These are the extended parameters of a feed. None of them is man­da­to­ry; you might just skip them.
Some are default pa­ra­me­ters used when mes­sa­ges are crea­ted.

Field name Purpose Constraints Example(s)
Link A link a user may click when the feed hea­der is dis­play­ed by a feed rea­der. E.g. a link to a page descri­bing the feed in mo­re de­tail, a link to the home page of your site, or a link to the feed itself. Optional.

Max. length: 255 characters*.

Must be a valid URL.

http://www.yourdomain.tld.en

http://www.mydomain.tld/en/feeds

Copyright Copyright notice of the feed. Optional

Max. length: 255 charac­ters*.

Copyright (C) MyCompany

Copyright {copy} {year}, {company}

Publication time Publication date and time of the feed. Auto­ma­ti­cal­ly up­da­ted when new feeds are ad­ded. Read-only.

Format: "yyyy-mm-dd hh:MM:ss".

2010-11-01
Time-to-live The time in mi­nu­tes a feed rea­der may lo­cal­ly cache this feed (incl. mes­sa­ges). After this time it should re-read it. Optional.

Numeric.
Max. length: 5 digits.
Default: 60 (= 1 hour)

60
Maximum age Default difference in seconds be­tween the start and the end pub­li­shing date / time of a mes­sage. Optional.

Numeric.
Max. length: 10 digits.

Default: 604800 seconds = 7 days.

604800
  * field may contain variable references