Is having no robots.txt file the same as having one and allowing all agents?

[pugh]

The site I am working on currently has no robots.txt file. However, I have just uploaded a sitemap and would like to point the robots.txt file to it.

Once I upload the robots.txt file, if I allow access to all agents, is this the same as when the site had no robots.txt file at all; do I need to specify crawler access on can the robots.txt file just contain the link to the sitemap?

[ITRIX]

According to me a sitemap is more important than robots.txt as it help a search engine bot in effectively crawling a website. Robots.txt is generally used to request (allow: or disallow:)a crawler not to crawl and index certain section of your website containing sensitive data. This is totally upto the crawler to respect the request by not crawling and indexing that sensitive part. However, it is a general practice among webmasters world wide to have a robots.txt file for each of their sites.  A common robots.txt with permission to access the entire website should look like this:

User-agent: *
Disallow:

Sitemap: http://www.yoursite.com/sitemap.xml

So if you want some section (folders, directories) of your site not to be crawled by a bot then you can use a robots.txt.

Yes logically its the same like having a robots.txt file granting all the access and not having one completely. Its just a difference between like something having 'by default". Having a robots.txt file doesn't guarantee a rank boost in the SERP. Hope it helps. For more understanding please refer these resources:

http://www.seomoz.org/learn-seo/robotstxt

http://www.robotstxt.org/robotstxt.html

Cheers