DASL Requirements (rev 02)
April 1, 1998
Saveen Reddy & Judith Slein
DAV has client-side search
- WEBDAV and HTTP provide support in GET & PROPFIND
- Benefit: simple server, more complex client
- Problem: inefficient use of network resources.
- Problem: It does not take advantage of server intelligence.
- Limitations hit even on simple queries "find all text files modified during the last week.”
DASL: Server-Side Searching
- client formulates a query
- server perform task of selecting the resources that fit the criteria
- This overcomes limitations of client-side searching.
Terminology
- Adopt from HTTP and DAV
- Add a few of our own ...
DASL Terms
- Search criteria - expression of terms that determines membership in result set
- Search Term - is an assertion about a resource
- Result Set - a response to a search request.
- Result Record Definition - defines what comes back in result set
- Result Record - A unit of information in result set for each match.
DASL Terms
- Search Scope - the the set of resources to be searched.
- Comparison Operator - evaluates the relationship between two values
- Sort Specification - how to sort the result set.
- Search Attribute - controls the search but not part of criteria (example: max time to spend on query)
- Query = search criteria + search scope + result record definition + sort specification + search attributes.
Query Semantics : General Requirements
- searches on content of any media type.
- searching for specific content inside a resource is a common operation.
- Navigate variants
- Navigate versions
- define result record
3 Parts to DASL
- Query Semantics: what the query must be able to express
- Query Transport: how to package and send the query
- Result Set Transport: how to package and send the query
Query Semantics: Scope
- Specify multiple, unrelated URIs for scope
- Resource-Based Scopes
- Depth (recursive search).
Query Semantics: Search Criteria
- Exact Matching for values
- Regular Expression Matching
- Comparisons
- support comparisons against: property values, literal values, and expressions.
Query Semantics: Content Comparisons
- support content-based operators like: NEAR, IN, CONTAINS, LIKE.
- Specify how linguistic stemming, phonetic searching, truncation, keyword expansion, and case-sensitivity apply to search.
- specify the relevance and ranking criteria for content-based searches.
Query Semantics: etc.
- Existence Assertions
- Complex Expressions
- use the logical Boolean operators (AND, OR, NOT) in search criteria
- Undefined properties and values
- Sort Order
- Maximum Number of Records
- Paged Results
- Hit Highlighting
Query Syntax Extensibility
- Standard Query Grammar
- Servers can support additional grammars.
- Natural Language Queries
Query Results
- Standard format for search results.
- Conducive to paged retrieval
- Ideally, same as PROPFIND result
Discovery Mechanisms
- Grammar Discovery
- Operator Discovery
- Scope Information Discovery
- Redirecting a Query: Arbiter Discovery
- No new mechanisms
Miscellaneous
How does DASL relate to or interoperate with:
- Authentication.
- Access Control (defined by WEBDAV)
- Internationalization (conform to the IETF Character Set Policy )