GET /prices.xml?params
http://subdomain.example.com/prices.xml? from=2006-08-08T00%3A00%3A00-07%3A00&to=2006-08-08T08%3A14%3A43-07%3A00
http://subdomain.example.com/markets/:market_id/prices.xml? from=2006-08-08T00%3A00%3A00-07%3A00&to=2006-08-08T08%3A14%3A43-07%3A00
http://subdomain.example.com/stocks/:stock_id/prices.xml? from=2006-08-08T00%3A00%3A00-07%3A00&to=2006-08-08T08%3A14%3A43-07%3A00
curl -u username:password http://subdomain.example.com/prices.xml? from=2006-08-08T00%3A00%3A00-07%3A00&to=2006-08-08T08%3A14%3A43-07%3A00
<?xml version="1.0" encoding="UTF-8"?>
<prices type="array">
<price>
<created-at type="datetime">2008-06-16T10:02:33-07:00</created-at>
<value type="integer">4000</value>
<stock><id type="integer">10</id></stock>
</price>
<price>
<created-at type="datetime">2008-06-16T10:02:33-07:00</created-at>
<value type="integer">6000</value>
<stock><id type="integer">9</id></stock>
</price>
<price>
<created-at type="datetime">2008-06-10T10:02:33-07:00</created-at>
<value type="integer">5000</value>
<stock><id type="integer">10</id></stock>
</price>
<price>
<created-at type="datetime">2008-06-09T10:02:33-07:00</created-at>
<value type="integer">5000</value>
<stock><id type="integer">9</id></stock>
</price>
</prices>
It should be noted that these price changes aren't enough to create to create the typical "price graph" just by plotting the data returned, since you still have to extrapolate the prices of the stocks at the time periods you are specifically interested. For example, if you are looking at Stock XYZ, if there hasn't been a stock price change reported from this service since 2 months ago for Stock XYZ then you can extrapolate that the price on every day since 2 months ago is still at that same price.
In other words, you can assume that the latest price returned from this service is the most current price.