Parsing all posts of a wordpress blog by tag. RSS or plugin?

I'm complete new to wordpress but I have to parse a complete blog into a another website. This should happen on a hourly base.

My question now is what should I use for this? The posts I need to parse are marked by a specific tag.

Can I use the RSS-Feed for this or is it limited and will on开发者_StackOverflow社区ly return me like the last 20 posts? Or is there any plugin out there which can return me all posts of a tag or category in an XML or JSON?

Thanks guys!

You can use RSS for this. You can set the feed limit on RSS in your Wordpress Blog Settings. The feed URL would be:

http://example.com/tag/tagname/feed

Check this page on the codex.