8. A computer-implemented method for determining relevance, and for semantic search and personalized advertising based on association, comprising: receiving a first text content, wherein the first text content comprises one or more terms each comprising a word or a phrase; identifying a first term in the first text content, wherein the first term represents a topic or category name, wherein the topic or category name includes the name of a concept or object, or a product or service or activity or event; receiving a dataset based on the topic or category name, wherein the dataset comprises a plurality of property names representing a plurality of properties associated with the topic or category name, wherein there are at least two property names in the dataset each having an association strength value, wherein the plurality of property names are divided into a first group and a second group based on whether the association strength value is above or below a pre-defined threshold; receiving a second text content, wherein the second text content comprises one or more terms each comprising a word or a phrase; and determining a relevance measure between the first text content and the second text content based on whether the second term matches a property name in the first group or in the second group.
8. A computer-implemented method for determining relevance, and for semantic search and personalized advertising based on association, comprising: receiving a first text content, wherein the first text content comprises one or more terms each comprising a word or a phrase; identifying a first term in the first text content, wherein the first term represents a topic or category name, wherein the topic or category name includes the name of a concept or object, or a product or service or activity or event; receiving a dataset based on the topic or category name, wherein the dataset comprises a plurality of property names representing a plurality of properties associated with the topic or category name, wherein there are at least two property names in the dataset each having an association strength value, wherein the plurality of property names are divided into a first group and a second group based on whether the association strength value is above or below a pre-defined threshold; receiving a second text content, wherein the second text content comprises one or more terms each comprising a word or a phrase; and determining a relevance measure between the first text content and the second text content based on whether the second term matches a property name in the first group or in the second group. 9. The method of claim 8 , further comprising: outputting the relevance measure.