The Boston Coordinated Access System (CAS) project by the City of Boston's Department of Neighborhood Development matches homeless individuals to housing vacancies based on need.
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Boston Coordinated Access System Build Status


The Boston Coordinated Access System (CAS) project was initiated by the City of Boston's Department of Neighborhood Development office to match homeless individuals to housing vacancies based on need.

The CAS matches vacancies to permanent supportive housing units to clients using a customizable rule-based system. Once a match is proposed by the system using these rules, the system verifies eligibility and coordinates communication around the housing opportunity between the client, Department of Neighborhood Development staff, Shelter Agencies and Housing providers.

See docs/Flow May Vouchers.pdf for a flow map that describes the process from voucher availability to person housed.

Copyright © 2016 Green River Data Analysis, LLC

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.

A copy of the license is available in


The City of Boston made a conscientious choice to release this project into the open source under a GPL. Our goal is to promote this opportunity, allowing Boston's investment to assist other municipalities and organizations, and realize the vision of a tool under continuous, collaborative improvement helping communities nationwide.

Looking ahead, we see the CAS codebase serving as a foundation for many housing match applications. By providing the functionality to connect housing seekers to eligible opportunities, and supporting communication workflows around the process, the system can be adapted to support a wide range of needs. It could support expansive affordable housing programs at a regional or state level; it could support efforts targeting a larger homeless population; or it could support a local housing project manage its vacancies.

The CAS can sit logically between other existing systems: it's designed now to pull housing inventory and person records from external data sources, and potentially write back updates. It could also work as a standalone system, serving as a canonical database of housing opportunities and housing seeker information. In either case, the CAS provides the fundamental logic and workflow support for identifying optimal housing options, and seeing a selection through to move-in day.

Application Design

The application is designed around the HUD Data Standards. You can find copies of some relevant documentation in the docs folder.

The application is written primarily in Ruby on Rails and we use RVM to select a ruby version. Other ruby version managers should work fine, as would manually installing the ruby version mentioned in the .ruby-version

The application uses postgres as a default primary data storage. Data connectors to other HMIS systems are not included in this release but a simple example method using CSV files is available. In Boston's deployment we have connections using various combinations of Microsoft SQL Server, SFTP of CSV and XML, and live API connections.

We've developed locally on OSX using homebrew and deployed to Ubuntu 16.04 using apt for dependencies.

Screen Shots

A Match in Progress

Image of a match in progress

Editing Program Roles

Image of a match in progress

Developer Prequisites

If you are unfamilar with contributing to open source projects on github you may first want to read some of the guides at:

There is a simple script to setup a development environment in bin/setup. To make it run smoothly you should have:

  • A running Ruby 2.3+ environment with bundler 1.11+ installed.
  • A local install of postgresql 9.4+ allowing your user to create new databases.

Once these are in place, bin/setup should:

  • Install all ruby dependencies.
  • Create initial copies of configuration files.
  • Create an initial database and seed it with reference data and a randomly generated admin user.
  • Add some example data that in production would come from your HMIS integration.

If all goes well you should then be able to run bin/rails server and open the CAS in your system at http://localhost:3000 using the email/password created during bin/setup. If not, read bin/setup to figure out what went wrong and fix it.

Hack on your version as you see fit and if you have questions or want to contibute open an issue on github.

Developer Notes

We use the following common rails gems and conventions:

  • haml for view templating
  • bootstrap for base styles and layout
  • sass for custom-css
  • simple_form for forms
  • kaminari for pagination
  • brakeman for basic security scanning.
  • rack-mini-profiler to make sure pages are fast. Ideally <200ms
  • helpers need to be explictly loaded in controllers. i.e. we have config.action_controller.include_all_helpers = false set
  • bin/rake generate controller ... doesn't make fixures and they are disabled in test_helper. We don't use them and instead seed data in test or let test create their own data however they need to.
  • it also doesn't make helper or asset stubs, make them by hand if you need one. See config/application.rb for details.