Related to the last comment - you are usually presented with a list of resources, with no meaningful, or independent description. A good gateway should have automatic, frequent, link checking, so the end-user has confidence that when a resource is selected, he or she can access it. Lots of people, with a massive diversity of interests, searching one particular service at the same time. Subject gateways seek to overcome these problems. All resources are checked and described by an independent cataloguer.
Descriptions are meaningful.
Keywords are appropriate for the end-users who want to locate such resources. Links are checked automatically by the gateway software. We have made the end-user look of the gateway as configurable as possible. Version one of the software was released some time ago, and is freely available. Currently, version two is being produced.