Powder your data with trust
Protocol for Web Description Resources (POWDER) use cases
Kai Scheppe
k.scheppe@telekom.de
Deutsche Telekom AG
The concept and purpose of POWDER
- POWDER facilitates the publication of descriptions of multiple resources such as all those available from a Web site
- These descriptions are always attributed to a named individual, organization or entity that may or may not be the creator of the described resources.
- This contrasts with more usual metadata that typically applies to a single resource, such as a specific document's title, which is usually provided by its author.
- POWDER provides a means for individuals or organizations to describe a group of resources through the publication of machine-readable metadata.
- Such meta data are encapsulated in Description Resources (DRs). These are typically represented in a highly constrained XML dialect that is relatively human-readable.
- The meaning of such DRs are underpinned by formal semantics (POWDER-S), accessible by performing a GRDDL Transform.
Design Goals and Constraints for grouping of resources
In designing a system to define sets of resources the following considerations were taken into account.
- It must be possible to define a set of resources, either by describing the characteristics of the resources in the set, or by simply listing its elements.
- It must be possible to determine with certainty whether a given resource is or is not an element of the Resource Set
- The ease of creation of accurate and useful Resource Sets is important
- It should be possible to write concise Resource Set definitions
- Resource Set definitions must be easy to write, be comprehensible by humans and, as far as is possible, should avoid including or excluding resources unintentionally
- It must be possible to create software that implements Resource Set definitions primarily using standard and commonly available components and specifically must not require the creation of custom parsing components
- So far as is possible, use of processing resources should be minimized, especially by early detection of a match or failure to match
Some aspects of POWDER
- Metainformation is stored separately and anywhere in discoverable Description Resources (DR)
- DRs are assertions made by the author or provider, until verified
- Trustmarks may be established through third party verification of assertions
- DR possess attribution, ascribing information about the Web resource's origins
- DR possess scope, defining the applicable range of the assertions, through the use of IRIs
- DR possess descriptors of the resources in question
- Operational semantics of POWDER are written in XML, easy to use and sufficient for everyday use
- Formal semantics of POWDER-S are written in RDF/OWL and may be written directly or obtained through a GRDDL transform
An example Description Resource
<?xml version="1.0"?>
<powder xmlns="http://www.w3.org/2007/05/powder#"
xmlns:ex="http://example.org/vocab#">
<attribution>
<maker ref="http://authority.example.org/foaf.rdf#me" />
<issued>2007-12-14</issued>
</attribution>
<dr>
<iriset>
<includehosts>example.com</includehosts>
<includepathstartswith>/foo</includepathstartswith>
</iriset>
<iriset>
<includehosts>example.org</includehosts>
<includepathstartswith>/bar</includepathstartswith>
</iriset>
<descriptorset>
<ex:color>red</ex:color>
<ex:shape>square</ex:shape>
<displaytext>Everything on example.com where the path starts with /foo
and everything on example.org where the path starts with /bar is red and square</displaytext>
<displayicon>http://example.org/icon.png</displayicon>
</descriptorset>
</dr>
</powder>
Advantages of POWDER
- Meta information is machine readable
- Through the use of IRIs possible usage is expanded
- Detailed grouping of resources through space separated lists of IRI components (POWDER) or regex (POWDER-S)
- Information about resources without retrieval
- Full attribution serves as the basis of trust
- Independent verification / trustmarks
- Targeted content discovery / filtering in PSN
- Repositories of DRs can aid in content discovery
- Anybody can make a claim about any Web resource
Potential first steps - a content provider's view
Migrating from regular meta information to DRs
- Create DRs and make them discoverable
- Move all meta data (i.e. keywords and child protection information)into the descriptors inside the DRs
- Link from the Web resources to the DRs via the link element
- Desribe the scope in the DRs
Enrichment of meta information
- DRs may be enriched with a wide range of meta data
Utilization of semantic information
- After transforming the data semantic searches can be performed
- Utilize the extra information via SPARQL or other appropriate queries
Example use cases for POWDER
Profile matching
- Searching for music videos with a mobile device the search engine will
- retrieve a device description from a repository
- match the retrieved URIs to a assertions/trustmarks that are mobileOK
- Match video metainformation to the available bandwidth
- The results are then filtered for only those URIs that fit the requesting profile
Creation of trustmarks
- A Web site specializes in content for children.
- A government institution monitors these sites regularly as condition for listing in a „white list“ of child safe sites.
- This list consists of a DR repository/Trustmarks verifying the assertions made by the individual Web sites