FF 1 : Modules A presentation by Robin Upton (2009-08-03) Latest version at Attribution – NonCommercial - ShareAlike .

FF 1 : Modules

A presentation by Robin Upton (2009-08-03)Latest version at www.altruists.org/ff13

Attribution – NonCommercial - ShareAlikewww.altruists.org

V1.2.0

http://www.altruists.org/ff13

Recommended Pre-requisite: FF12: Clients

3

What is an F2F Module?

A module is a digitally signed, uniquely identified set of resources:

Modules are blueprints for soft-nodes, defining their behaviour,in the same way that XVMs are blueprints for soft-systems.

rdf:about http://friend2friend.net/modules/lib/ MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCwt5pEliqkVR6ZV5umPoRpwmLlNfG6QEpKju7VM7aHlnJDn1/mS1Gg82+BXAXA9EhTNoLrg7Pi6X0X9q7iRS5hrBbR10ZNyBkAuxQdPgaQINMBo7PopDokaoIS4yQTJjm3x+x1SLqWBlMKNsS4od9eHMZLLpysziYQDQGUqFIi/wIDAQAB

pkey

Services Filters

Displays Images

Scripts Hooks

Datastores

ResourcesModules can have 7 types of resources:

Clientside

Serverside

image SVG image<svg:svg>

filter Automated XSL Transform

service Extended XSL Transform

datastore XML data fileWhen will Bush get convict

script XML instruction file

display XSL Transform

hook Set of XSL Transforms

Requesting Resources

Datastores are only requested from services running at that node itself:

Most resources are requested using a URI (Universal Resource Identifier)

image <imagereq function=”uri”>

display <displayreq function=”uri”>

hook <hookreq function=”uri”>

filter (not requested)

datastore

<servicereq function=”http://friend2friend.net/services/bag-read”>

<datastore-name>NCName</datastore-name><itemid>1</itemid><itemid>8</itemid>

</service>

service <servicereq function=”uri”>

script <scriptreq function=”uri”>

Images

Module images are Scalable Vector Graphic (SVG) documents

rdf:about = <uri>

src = <path>

version = <number>

When clients process an <imagereq>, they request this resource by URI from

their F2F soft-system:

ClientClient Soft-Soft-systemsystem

enabled = {0, 1}

<svg:svg>

All resources can take this attribute, but it is not shown

again, for brevity

Where the server can find the SVG file on disk.

<svg:svg>

uri src

<imagereq function=”uri” x=”24” y=”24”/>

Notation!

Required attributes are shown in bold,others are optional

Displays

Module displays are XSL Templates, applied by clients:

rdf:about = <uri>

src = <path>

version = <number>

They are requested by <displayreq> items,

which tells clients to request the appropriate

XSL from the server.

Although all resources except datastores need this attribute,

it is not shown again, for brevity

ClientClient Soft-Soft-systemsystem

uri src

<displayreq function=”uri”>...optional XML...</displayreq>

Hooks

Hooks are identified by URI:

compiled list of handlers

rdf:about = <uri>

<handler namespace = {<uri>, “”, “*”} src =”<path>”/>

On this, modules can hang their own handlers, which link a namespace to an XSLT script:

Soft-Soft-systemsystem

uri src<hookreq><hookreq>

<hookreq function=”uri”>...XML Data...</hookreq>

http://www.altruists.org/ff11

They are explained in detail in presentation /FF11.

<handl

er>

<ha<h

Filters

Module filters, to automate the soft-system, are defined as follows:

rdf:about = <uri>

position = {“bottom”, “exec”, “top”}

http://www.altruists.org/ff9

These are used by the soft system when processing messages and servicereqs as explained in presentation /FF9.

Filters contain one <down> and/or <up> item,which reference the XSLT that implements them,

and optional process-directives or a privilege:

<{up,down} src=<path> privilege = {“*”, 0, 1, 2...} p.d’s />

privilege confers on scripts for a number of crunches (or, with *, an unlimited number) the access permissions of the

module, rather than those of the packet being filtered.

Scripts

privilege = {“*”, 0, 1, 2...}

Module scripts are chunks of XML to be interpreted.

rdf:about = <uri>

src = <path>

default = {“allow”, “deny”}

role = <uri>

These are used by the soft system in a similar way to shell scripts, to automatic actions on system shutdown, installation etc.

This defines the purpose of this script, which is one of a fixed set.

Services

privilege = {“*”, 0, 1, 2...}

Module services augment the core services, detailed as follows:

visibility = {“protected”, “public”, “private”}

output = {“*”, <path>}

rdf:about = <uri>

input = {“*”, <path>}

src = <path>

default = {“allow”, “deny”}

http://www.altruists.org/ff5

The servicereq processing model is explained in detail by /FF5.

Protected services are accessed by a message to the node.

Services can callout to public services without messaging or access control.

Private services are invisible to other soft-

nodes.

midput = <path>Paths to XSDs for runtime validation

Datastores

Datastores are XML files at the soft-node, detailed as follows:

rdf:ID = <NCName>

ServicesServices Soft-Soft-systemsystem

IDsrc

<some XML data>

When will Bush get convict

When will Bush get convict

The identifier exposed to scripts.It does not need to be universally

unique, only unique within this node.

<servicereq function=”http://friend2friend.net/services/bag-read”><datastore-name>fish</datastore-name><itemid>1</itemid>

</service>

Datastores are accessed through the bag-* and xml*

services at the soft node.

schema = <path>

src = <path> Path to a schema to validate this.

Alternative Syntax

Standard (tidy) syntax:

<displayreq function=”uri”>... optional XML ...

</displayreq>

<imagereq function=”uri”/><imagereq>

<function>uri</function></imagereq>

<displayreq><function>uri</function>(<data>... XML ...</data>)

</displayreq>

<hookreq function=”uri”>... required XML ...

</hookreq>

<hookreq><function>uri</function><data>... XML ...</data>

</hookreq>

Two forms are available for the following request items:

<svg:svg>

Expanded (nestable) syntax:

http://friend2friend.net/

If they need privileged accesses to other module’s resources, modules must declare this, so these privileges can be granted on installation.

Module Requirements

http://friend2friend.net/modules/window/

http://friend2friend.net/modules/desktop/

Modules are currently referenced only using URI. Reference by version may be useful for forward compatibility

http://friend2friend.net/modules/dev/

Each module must have an XSD, with its own target namespace.

Module Datatypes

Modules may use xml data defined by other modules,though this means adding that module to the list of requirements. It is usually only helpful for modules which are already required.

Modules services should use F2F elements as arguments if an appropriate one exists, or define their own otherwise.

Summary

Module resources offer complimentary functionality.

Recommended Follow-up: FF14: Software Design

http://www.altruists.org/ff14

Soft-nodes are instances of installed modules.

Most resources are identified by URI and

requestable through XML.

Services Filters

Displays Images

Scripts Hooks

Datastores

uri

Services FiltersDisplays Images

Hooks

Datastores /f2f