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From Grant Ingersoll <>
Subject [PROPOSAL] Lucene Connector Framework
Date Wed, 06 Jan 2010 18:57:14 GMT

On behalf of the Lucene PMC, I'd like to propose incubation for a new Lucene subproject called
the Lucene Connector Framework.  I think we have all the necessary bits in place for the proposal
to go forward, but would appreciate any discussion/questions.

Grant Ingersoll


------  Wiki Text Copied Below -----

Lucene Connector Framework


Many, many search engines, as well as other applications, have a need to connect with content
repositories (SharePoint, CMS, Documentum, etc.) in a standard manner. The Lucene Connector
Framework (LCF) is a project aimed at building out these connectors in open source under the
Apache brand.


The goal of LCF is to create a viable Lucene subproject aimed at delivering a best of breed
connector framework under the Apache Lucene name. As a framework, the project will not only
provide a way to connect to individual repositories, but also a mechanism for plugging in
new connectors or custom connectors in a straightforward manner.

A connector framework is vital for search engines and other tools that need to access data
located in corporate repositories. By abstracting the problem into a framework, applications
can code to a set of well-defined interfaces instead of having to use a different interface
for each connector.

Connector Framework is an extendible incremental crawler, which uses a database to manage
configuration and crawl history, and provides reasonably high performance in accessing content
in multiple repositories for the main purpose of search engine indexing. Connector Framework
also establishes a repository-specific security model which can be used to limit search user
access to repository content based on a user's identity. Connector Framework also includes
existing connectors and authorities for:

	• File system
	• Windows shares
	• JDBC-supported databases
	• RSS feeds
	• General websites
	• LiveLink [from OpenText]

	• Documentum [from EMC]
	• SharePoint [from Microsoft]

	• Meridio [from Meridio]
	• Memex [from Memex]
	• FileNet [from IBM]

Key design points for Connector Framework are as follows:

	• Extendability - you can add new connectors for new repositories, and new authorities
for specific repository security models
	• Incrementality - the ability to process only what changed between crawls, in a repository-specific
	• Restartability - using a database with ACID properties to insure that crawls are safe
against process interruption or machine shutdown
	• Security - establishing a model of security tokens that allows a search engine to enforce
a repository's security model
	• Limited footprint - ability to operate reliably within a fixed amount of process memory,
regardless of configuration
	• Performance - management of connector-specific resources to maximize overall thoughput
	• Transparency - ability to generate reports on the activity of all crawls and repository


MetaCarta originally approached Grant Ingersoll from the Lucene PMC about donating their existing
connector framework to the Lucene PMC. After some discussion about accepting it as a software
grant, the PMC decided it would be best to incubate the project first.


The Connector Framework fills an often significant gap in the Lucene experience, namely, how
to get content locked away in a content repository into Lucene/Solr/Nutch/Mahout/Tika. Naturally,
many other tools (search engines and others) will also have this same problem. A Connector
Framework would also be useful for someone wishing to migrate between content repositories,

Current Status

Connector Framework has been under development and in use in the field for close to five years,
deployed on a MetaCarta search appliance. Almost all development of the project has been done
by Karl Wright ( ). Some individual connectors were developed initially
by contractors hired by MetaCarta, Inc., but maintenance and further development is currently
handled by the MetaCarta team.

Development of Connector Framework can therefore be viewed as core framework development,
plus development of individual connectors. Core framework development is currently not a terribly
collaborative process, as there are no maintainers of the core functionality other than Mr.
Wright. Development of new connectors has been done in the past in a much more collaborative
way by supplying a developer with a "development kit", and then integrating the resulting
connector (with whatever changes might have been necessary) into the source tree.

Reasonable efforts have been made to maintain the generality of the code base during the time
that MetaCarta has owned it. Nevertheless, certain MetaCarta-specific changes have been made
which may require review and modification. The following areas probably need to be addressed
in the code before graduation can occur:

	• Branding. The UI brands it as a MetaCarta project.

	• Package names. Package names would have to be changed.
	• How Connector Framework handles document delivery needs to be generalized, at least for
a single, configurable target output connector, and perhaps for multiple, independently-configurable
targets. Simple example output connectors need to be written. Work in this direction is currently
underway at MetaCarta and may or may not be complete at the time of the code handover.

	• Connector Framework-specific dependent package modifications need to be addressed somehow.
For instance, the following projects that Connector Framework depends upon have been modified,
but the modifications have not been accepted upstream: commons-httpclient NTLMv2 and NTLM2
support [RSS, Web, SharePoint, Meridio, and Livelink connectors]; commons-httpclient custom
HTTPS protocol factory support [Web, SharePoint, Meridio, and Livelink connectors]; xerces
ability to handle non-legal RSS feeds [RSS and Web connectors]

	• MetaCarta-specific features, like document templates, are explicitly handled by the UI
and the infrastructure. These features should be generalized so that they are controlled by
the choice of output connector.

	• Some specific hooks, namely support for configuration change notification, and for database
maintenance notification, may need to be made more generic.
	• Share Connector has a "fingerprinting" feature, which prefilters documents based on a
document type it surmises using a document inspection technique. This feature is only viable
at the moment for very basic document types. It should either be removed, or generalized significantly
to be much more flexible.
	• Documentation needs to be fleshed out, including javadoc and overall usage documents.
	• Tests need to be written and/or ported from MetaCarta's test suite.

Longer term, the project will likely grow into a more distributed crawler, where multiple
machines might well be involved in coordinated crawling activity.


Building the community using a meritocratic approach is very important to the success of LCF.
We know many, many people in the search space (and otherwise) have either written their own
connectors or are in need of connectors. Thus, we expect a meritocratic community will lead
to widespread participation.


Our hope is that our existing code, features and capabilities will attract a large community
of both developers and users. We also believe that other organizations will find this project
interesting and relevant, and contribute resources.

The user community of LCF would be similar to that of the other Lucene projects, and in many
cases they would overlap.

Core Developers

See the initial committer list below.


We expect LCF will align quite well with the existing Lucene community and will also provide
significant value to other ASF and non-ASF projects as well as many companies and individuals
looking to access their content repositories in a programmatic fashion.

Known Risks

Orphaned Products

The Connector Framework is an important piece of any search engine, including MetaCarta's,
as it provides the primary mechanism for getting content out of a repository and into the
search engine's index. Thus, we don't expect it will be orphaned anytime soon. Once the project
is established and the code is available, we expect to attract not only other search companies,
but others with similar needs.

Inexperience with Open Source

Grant Ingersoll, Ryan McKinley and Simon Willnauer provide the majority of the experience
with Open Source at the ASF, but all of the initial committers are familiar with Open Source
and have contributed to other open source projects.

Homogeneous Developers

The current list of committers are mostly members of either the MetaCarta or Lucid Imagination
developer team, but several are not. Additionally, we are actively recruiting other developers.

Reliance on Salaried Developers

We have a variety of committers represented. Some are being paid to work on the project and
some are not.


Connector Framework itself has no real cryptography component, although it does currently
obfuscate passwords it saves to the database or to a configuration file using a proprietary
algorithm. The algorithm is present simply to avoid using cleartext and is not secure in any
sense other than by obscurity.

Various connectors, such as Share Connector, Web Connector, RSS Connector, SharePoint Connector,
LiveLink Connector, and Meridio Connector make use of cryptographic principles via secondary
libraries. Specifically, these connectors support NTLM, NTLMv2, and NTLM2 Session authentication
via commons-httpclient and jCIFS. The changes to commons-httpclient necessary to support these
varieties of Windows protocols have not yet been accepted upstream by the Apache httpclient

It is unknown at this time exactly to what degree the Oracle JDBC driver, the jtds JDBC driver,
or the Postgresql JDBC driver uses cryptography. Also, the FileNet API class, the Memex API
classes, the OpenText LAPI api classes, and the Documentum DFC classes all may or may not
use cryptography.

Legal Concerns

Some of the connectors in the existing framework require paid licenses to use. We will need
to evaluate each connector to see what can be appropriately included. For those connectors
that require a paid license, we will need to determine a plan for including the wrapper code
without the underlying bindings in a legal manner. We expect we can provide the wrapper code
without the binding and that the code will thus only be compilable by someone who has access
to the binding. (This is what Google has done for their individual connectors). Longer term,
we expect to demonstrate to the companies with proprietary connectors why it is more valuable
for them to open up their specific connector pieces to give broader access to people looking
to leverage their content in the repository.


The project is being rebranded from a MetaCarta internal name to the Lucene Connector Framework,
which will be an ASF mark.

Relationships with Other Apache Products

We expect almost all of the Apache Lucene ecosystem will benefit from having a standard way
of connecting to content repositories. Additionally, users of UIMA should also benefit. We
also see an especially tight connection with Tika, as much of the content in these types of
repositories are "rich" document types which will then need their content extracted.

An Excessive Fascination with the Apache Brand

All of us are familiar with the value that Apache brings to a project in building out a community.
We also are all significant users of Apache Lucene and related tools (Solr, Nutch, Mahout,
Tika) and expect a close relationship with those projects will help significantly grow the
LCF community.


MetaCarta has end-user documentation for Lucene Connector Framework, which might function
as the core the open-source end-user documentation. The documentation is in LaTeX form, and
thus usable sources can readily be extracted. Research as to any ownership issues for the
documentation as it stands still needs to be examined.

The existing java doc of the code, while fairly extensive, needs review and perhaps augmentation
to insure it meets the needs of an ASF project. Significant attention to maintaining its accuracy
was made during MetaCarta's ownership of the code base.

Initial Source

All initial sources will be coming from MetaCarta, Inc., with the goal of folding in changes
from others shortly thereafter.

Source and Intellectual Property Submission Plan

Code IP grants need to be made from MetaCarta, Inc. But, in addition, several connectors (notably
Documentum, LiveLink, Memex, and FileNet) rely directly on client API's in order to be compiled.
Another connector (JDBC) relies on the existence of the Oracle JDBC Driver in the classpath
in order to enable crawls against Oracle databases.

It is unlikely that EMC, OpenText, Memex, or IBM would grant Apache-license-compatible use
of these client libraries. Thus, the expectation is that users of these connectors obtain
the necessary client libraries from the owners prior to building or using the corresponding
connector. An alternative would be to undertake a clean-room implementation of the client
API's, which may well yield suitable results in some cases (LiveLink, Memex, FileNet), while
being out of reach in others (Documentum). Conditional compilation, for the short term, is
thus likely to be a necessity.

Other external dependencies, such as jCIFS for the Share Connector, are licensed with LGPL,
and thus may need to be treated in a manner similar to the closed API's even though they are
open source. These include the postgresql JDBC driver, and JTDS.

The Lucene Connector Framework core and individual connectors are completely separable, and
many of the connectors require no third party licenses. Therefore, there is significant utility
for this project even in the absence of any third-party software grants, or clean-room engineering.

The software grant will be faxed to the Apache Software Foundation if and when the proposal
herein described is accepted. MetaCarta patents are not infringed by this grant. Also, MetaCarta
trademarks are not included in this grant.

External Dependencies

The project dependencies, other than on other Apache projects, are as follows:

The ConnectorFramework core currently uses the Bitmechanic JDBC pool driver, which is BSD
licensed, and the Postgresql JDBC driver, which is also BSD licensed.

The LiveLink Connector relies on LAPI, which is privately licensed by OpenText. The Documentum
Connector relies on DFC, which is privately licensed by EMC. The Share Connector relies on
jCIFS, which is LGPL. The Memex Connector relies on privately licensed java libraries from
Memex. The FileNet Connector relies on privately licensed java libraries from IBM.

Required Resources

	• Mailing lists
		• connectors-private (with moderated subscriptions)
		• connectors-user@
		• connectors-dev@
		• connectors-commit@
	• Subversion directory

	• Website
		• Confluence (CONNECTORS)
	• Issue Tracking

Initial Committers

Names of initial committers with affiliation and current ASF status:

	• Karl Wright (kwright at metacarta)
	• Josiah Strandberg (jstrandberg at metacarta)
	• Ken Baker (bakerkj at metacarta)
	• Marc Meadows (mam at metacarta)
	• Grant Ingersoll ( gsingers@a.o Lucid Imagination, ASF Member)

	• Brian Pinkerton (brian.pinkerton at Lucid Imagination)
	• Simon Willnauer (simonw at apache org, Committer on Lucene Java and Lucene Open Relevance
	• Ryan McKinley (ryan at apache org, Committer on Lucene and Solr)

	• Robert Muir (rmuir at apache org, Committer on Lucene and Open Relevance)
	• Sami Siren ( siren@a.o , Committer on Nutch and Tika)

	• Otis Gospodnetic ( otis@a.o , Committer on Lucene, Solr, Nutch, Mahout, and Open Relevance

	• Shalin Shekhar Mangar ( shalin@a.o , AOL, Committer on Apache Solr)

	• Noble Paul ( noble@a.o , AOL, Committer on Apache Solr)

	• George Aroush (george at, Committer on Lucene.Net)



	• Grant Ingersoll

Nominated Mentors

	• Grant Ingersoll
	• Jukka Zitting
	• Gianugo Rabellino

Sponsoring Entity

	• Apache Lucene PMC: Message ID: in private@lucene.a.o

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