Publishing Your Metadata

For other users to discover your metadata within the Canadian Geospatial Data Infrastructure, you need:

1. a search server that connects to your database
2. a discovery mechanism, such as the GeoConnections Discovery Portal (http://geodiscover.cgdi.ca).
3. Your search server will use a specific search protocol to receive queries and send answers to those queries.

A search server is a program on a computer that is connected to the Internet. It accepts search queries from other users (via clients) through the Internet, then queries a database connected to the same local area network (LAN) as its host computer. The database returns the result (answer to the query) to the search server, and the search server returns the result to the Internet client that originated the request.

Note that there are several commercial and “shareware” search servers available, and it is unlikely that you have to develop one from scratch. Click on search servers for some examples.

The discovery mechanism must know the Internet address (IP address) of your search server and, depending on the search protocol, the database name and the specific port to connect to on your server. All this information is provided as product registration information (in the directory).

A search protocol is a standard way of asking questions (or queries), getting answers, and exchanging information between two computers over the Internet. A search protocol is like a technical language; it specifies the transport mechanism for the information flow between the two computers.

Before you start It’s important to understand the difference between a user and a client. In the case of the GeoConnections Discovery Portal, the GeoConnections Discovery Portal is the client to the search server. Think of a chain of translation: Giuseppe speaks Italian and communicates via the phone, Antoine speaks Italian and French and uses the phone and email, John speaks French and communicates using email. John emails a question to Antoine in French, Antoine translates it to Italian and relays it to Giuseppe via a phone call. Giuseppe responds in Italian, Antoine translates it to French and emails the response to John. In this case, the phone and email are communication protocols and the languages (French and Italian) are communication profiles. When searching for geospatial data, the user sends a question to the GeoConnections Discovery Portal in HTTP/HTML, the GeoConnections Discovery Portal translates it to Z39.50/GEO and sends it to the search server. The server responds in Z39.50/GEO to the GeoConnections Discovery Portal, which translates it to HTTP/HTML. In this domain, the HTTP and Z39.50 are the communication protocols, and the profiles (or languages) are GEO and HTML.