Transcript The New Paradigm for Geospatial Semantic Web Services

Ontology-enhanced Semantic
Request and Response (OSRR) The New Paradigm for Geospatial
Semantic Web Services
Xuan Shi
West Virginia University
[email protected]
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
Problems with 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 Webrelated.
Desktop
GIS
Problems with Web services
 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
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”
matchType: a subclass of hex code.
• If the value = “A”, matchType means “10” !
 What should I do if matchType = “A” ?!
Hex numbers use 16 digits:
0123456789ABCDEF
OWL-S/WSMO
Service
End Users
Service
Requester
Service
Semantics
Service
Provider
Virtual Travel Agency (VTA) use case of service aggregation/mediation
(Modified from Semantic Web Services Tutorial authored by Stollberg, et al. 2005)
- 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?
OSRR – “O” for Service
Discovery and Matchmaking
 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.
Semantic Interoperability
The word “semantic” represents the meaning
of. The “semantics” of something is the
meaning, or an interpretation of the meaning,
of something.
Ontology could be described as a formalized
and shared specification of a common
conceptualization of a domain knowledge
(Gruber, 1993; Uschold, et al., 1996),
Semantic Ambiguity
HTML is not semantic, for it is not machine-processable
WSDL is not semantic, although it is machine-processable
Semantic Interoperability
Ontology = <taxonomy, logical inference rules>, and
taxonomy can be expressed as Taxonomy = <{classes},
{relations}> (Alesso, 2004).
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
SW vs. SWS
Concepts defined in Semantic Web are meaningful
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:dc="http://purl.org/dc/elements/1.1/"
xmlns:foaf="http://xmlns.com/0.1/foaf/" >
<rdf:Description rdf:about="">
<dc:creator rdf:parseType="Resource">
<foaf:name>Sean B. Palmer</foaf:name>
</dc:creator>
<dc:title>The Semantic Web: An Introduction</dc:title>
</rdf:Description>
</rdf:RDF>
Terms used in WSDL are meaningless symbols
Limitations of RDF/OWL
Limitations of RDF/OWL
RDF/OWL does not understand: 2 + 3 = 5
- 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
Semantic Interoperability
Consensus vs. Logic Modeling
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
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)
Semantic Interoperability
- beyond the logical relationships
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)
A touches C
B touches D
B intersects A
B intersects C
How to define the topological
relation between the geometric
features through logical modeling?
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 ?
Semantic Interoperability
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Objective
OR
Subjective
relationship
among
geometric
features?
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B
5
E
4
D
C
3
A
2
?
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We need more consensus, agreements, standards, not Logic Modeling
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Thank You!
Questions?