Re: [Gnumed-devel] LDAP

[Tony Lembke]

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.

Terry,

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.

Regards,

Tony Lembke

Further reading
----------------------
Introduction to LDAP
           <http://www.ldapman.org/articles/index.html>
LDAP in action
            
<http://www.linuxworld.com/linuxworld/lw-1999-07/lw-07-ldap_1.html>
Lighting up LDAP
           
<http://www.linuxworld.com/linuxworld/lw-1999-07/lw-07-ldap-
tutorial.html>
An overview of LDAP-based directory service from the University of 
Michigan
           
<http://www.umich.edu/~dirsvcs/ldap/doc/guides/slapd/1.html#RTFToC1 >
openLDAP server
           <http://www.openldap.org>
web2ldap
          <http://www.web2ldap.de>