Inline Vs. External Policy Attachment SCA Policy Framework Sanjay Patil Anish Karmarkar

Inline Vs. External Policy Attachment Comparison Criteria Inline Policy Attachment (IPA) External Policy Attachment (EPA) Separation of roles: Developer (creates composite) Deployer (attaches policy sets) Mixes the two roles. Simpler model when SCDL documents are to be manually edited for attaching policy sets Maintains separation of the roles. Composite developer does not have to deal with policy sets. Enables independent management of the policy attachment data (separate from that of SCDL) Domain-wide policy attachment Not supported Easier to describe domain-wide policy attachment rules Fine grained policy attachment (per message/operation) Complicates the SCDL Syntax (by duplicating the relevant message/ operation constructs in the SCDL for the purposes of inline policy attachment) Expressions can be formulated for externally attaching policy sets at the message/operation level without requiring any changes to the SCDL metamodel

EPA is sufficient, prevalent and simpler EPA supports all the use cases addressed by IPA and more Usage of EPA seems to be more prevalent Supporting both the mechanisms (EPA and IPA) makes the specs complex Definition of each mechanism Processing rules when EPA and IPA are used together

Other Considerations … What does it mean to disallow IPA but still allow component implementation code to specify defaults for policy sets? How to handle the scenario where a composite developer wants to experiment with attaching different policy sets to a SCDL without involving the external policy attachment mechanism?

Proposal Option I: Support only EPA, remove support for IPA, and disallow component implementation code to specify policy defaults Cleaner architecture Simpler specifications and conformance rules Minimal/no loss of functionality Option II: IPA as an optional feature, not to be used together with EPA (Note: an attribute on composite element indicates whether IPA or EPA is to be used, with EPA as the default) Allows use of IPA while reducing complexity (no need to define overriding rules, etc)

Bindings Arguments for the Inline Vs. External Policy Attachment discussion also apply for bindings attachment Treatment of bindings attachment can be based upon the resolution for Policy Attachment