</title>
                  <link>http://www.flickr.com/photos/davidleong/373343287/</link>
                  <description>[....]</description>
                  <pubDate>Mon, 29 Jan 2007 06:40:42 -0800</pubDate>
                  <dc:date.Taken>2007-01-28T11:31:31-08:00</dc:date.Taken>
                  <author>nobody@flickr.com (mountainhiker)</author>
                  <guid isPermaLink="false">tag:flickr.com,2004:/photo/373343287</guid>
                  <media:content
                    url="http://farm1.static.flickr.com/127/373343287_df43da61f7_m.jpg"
                    type="image/jpeg" height="160" width="240"/>
                  <media:title>Odd Tree</media:title>
                  <media:text type="html">[....]</media:text>
                  <media:thumbnail
                    url="http://farm1.static.flickr.com/127/373343287_df43da61f7_s.jpg"
                    height="75" width="75"/>
                  <media:credit role="photographer">mountainhiker</media:credit>
                  <media:category scheme="urn:flickr:tags">snow tree vancouver northvancouver
                                  grousemountain</media:category>
                </item>
                <item>
                [....]
                </item>
              </channel>
            </rss>
         

Note the following about this XML fragment:

Let’s take a closer look at the extensions used in the RSS 2.0 Flickr feed:

It’s interesting to look at how all the Flickr metadata is expressed in the other feed formats. The following:

http://api.flickr.com/services/feeds/photos_public.gne?tags=tree&format=atom

shows that Atom 1.0 is natively able to encode much of the information for which Media RSS is being used in RSS 2.0. The Atom feed does, however, use a Dublin Core extension to mark up a date.

Let’s now return to the feed formats supported by Flickr other than RSS 2.0, RSS 1.0, and Atom 1.0. To get a start at understanding the various formats, load a Flickr feed, which will by default be in Atom 1.0, and replace the format parameter with the alternatives. For instance, if you are curious about CDF, change the following:

http://api.flickr.com/services/feeds/photos_public.gne?tags=tree

to the following:

http://api.flickr.com/services/feeds/photos_public.gne?tags=tree&format=cdf

In the following sections, I’ll mention some but not all of formats supported in Flickr feeds.

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