The concept of prior art is present in every system of patent law. According to the German Patent Act (PatG), the prior art comprises "all knowledge which has been made available to the public by way of written or oral description, by use, or in some other way, before the date which is decisive for the purposes of the priority of the application." (§3, para. 1, PatG)

The territorial nature of patent law and the multiplicity of different forms of property rights and rules relating to them mean that prior art does not always mean the same thing. Indeed, prior art has a different meaning for the purposes of the examination of a German utility model:

"The prior art comprises all knowledge which has been made available to the public by way of written  description or by use within the territory in which this Act is applicable, before the date which is decisive for the purposes of the priority of the application." (§3, Abs. 1, GebrMG (German Utility Model Act))

This example makes it clear that a wide variety of legal regulations need to be taken into account to ensure the effective international validity of strategic publications.

A multiplicity of forms of disclosure can count as prior art. The German Patent and Trademark Office provides the following examples in this regard:

• your own prior disclosures and publications
• presentations, posters
• research proposals, diploma theses and student research projects (if published)
• doctoral theses, final reports (if published)
• guided tours, displays at trade fairs
• press publications
• operating instructions
• prior use which is known to the public

In order to produce a legally exploitable strategic publication, it is important that the publication is actually deemed to be prior art and can be verified as such. In the case of many of the forms set out above, it is difficult to provide unambiguous proof. Particularly with regard to the unambiguous nature of the publication date and of the scope of the details disclosed (e.g. internal structure of a device, method of operation), many forms of disclosure of prior art are unsuitable for the purposes of deliberately making strategic publications.

Patents and published patent applications are deemed to be prior art. The content and date of patents can be verified without ambiguity. For patents, the requirements relating to a full description of the invention and the level of searchability are very high and it is hardly possible to influence this at all.

According to European, US and Japanese patent law, patent applications are published 18 months after being filed (cf. international validity). At the point in time when the application documents are filed, the content is already deemed to be prior art which is prejudicial to novelty in the territory in which patent protection is applied for. However, this does not apply outside of that territory as such, or for examinations of the "inventive step" (obvious inventions). Upon the publication after 18 months, that which is described in the documents is deemed to be completely valid prior art in the sense of a written publication (exception: in the USA the legal fiction relating to the prior art at the point in time of the application also applies for the purposes of the assessment of the inventive step).

In addition, the burdensome formal requirements as well as issues of time and economy (high costs) are reasons not to make patent applications which are sought only for the purposes of creating prior art.

The validity of publications on the Internet as prior art for the purposes of patent and utility model law is disputed. For example, the German Utility Model Act expressly requires a "written description" and in US patent law a "printed publication" is required for foreign prior art. The higher courts have not clarified whether an online publication is deemed to be "written", "oral" "any other form" or in fact to be "printed".

In addition, websites are transient and can be subsequently amended. It is often difficult to prove the publication date of a particular item of content. It must additionally be proved that the content has not been subsequently amended. However, websites can be provided with a reliable, traceable publication date with the aid of special digital authentication and time-stamping procedures.

On an international level it is the case that online publications can be means of disclosing prior art if a verifiable date is provided. However, it is still disputed whether the online publication is a safe, independent means of disclosure. As an addition to a printed publication, it can perform the practical aspect of actual distribution.

Subject to certain conditions, verifiable prior use at trade fairs and in presentations creates prior art. The difficulty here is often evidencing the technical details used, and the fact that the applicability of a prior use as prior art is territorially limited for patent-law purposes. For example, a prior use carried out in Germany is not deemed to be prior art in the USA (cf. international validity).