00:04:06 benws has joined #poe 12:38:06 RRSAgent has joined #poe 12:38:06 logging to http://www.w3.org/2017/04/11-poe-irc 12:38:17 scribe: victor 12:38:36 victor launches the question: "what is the scope of the Formal Semantics Note"? 12:38:40 Meeting: POE formal semantics discussion 12:38:55 making reference to the document sent on the 27th of March. 12:39:21 simon: victor has proposed 5 reasoning tasks 12:40:50 simon: the validator is related to the test suite. 12:40:59 victor: there are at least three possible ways of implementing this 12:41:14 simon: everybody should be able to validate that the ODRL expressions they write are valid 12:41:31 simon: thinkgs like "has no assignee" etc. should be flagged 12:42:07 simon: there are syntactic contraints to validate (maybe SHACL maybe TestCases in a custom-made implementation) 12:42:23 s/contraints/constraints 12:42:59 ivan: the test suite is a must. But there should be an external validator, something like SHACL or similar so that testing software is not done by hand. 12:43:51 ivan: from the three mentioned options (SHACL/SWRL/FOL) I prefer the first one if the things settle down. 12:44:44 ivan: SWRL and FOL could be used but having SHACL, these options look more complex. 12:45:13 simon: we need an "invalid" class (victor: not attribute?) 12:45:46 simon: we need to define these constraints first, abstractly, independently on how the validating software runs. 12:45:56 ivan: +1 12:46:18 simon: we can start this activity actually now 12:47:12 ivan: ok 12:47:52 sabrina: I would also focus on "what we have to do". We have to validate not only the syntax but also the model. 12:47:54 all: yes 12:50:09 victor: the word Syntactic in the document is an evident typo 12:53:55 topic: transformation between serializations 12:54:31 simon: ODRL users using XML/JSON have agreed to use the XML and JSON-LD serialization of RDF respectively 12:54:57 victor: if this is the case, we dont need transformation software at all :) 12:55:12 victor: is it of any value what has been done in other W3C Specs? 12:55:19 ivan: not really 12:56:06 sabrina: in any case, transformations can be made to a single syntax all-to-one and one-to-all 12:57:09 simon: regardless the transformation software, having an abstract syntax is stuff for a "formal semantics" note 12:57:21 victor: agree 12:58:18 topic: The profiler 12:58:42 victor: a profiler tells you which profiles are being used, given a piece of ODRL 12:59:04 ivan: perhaps this is also SHACL, so this would be a part of the validator 12:59:38 present+ sabrina 12:59:57 simon: Profiles may allow "breaking the model", like for example having constraints out of any permission. Then, RDF shapes would be great. 13:00:19 present+ victor 13:00:28 topic: satisfiability checker 13:00:59 "whether a odrl policy can be satisfied" given a set of policies. 13:01:05 simon: this is strongly related to the authoriser. 13:02:00 ivan: is this fundamentally different than "use an OWL reasoner" on the combination of policies and actions? 13:03:07 simon: i have implemented this authoriser in the past facing problems beyond the OWL representative power. I used 13:03:55 simon: the authoriser is something to be discussed within the entire W3C Working Group. 13:05:42 victor: +1 13:07:43 simon: https://aic.ai.wu.ac.at/~polleres/presentations/20150325NORMAS_Linked_Data_Policies_in_ODRL.pdf Towards Formal Semantics for ODRL Policies 13:07:54 http://link.springer.com/chapter/10.1007%2F978-3-319-21542-6_23 13:11:42 ivan: why not with SPARQL queries? using SPARQL as a FOL engine. 13:12:02 simon: well, this is in SHACL too. 13:12:56 simon: One example on dates. where is the property value I have to check against? 13:14:21 victor: in order to have an authorisation system we need to have an architecture with something called "context", telling you which is the age of the user, today's date, etc. 13:15:01 sabrina: this is the same as in other policy languages 13:15:21 sabrina: +1 13:16:23 ivan: I am afraid that this introduces complexity 13:16:52 simon: and also, many of the constraints will never be able to be validated 13:18:46 +1 for the blackbox 13:19:07 ivan: where do we go from here? 13:20:14 ivan: except writing a custom designed checker, what can we do? 13:22:02 simon: under the assumption that some duties/constraints can be fulfilled or not (and validated by a blackbox) we can describe the authorisation check. also we can tackle the merging policies with a conflict resultion strategy 13:25:31 victor recalls the work of OASIS XACML and the good precedent it created, but he thinks that support from the rest of the W3C Working Group is important. 13:25:38 http://link.springer.com/chapter/10.1007%2F978-3-319-21542-6_23 13:27:51 benws has joined #poe 13:28:56 victor and sabrina agree. 13:29:46 ivan: skeptical about the readers of the documents 13:31:37 victor: there are two activities discussed today: (1) writing SHACL shapes for validation (2) Formal semantics for several purposes (conflict detection, merging policies) 13:31:43 ivan: we can decide that later. 13:31:56 sabrina: they are useful, wherever they are published 13:32:12 present: victor, sabrina, simon, ivan 13:32:44 ivan: we have to communicate to the group, we have to schedule a workplan 13:32:48 present+ 13:33:59 simon: there are hidden constraints in the language which needs to be identified. 13:34:35 victor: why dont we open a wiki to work togethere? 13:35:00 simon: wikis are easier to maintain 13:35:36 simon: before the meeting of may we can start moving from the paper to html and adapting to the new situation 13:36:14 ivan: are you saying that we have to identify constraints in the text that need to be formalized? 13:36:17 simon: yes 13:36:42 ivan: if we had that list.... ...should that list be part of the normative spec? 13:37:06 ivan: as part of the vocab document we may want to have a normative appendix referring to that list. 13:37:36 simon: similar approach was followed in SHACL 13:38:00 simon: the PROV group does the same with a single document devoted to constraints. 13:38:21 ivan: we have to report to the group 13:38:36 victor: right now? can't we wait until we have results? 13:38:51 ivan: what is the effort to reach that list? 13:39:19 simon: there are many vaguely defined things that needs to be fixed first. we have many github issues already.... 13:39:49 simon: we need Renato's expertise and external feedback. this can take long. 13:40:31 simon: please think of relation/target and how the specificities of the UML model is having impact on the RDF representation 13:41:14 ivan: the normative text should be full-proof before we reach CR 13:49:17 simon: launches his concern on the spec to be precise enough 13:49:30 ivan: urges simon to make this thought public in the next call 13:50:47 rrsagent, draft minutes 13:50:47 I have made the request to generate http://www.w3.org/2017/04/11-poe-minutes.html ivan 13:58:36 benws has joined #poe 15:11:00 ivan has joined #poe