XCON data modeling

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XCON data modeling NETCONF, RDF and
othersdraft-schulzrinne-sipping-emergency-req-01
draft-sipping-sos

• Henning Schulzrinne
• Dept. of Computer Science
• Columbia University

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Executive summary

• XCON is an instance of a standard problem ? avoid
  the IETF tendency to create one-off protocols
• excusable a decade ago, recipe for delay now
• Provide both semantic (tightly constrained) and
  user interface-oriented interface
• Use XForms where user interface is needed
• Consider NETCONF for object content manipulation
  and state retrieval

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Data representation models

• Document model
• structured document
• RPC model
• set/get variables
• Data models
• RDF
• NETCONF
• user-interface oriented

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Semantic description

• Tightly described set of properties
• No expectation that user interface would directly
  correspond to each element
• No I18N issue ? application maps description
  elements to UI elements in appropriate language
• translation into other languages done by client
• and may derive some parts through local policy,
  rather than user input
• Well-defined extension policy

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RDF

• Resource Description Framework (RDF) is a
  language for representing information about
  resources in the World Wide Web.
• describing resources in terms of simple
  properties and property values

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RDF, contd.
W3C RDF primer
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RDF/XML example
lt?xml version"1.0"?gt ltrdfRDF xmlnsrdf"http//w
ww.w3.org/1999/02/22-rdf-syntax-ns xmlnscontact
"http//www.w3.org/2000/10/swap/pim/contact"gt lt
contactPerson rdfabout"http//www.w3.org/People
/EM/contactme"gt ltcontactfullNamegtEric
Millerlt/contactfullNamegt ltcontactmailbox
rdfresource"mailtoem_at_w3.org"/gt ltcontactperso
nalTitlegtDr.lt/contactpersonalTitlegt lt/contactPe
rsongt lt/rdfRDFgt
identifies the thing subject (a URI) property
predicate value object
W3 RDF primer
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More about RDF

• Generally, meta data
• RSS is most common usage
• Also used in Composite Capabilities/Preferences
  Profile (CC/PP)
• Has schema-like capability to describe
  vocabularies
• Allows trees with nodes and relationships
  (is-a, has)

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RDF evaluation

• Good
• limited parameter-value expressiveness
• type definition
• tools available
• Bad
• static document, does not define protocol to
  get/set elements
• would need XCAP, XPath or similar

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NETCONF

• The NETCONF protocol defines a simple mechanism
  through which a network device can be managed,
  configuration data information can be retrieved,
  and new configuration data can be uploaded and
  manipulated. The protocol allows the device to
  expose a full, formal, application programming
  interface (API).
• http//www.ietf.org/internet-drafts/draft-ietf-net
  conf-prot-05.txt
• Defined to run over HTTP, BEEP, UDP,

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NETCONF, contd.
content
configuration data
operations
ltget-configgt ltedit-configgt
RPC
ltrpcgt ltrpc-replygt
application protocol
BEEP, SSH, SSL
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NETCONF

• Data
• configuration data writable ? ltget-configgt
• state data read-only, statistics ? ltgetgt
• Leaves privacy and authentication to transport
  layer
• Supports Xpath and subtree filtering
• Supports multiple data stores
• default ltrunninggt
• ltcandidategt allows incremental update commit

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NETCONF RPC
ltrpc message-id"101" xmlns"urnietfparamsxmln
snetconfbase1.0"gt ltrock-the-house
xmlns"http//example.net/rock/1.0"gt ltzip-codegt2
7606-0100lt/zip-codegt lt/rock-the-housegt lt/rpcgt
ltrpc-reply message-id"101" xmlns"urnietfparams
xmlnsnetconfbase1.0"gt ltsome-contentgt lt!--
contents here... --gt lt/some-contentgt lt/rpc-replygt

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NETCONF subtree filtering
ltrpc message-id"101" xmlns"urnietfparamsxmln
snetconfbase1.0"gt ltget-configgt ltsourcegt ltrun
ning/gt lt/sourcegt ltfilter type"subtree"gt lttop
xmlns"http//example.com/schema/1.2/config"gt lt
users/gt lt/topgt lt/filtergt lt/get-configgt lt/rpcgt
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NETCONF operations
get Retrieve all or part of state configuration
get-config Retrieve all or part of a specified configuration.
edit-config merge/create/replace/delete with possible roll-back
copy-config completely replaces configuration
delete-config delete a configuration datastore
lock lock configuration data store
unlock unlock configuration data store
close-session graceful termination releases locks
kill-session abort connection
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NETCONF capabilities advertisement
lthello xmlns"urnietfparamsxmlnsnetconfbase
1.0"gt ltcapabilitiesgt ltcapabilitygt urnietfp
aramsxmlnsnetconfbase1.0 lt/capabilitygt ltc
apabilitygt urnietfparamsxmlnsnetconfbase
1.0startup lt/capabilitygt ltcapabilitygt http
/example.net/router/2.3/coremyfeature lt/capabi
litygt lt/capabilitiesgt ltsession-idgt4lt/session-idgt
lt/hellogt
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User-interface oriented

• Describe suggested rendering on controlling
  client without client knowing meaning of controls
• element names are just labels
• e.g., cant gateway to other systems based on
  equivalence
• user interface can change at any time
• Element names are text strings, not XML elements
• no schema verification possible

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User-interface oriented

• Client software does not need to understand
  meaning of terms just variables and prompts
• includes necessary prompts and structure
• needs to be translated into different languages
  by server
• Existing work XForms
• http//www.w3.org/MarkUp/Forms/2003/xforms-for-htm
  l-authors
• Allows use of CSS to render on variety of devices
• Allows use of JavaScript for client-side
  verification
• Specifies type of control (selection), not
  rendering (radio button, select list)
• Suggestion allow as alternate representation

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XForms example
lthhtml xmlnsh"http//www.w3.org/1999/xhtml xm
lns"http//www.w3.org/2002/xforms"gt lthheadgt lth
titlegtSearchlt/htitlegt ltmodelgt ltsubmission
action"http//example.com/search
method"get" id"s"/gt lt/modelgt lt/hheadgt lthbod
ygt lthpgt ltinput ref"q"gtltlabelgtFindlt/labelgtlt/in
putgt ltsubmit submission"s"gtltlabelgtGolt/labelgtlt/s
ubmitgt lt/hpgt lt/hbodygt lt/hhtmlgt
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Conclusion

• If desired, XForms provides rich user interaction
  environment
• NETCONF provides flexible configuration retrieval
  mechanism, with extensibility
• incremental configuration commit
• stored configurations (startup, running,
  candidate)
• XPath and subtree selection
• no constraints on configuration content