42. A machine implemented method comprising: receiving by a search engine, from a content searching or consuming application, a search expression having a plurality of recursively embedded sub-expressions, the search engine and the content searching or consuming application being operated on one or more different or same computing devices; receiving a content page nominally associated with the search expression, or access information of the content page, by the search engine; generating in response, by the search engine, one or more scores indicative of relative relevance of a content page or one or more portions of the content page to the search expression, wherein the generating by the search engine comprising recursively generating one or more scores for one or more structures indicative of relative relevance of the content page or one or more portions of the content page to each of the recursively embedded sub-expressions, wherein a structure includes substructures, wherein at least one of the recursively generating is based at least in part on a distance function, and a scoring function, wherein the distance function measures distances between sub-structures within the structure being scored to facilitate determining of mutual relevance of occurrence positions, and wherein the scoring function is positionally sensitive, yielding different scores for at least some different occurrence positions of a search sub-expression in substructures of the structure being scored, irrespective of substructure category memberships; and conditionally providing or not providing the content page or one or more portions of the content page, or access information of the content page or one or more portions of the content page, to the content searching or consuming application, by the search engine, based at least in part on the generated one or more scores.
42. A machine implemented method comprising: receiving by a search engine, from a content searching or consuming application, a search expression having a plurality of recursively embedded sub-expressions, the search engine and the content searching or consuming application being operated on one or more different or same computing devices; receiving a content page nominally associated with the search expression, or access information of the content page, by the search engine; generating in response, by the search engine, one or more scores indicative of relative relevance of a content page or one or more portions of the content page to the search expression, wherein the generating by the search engine comprising recursively generating one or more scores for one or more structures indicative of relative relevance of the content page or one or more portions of the content page to each of the recursively embedded sub-expressions, wherein a structure includes substructures, wherein at least one of the recursively generating is based at least in part on a distance function, and a scoring function, wherein the distance function measures distances between sub-structures within the structure being scored to facilitate determining of mutual relevance of occurrence positions, and wherein the scoring function is positionally sensitive, yielding different scores for at least some different occurrence positions of a search sub-expression in substructures of the structure being scored, irrespective of substructure category memberships; and conditionally providing or not providing the content page or one or more portions of the content page, or access information of the content page or one or more portions of the content page, to the content searching or consuming application, by the search engine, based at least in part on the generated one or more scores. 45. The method of claim 42 , wherein the plurality of recursively embedded sub-expressions comprise first and second sub-expressions specifying first and second matching criteria for first and second content pages respectively, and the search expression further comprises directive directing return or non-return of the first or second matching content page.