Chapter 6: Modeling and Representation Service-Oriented Computing: Semantics, Processes, Agents – Munindar P. Singh and Michael N. Huhns, Wiley, 2005

Chapter 62Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Highlights of this Chapter Integration versus Interoperation Common Ontologies Knowledge Representations Relationships Hierarchies Modeling Fundamentals Unified Modeling Language (UML)

Chapter 63Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Integration versus Interoperation Tight couplingLoose coupling

Chapter 64Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Modeling and Composing Services

Chapter 65Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Dimensions of Abstraction: 1 Information resources are associated with abstractions over different dimensions, which capture knowledge that is relevant for interoperation. These may be thought of as constraints that must be discovered and represented Data Domain specifications Value ranges, e.g., Price >= 0 Allow/disallow null values

Chapter 66Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Dimensions of Abstraction: 2 Structure Taxonomic representations and relationships such as in schemas and views, e.g., securities are stocks Specializations and generalizations of domain concepts, e.g., stocks are a kind of liquid asset Value maps, e.g., S&P A+ rating corresponds to Moody’s A rating Semantic data properties, sufficient to characterize the value maps, e.g., some stock price databases consider daily averages; others closing prices Cardinality constraints Integrity constraints, e.g., each stock must have a unique SEC identifier

Chapter 67Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Dimensions of Abstraction: 3 Process Procedures, i.e., how to process information, e.g., how to decide what stock to recommend Preferences for accesses and updates in case of data replication (based on recency or accuracy of data) Preferences to capture view update semantics Contingency strategies, e.g., whether to ignore, redo, or compensate Contingency procedures, i.e., how to compensate transactions Flow, e.g., where to forward requests or results Temporal constraints, e.g., report tax data every quarter

Chapter 68Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Dimensions of Abstraction: 4 Policy Security, i.e., who has rights to access or update what information? (e.g., customers can access all of their accounts, except blind trusts) Authentication, i.e., a sufficient test to establish identity (e.g., passwords, retinal scans, or smart cards) Bookkeeping (e.g., logging all accesses)

Chapter 69Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Value Maps: 1 A value map relates the values expressed by different services Key properties Totality Order preservation Consistent inversion

Chapter 610Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Value Maps: 2

Chapter 611Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Ontology A specification of a conceptualization or a set of knowledge terms for a particular domain, including The vocabulary: concepts and relationships The semantic interconnections: relationships among concepts and relationships Some simple rules of inference and logic Some representation languages for ontologies: Uniform Modeling Language (UML) Resource Description Framework Language Schema (RDFS) Web Ontology Language (OWL) Some ontology editors: Protégé, Webonto, OilEd

Chapter 612Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Common Ontologies A shared representation is essential to successful communication and interoperation For humans: physical, biological, and social world For computational agents: common ontology (terms used in communication) Representative efforts are Cyc (and Opencyc) WordNet (Princeton); LDOCE; OED Several upper-level ontologies, including by IEEE Mostly stable concepts such as space, time, person, which can be used within various domains

Chapter 613Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Ontologies and Articulation Axioms Mapping by hand, but with tool support Developing a common ontology: All at once Incrementally via consensus

Chapter 614Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Knowledge Representation Expressive power Procedural (how) versus declarative (what) Declarative pros: enables standardization, optimization, improved productivity of developers Declarative cons: nontrivial to achieve and causes short-term loss of performance Trade-offs shifted by Web to favor declarative modeling

Chapter 615Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Frames versus Descriptions Frame-based approaches are like object-oriented representations: Intuitive but rely on names of classes and properties to indicate meaning Description logics provide a computationally rigorous means to represent meaning; difficult for people Managing this trade-off is a major challenge for Knowledge Representation

Chapter 616Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Exercise: Which Conceptualization is Most Expressive and Flexible? awg22SolidBlueWire(ID5) blueWire(ID5, AWG22, Solid) solidWire(ID5, AWG22, Blue) wire(ID5, AWG22, Solid, Blue) wire(ID5)^size(ID5, AWG22)^type(ID5, solid)^color(ID5, Blue)

Chapter 617Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Mappings among Ontologies Term-to-term (one-to-one), e.g., hookupWire O1 => wire O2 Many-to-one, e.g., solidWire O1 (x, size, color) ^ strandedWire O1 (x, size, color) => wire O2 (x, size, color, (Stranded|Solid)) Many-to-many, e.g., solidBlueWire O1 (x, size) ^ solidRedWire O1 (x, size) ^ strandedBlueWire O1 (x, size) ^ strandedRedWire O1 (x, size) => solidWire O2 (x, size, (Red|Blue)) ^ strandedWire O2 (x, size, (Red|Blue))

Chapter 618Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Unified Modeling Language (UML) for Ontologies (Class Diagrams)

Chapter 619Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Comparison of Modeling Languages

Chapter 620Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Chapter 6 Summary Shared models are essential for interoperation Based on shared ontologies or conceptualizations Good models must accommodate several important considerations Modeling requires several subtle considerations Declarative representations facilitate reasoning about and managing models Formalization enables ensuring correctness of models and using them for interoperation