Semantic Technologies for Systems Engineering Steven Jenkins Jet Propulsion Laboratory California Institute of Technology* * Institutional affiliation for identification purposes only. Not speaking on behalf of JPL or Caltech.

Agenda Short background on Semantic Technolgies and their relationship to Systems Engineering Information and status update on the proposed ST4SE Foundation Relationship of ST4SE to SysML 2 Questions and answers

What are Semantic Technologies? By semantic technologies we mean the technologies (and associated theory and practice) of the Semantic Web The Semantic Web is a Web of actionable information—information derived from data through a semantic theory for interpreting the symbols. The semantic theory provides an account of “meaning” in which the logical connection of terms establishes interoperability between systems. [1] The Semantic Web provides a common framework that allows data to be shared and reused across application, enterprise, and community boundaries. [2]

Semantic Web and Systems Engineering Systems engineering is inherently a synthetic activity–uniting information across multiple disciplines, across organizational boundaries, across multiple development phases Agreement on syntax and semantics for concepts and properties for this disparate information is essential to avoid unnecessary costs and delays due to work of translation unnecessary risks due to errors in translation SysML provided a start at such agreement, but is weak in two areas: Limited taxonomy of concepts: almost everything is a block Weak semantics: lack of strong logical foundation

Semantic Technologies: Resource Description Framework and Schema Resource Descripion Framework (RDF) [3] is the standard model for data interchange on the Web Fundamental construct: triples of (subject, predicate, object) For example: ”Europa Clipper is an Orbiter” Note that all three terms are Web Uniform Resource Identifiers (URIs): the Semantic Web namespace is global JPL’s term EuropaClipper W3C’s term type JPL IMCE’s term Orbiter RDF Schema (RDFS) provides simple semantics, e.g., subClassOf http://jpl.nasa.gov#EuropaClipper, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://imce.jpl.nasa.gov#Orbiter

Semantic Technologies: Web Ontology Language (OWL) From the W3C [4]: The W3C Web Ontology Language (OWL) is a Semantic Web language designed to represent rich and complex knowledge about things, groups of things, and relations between things. OWL is a computational logic-based language such that knowledge expressed in OWL can be exploited by computer programs, e.g., to verify the consistency of that knowledge or to make implicit knowledge explicit. OWL is the most widely-used Knowledge Representation (KR) language in the world—by a wide margin OWL provides full Description Logic semantics (and beyond) Powerful yet tractable reasoning capabilities OWL Ontologies can be exchanged as RDF documents

More on OWL The Description Logic subset of OWL (OWL2 DL) is carefully chosen to balance expressivity (i.e., richer semantics) with computational complexity of reasoning In particular, practical reasoning algorithms exist that are both sound: all inferences drawn are valid complete: all valid inferences are drawn These algorithms have been implemented in both commercial and free software that is widely used In addition, these reasoners can detect various errors such as inconsistencies or unsatisfiable (i.e., overconstrained) classes Information expressed in OWL can be semantically validated We have an opportunity to catch errors on every exchange

Semantic Technologies: SPARQL Protocol and RDF Query Language RDF and RDFS, among other things, establish standards for how information can be stored and retrieved in bulk We also need the ability to ask questions about information What is the measured mass of the flight system? What are all the (recursively) contained components of the flight system? What requirements refine R.12345? Does every component have a supplier? SPARQL [5] is a language and distributed query protocol for questions of this type Numerous commercial and free implementations are available

ST4SE Foundation The ST4SE Foundation is an idea in development It does not (yet) exist as a legal entity It arose from discussions at the Third JPL/NASA Model-Based System Engineering Symposium and Workshop (January 2017) It is modeled after successful open-source software development efforts such as Apache and Eclipse Its charter is to promote and champion the development and utilization of ontologies and semantic technologies to support system engineering practice, education, and research. Interim leadership by Dinesh Verma, Executive Director, U.S. Systems Engineering Research Center and Chi Lin, Integrated Model-Centric Engineering Program Manager, Jet Propulsion Laboratory

ST4SE Will Work to build consensus around principled, rigorous use of systems engineering language Not just capturing current usage, but proposing normalized usage that entails semantic rigor Capture and formalize this consensus in formal ontologies using well-established languages and techniques from Knowledge Representation Collect and promulgate methodological guidance for development of related ontologies from industry and academia Collect and encourage development of related rules and tests based on the ontological principles for model checking Encourage development of software to support semantic model-building, reasoning, and analysis Provide advocacy and training for more rigorous practice supporting these artifacts and tools

Candidate Governance Structure Steering Group own the initiative charter and ensures that activities adhere to it; provides programmatic guidance Working Groups are formed for specific projects; many will originate in proposed contributions from core team members or others Core Team ensures architectural coherence; provides technical guidance in both SE and Semantic technology Steering Group (4 to 6 members) Working Groups (unlimited) Core Team (8 to 10 members)

ST4SE Status Steering Committee meets biweekly by telecon and occasionally face- to-face Primary focus is on setting up the legal entity Core Team meets biweekly by telecon and occasionally face-to-face Primary focus is on Setting up tools for collaborative development Tutorials on Semantic Web Examination of candidate ontologies

ST4SE and SysML 2 One of the key objectives of SysML 2 is improved formalism and logical rigor for SysML Obviously, there is a great deal of overlap with ST4SE ST4SE will work closely with SysML 2 to ensure that our products are compatible and mutually reinforcing At least one person on the ST4SE Core Team is active in SysML 2

Questions?

References Shadbolt, N., Hall, W., Berners-Lee, T., The Semantic Web Revisited, IEEE Intelligent Systems, 2006. World Wide Web Consortium, W3C Semantic Web Activity. World Wide Web Consortium, Resource Description Framework (RDF). World Wide Web Consortium, Web Ontology Language (OWL). World Wide Web Consortium, SPARQL Query Language for RDF.