1. A method for extending a tag of an information resource in an information network, the method comprising: providing a group of tags, stored in a database, in a user interface, wherein the group of tags comprises a plurality of tags including at least a first extended tag created by a user, the first extended tag comprising a first expression including one or more operands, one or more operators and one or more first values, wherein the each of the one or more operands is the same as another tag in the group of tags; selecting at least one tag out of the group of tags and linking the at least one tag to an address of an information resource using the user interface, wherein linking the at least one tag includes storing the tag in a tabular format, and in a record including the address of the information resource and the tag, and zero or more other tags, and wherein the at least one tag directly points to the address of the information resource to link the at least one tag to the address of the information resource; extending the at least one tag linked to the address of the information resource to form a second extended tag, such that the resulting second extended tag is a semantically structured string of characters comprising at least its own respective first expression including at least its own respective first operand, first operator and first value, wherein the at least one tag is the respective first operand; identifying, from the group of tags, two or more first expressions having identical first operands and identical first operators and replacing the first values of the identified two or more expressions by a first placeholder, such that a first class of extended tags including the identical first operands, the identical first operators, and the first placeholder is built, wherein selecting the at least one tag comprises selecting an entry from the first class of extended tags; wherein the second extended tag further comprises a directive indicative of an action to be initiated if the expression, is evaluated as true, wherein the directive is selectable in the user interface from a directive contribution registry; and evaluating the second extended tag by a parser, and if the evaluation is evaluated to be true, interpreting and initiating the action of the directive and executing a result of the interpretation by an action unit.