RE: [tosca] Accessing nested properties

[Chris Lauwers <lauwers@ubicity.com>]

Hi Paul, 

You are correct that the syntax for navigating the TOSCA topology graph needs a lot more work. Calin and I have made a number of proposals in the past to address this, based on a concept we call TOSCAPath (which tries to combine graph traversal with JSONPath concepts). This is something we'd love to get into the 2.0 spec.

As a workaround for your issue, could you specify a target node type in your requirement definition? If you had a target node type, then the current get_property syntax would allow you to identify the capability property as follows:

   get_property: [ TARGET, <capability_name>, <capability_property_name ]

Chris



-----Original Message-----
From: tosca@lists.oasis-open.org <tosca@lists.oasis-open.org> On Behalf Of Paul Jordan
Sent: Monday, December 6, 2021 10:03 AM
To: tosca@lists.oasis-open.org
Subject: [tosca] Accessing nested properties

I recently came across a sytax restriction. Not sure if the TC have already discussed this.

Consider the valid syntax:


node_types

 ÂÂÂ <node_name>:

 ÂÂÂ derived from: <node_type_name>

 ÂÂÂ requirements:

 ÂÂÂ -ÂÂÂ <requirement_name>

 ÂÂÂ ÂÂÂ capability: <capability_type_name>

 ÂÂÂ ÂÂÂ relationship:

 ÂÂÂ ÂÂÂ ÂÂÂ type: <relationship_type_name>

 ÂÂÂ ÂÂÂ ÂÂÂ interfaces:

 ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ <interface_name>:

 ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ operations:

 ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ <operation_name>

 ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ inputs:

 ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ <parameter_name>

 ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ type: <datatype_name>

 ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂ value: ( get_property: [ SOURCE, .... ] }


Now, note that the capability referenced by <capability_type_name> may 
have properties. However according to V2.0 draft Section 4.4.2 there 
does not seem to be a valid syntax to reference the capability property 
from within the get_property clause.

There seems to be a need for a general purpose syntax to permit 
selection of a single parameter value from a valid TOSCA template of 
arbitrary depth and complexity; something like JSONPath or the less well 
supported YAMLPath.

Regards

Paul Jordan



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