W3C | Architecture Domain | Web Architecture

Quality of Service

on the tension between reliability and scalability

taken from old research notebook

another source: reliabe links

see also: metadata architecture

Resource Discovery
Finding relavent resources. Traversing a link can be considered a special case of resource discovery. Other examples:
In a fault-tolerant, distributed system, reliability is a measure of how many times a given computation succeeds out of the number of times it is attempted. So to define reliability of resource discovery in general and specifcally linking, we must define what it means to succeed or fail.

The acceptable level of reliability will vary between applications, and even between users. A reliable system is one in which any party may achive arbitrarily high reliability by investing sufficient resources.

The defintion of "success" will vary as well. Successful link traversal generally means finding a resource with perfect precision and recall, and retrieving an authentic representation of the resource in a timely fashion.

In a database query or index search, precision is a measure of how many of the results are relavent. Recall is a measure of how many of the relavent items are in the results. Related failures include:
Availability and Latency
Availability means that a resource can be retrieved: the server is up and reachable via the network. Latency is a measure of the amount of time between the initation of a request and the completion of the request. Related Failures:
Authenticity means getting the right data. Failurs include:
Access Control
Access to resources may be restricted to authorized parties. Copyright, Ownership, Charging, Payment systems
Attributes and Meta-Information
indexing information often used during searching. I finally found a definition of "meta-information" that I like:

Metadata has two main functions:

  • to provide a means to discover that the data set exists and how it might be obtained or accessed; and
  • to document the content, quality, and features of a data set and so give an indication of its fitness for use.
WAIS through the Web - About Metadata

The question arises: whence comes the list of attributes? What's the expressive capability, structure, and meaning of attribute values?

We can look to directory systems like DCE CDS, Prospero and X.500, or to frame-based knowledge bases like Algernon and Lincks.