If you want to develop a pure GIS Viewing or Editing web based application that only talks to your Feature Classes in ArcSDE then Weave does not compete in this space. Weave is not about being another WebADF, Flex and JavaScript API. ESRI for example is about GIS, Weave is about Business Systems Integration where GIS is one of the Integration technologies that we work with. Such systems may be Relational Databases, Property Management Systems, Document Management Systems, Asset Management Systems, and others. GIS provides the spatially enabling path for these systems and most of the time it is the main integration the Weave user will work with.

This same argument can also be applied to other mapping products, e.g. Erdas Appollo, ArcIMS, MapExtream, etc

The following bullet points summarise the answer to a typical question such as "For an ESRI developer, what does Weave provide on top of the ESRI technology which ESRI is not providing already?".

Insulate the developer from the lower level api's of the particular system.
Provide easy access to spatial features in a variety of Spatial Engines.
Has advanced Security at all levels of the Weave system including restricting access to entities, data, clients,etc
Connection Pooling across all connections (spatial and database)
Ability to write plugins that contribute code to the Weave subsystem.
Work seamlessly with Spatial and Non-Spatial Data.
Integrate with multiple Map Engines regardless of the underlying Spatial Vendor.
Create multiple client front ends without having to write any code.
Write custom code to enhance a client(s) Views and Actions.
Natural Language Geocoding Engine.
Built in reporting engine Business Intelligence Reporting Tools (BIRT) that enables the creation of sophisticated multi page Reports that can exported in a variety of formats (pdf, doc,xls, etc)
Openness - Use of open, non-proprietary APIs and SDKs and support for multiple database and spatial engines
Integration of Spatial Data - Powerful data integration from multiple spatial data sources such as Oracle Spatial, ArcSDE, Shapefiles, PostGIS, WFS, GML and others
Integration of Non-Spatial Data - Powerful data integration from multiple JDBC and ODBC non-spatial data sources
Integration of Map Services - Simultaneously work with many map services such as WMS, ArcIMS, ArcGIS Server, MapXtreme, Image Web Server, MapServer and others
Insulation - The data complexity is hidden from the end users
Simple configuration - Minimise/consolidate configuration information
Centralised - The configuration is controlled by the site administrator from a single location
Web/Browser-based - Weave has browser-based clients using JavaScript and HTML. No browser plugins are required
Customisable/Expandable - Weave can be customised and expanded by third parties. Weave has been built with its own open software development kit which is supplied with the product
Minimal footprint - Minimal requirements to integrate data sources (i.e. no selection tables, no forced schemas)
Scalable - A multi-tier architecture is supported
Security - Role based access control to interfaces, data, and reports

A key Weave strength is the ability to get a site up and running with the integration of multiple Spatial, Map, and Data Engines quickly where as doing that with ESRI products you will be starting from a very basic level. If the site needs to integrate with other systems that are outside the ArcSDE environment regardless if they are spatial or non-spatial then Weave at a high level is a good fit.

Browser not supported