Introduction to Verity Gateways


A Verity gateway provides access to data in a repository. Verity provides a standard gateway for access via a file system. Verity also provides optionally-priced gateways that allow repository access via

HTTP

 

ODBC

 

Lotus Notes

 

Documentum

 

Microsoft Exchange

 

The gateway defines a repository. A repository can be any logical unit that makes sense; for example; the Verity file system gateway defines a repository to be the file system of a particular host. The Verity HTTP gateway defines a repository to be a URL specified by a regular expression, which allows any subset of the Internet to be a repository.

You can think of a gateway as a read-only access method; for example, the Verity file system gateway and the HTTP gateway could read the same documents, with the file system gateway providing access via NFS or a local file system and the HTTP gateway providing access via a web server. The documents could be in text format, PDF, Word, or in one of many other kinds of formats.

The mechanism that extracts the contents of a document from its format is called a filter. A filter is not part of a gateway, although gateways and filters are used together. Verity provides filters for many of the most common types of documents; however, if your gateway provides access to a repository of documents for which Verity does not provide a filter, you will need to provide a filter to go with your gateway. For information about writing filters, see the Verity Developer’s Kit Programming Reference.

Data is sent to the Verity engine via a stream of tokens. The gateway is responsible for accessing the data in a repository and creating tokens from it. The Verity engine invokes the gateway whenever data is needed; typically, this occurs whenever a document is needed; for example, for viewing or indexing.

The gateway is also responsible for determining the documents and fields a user can access. Document-level security is typically implemented via access control lists (ACLs). Field-level security is typically implemented via limiting the visible field schema or by limiting the values that can be seen for a field. The Verity engine invokes the gateway security whenever it is needed; for example, during retrieval of a specific document, indexing of a collection, or filtering of a result list.

The following diagram shows the conceptual relationship between repositories, gateways, filters, and the Verity engine.