1、DiGIR,1,DiGIR Distributed Generic Information Retrieval,Stan Blum, Dave Vieglais, P.J. Schwartz,DiGIR,2,Project Goals,To define a protocol for retrieving structured data from multiple, heterogeneous databases To build a reference implementation of said protocol,DiGIR,3,Design Goals,To use open proto
2、cols and standards, such as HTTP, XML, and UDDI to leverage existing and emerging technologies To de-couple the protocol, software and semantics To automate the establishment of a new data provider as much as possible,DiGIR,4,High-level Architecture,Protocol Provider Portal Registry,DiGIR,5,Protocol
3、,Defines request and response message formats for communication between Provider and Portal Assumes Providers conform to a known federation schema Remains flexible to allow for federation schema pluggability,DiGIR,6,Provider,Makes structured data available to portals Communicates via protocol compli
4、ant messaging only Complies with a known federation schema Supplies meta-data to describe data classification and availability,DiGIR,7,Portal,The entry point for a “user” Can make requests of N number of providers Communicates via protocol compliant messaging only Queries registry for available prov
5、iders Can determine, based on provider meta-data, whether a provider should be queried,DiGIR,8,Project Information,The DiGIR project is a collaborative effort DiGIR is currently established as an open source project on SourceForge (http:/). Further documentation is available on the SourceForge site.
6、Please join us in collaborating!,DiGIR,9,Protocol Details,DiGIR,10,Protocol Details,Specified in an XML Schema (.xsd) Intended to work in conjunction with federation schemas, also expressed as XML Schemas Actual request and response documents are instance documents conforming to both the protocol sc
7、hema and a federation schema,DiGIR,11,searchmyDiggableBipesDB1112Bipes,DiGIR,12,Request Explanation,Composed of elements from the protocol namespace (default) and the schema namespacecontains information about the payloadcontains dbName, filter, and record specification (will also specify result for
8、mat)is effectively an XML representation of a SQL where clause This search request is for the first 50 specimen records that are genus Bipes and were found in the months of November or December.,DiGIR,13,Filter Building,LOPs (logical operators)Can be nested,COPs (comparison ops)(multi value),DiGIR,1
9、4,What “binds” the schemas?,The protocol schema defines various abstract types and elements:A federation schema must define searchable concepts, or groups of them, as substitutable for these abstract elements or extensions of the abstract types,DiGIR,15,DiGIR,16,Why “bind” like this?,To provide data
10、-typing (string, numeric, etc.) for various concepts within operators at an abstract level (e.g. LIKE only valid for string data; IN allows for multiples, but in a controlled fashion) To allow for federation schemas to simply classify data as types without having to redefine/extend operators,DiGIR,1
11、7,Request Issues,Do we need another abstract element such as dateSearchCondition? What information will be useful in the header? How should we specify the format of the results? What standard formats should be offered (I.e. brief, full?). Will tblName be part of the meta-data required of providers?
12、What concepts of Darwin Core 2 are searchable?,DiGIR,18,Response Prototype,DiGIR,19,Response Issues,How do we format and validate the response content? What elements are needed for the , if any? Do we always have diagnostics, or only if there is an error? Should a finite set of diagnostics be create
13、d and maintained in its own XML Schema? Will there ever be a diagnostic that is specific to a federation schema?,DiGIR,20,Provider Details,DiGIR,21,Provider Details,Implemented as a web application that answers questions Interface is not specific to a particular information domain No state informati
14、on is recorded Each request is treated as unique and uninfluenced by previous requests Must always generate a valid response Consists of four key components Request handler Filter handler Result set cache Response generator,DiGIR,22,Request Handler,Receives XML document Validates document Generates
15、internal structures for further processing,DiGIR,23,Filter Handler,Internal structural representation of filter (query) structure Responsible for generating a native query string for querying the database Communicates with UDDI to obtain standard database definition Custom configured to work with sp
16、ecific database implementation,DiGIR,24,Result Set Cache,Contains the results of applying a query Responsible for generating the response records in the requested format Somewhat directly integrated with the response generator,DiGIR,25,Response Generator,Generates the response XML document Serialize
17、s the response header information Serializes diagnostic information Serializes the requested subset of records,DiGIR,26,Provider Configuration,DiGIR,27,Portal Details,DiGIR,28,Portal Details,Divided into two distinct components: a presentation layer and PortalServices The presentation layer supports
18、 the UI and translates requests (HTTP requests from forms or links) into protocol compliant XML requests The presentation layer also handles all display issues involving the responses, such as format, sorting, collating, etc The presentation layer is envisioned to be an application server/web server
19、 implementation,DiGIR,29,Portal Details,PortalServices handles all external network activity (UDDI calls, provider calls, etc) PortalServices limits provider calls to those necessary based on provider meta-data PortalServices threads provider calls for increased performance (I.e. response time) Port
20、alServices is envisioned to be a webapp and supporting classes running within an application server, such as TomCat,DiGIR,30,PortalServices,RegistryAccess ProviderCache PortalConfig PortalServlet PortalRequestHandler ProviderFilterer Marshallers,DiGIR,31,Portal Issues,What information will be stored in UDDI about a provider? What information will be known for communicating with a Provider (I.e. IP address, port, etc?) What meta-data will be provided and what are the rules for using such data for provider filtering? What requirements are there for logging and monitoring?,
