1. Source_type = client application ID

In the triples table, source_type points out where the triple comes from. When source_type < 10, they have default values in environment.rb file. When source_type > 10, they have reference in client_application table. In that table, records with id=0-10 are not useful, so they can be replaced with dummy records as default ones in the environment setting.

For others: RANDOM_LINKS              = 0 BROWSER_BOOKMARKS_UPLOAD  = 1 PERSONAL_LINKS            = 2 #single link DELICIOUS_IMPORT          = 3 MAGNOLIA_IMPORT           = 4 GIVEALINK_EXTENSION       = 5 ADDTHIS_LINKS             = 6

2. Table for tracking spam/invalid urls

url_spam_suggestions table is for tracking the validity or other properties for urls. The column "flag" has three valid values: spam, no_head_response,no_body_response . spam - user report that one url might be spam; There is a API method named Url.reportSpam() which can add records to this table with flag spam. no_head_response - cannot get http head response from a url; no_body_response - cannot get the body from a url, but can get the http head response, the code is also stored in the database as http_resp_code;