- From: Eliot Christian <echristi@usgs.gov>
- Date: Sun, 07 Nov 1999 06:14:19 -0500
- To: www-webdav-dasl@w3.org
I am involved in the W3C XML Query work, which has a specific requirement to coordinate with the IETF DASL work. The XML Query work needs to address protocol issues up front and also needs to document some Use Cases to help focus the work. I offer for consideration the following Use Case as a way to introduce some of the protocol considerations of an application using XML Query. I would very much like to know if you think this makes sense from the DASL perspective, and especially any specific suggestions to improve it ;-) --------------------------------------------------------- XML Query Use Case: Referral Search In this case, the user of XML Query begins with a text search at a referral service, using just one English word. This results in a number of candidate collections, each one titled and ranked by score. The user selects a collection and gets a more precise search facility that is particular to the selected collection. The user constructs a Boolean XML Query and then receives a set of document scores and titles which satisfy the query. A narrative of the interactions involved in this case is provided below, numbered as steps alternating between client and server. (Specific syntax and storage mechanisms are not meant to be implied by this narrative.) (1) Client - The user designates that query processing is to be performed by a particular service (e.g. host:port) and a particular collection of XML documents (e.g., named structure in a file system). The client offers a facility to construct an XML Query consisting of words in English. The client sends the user's query to the designated service. (2) Server - The designated service processes the query against the designated collection of XML documents, applying criteria appropriate for a full-text search. The service causes delivery to the client of XML representing a named "result set" pointing to XML documents within the collection that satisfy the query. Each member of the result set has a structure composed of a score for the set member, a name for the set member, and a handle for retrieving the set member (e.g., URL). (3) Client - The client presents to the user the result set XML document delivered from the query processing in step 2. When the user selects a particular member of the result set, the client causes delivery to the original service of a second XML Query. In this second query, the query is to be processed against the result set constructed in step 2, and the querying is to select the specific set member based on the retrieval handle supplied. (4) Server - The service retrieves the XML document designated by the set member retrieval handle and causes delivery of the XML document to the requesting client. This XML document itself describes another collection of XML documents available on a service elsewhere. Its structure includes a service title, a pointer to the schema for the collection, and a handle for accessing the collection (e.g., a URL including the service host:port and named structure in a file system). (5) Client - The client presents to the user the retrieved XML document delivered from the process in step 4. When the user selects the handle for accessing the described collection, the client retrieves the collection schema from the network and presents to the user a facility to construct an XML Query. This facility now includes search constraints based on the schema, not only full-text but title, originator, subject, date, and place. The user constructs a Boolean search and this XML Query is delivered to the referred service and collection. (6) Server - The designated service processes the query constructed in step 5 against the designated collection of XML documents, applying the Boolean search criteria using the structure in the XML schema. The service causes delivery to the client of an XML document pointing to a number of XML documents that satisfy the query. --------------------------------------------------------- Eliot Christian, US Geological Survey, 802 National Center, Reston VA 20192 echristi@usgs.gov Office 703-648-7245 FAX 703-648-7112 Home 703-476-6134
Received on Sunday, 7 November 1999 07:13:45 UTC