15. The method according to claim 14 , wherein said mutual dependencies relates to appraising of said entities so that that a user may achieve the most cost efficient configuration of desired entities.
14. A method of establishing a transaction configured by at least one set of web based data sources, wherein at least two of said web based data sources are accessible via web-servers, and at least one set of entities comprises at least two entities accessible via different web-servers, the method comprising: establishing at least one query, said query comprising a configuration of one or more desired entities, searching in at least two of the web-servers for entities matching the configuration, said search comprising searching for a combination of at least two different entities, a first entity and a second entity being includable in the at least two different entities, and presenting at least one of the found set of entities to a user, the method being implemented on a computer, the computer comprising one or more central processing units, one or more memories and one or more network interfaces to one or more networks, the computer further comprising a search engine comprising program code which, when executed on said one or more central processing units performs a search on the basis of user inputted search criteria, a user interface comprising at least one monitor displaying in dependency of said program code, the different entities being entities which may be bought from different web-based data sources, said search engine being configured to performing a search for said configuration on at least two different web-bases data sources for said combination, said search engine presenting at least one found configuration of different entities by means of said user interface, said search engine taking mutual dependencies between said entities into consideration, and said search engine availing an order input defining a configuration determined on the basis of said at least one found configuration presented by means of said user interface.