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Re: [Gnumed-devel] LDAP

From: Tony Lembke
Subject: Re: [Gnumed-devel] LDAP
Date: Sat, 17 Aug 2002 00:48:44 +1000

On Friday, August 16, 2002, at 08:46 AM, richard terry wrote:

Tony, how about a quick explanation of what LDAP/Server is, how it functions
etc, displays info etc.


I'm not an expert on LDAP but this is my understanding. I'm sure others on the list are more familiar with it then I.

LDAP (Local Access Directory Protocol) is an internet standard for supplying directory services.

The protocol is a bit like SQL language - ask a standard question of an LDAP server and you get a text response. Info is returned as text -you need a client to display it in a meaningful way.

An LDAP database is designed to contain any sort of directory information. The protocol is built into many email clients such as Outlook and Navigator and Apple Mail - if you have set a LDAP server address, and enter a name, the application will query that LDAP server for the appropriate email address. You can use them for much more than just storing emails - they can store any set of data including text, numbers, dates, keys and images.

You define the objects and attributes of data for a particular database in a 'schema'.

The database in a LDAP server is a 'flat' , hierarchial database, as opposed to a relational database. All information about an entry is in the one record.

You therefore do not 'normalise' everything, which wouldn't appeal to Horst's sense of order and would probably make it inappropriate for storing all the demographic data. LDAP servers often have a full database as the backend (like postgresql).

The advantages of LDAP servers are
- that they are fast for read access and searching. (they are not so good for information that is frequently updated). - they provide data in a cross-location,cross-platform and cross-application standard
-  you can very precisely set access/ editing rights
-  it is relatively easy to design your own schema
- they are designed for replication - it is easy to have LDAP servers update each other, or to collate information from a number of servers. - it is standards based. A number of clients are already configured to use them.

The way I see it fitting in to gnumed is that when, say, writing a letter to a physician, when you enter their name, if the address/email/phone number are not available on your system, gnumed would query the ldap server for the information. If your division used the ldap server for its resource directory, it would seamlessly always be up to date for you, too. Each practice would not have to store the same information. If all the divisions in NSW used a LDAP server, the information that is common to the state sphere would be shared between them and their member GPs. And, if all the states used a common LDAP server, the federal information would be up to date. And if we had to send a letter to a physician in Germany, our LDAP could check with Karsten's for the address.

You can, as Alan says, use LDAP as a directory for anything, such as IP address of servers. The domain name system is like an LDAP.

I'll fiddle around with the server and some schemas and post them to the list for consideration.


Tony Lembke

Further reading
Introduction to LDAP
LDAP in action
Lighting up LDAP
An overview of LDAP-based directory service from the University of Michigan < >
openLDAP server

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