RSS 2.0 does not specify that a unique id must be set for items. Consequently, many RSS feeds do not specify such an id. %(note)(The rival "Atom":/Atom format does specify a required unique id, however the format is less widely used)% used)

This presents a problem when one implements a blog reader, because in order to know which RSS items are new, one needs to know which RSS items are old. If there is no way of knowing which are already present on the system because there is no unique identifier, other methods of divining a unique property for an item must be used.

h2. RSS Uniqueness methods:

* Link - most RSS items contain a link, although it is not required. Links are generally unique, and they are very convenient for a globally unique identifier.

* Hash - most common method, simply hashing the entire item results in a somewhat unique id. This is however vulnerable to repeated feed items.

RSS 2.0 does not specify that a unique id must be set for items. Consequently, many RSS feeds do not specify such an id. %(note)(The (The rival "Atom":/Atom format does specify a required unique id, however the format is less widely used)

This presents a problem when one implements a blog reader, because in order to know which RSS items are new, one needs to know which RSS items are old. If there is no way of knowing which are already present on the system because there is no unique identifier, other methods of divining a unique property for an item must be used.

h2. RSS Uniqueness methods:

* Link - most RSS items contain a link, although it is not required. Links are generally unique, and they are very convenient for a globally unique identifier.

* Hash - most common method, simply hashing the entire item results in a somewhat unique id. This is however vulnerable to repeated feed items.

RSS 2.0 does not specify that a unique id must be set for items. Consequently, many RSS feeds do not specify such an id. (The rival "Atom":/Atom format does specify a required unique id, however the format is less widely used)

This presents a problem when one implements a blog reader, because in order to know which RSS items are new, one needs to know which RSS items are old. If there is no way of knowing which are already present on the system because there is no unique identifier, other methods of divining a unique property for an item must be used.

h2. RSS Uniqueness methods:

* Link - most RSS items contain a link, although it is not required. Links are generally unique, and they are very convenient for a globally unique identifier.

* Hash - most common method, simply hashing the entire item results in a somewhat unique id. This is however vulnerable to repeated feed items.

RSS 2.0 does not specify that a unique id must be set for items. Consequently, many RSS feeds do not specify such an id.

This presents a problem when one implements a blog reader, because in order to know which RSS items are new, one needs to know which RSS items are old. If there is no way of knowing which are already present on the system because there is no unique identifier, other methods of divining a unique property for an item must be used.

h2. RSS Uniqueness methods:

* Link - most RSS items contain a link, although it is not required. Links are generally unique, and they are very convenient for a globally unique identifier.

* Hash - most common method, simply hashing the entire item results in a somewhat unique id. This is however vulnerable to repeated feed items.

RSS 2.0 does not specify that a unique id must be set for items. Consequently, many RSS feeds do not specify such an id.

This presents a problem when one implements a blog reader, because in order to know which RSS items are new, one needs to know which RSS items are old. If there is no way of knowing which are already present on the system because there is no unique identifier, other methods of divining a unique property for an item must be used.

h2. RSS Uniqueness methods:

* Link - most RSS items contain a link, although it is not required. Links are generally unique, and they are very convenient for a globally unique identifier.

* Hash - most common method, simply hashing the entire item results in a somewhat unique id. This is however vulnerable to repeated feed items.