1. A system comprising: one or more processors; a server configured to receive, from a client, a selection of a particular template of a plurality of templates, each template comprising a plurality of properties; a field generator, in the server, configured to analyze the plurality of properties specified in a selected template to create a control for selecting a property of the plurality of properties; and a graphic user interface generator, coupled to the field generator, configured to create a form that comprises a field and the control for selecting the property to which corresponding input in the field is to be compared, and further configured to send, from the server to the client, the form; wherein search input received via the form comprises a particular property of the plurality of properties and a corresponding particular input which is to be compared against values corresponding to the particular property in one or more data structures of one or more data sources.