Constraints and Capabilities Workshop

Oracle Position

Ashok MalhotraGreg Pavlik

Background

Position based on lessons learned:– Product implementation experiences.– Work on WSDL 2.0 Features and Properties, WS-

Reliability as well as WS-Policy.

While we agree that a declarative, assertion-based design is desirable, we think F&P and WS-Policy have shortcomings. WS-Policy allows composition of assertions from different domains. F&P needs compositors.

Summary

A policy is a collection of domain expressions.

Domain functionality cannot be combined.

Two distinct varieties of domains that must be treated differently:

– Domains that influence message content.– Domains that convey information about the service.

Domains

A domain is an orthogonal axis of functionality.

A policy is a collection of independent domain expressions.

Functionality for a domain is expressed using domain-specific formalisms and syntax.

Domain Dichotomy

Two kinds of domains…

Some domains influence message content (headers and bodies).

– e.g. Security, Reliability

Other domains convey information about the service and may be in various ways e.g. used to decide whether to use the service.

– Privacy (P3P)– Auditing/Logging

Domains that Influence Message Content

For example: security, reliability, transactions.

Functionality expressed as assertions connected by operators (compositors) such as all, choice, exactlyOne.

Client and server must agree on/select message policy.

Domain functionality may be ‘required’ or ‘supported’.

Domains that Influence Message Content (continued)

Client is configured or generated to conform to selected policy alternative.

Messages need to indicate which policy alternative is followed.

Server verifies that policy is adhered to.

Informational Domains

Informational assertions do not affect message content. They convey information about the service that may be used in several ways.

Informational domains are not ‘required’ or ‘supported’.

In some cases the client may insist that some advertised policy be enforced and may verify this.

Informational Domains

Several service characteristics may influence whether a client will use a policy or not: e.g. legal contract, privacy policy.

Decision could be made by man (lawyer reads legal contract) or machine (EPAL, WSPL).

Such characteristics could be used as part of the service discovery process.

Policy Attachment and Access

The policy may be associated with a service in several different ways: attached to WSDL, UDDI, RDDL, WSIL, etc.

Several policies may apply to a service. Policies may be managed as documents in

a document library with change control etc. Need a standard mechanism to:

– Access the entire policy for a service endpoint.– Access the policy details for a particular domain.

This mechanism would return a policy that may be composed of policy fragments from several related sources.

Policy Attachment and Access

Policies will evolve and may change during a conversation.

Messages should identify the policy they adhere to and if the policy changes during the conversation a fault should be signaled.

Recapitulation

A policy is a collection of domain expressions.

A domain’s functionality is described (and combined) using a domain-specific formalism.

Functionality for different domains cannot be combined.

Domains that influence message content and domains that provide information about the service are fundamentally different and must be treated differently.