Ontology-enhanced Semantic Request and Response (OSRR) - The New Paradigm for Geospatial Semantic Web Services

Overview  Web services – problems in the old paradigm  Semantic Web services – goals and chaos  OSRR – an alternative solution and challenge  Semantic Interoperability – consensus vs. logics

Web services

 Ambiguity in definition – Web service may NOT have any relation with the Web.  Web service is the solution of software interoperability, taking the places of CORBA and DCOM – A service is a functional component of the software package, accessible through programming interface (API)  (Web) service is not a Web site, or Web- related. Problems with Web services

Desktop GIS

 Geographers, and other scientists and engineers who are not programmers, cannot use Web services even if they can find the required services that are only accessible through APIs  Web Services Description Language (WSDL) defines the programming interface at the syntactic level, not semantic – even programmers cannot understand the meaning of the service Problems with Web services

Semantic Web services  Goal – enable the dynamic and automatic service discovery, matchmaking, composition and invocation

Semantic Web services  Chaos – service registry died !  SAWSDL – targets service interface  OWL-S/WSMO – assumption-based, target Web site related activities  Dynamic invocation has been ignored

SAWSDL  Add semantic annotation onto WSDL elements matchType: a subclass of string. What does matchType mean if the value = “A” What does matchType mean if the value = “A” matchType: a subclass of hex code. If the value = “A”, matchType means “10” ! If the value = “A”, matchType means “10” ! Hex numbers use 16 digits: A B C D E F  What should I do if matchType = “A” ?!

OWL-S/WSMO Virtual Travel Agency (VTA) use case of service aggregation/mediation (Modified from Semantic Web Services Tutorial authored by Stollberg, et al. 2005) Service Requester Service Semantics Service Provider Service End Users - Supposed semantic Web is available (not true) - Supposed the required services can be discovered (not true – no service registry) - Supposed the discovered services have a feature of "exact match" to those proprietary ontology definitions (since same services may have different APIs and WSDLs, discovered services may be similar or related to each other) But even OWL-S is not compatible with WSMO, let alone any solution to the semantic interoperability.

Dynamic service invocation  The dynamic invocation of Web services is envisioned as “without any reprogramming, a software system could have the flexibility to use various services that do the same kind of job but have different APIs” (Burstein, 2004)  Such a statement means that: – Service semantics (what services do) are not the same as service interfaces. – Service semantics can be the same (do the same job) but the service interfaces are different.

Standardized APIs for ALL Kinds of Services: Function getService(String request): String response Input: a1, a2, x2, x3, y1, y3 Output: z1, z2, z3 Input: x1, x2, y1 Output: m1, m2 Input: x1, x2, y1, y2 Output: z3

Semantic Request and Response

 Geographers, and other scientists and engineers who are not programmers, can use Web services through SRR when they can find the required services

Reverse Engineering For a Reconstruction

OSRR – “O” for Service Discovery and Matchmaking  Semantics of Web services – What are the Web services and what functions do they offer? – How does the service requester send the request to deploy the service and function? – What service output result can the requester expect after the invocation?

 Five building blocks in OSRR 1. Service domain and function category description 2. Format of the service request input XML document 3. Format of the service response output XML document 4. Service request input requirements: defines the template for service request 5. Service response output prototype: defines the template for service response. OSRR – “O” for Service Discovery and Matchmaking

Semantic Interoperability Ontology could be described as a formalized and shared specification of a common conceptualization of a domain knowledge (Gruber, 1993; Uschold, et al., 1996), The word “semantic” represents the meaning of. The “semantics” of something is the meaning, or an interpretation of the meaning, of something.

Semantic Ambiguity HTML is not semantic, for it is not machine-processable WSDL is not semantic, although it is machine-processable

Veltman (2004) concluded that, “a semantic Web which deals only tangentially with meaning might more accurately be called the transactions web (EDI redivivus) or the logic web”. Those who designed semantic Web consider that, “logical meaning is the only objective dimension of meaning; that all other meaning is subjective and therefore unimportant. In this view, the semantic web rightfully limits itself to the realms of logic. In science, technology and business this claim leads to pragmatic results”. Semantic Interoperability Ontology =, and taxonomy can be expressed as Taxonomy = (Alesso, 2004).

Semantic Interoperability SW vs. SWS Concepts defined in Semantic Web are meaningful Terms used in WSDL are meaningless symbols <rdf:RDF xmlns:rdf=" xmlns:dc=" xmlns:foaf=" > Sean B. Palmer The Semantic Web: An Introduction

Limitations of RDF/OWL

- Service a provide address geocoding service that retrieves the latitude and longitude of an input address - Service b provides a service to convert latitude and longitude into another coordinate pairs with a different projection system such as UTM - Service c provides a service to directly retrieve the UTM x, y coordinates from the input address Service c = a + b RDF/OWL does not understand: = 5

Semantic Interoperability Consensus vs. Logic Modeling What is the ontology and semantics of the Prime Meridian? Is Prime Meridian based on consensus or logic modeling? Is GML a formalized, shared specification of a common conceptualization? “First Class High Way” (USGS) = “Interstate Road” (USDOT) Modeling Prime Meridian ? Amsterdam, Athens, Bern, Helsinki, Lisbon, New York, Oslo, Peking, Paris, Rome, Tokyo, or Stockholm …? In scientific research, we just need one evidence to deny a hypothesis or theory

Owner a: Polygon A (1,3 3,5 5,3 3,5 1,3) Owner b: Polygon B (2,5 4,7 6,5 4,3 2,5) Owner c: Polygon C (4,4 6,6 8,4 6,2 4,4) Owner d: Polygon D (4,5 5,6 7,4 6,3 4,5) Owner e: Polygon E (2.5,4.5 3,5 4.5,3.5 4,3 2.5,4.5) Semantic Interoperability - beyond the logical relationships A touches C B touches D B intersects A B intersects C C contains D D is contained by C E is the difference of A and B … … ? What is the Union of A and B Excluded by the Difference of A and B ? How to define the topological relation between the geometric features through logical modeling?

A B CD 0, E Semantic Interoperability We need more consensus, agreements, standards, not Logic Modeling ? Objective OR Subjective relationship among geometric features?

Thank You! Questions?