Data Grid Research Group Dept. of Computer Science and Engineering The Ohio State University...

Data Grid Research GroupDept. of Computer Science and EngineeringThe Ohio State UniversityColumbus, Ohio 43210, USA

David Chiu & Gagan Agrawal

Enabling Ad Hoc Queries over Low-Level Scientific

Data Sets

2D. Chiu & G. Agrawal. Enabling Ad Hoc Queries over Low-Level Scientific Data Sets

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Presentation Outline

• Motivation‣ Current Trends in Scientific Data Management‣ Problem Discussion

• Data Registration Indexing‣ Metadata Extraction‣ Transformation

• Service Composition

• Conclusion


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Increased tremendously over the years

Scientific Data Sets

• The collection of scientific data has increased over the years with new instruments, simulations, etc.

• Data sets are stored in repositories around the globe

• Just within U.S. entities in the geospatial domain‣ NOAA: oceanic, climate, water

quality, ...‣ NASA: ozone, air quality, tropical, ...‣ NRCS: land quality, watershed, ...


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Data Repositories

Web or Data Grid InfrastructureMass StorageSystems (MSS)


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• Data sets are typically low level, i.e., ‣ Unstructured or semi-structured0101071895 0.34 -2.45 0.50 -0.65 -0.62 -0.71 0.00 -0.96 0101071896 -1.71 0.49 0.27 -0.79 -1.53 0.60 0.09 -2.210101071897 -0.53 0.14 4.32 1.95 -1.55 -1.68 -1.32 -0.690101071898 1.90 -2.64 -1.70 1.11 -2.18 -1.08 -0.53 -0.250101071899 0.44 0.97 1.65 -0.71 -2.02 -2.10 -0.50 -2.030101071900 -1.65 1.19 -1.34 0.57 -1.37 7.00 -0.48 -1.77 . . .

• However, data is well-documented‣ Accompanying XML-based metadata describing data sets is

typically required in today’s repositories


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Data Repositories

Mass StorageSystems (MSS)

Grid/Web Services & portals

Web or Data Grid Infrastructure


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Data Repositories in the Global Scale

US EU

AU ...

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D. Chiu & G. Agrawal. Enabling Ad Hoc Queries over Low-Level Scientific Data Sets

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What Do the Users Want?

US

EU

AU

...

I don’t care where data is located.

I also want to share my own data with others!

Don’t just give me the data, but...

- Transform it - Manipulate it - Compose it with other processes and data sets

And do this with the least amount of work required from me!

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System Goals

• To enable queries over low level data sets, which involves:‣ identification of relevant data sets‣ automatic planning for the composition of dependent

services (processes) for derivation

• ... while being non-intrusive to existing schemes, i.e.,‣ avoids a standardized format for storing data sets‣ accommodates heterogeneous metadata‣ this system should - fit - into existing MSS and scientific

computing infrastructures (Data Grid & the Web)

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That’s good and all, but...

Challenges

• Not without challenges...‣ dealing with metadata from multiple entities‣ efficiently identifying relevant data sets‣ planning and executing accurate service compositions on

the spot

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That’s good and all, but...

Challenges

• Not without challenges...‣ dealing with metadata from multiple entities‣ efficiently identifying relevant data sets‣ planning and executing accurate service compositions on

the spot

DOMAIN KNOWLEDGE & SEMANTICS

• And without question, the need for

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The AUSPICE System

AUSPICE: Automatic Service Planning and Execution in Cloud/Grid Environments

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The Semantics Layer

A Need for Domain Level Knowledge

• Assume the following service retrieves a satellite image pertaining to (x,y) with resolution respective to r

• Questions to ask the system:‣ How to deduce that this service can be used?‣ How to determine what information is needed for input?‣ Did the user provide enough information to invoke this service?

get_sat_image(double x, double y, double r)

inputsTo inputsToinputsTo

longitude latitude grid_size

outputsTo

satellite image

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In the Semantics Layer

Applying Domain Information

Domain concepts can be derivedfrom executing a service

Domain concepts can also be derived from retrieving an

existing data setService parameters representdifferent domain concepts

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Data Registration Service

Indexing Data Sets

• Handling heterogeneous metadata

• For instance, just within the geospatial domain,

Country Metadata Standards

US CSDGM

AU, NZ ANZLIC

EU ???

CDN ???

... ...

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Indexing Data Sets

• Handling heterogeneous metadata

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Indexing Data Sets

• Metadata Transformation

. .

.

(transform to spatial index)

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Indexing Data Sets

• Metadata to DB transformations

. .

.

insert

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Indexing Data Sets

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Indexing Data Sets

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Indexing Data Sets

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In the Semantics Layer

Applying Domain Information

Data registration simplifies identification process within

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Indexing Services

• Services (inputs, outputs) are also registered in much the same way

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The Planning Layer

Service Composition: An Example

A subset of the ontology (unrolled)

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The Planning Layer

Service Composition

begin compSrvc(concept, Q[...])W := ()

//perform DFS starting from conceptlet v := concept be the currently visited node

if v is a data type then W := (W, index.getData(v, Q))

else //v is a servicelet (p1,..,pn) be v’s params

//recursive call on each piW := (W, (v, compSrvc(p1, Q), ... , compSrvc(pn, Q)))

end if

return Wend

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The Planning Layer

Service Composition: An Example

Ontology (unrolled)

A Derived Execution Plan This is what data registration provides

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Planning Times

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Conclusion

• The AUSPICE System...‣ unifies heterogeneous metadata‣ extracts certain metadata attributes and indexes low level

data sets and services for fast access from distributed repositories

‣ automatically composes these services and data sets to answer user queries

• Questions - Comments?‣ David Chiu [email protected]‣ Gagan Agrawal [email protected]

Data Grid Research Group Dept. of Computer Science and Engineering The Ohio State University...

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