4. The processing device according to claim 1 , wherein given a first search query containing keywords, the search device searches for an object that is matched with all of the keywords, the acquisition code is configured to acquire, for each category contained in the hierarchical structure, first frequencies of the name of the category and the keywords co-occurring in the first search query given to the search device, when at least a part of the distribution of the acquired first frequencies in the hierarchical structure is in conformity with a first distribution pattern that is one of the at least one distribution pattern, the identification code is configured to identify the position in the hierarchical structure of a category of which the name is given by the keyword based on the conformed part in the hierarchical structure and the position pre-associated with the first distribution pattern, and the first distribution pattern is a distribution pattern in which some of frequencies, in comparison to other frequencies, are lower with reference to a given comparison criterion, and is pre-associated with the positions of the lower frequencies.
4. The processing device according to claim 1 , wherein given a first search query containing keywords, the search device searches for an object that is matched with all of the keywords, the acquisition code is configured to acquire, for each category contained in the hierarchical structure, first frequencies of the name of the category and the keywords co-occurring in the first search query given to the search device, when at least a part of the distribution of the acquired first frequencies in the hierarchical structure is in conformity with a first distribution pattern that is one of the at least one distribution pattern, the identification code is configured to identify the position in the hierarchical structure of a category of which the name is given by the keyword based on the conformed part in the hierarchical structure and the position pre-associated with the first distribution pattern, and the first distribution pattern is a distribution pattern in which some of frequencies, in comparison to other frequencies, are lower with reference to a given comparison criterion, and is pre-associated with the positions of the lower frequencies. 7. The processing device according to claim 4 , wherein one distribution pattern of the at least one distribution pattern is a second distribution pattern in which frequencies are all higher than a frequency presenting the absence of co-occurrence with reference to a given comparison criterion, and is pre-associated with the position immediately below the frequency at the end in the sequence of the frequencies, and when a first part that is at least a part of the distribution of the acquired frequencies in the hierarchical structure is in conformity with the first distribution pattern and a second part that is at least a part of the distribution of the acquired frequencies in the hierarchical structure is in conformity with the second distribution pattern, the identification code is configured to identify the position in the hierarchical structure of a category of which the name is given by the keyword based on the second part and the position pre-associated with the second distribution pattern.