Syntactic Mediation in Grid and Web Service Architectures

Syntactic Mediation in Grid and Web Service Architectures Martin Szomszor Terry R. Payne Luc Moreau University of Southampton myGrid [ http://www.mygrid.org.uk]

Syntactic Mediation… Cambridge online dictionary defines mediation as: Verb [I or T] “ to talk to two separate people or groups involved in a disagreement to try to help them to agree or find a solution to their problem” Syntax The structure and organisation of information Syntactic mediation To mediate between two parties who not agree on syntax

… in Grid and Web Services Questions to be answered When is syntactic mediation required? What are the current solutions? How can they be improved? Use Case Taken from a Bioinformatics Grid application Our solution Intermediary representation of data in OWL Mappings between XML and OWL Conclusions and further work

Grid and Web Services Grid Coordinated resource access Service oriented view of resource access Web Services Architecture Supporting the service oriented view Resources exposed through Web Service interfaces This powerful model enables complex collaboration of disparate resources, typically through the use of workflow

myGrid - Bioinformatics In-silico experimentation myGrid is service orientated Steps in the experimental process correspond to Web Service invocations Taverna - The Virtual Workbench Compose Edit Execute Monitor View results

A Bioinformatics Use Case Get some sequence data and perform a sequence alignment Sequence alignment checks for similarities between different sequences Many sequence data repositories XEMBL DDBJ-XML Many sequence alignment services NCBI Blast …

Bio Example - Workflow Two stages More than one service for some stages Get Sequence Data Sequence Data Alignment Result Sequence Alignment XEMBL Service DDBJ-XML Service NCBI Blast Accession Number

Bio Example - Workflow Two possible concrete workflows Using XEMBL Service Using DDBJ-XML Service Accession Number XEMBL Service Sequence Data Alignment Result NCBI Blast Service Accession Number DDBJ-XML Service Sequence Data Alignment Result NCBI Blast Service

Syntactic Compatibility Is the output from one service compatible with the input to another service? Conceptually the same type But different syntactic types XEMBL Service Sequence Data NCBI Blast Service XEMBL Service BSML Sequence Record NCBI Blast Service FASTA Formatted Sequence

Syntactic Mediation When a syntactic miss-match occurs, some additional processing is required We define this processing as syntactic mediation Current solutions Explicitly defined transform (e.g. XSLT) Hard coded black-box components

Assisted Mediation How can we achieve this? Use ontologies for a common conceptual model of the data Describe how parts of the data schema (XML-Schema) correspond to parts in the semantic schema (OWL) Transform data sets into their corresponding conceptual representations Use conceptual representation as a common model to mediate between services's data models

Syntactic Mediation XEMBL Service NCBI Blast Service FASTA Formatted Sequence Alignment Results Conceptual representation of sequence data Transform XML output from XEMBL service to OWL concept instance Serialise OWL concept instance to XML for input to NCBI Blast Service BSML Sequence Record Accession Number

Bioinformatics Use Case: Sequence Data Ontology authors journal title Key: Object property Subconcept Sequence_Data description accession_id sequence has_feature has_reference Reference Sequence_Feature location Feature_Source lab_host isolate mol_type organsim Feature_CDS translation product protien_id Sequence_Location start end BSML_Sequence_Data date_created date_last_updated DDBJ_Sequence_Data version division

Transformation of XML to OWL <Sequence ic-acckey="AB000059"> <Feature-table> <Feature class="SOURCE"> <Qualifier value-type="isolate” value="Som1"/> <Qualifier value-type="organism” value="Feline …”/> <Interval-loc startpos="1" endpos="1755"/> </Feature> </Feature-table> </Sequence> Sequence Data Accession_ID Feature Source Location has-Feature isolate organism has-location start end AB000059 Som1 Feline … 1 1755

Transformation of OWL to XML Sequence Data Accession_ID Feature Source Location has-Feature isolate organism has-location start end <DDBJXML> <ACCESSION>AB000059</ACCESSION> <FEATURES> <source> <location>1..1755</location> <qualifiers name="isolate">Som1</qualifiers> <qualifiers name="organsim">Felis ...</qualifiers> </source> </FEATURES> </DDBJXML> AB000059 Som1 Feline … 1 1755

Mapping Language We present a simple mapping language to describe the transformation of data from XML to OWL Mappings are bi-directional XML to OWL OWL to XML Hierarchical view of both data models Template is applied to match source model and create destination model Data values are mapped from source to destination via variable assignment

Example Mapping 1 Mapping an attribute value <Sequence ic-acckey="AB000059"> Sequence Data Accession_ID {xml} Sequence[ic-acckey = $accession] <-> {owl} Sequence_Data( Accession_id($accession)) $accession AB000059

Example Mapping 2 Mapping an element value Sequence Data sequence {xml} Sequence( seq-data($sequence)) <-> {owl} Sequence_Data( sequence($sequence)) $sequence <Sequence> <seq-data>aatagagtg…</seq-data> </Sequence> aatagagtg…

Example Mapping 3 Mapping an group of element values <Reference> <RefAuthors>Horiuchi M.</RefAuthors> <RefTitle>evolutionary…</RefTitle> <RefJournal>Unpublished</RefJournal> </Reference> Reference author {xml} Reference( RefAuthors($author), RefTitle($title), RefJournal($journal)) <-> {owl} Reference( author($author), title($title), journal($journal)) title journal Horiuchi, M. Evolutionary… Unpublished

Example Mapping 4 Split and join <location>1:1755</location> Sequence_Location start {xml} location( split($start, “:”, $end) ) <-> {owl} Sequence_Location( start($start), end($end) ) end 1 1755

Example Mapping 5 Mapping an sequence of elements <feature-table> element contains a sequence of <Reference> elements <feature-table> <Reference> <RefAuthors>Horiuchi M.</RefAuthors> <RefTitle>evolutionary…</RefTitle> <RefJournal>Unpublished</RefJournal> </Reference> <Reference> <RefAuthors>Horiuchi M.</RefAuthors> <RefJournal>EMBL/GenBank/DDBJ…</RefJournal> </Reference> </feature-table>

Example Mapping 5 Each <Reference> element corresponds to an instance of the ‘Reference’ concept Reference author title journal Reference author journal Sequence_Data has-reference has-reference Horiuchi, M. Evolutionary… Unpublished Horiuchi, M. EMBL/GenBank/DDBJ…

Example Mapping 5 The ellipsis (…) construct is used to denote this behaviour {xml} feature-table( Reference( RefAuthors($author), RefTitle($title), RefJournal($journal) )… ) <-> {owl} Sequence_Data( Reference( author($authors), title($title), journal($journal) )… ) sequence

Mapping Language Engine Java component built on Dom4J and Jena Input: Mapping and Data set (XML or OWL) Output: Data set (XML or OWL)

Transformation Process Four stages Create data model for input DOM4J for XML JENA for OWL Parse mapping Apply source mapping to bind variables Apply destination mapping and create new instance filling variables with their corresponding values from the source

Assisted data mediation for WS XEMBL Service NCBI Blast Service BSML Sequence Record Accession Number FASTA Formatted Sequence Alignment Results Conceptual representation of sequence data Transform XML output from XEMBL service to OWL concept instance Serialise OWL concept instance to XML for input to NCBI Blast Service

Assisted data mediation for WS XEMBL Service NCBI Blast Service FASTA Formatted Sequence Alignment Results Mapping Language Engine Mapping Mapping Language Engine Mapping BSML Sequence Record Accession Number OWL instance

Comparison of Approaches Create one mapping to conceptual model Must create mappings to all other compatible formats Addition of Data 1 mapping from each data format to its conceptual model. For n compatible data formats, n mappings required 1 mapping for each pair of compatible data formats. For n compatible formats, n 2 mappings required Number of Mappings Mappings from data format to common conceptual model Direct mappings between compatible data formats

Why OWL? Expressive Power Complex concept specifications Reasoning power Subsumption and concept classification Classification of data Given an XML document and some mappings, it would be possible to find which mappings are valid and therefore what are the possible conceptual models for the given document

Conclusions By using mappings from XML documents to OWL instances, we can automatically transform a portion of data from one representation to another, providing both share a common conceptual model This can be used to rectify data incompatibilities that occur in workflows with data flow between services - assisted mediation

Further Work Add regular expression support More powerful than our existing split and join operators Mapping Repository Current implementation assumes that mappings are know We cannot assume that end users are able to write mappings Ideally, a repository of mappings would be available to users allowing them to find the appropriate mapping Domain experts could create mappings and upload them to the repository Would allow us to support further automation Suggest mappings to user

Syntactic Mediation in Grid and Web Service Architectures

More Related Content

What's hot (20)

Similar to Syntactic Mediation in Grid and Web Service Architectures (20)

Recently uploaded (20)

Syntactic Mediation in Grid and Web Service Architectures

Editor's Notes