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The Security Property in AUCQL
A Query Language for Semistructured Data with Metadata Properties
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Basics

Security protects access to a node. In our data model, edges can have a (required) SECURITY property to restrict access to sensitive nodes. We assume that the security is an encrypted certificate. If the user possess a certificate and informs the database in a query that they have a certificate, then the user has access to any node protected by that certificate.

In all the examples below and elsewhere at this site, the security is given in plain text rather than as an encrypted string for expository purposes only.

In the movie database, the SECURITY is missing from many of the edges, which means that if a user can gain access to the from node for that edge, then they can extend a path to the to node through that edge. For the remaining edges, the SECURITY is a required property, meaning that the query must match the property to traverse the edge. The SECURITY property is matched by giving the appropriate certificate. The SECURITY can evolve over transaction time, or any of the other properties in the label.

Open to everyone

To understand the important role of security, let's start with a simple query that does not explicitly mention security at all.
What are the names of movie stars?:
SELECT *
FROM   movie Movie,
       Movie.stars.name Name;

The query result is duplicated below.
Movie Name
&Star_Wars_IV Bruce Willis
Only one name in one movie appears since information about the other movie requires an 'over 18' certificate.

Over 18 level of security

Let's announce in the query that we have a certificate which permits access to 'over 18' protected information.
What are the names of movie stars, I'm 'over 18' folks!:
SET DEFAULT PROPERTY (security: 'over 18');
SELECT *
FROM   movie Movie,
       Movie.stars.name Name;

The query result is duplicated below.
Movie Name
&Star_Wars_IV Bruce Willis
&Color_of_Night Bruce Wilis
&Color_of_Night Bruce Willis
See the transaction time examples to learn why there are three rather than two or four tuples in the result.

Other security levels

There are three security certificates in the example movie database. Let's look at all the nodes for each certificate.
All nodes at different levels of security.:
SELECT *
FROM   (SECURITY: 'over 18, subscriber, paid')* All,
       COALESCE(SECURITY, All) Security;


                                                                                                                                                                                                                                     
Curtis E. Dyreson, Michael H. Böhlen, and Christian S. Jensen © 1998-2000. All rights reserved.
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