Ontology-driven Automatic Geospatial-Processing ... - Semantic Scholar

Ontology-driven Automatic Geospatial-Processing Modeling based on Web-service Chaining Liping Di, Peisheng Zhao, Wenli Yang, Peng Yue Center for Spatial Information Science and System, George Mason University 6301 Ivy Lane, Suite 620 Greenbelt, MD 20770 represents the knowledge of geospatial domain experts on Abstract- Earth System Science (ESS) research and applications often involve in collecting, analyzing and modeling with distributed heterogeneous geospatial data. Those data are processed step-by-step in geospatial analysis systems to extract information and knowledge products for applications and decision makings. Conceptually, such a step-by-step process forms a geospatial processing model that represents the knowledge of geospatial domain experts. This paper presents a study on ontology-driven automatic creation and execution of geospatial processing models in GeoBrain, a Web-service based geospatial knowledge system, to produce user-specific products. Web Services and Service-Oriented Architecture (SOA) provide a framework to support interoperable machine-to-machine interaction over a network. Web service chaining aimed to solve complex application tasks is changing the way of developing and deploying applications. By wrapping data and processes with Web services, it is easy to transform a geospatial processing model into a service chain. From design (knowledge), instantiation (information) to execution (data), this paper illustrates the whole life cycle of the geospatial-processing modeling and relevant implementation in GeoBrain. Ontology is usually used to capture domain knowledge. In this paper, a number of ontologies, including geospatial scientific ontology, geospatial data ontology and geospatial processing ontology, are introduced as the knowledge base to present geospatial domain terms and concepts, linkage between concepts and datasets, relationships among heterogeneous data, and associations between processes and data. By these ontologies, data and processes can be used for more effective discovery, automation, integration, and reuse across multiple diverse applications.

I INTRODUCTION

how to produce an application-specific product from available raw data sources [2]. Currently, only a few trained people have such knowledge. As the result, the use of geospatial data is largely limited by the availability of such professionals. This situation has significantly hampered the wide use of geospatial data for societal benefits. It is well known that more and more geospatial data and processes are available online as services. This paper presents a study on automatic creation and execution of geospatial processing models based on users’ product specifications in GeoBrain [3][4], a Web-service based geospatial knowledge system, to produce the user-specific products. The whole life of the modeling process, including model design (knowledge capture), model instantiation (information fusion) and model execution (data generation), is implemented based on the semantic and syntactic interoperability between data and processes. Ontology as “specification of a conceptualization” [5] is often used to capture domain knowledge explicitly to achieve semantic interoperability. By defining geospatial domain terms and concepts,

linkage

between

concepts

and

datasets,

relationships among heterogeneous data, and associations between processes and data in ontologies, data and processes can be used for more effective discovery, automation,

integration,

and

reuse

across

various

Earth System Science (ESS) research and applications

applications. Thus, the automatic creation of geospatial

often involve in collecting, analyzing and modeling with a

processing models can be driven by the knowledge

huge

represented

amount

of

multi-source,

multi-scale

and

in

geospatial

and

application-specific

multi-discipline geospatial data [1]. Those data are

ontologies [6] [7]. According to the World-wide Web

processed step-by-step in geospatial analysis systems to

Consortium (W3C), a Web service is a software system

extract

for

designed to support interoperable machine-to-machine

applications and decision makings. Conceptually, the

interaction over a network [8]. The Service-Oriented

step-by-step processes from the raw data to a user-specific

Architecture (SOA) provides a framework to support the

product form a geospatial processing model. The model

service discovery and invocation in a standardized way.

information

and

knowledge

products

Web service chaining aimed to solve complex application

A composite process consists of other (atomic or composite)

tasks is changing the way of developing and deploying

processes by specifying control constructs such as

applications. By wrapping data and processes with Web

Sequence and If-Then-Else. One crucial feature of a

services, it is easy to transform a geospatial processing

composite process is its specification on how the outputs of

model into a service chain (instantiation) and execute it

a particular subprocess can be accepted by the inputs of

regardless their syntactic heterogeneity.

other particular subprocesses, i.e. data matching. Building

The reminder of this paper is organized as follows. In

a composite process usually takes advantage of backwards

section 2, we define the geospatial processing model. In

reasoning, i.e., from the goal state to the initial state.

section 3, we discuss the ontology-based knowledge base.

Generally, a number of inputs for subprocesses are

In section 4, we discuss the catalog service. In section 5,

required to derive the composite process. These inputs may

we discuss the life cycle of modeling and relevant

or may not physically exist and, in the latter case, need

implementation. And finally in section 6, we present the

further processes to generate them. This process goes on

conclusions and future work.

until all information needed for inputs physically exist. At that point, a tree-like composite process is constructed [9]. The composite process is a geospatial processing model in

II GEOSPATIAL PROCESSING MODEL A geospatial process transforms geospatial data from

which the components and control structures contain the

one state to another state. Generally, geospatial process can

knowledge of a specific application domain. Following is

be classified as 1) atomic process, which runs

an

independently, and 2) composite process, which consists of

susceptibility, which is composed of slope, aspect and

a sequence of processes in a predefined pattern. A

landslide atomic processes with sequence and split control

geospatial processing model is a composite process.

structures. And the inputs of landslide process come from

A geospatial process is defined by its inputs, outputs and operation. The concepts and relationships among these characters are specified in ontologies. Each process has

example

of

composite

for

the outputs of slope and aspect processes.

conditional inputs (specifying the preconditions and the



relationship conditions between the inputs and the



and data inputs (specifying the actual data required by the



operation, such as data URL).



The operation uses a

certain geo-processing algorithm to transform the state of data inputs in conjunction with conditional inputs. The



outputs usually represent a new geospatial data product



(i.e., the goal state), including actual data and its metadata.



Following

is

an

example

of

ISODATA

image

classification process: