Platform Team/Package Management System

Summary

Sweets is a Package Management System based on Zero Install, a decentralized cross-distribution software installation system. It is intended to distribute various software projects created in the Sugar ecosystem, such as libraries, sugar itself, and sugar activities.

This new distribution method is initiated assuming that:

• The method to share software projects should to be as convenient as possible.
• It is important to stimulate users into becoming doers, to modify existing activities, and to share the results of their experiments with other people, i.e., a distribution method should handle different variants of the same project.
• This distribution method is not intended to be the only one, but is targeted more towards direct distribution—from software creators to software users.

The purpose is to create a new distribution method instead of reusing:

1. .xo bundles
   • Work smoothly only for pure python activities, and only if all (and the same) dependencies are installed on all systems. They stop working smoothly if activities use non-standard dependencies or contain binaries.
   • But, are not effective in supporting the use of multiple versions of software, e.g., the results of experiments (the work) of different doers, simultaneously. Users must manually handle the variety of activity versions, e.g., sort out all the local bundles or directories in ~/Activities.
2. native packages
   • Not the shortest way to connect developers with users.
   • In most cases, they don't support multiple versions of the same project.
   • They don't work at all for sharing results of experiments.

At the same time, existing distribution methods are reused in Sweets:

1. .xo bundles is a subset of the Sweets workflow
   • It is possible to bundle an entire directory as a sweet project to use it as a regular .xo file.
2. native packages
   • Sweets is not intended to create one more GNU/Linux distribution. It distributes only projects that people create within the Sugar community; all other software, i.e., dependencies, will be reused from native packages.
   • For cases like Sugar deployments, using the more centralized, regular repositories (third party or official GNU/Linux distributions with native packages) makes more sense. These native packages of Sugar software will be included in Sweets, as well. When people start using Sweets on top of these Sugar distributions, they will have the chance to choose between natively packaged Sugar components and components that came directly from software creators.
   • It is possible, when there is a need, to automatically package sweets into native packages. See Sweets Distribution, for example.

Zero Install basis

Sweets is entirely based on Zero Install. Sweets might be treated as a tools and infrastructure wrapper around Zero Install. See Zero Install's home page, http://0install.net/, for detailed information. And the design page in particular.

Dictionary

A list of terms to understand the basic concepts of Sweets.

Zero Install, 0install

Decentralized cross-distribution software installation system that Sweets is based on.

Sweets

Package management wrapper around Zero Install.

sweet, sweet project

Distribution entities in Sweets, i.e., packages. In other words, software projects that have recipe files in their sources that are being released via Sweets.

feed

A file in XML notation that contains information about all possible variants of the software, i.e., implementations, that can be launched.

interface

This is the cornerstone of Zero Install and, thus, Sweets, as well. To make a feed useful for other people, they are placed somewhere on the Internet to be accessible via HTTP/FTP (http://sweets.sugarlabs.org for the Sweets case). The full Web url, such as http://0install.net/2006/interfaces/ZeroInstall-GUI.xml, is a unique identifier of a distribution entity within Zero Install/Sweets. This powerful identifier is named the interface.

This url is all that is needed to run software from everywhere there is a connection to the Internet.

implementation

One or several bundles that contain one particular implementation of software projects that are being distributed via Zero Install. Implementations are attributed with versions, stability levels, targeted machine architectures, and OS types. It is possible to have several implementations for the same software version if there are differences between launching them on different OSes or machine architectures. Another important attribute of implementations are dependencies of this particular implementation, formed as a list of interfaces. Feeds contain information about all existing implementations in order to let Zero Install choose the right one on the client side, taking into account tons of details, like machine architecture, OS type, stability levels, or dependency restrictions.

recipe

On the Zero Install level, developers work with feeds manually. In the Sweets case, the regular way is to use recipes (but it is still possible to fallback to using feeds at any time). In short, it is an analog of spec files in GNU/Linux distributions, e.g., RPM .spec files or debian/ directories in Debian. Recipes do not specify ready-to-launch implementations like feeds do, but rather, only describe the lastest software version. The feed will be generated automatically on a server (along with preserving the history of versions) after releasing a new version of the software.

Short form for sweet interfaces

Within Sweets, it is possible to omit the http://sweets.sugarlabs.org/ prefix for sweet interfaces so as to make usage more expressive, e.g., in recipe files. It is always possible to use the full interfaces.

Implemented interfaces

One particular sweet implements one or several interfaces according to its recipe files. The reason for having several interfaces is that the same sweet might represent itself, e.g., http://sweets.sugarlabs.org/~alsroot/browse, and the upstream sweet that was used as a basis for the current one, e.g., http://sweets.sugarlabs.org/browse. Furthermore, on the client side, it will be possible to get implementations from ~alsroot/browse while launching browse sweet.

Associated interfaces

Associated interfaces is the alternate way to setup upstream-downstream relations between interfaces. If a recipe file mentions some interfaces as associated, implementations from these interfaces will be added to the implementations list of the current one. For example, if the http://sweets.sugarlabs.org/sdk/sugar interface (the pure sweet Sugar Shell) contains http://sweets.sugarlabs.org/base/sugar (an alias to the natively packaged Sugar Shell) as an associated interface, it will be possible while launching sdk/sugar, to run natively packaged sugar that came from base/sugar.

local sweet

It is an important high-level concept in Sweets, which is intended to make the development process of sweet projects more comfortable. Technically, it is the source software of the sweet project (i.e., with a recipe file) placed somewhere in the file system and registered in the local Sweets instance as a single implementation for interfaces it implements. It is always possible to run this local sweet directly by using the full filesystem path as an interface, but its most useful feature is reuse of the local implementation in routine Sweets workflows. For example, if sugar-toolkit sources were cloned to the ~/src/sugar-toolkit directory, then while running a sugar sweet, it would become possible to reuse local sugar-toolkit sources as a regular implementation.

sweet package

Using the http://packages.sugarlabs.org Web UI, it is possible to create a repository with native packages from released sweets.

Sweets Distribution

It is a repository with Glucose and Fructose sweet packages based on sdk/ sweets.

Further reading

• Sweets Usage - A guide to know how to launch software using Sweets.
• Sweets Packaging - A guide to know how to make your software accessible via Sweets.
• Infrastructure Map - An overview of the Sweets software world.

Getting involved

• Report on bugs.
• Read the HACKING file to know how to contribute with code.

Resources

• Sources.
• Recipe files specification.