Understanding eXtensible Rights Markup Language - XrML

XrML is the eXtensible Rights Markup Language that is used to control the content with the help of licensing policies. The policies to use a content could be something like using it a once or repeatedly, sharing or non-sharing and so on.

Rules for the usage of the content are framed and then verified that the content is used according the Rules formed. The mechanism of control is there for any user and it is adjusted according to the user who is accessing the content.

Different controls are there in place for the copies and for the content that is used by many users in a workflow environment. This digital rights management is an emerging technology.

A common language like the XrML helps in interoperation among the users and for the smooth workflow between multiple users and applications. The base for this XrML comes from the Xerox PARC’s DPRL (Digital Property Rights Language) which came to existence in the year 1996.

A set of terms and processing rules is defined in the XrML framework. The core concepts and the terms that are used it the emerging digital rights technology and the XrML are Principal, License, Grant, Right, Resource, and Condition. These terms can be explained as:

· Principal: An XML Digital Signature is created to demonstrate possession of the key by an authenticated individual. This individual is the Principal. An authentication mechanism in XrML is used for this purpose.

· License: This is the right to grant access to the resources which needs digital rights. The rights are given to certain principals with conditions that apply to the principals.

· Grant: This is the right that is issued under certain conditions to the principal for using a particular resource.

· Right: An action performed against a resource is called the right. This action could be read, write, modify, install, delete, play, transfer, and many more.

· Resource: The resource is an object for which the rights are given for the principal to perform some action. Examples of resource could be audio, image, books, movies etc. Services like the email could also be termed as the resources.

· Condition: A condition is an obligation that should be met by the principal while they are using a resource. These conditions may be time bound or it may be the number of times that particular resource is used.

XrML used XML schema, XML Namespaces, and XML Digital Signatures in it. The usage of these is for the purpose for which each of them were created. The types are defined using the Schema that is used in the XrML. Name conflicts are avoided by the usage of the Namespaces. For creating signed licenses the XML Digital signatures are used.

A sample of the tags that are used in creating a license for a particular resource is given below. Most of the tags used are self explanatory.

<license xmlns:dsig='http://www.w3.org/2000/09/xmldsig#'>
<inventory>
<keyHolder licensePartId="xxx">
<info>
<dsig:KeyValue> xxx</dsig:KeyValue>
</info>
</keyHolder>
<cx:digitalWork licensePartId="xxx">
<cx:locator>
...
</cx:locator>
</cx:digitalWork>
</inventory>
<grantGroup>
<keyHolder licensePartIdRef="xxx" />
<sx:fee> xxx</sx:fee>
<grant>
<cx:play />
<cx:digitalWork licensePartIdRef="xxx" />
<sx:validityIntervalFloating>
...
</sx:validityIntervalFloating>
</grant>
<grant>
<cx:print />
<cx:digitalWork licensePartIdRef="xxx" />
<sx:exerciseLimit>
...
</sx:exerciseLimit>
</grant>
</grantGroup>
<issuer>
<dsig:Signature>
xxx
</dsig:Signature>
<details>
<timeOfIssue>xxx</timeOfIssue>
</details>
</issuer>
</license>

In the above code snippet the license tag encloses the necessary tags that are use for the rights management of the resources. The inventory for which the rights are managed is given in the <inventory> tag. The key holder for the resource is given in the <keyholder> tag.

A tag like the <cx:locator> is used to locate the resource for which the rights are to be managed. The group for which the license is granted is given in the <grant> tag. There are multiple <grant> tags so that different users are given the rights.

They are commonly grouped under the <grantGroup> tag. The issuer of the license is identified in the <issuer> tag where you also get details like the time of issue within the <details> tag. For more information and the ways of using the XrML you can refer to the specifications found in the web. A simple search on this topic would throw you a lot of examples on this topic.