Geospatial Semantic Web Blog

Downloading files is one of the most frequently performed task on the Internet. Today there are many protocols for downloading files — e.g., HTTP, FTP and bittorent. Different sites (e.g., Linux distributions, OpenOffice) offer downloads in some or all those protocols. Metalink is a new XML-based markup language and technology for unifying file downloads across multiple protocols. Digging deeper into the Metalink format representation, I find some surprises — the use of tagging and expressive content description.

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Geonames announced a new experimental service that includes thumbnail images of geographical locations in its query results. For example, a search query to lookup London UK will return a thumbnail image of London. All thumbnail images produced by Geonames are acquired from various geographical location pages on Wikipedia.

Marc at Geonames Blog introduces this new feature:

Thumbnail images for wikipedia articles are a new experimental addition to the geonames webservices, the full text search and the maps mashup. Around a third of all articles on geonames have thumbnail images. A simple algorithm determines which image to use as thumbnail if more than one image could be parsed from the original article.

I think this new feature could be useful to many Web mashup applications, especially those that need to display photos of some arbitrary geographical locations — maybe in a semantic-web travel tool.

According to a December 2006 survey by the Pew Internet & American Life Project, tagging is gradually becoming a popular culture among the US Internet users.

28% of the US Internet users have tagged or categorized content online such as photos, news stories or blog posts. On a typical day online, 7% of the Internet users say they tag or categorize online content.

The proportion of women and men who tag is about equal — 29% men vs. 27% women. Other demographics are as the follows.

Taggers look like classic early adopters of technology. They are more likely to be under age 40, and have higher levels of education and income.

Taggers are considerably more likely to have broadband connections at home, rather than dial-up connections. Men and women are equally likely to be taggers, while online minorities are a bit more likely than whites to be taggers.

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A question that most parents with teenage children often ask is “where are you?”. To help to answer this question, wireless service providers begin to offer location-based services that allow parents to monitor the whereabouts of their children on home computers.

To determine the location of a cellphone user, a service makes use of wireless signals from the cellphone. Based on the cellphone’ signal strength, the service is able to compute the relative position of the user from a group of cell towers. Knowing the geographical location of the user’s cellphone (i.e., a latitude/longitude value pair), the service then perform “reverse geocoding” to determine the location of the user.

In theory, the service works. In practice, however, there is a problem that was quite unexpected. Here is the problem:
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