## 2 Background  
### Innovation Lifecycle  
Looking at the comprehensive patent trajectory, first, a company or inventor seeks patent protection for a novel idea. Then the application is drafted by a patent attorney who possesses expertise in both technical and legal aspects. This application consists of claims that define the envisioned extent of protection. A patent is granted if these claims demonstrate that the idea is unique and novel in comparison to prior art. Almost all these stages require preliminary prior art searches, even during the initial stages of patent drafting, which might aid in improving the patent application [16]. Therefore, patent retrieval plays an influential role at various stages of the patent lifecycle.  
Below is a summary of the stages of the patent lifecycle involving prior art searches to support a range of activities.  
Stage 1: Conceptualization  
* At the beginning of the patent lifecycle, technology research is conducted to identify and incorporate cutting-edge technologies within a specific field to create novel solutions [8]. As a result, many prior art searches are conducted for patent landscaping.  
Stage 2: Pre-Filing Stage  
* Afterwards, in the pre-filing stage, innovators perform prior art searches to evaluate the originality or novelty of the invention before submitting a patent application [17].
* In the patent application drafting stage, lawyers and inventors write patent applications and refine claims by finding pertinent prior art.  
Stage 3: Examination Stage  
* During the patent examination stage, examiners analyze the novelty, non-obviousness, and industrial applicability of the invention by conducting targeted patent prior art retrieval searches.  
Stage 4: Prosecution Stage
* In the patent prosecution stage, the examiner's objections are addressed by carrying out extended novelty searches on relevant prior art.  
Stage 5: Post-Grant Stage
* In the post-grant stage, infringement and clearance inspections prior art searches are conducted by patent owners to find prospective infringers or ensure compliance.
* Technology watch and competitor analysis involve continuous tracking via numerous prior art searches to stay abreast of new developments and innovations made by rivals.
* Specific prior art searches are performed for portfolio assessments, licensing, and legal issues to make informed strategic decisions.
* Infringement and invalidity searches are performed on relevant prior art to lend credence to legal claims in court cases. When presenting evidence in court and developing legal arguments, these searches are crucial.
* Renewal and maintenance searches on prior art are essential for retaining patents by spotting relevant changes and guaranteeing that decisions made regarding the retention of patents are compliant.  
Figure 1 shows different patent prior art searches that are needed at various stages of the patent lifecycle.  
A high degree of domain understanding is needed for all these patent-related prior art searches and, even if such expertise is available, it needs to be coupled with extremely complex and intelligent analytics to offer users interactive and cognitive assistance [8]. The principal objectives of patent prior art search and retrieval are to guarantee compliance and shape strategic choices in legal and corporate contexts by securing, safeguarding, and leveraging patent rights. Figure 2 shows the patent searches performed at various stages of the innovation lifecycle.  
Figure 1: Patent searches to retrieve patent documents at different stages of the patent lifetime.