Prior art constitutes all the information available to the public (both patent and non-patent literature) all over the world before a given date that might be relevant to the claims of originality. Patent literature includes issued patents and pending patent applications. Non-patent literature includes any piece of information accessible to public, before the date of invention being filed.

Any information can be qualified as a prior art, if the same is publicly accessible before the date of filing of claimed invention

Prior art references can be classified into the following types:

1. Printed publications:

Publications which are made accessible to the general public with common interest is considered as valid prior art. Including already published patent application.

2. Oral presentations:

Orally presented paper can be considered as a prior art,  if written copies are available without restriction

3. Public displays:

Publicly Displayed documents can be considered as a prior art, even if the duration of display is for only a few days and the documents are not distributed by copies or indexed in a database.

4. Online Publications:

Webpage information may be considered as prior art, even if it is removed after few days from the information posting date, provided if you have the proof (such as timestamp information) of WebPages information was available to public.

5. Unpublished patent applications:

Patent applications are usually published after 18 months from the earliest priority date of the application. Patent applications are usually not published until 18 months after initial filing date of the application. Such patent applications which have already been filed, but not published can be considered as prior art.

Information not considered as Prior art:

• Any information published, after filing date of a claimed invention is not usually considered as prior art. Information kept secret such as trade secret, information provided to employees and others in place of Non-Disclosure Agreements (NDA) are not regarded as prior art.
• Confidential documents which are created and distributed internally within an organization could not be considered as prior art; even though, it has been distributed internally.

By Senthil