Updated Requirements document

There seems to have been some problem with the original submission. I'm
received complaints that people are getting a truncated file (only two
pages of the total nine appear). So, I am submitting a corrected
version: draft-reddy-dasl-requirements-01.txt 

As soon as I get back in town (Wednesday morning -- Dec. 10) I will
update the DASL web pages to point to the correct version of the
document. 

I am also including the complete text of the draft below so that people
can see this immediately. 

Thanks, 
Saveen 

----


                                                S. Reddy
INTERNET-DRAFT                                  Microsoft Corporation
draft-reddy-dasl-requirements-00.txt            November 19, 1997

Expires May 24, 1998


                Requirements for DAV Searching and Locating


     Status of this Memo

     This document is an Internet draft. Internet drafts are working
     documents of the Internet Engineering Task Force (IETF), its areas
     and its working groups. Note that other groups may also distribute
     working information as Internet drafts.

     Internet Drafts are draft documents valid for a maximum of six
     months and can be updated, replaced or obsoleted by other
     documents at any time. It is inappropriate to use Internet drafts
     as reference material or to cite them as other than as "work in
     progress".

     To learn the current status of any Internet draft please check the
     "lid-abstracts.txt" listing contained in the Internet drafts
     shadow directories on ftp.is.co.za (Africa), nic.nordu.net
     (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
     coast) or ftp.isi.edu (US West coast). Further information about
     the IETF can be found at URL: http://www.ietf.org/

     Distribution of this document is unlimited. Editorial comments
     should be sent to the author (saveenr@microsoft.com).

     Abstract

     The Distributed Authoring and Versioning protocol [WEBDAV] defines
     simple mechanisms to assign and retrieve values for properties.
     This document presents a list of features in the form of
     requirements for a DAV Searching and Locating (DASL) protocol, an
     extension that improves the efficiency and utility of searching
     operations for resources whose properties or content meet client-
     defined criteria.













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     1 Introduction


     The DAV methods INDEX, PROPFIND, and the HTTP 1.1 method GET are
     sufficient to allow a client to locate those resources that meet a
     set of conditions on their properties or content. However, these
     methods are inefficient for some simple, common search scenarios.

     For example, in a typical publishing environment a client may wish
     to find "all the text documents modified within the last week."
     DAV clients must repeatedly invoke the INDEX and PROPFIND methods
     to traverse the server namespace, retrieve property values, and
     then determine which resources meet the criteria. This procedure
     is a functional solution. However, it has several limitations.

     First, this procedure makes inefficient use of network resources.
     The client must repeatedly invoke the INDEX method to recurse the
     server namespace. Likewise, repeated calls to PROPFIND are
     required for all of the resources that are being examined,
     resulting in the transmission of data even for resources that will
     fail to meet the criteria.

     Second, it makes inefficient use of server intelligence. Servers
     capable of supporting a criteria-based search for resources can
     use well-defined mechanisms to expedite the generation of the
     results. These techniques include caching of intermediate search
     results and the use of indices. If the logic is left solely to the
     client, neither client nor server can take advantage of these
     features.

     Third, this simple DAV search procedure cannot efficiently search
     the content of resources. To search content would require a DAV
     client to retrieve the entire content of each resource that is to
     be examined.

     These limitations are severe enough for even simple search
     scenarios that DAV needs extensions to specifically address them.


















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     2 Terminology


     Search Criteria - a set of conditions that must be true for a
     resource to be included in the search result.

     Result Set - the set of result records transmitted to the client
     as the response for a search request.

     Result Record - a unit of information appearing in the result set.
     Each Result Record corresponds to a specific resource that meets
     the search criteria.

     Search Scope - the set of resources to be searched.

     In addition to the terms defined above, this document uses the
     terminology consistent with the HTTP 1.1 specification [HTTP] and
     the WEBDAV specification [WEBDAV]





































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     3 Requirements


     3.1 Search Criteria


     3.1.1 Boolean Expressions


     It must be possible to use Boolean operators (AND, OR, NOT) in the
     search criteria.

     Often criteria involve the evaluation of several conditions
     simultaneously. For example, a stereotypical query might ask for
     "those documents modified by user X within some period of time Y."
     Boolean operations are necessary to provide support for these
     common queries.


     3.1.2 Relative Comparisons


     It must be possible to specify criteria on ordered relations such
     as "less than" or "greater than" for property values.

     Many common searches involve relative comparisons. For example, a
     stereotypical query might ask for "those documents under 10K in
     size". Relational operations are necessary to provide support for
     these common queries.


     3.1.3 Simple Searches on Content


     It must be possible to perform simple searches on content of any
     media type.

     Searching for specific content inside a resource is a common
     operation. Examining resource content is generally less efficient
     than examining only the resource's properties because the size of
     the content is generally much larger than that of the properties.
     DASL must provide a mechanism to provide searching on content of a
     resource to provide for this scenario.


     3.1.4 Variants


     It must be possible for searches to occur across multiple variants
     of resource and to target specific variants.
     The WEBDAV working group is addressing the standardization of
     mechanisms for authors to use when submitting variants to the
     server. DASL must provide mechanisms that can intelligently query
     on those variants.


     3.1.5 Exact Matching


     It must be possible to specify exact content matches, and the
     absence of an exact content match.



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     3.1.6 Regular Expression Matching


     It must be possible to specify a search with matching operators
     with the expressive power of regular expressions.

     The power and frequent use of the Unix utility "grep" highlights
     the value of regular expressions for searching large bodies of
     content.


     3.1.7 NEAR operator

     It must be possible to specify searches for content matches of
     terms that are near each other within a document.


     3.2 Results


     3.2.1 Result Record Definition


     The client must be able to identify the properties or content of
     interest for the result records.

     Search criteria and search result records may not overlap. For
     example, a query might ask for "the authors of those documents
     under 10K in size". In this case, the criterion relates to the
     size, but the desired result record relates only to the author.


     3.2.2 Standardized Results Format


     DASL must define a standard format for search results.
     For the sake of interoperability, it is desirable that server
     result formats be standardized so that regardless of the type of
     query syntax used, clients are guaranteed to successfully
     understand the results of a query.


     3.2.3 Paged Search Results


     DASL search results must be conducive to paged retrieval.

     Paged retrieval is necessary if result sets are very large and if
     clients must also present a responsive interface to a user. In
     this scenario clients need to access portions of the search result
     at specific times. DASL search results must be defined so that
     paged search results are possible.


     3.3 Search Qualifiers


     3.3.1 Search Scope


     It must be possible for the client to specify a number of
     different, unrelated URIs over which the search is to range.



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     3.3.2 Search Depth


     It must be possible for the client to specify the "depth" of a
     search for a search scope URI.

     Users often intend to scope their searches either to the immediate
     children of a container or to extend the search recursively to the
     container's children. Furthermore, depth control is needed to
     prevent servers from performing unnecessary work.


     3.3.3 Search References


     It must be possible for the server to refer the client to other
     resources in order to continue a search.

     For example, a client may ask the resource http://ren/stimpy to
     perform a search over http://foo/bar and http://blah/mumble.
     However http://ren/stimpy may not be able to perform the search
     itself and so will need to be able to inform the client that it
     should submit its search request directly to http://foo/bar and
     http://blah/mumble.


     3.4 Search Query Syntax


     3.4.1 Simple Query Syntax


     The DASL extensions must define a query syntax that provides
     simple searching functionality.

     For the sake of interoperability, DASL servers must be expected to
     offer a basic set of searching capabilities. Likewise, clients
     need a standard, simple syntax by which to access those
     capabilities.


     3.4.2 Extensible Query Syntax


     DASL extensions must support the extensible use of alternate query
     syntax.

     Servers that support searching capabilities may wish to expose
     those capabilities through DASL. This may be the case if the
     simple query syntax is not robust enough to support the server's
     capabilities.


     3.4.3 Query Syntax Discovery


     It must be possible for clients to discover which syntaxes a
     server supports.

     If a server is capable of supporting several search syntaxes, the
     client needs to determine which syntaxes are supported.



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     3.5 Authentication


     The DASL specification should state how the DASL extensions to
     WEBDAV interoperate with existing authentication schemes, and
     should make recommendations for using those schemes.


     3.6 Access Control


     The DASL specification should state how the DASL extensions to
     WEBDAV interoperate with the ACL mechanisms supported by WEBDAV,
     and should make recommendations for using those schemes.


     3.7 Internationalization


     DASL extensions must describe how to perform searches on
     internationalized content and properties. Information intended for
     user comprehension must conform to the IETF Character Set Policy
     [CHAR].




































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     4 References


     [CHAR] H.T. Alvestrand, "IETF Policy on Character Sets and
     Languages", June 1997, internet-draft, work-in-progress, draft-
     alvestrand-charset-policy-02.txt.

     [HTTP] R. Fielding, J. Gettys, J. C. Mogul, H. Frystyk, and T.
     Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2068,
     U.C. Irvine, DEC, MIT/LCS, January 1997.

     [WEBDAV] Y. Y. Goland, E. J. Whitehead, Jr., A. Faizi, S. R.
     Carter, D. Jensen, "Extensions for Distributed Authoring and
     Versioning on the World Wide Web", October, 1997, internet-draft,
     work-in-progress, draft-ietf-webdav-protocol-04.txt.Authors'
     Addresses







































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     5 Author's Addresses


     Saveen Reddy
     Microsoft Corporation
     One Microsoft Way
     Redmond WA, 9085-6933
     EMail: saveenr@microsoft.com


     Expires May 24, 1998












































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Received on Tuesday, 9 December 1997 00:03:53 UTC