10. An apparatus comprising: at least one storage device storing instructions; and a processor to execute the instructions to: receive a corpus of textual listings, textual listings, in the corpus, including one or more advertisements, the one or more advertisements including text without a grammatical structure; identify main concept words and attribute words in the corpus, when identifying the main concept words and the attribute words, the processor is to: tag, in each textual listing of the textual listings, at least one word as a head noun word based on at least one of: a previously identified main concept word, or a head noun identification rule, tag, in the textual listing and after tagging the at least one word, remaining nouns as at least one modifier word, and assign one word of the at least one head noun word as a main concept word and one word of the at least one modifier word as an attribute word; cluster words in the corpus based on at least one of the main concept words or the attribute words according to at least one clustering rule, the at least one clustering rule including at least one of: a first rule relating to clustering two quantitative attribute tokens based on a frequency of appearance of the two quantitative attribute tokens in a same listing, a second rule relating to clustering of a quantitative attribute token with a qualitative attribute token, or a third rule relating to clustering a first token and a second token based on characters of the first token being included in the second token; and provide, after clustering the words, the main concept words and the attribute words as at least a portion of a semantic model.
11. The apparatus of claim 10 , where the at least one clustering rule includes at least two of the first rule, the second rule, or the third rule.