Digital Object Architecture: Building Information Management Infrastructure for Networks

Digital Object Architecture:Building Information Management

Infrastructure for Networks

20 September 2010

Larry LannomCorporation for National Research Initiatives

http://www.cnri.reston.va.us/http://www.handle.net/

Corporation for National Research Initiatives

Three Initial Networks

• About 30 – 35 years ago, DARPA funded the creation of three seminal packet networks – ARPANET, Packet Radio, Packet Satellite

• The Internet came about from a desire to link the three of them

• Ethernet occurred in parallel, led by Xerox Parc researchers, and other network types followed

• The resulting architecture was independent of the number and type of networks or who ran them.


• The Internet would be a global information system.• An open-architecture would be used to combine

different networks based on open and well-known interfaces, protocols & objects.

• A new communications-oriented host protocol (TCP/IP) would be created to replace the original ARPANET host protocol (NCP).

• The concept of global addressing and IP addresses would be introduced to identify individual machines anywhere on the global Internet.

Key Decisions


Comments on the Key Decisions

• The architecture is robust in the presence of many different network types and many outages.

• Gateways provided IP routing and Network "Impedance Matching".

• TCP accommodated end-end protocol:— different packet sizes, duplicates, error

detection, losses due to tunnels, mountains, jamming, etc.

• Separate network administrations were permitted, which allowed the Net to grow.

• DNS not technically critical, but helped users.


Understanding the Big Picture

• Many things were done well from the outset; with 20/20 hindsight, some could have been done better.

• The context was critical:– Mostly mainframes, few time-sharing systems– No PCs, workstations, LANs– One dominant carrier in the US– Government facility initially

• What is important at the time may be only apparent with hindsight; but also what seems important at the time may not turn out to be so important later on.


• What is so hard about it?– Making it scalable over platforms, size and time– Achieving Critical Mass

• Getting Buy in:– Pleasing many essential participants– Displacing prior capabilities– Structuring matters to deal with concerns about empire

building• It’s a lot easier to create brand new capabilities than

to affect existing means of operation.

Infrastructure Development


Infrastructure Creation is a Subtractive Process

• Infrastructure reduces a common, shared capability to its basic and essential attributes.

• These attributes are not always recognized or understood up front.

• Upon further scrutiny, capabilities are usually deleted from a well-conceived architecture over time.

• Consensus develops when no more can be removed without disabling the infrastructure.


What is the Information Management Problem?

• Managing information in the Net over very long periods of time – e.g., centuries or more.

• Dealing with very large amounts of information in the Net over time.

• When information, its location(s) and even the underlying systems may change dramatically over time.

• Respecting and protecting rights, interests and value.


• Allows for arbitrary types of information systems.• Allows for dynamic formatting and data typing.• Can accommodate interoperability between multiple

different information systems.• Allows metadata schema to be identified and typed.

A Meta-level Architecture


• To reformulate the Internet architecture around the notion of uniquely identifiable data structures.

• Enabling existing and new types of information to be reliably managed and accessed in the Internet environment over long periods of time.

• Providing mechanisms to stimulate innovation, the creation of dynamic new forms of expression, and to manifest older forms.

• While supporting intellectual property protection, fine-grained access control, and enable well-formed business practices to emerge.

Digital Object Architecture: Motivation


Digital Object Architecture Technical Components• Digital Objects (DOs)

– Structured data, independent of the platform on which it was created– Consisting of "elements" of the form <type,value>– One of which is its unique, persistent identifier

• Resolution of Unique Identifiers– Maps an identifier into "state information" about the DO– Handle System is a general purpose resolution system

• Repositories from which DOs may be accessed– And into which they may be deposited

• Metadata Registries– Repositories that contain general information about DOs– Support multiple metadata schemes– Can map queries into unique DO specifications (via handles)


• Defined data structure, machine independent.• Consisting of a set of elements:

– Each of the form <type,value>– One of which is the unique identifier

• Identifiers are known as "Handles":– Format is "prefix/suffix"– Prefix is unique to a naming authority– Suffix can be any string of bits assigned by that authority

• Data structure can be parsed; types can be resolved within the architecture.

• Associated properties record, and transaction record, contain metadata and usage information.

What is a Digital Object?


• Create a cohesive interoperable collection of repository-based systems.– Initially, perhaps, around a core set of projects,

content, applications and/or organizations• Demonstrate interoperability between different

repository collections.• Develop procedures to insure continued accessibility

to key archival information.

Interoperability & Federated Repositories


Repository Notion

Any Hardware & SoftwareConfiguration

Logical External Interface

DOP

DigitalObject Protocol


Repository

• Each Digital Object has its own unique & persistent ID.• Content Providers assign IDs.• Could be upwards of trillions of DOs per Repository.

Objects may beReplicated in

Multiple Repositories

Repositories & Digital Objects


• Distributed identifier service on the Internet• First general purpose resolution system• Can be used to locate repositories that contain digital objects

given their handles – and more!• Other indirect references

– Public Keys, Authentication information for DOs• Accommodates interoperability between many different

information systems

The Handle System


• The basic Architecture of the Handle System is flat, scaleable, and extensible.

• Logically central, but physically decentralized.• Supports Local Handle Services, if desired.• Handle resolutions return entire "handle records" or

portions thereof.• Handle Records are also:

– digital objects– signed by the servers– doubly certificated by the system.

Attributes of the Handle System


Resolution Mechanism

Multiple SitesMultiple Servers

Handle System<www.handle.net>

Handle

• System is non-nodal• Scaleable & Distributed• Supports global (and local) resolution• Has backup for reliability, mirroring for efficiency

Handle Record


• Managing Digital Objects for long-term access is a key challenge.

• Initial technology components are available; industry is expected to generate more over time.

• Third-party value-added providers in the private sector will ultimately shape the long-term evolution.

• Interoperability and reliable information access is a critical objective.

• A diversity of applications (with user-friendly interfaces) need to be developed & deployed.

Conclusions


Phone Guy Perspective

Purpose of Digital Object

• Today's architectures and paradigms, including leading edge technology, operate on the circuit switched telephone equivalent of data storage.– A "dumb" system for payload data storage ("the circuits").– A separate system for management, control, and metadata

("the signaling network").• As a consequence, these systems are limited in robustness,

security, interoperability, extensibility, cost effectiveness, vendor independence, and functionality.

Create the foundation for data storage and retrieval, equivalent to what packet data did for communication.

Urs Muller, Net-Scale

Today's Paradigms

Data management

Data

DataData

Data

Data

Data

• Access control• Key management• Provenance infrastructure• Version control• MetadataData storage

User

Request

Data

Examples:• Documentum (EMC)• SharePoint, MOSS 2007 (Microsoft)• FileNet (IBM)• 10g, Stellent (Oracle)• LiveLink (OpenText)• Alfresco (open source)

Authentication


What Happens When Data Is Moved

Data management

Data

DataData

Data

Data

Data

Data storage

Data

• Loss of access control• Loss of key management• Loss of provenance infrastructure• Loss of version control• Loss of metadata


• Use of separate and different systems for storage of the (payload) data and the data management.– Creates a centralized system.– Poor interoperability.– Heavy vendor and product dependence.

• The data management system is a fragile huge single point of failure which requires heavy protection to make a solution usable.– This is similar to the signaling network and out of band data in a circuit

switched traditional telephone network.• Poorly suited to reach these key requirements for the DoD:

– High degree of global data distribution and replication (a super robust network, data is available where needed).

– Vendor independence.– Interoperability among vendors and multiple technology generations (like

the Internet).– Access control "travels" with the data and does not need to be replicated

each time the data is copied onto a different system (e.g., a laptop).

Limitations of Today's Paradigms


Digital Object Architecture

Data

• Access control• Key management• Provenance infrastructure• Version control• Metadata

Data Data

Data

Digital Object Repository

Data


A Digital Object Is Moved

Data management remains intact:• Access control• Key management• Provenance infrastructure• Version control• Metadata

Digital Object Repository

Data Data Data

Data Data Data


A Solid Foundation

The Digital Object Architecture provides a solid foundation for the creation of:• A highly distributed, robust, and scalable data storage and retrieval

infrastructure.– Digital Objects are self-contained and don't depend on a separate centralized

data management subsystem. This dramatically improves scalability.

• A highly secure data storage and retrieval infrastructure.– By eliminating a centralized security paradigm which is a single point of failure

and greatly vulnerable to attacks.– Security is distributed. A successful attack reveals very little reward (each

digital object has to be attacked separately).

• A highly "future proof", extensible, interoperable, and vendor independent data storage and retrieval infrastructure.– By greatly reducing the complexity for exchanging data without breaking

access control, provenance, version control, etc.

The Digital Object Architecture provides a far superior foundation for realizing these essential properties compared to today's paradigms.


Comparison to Data Communication

Circuit Switched (old phone)(~ traditional architectures)• Data has no "intelligence" and is managed by

a large central system (signaling network).

Packet Based (Internet)(~ Digital Object Architecture)• Data management information is embedded

with the data itself (packet header).– The packet itself knows what it is,

where it is coming from and where it is going to.

– The network can be simpler, far more flexible and robust.

Today, few people dispute that packet routing is superior to circuit switching for data communication.

– A few decades ago the differences were not so clear. After all, data can easily be exchanged over a circuit-switched network.

Compared with today's paradigms, the Digital Object Architecture will lead to far more flexibility, diversity, technology independence, and overall usage for data storage and retrieval.


Example From the Real World

• Circuit switched past: When a 5ESS switch was down, all calls to the affected area were out, leaving a whole region without communication.

• Current Internet: On December 19, 2008 three undersea cables were cut between the Middle East and Europe. Data traffic was severely impacted but communication remained intact.

We expect the Digital Object Architecture to create a paradigm shift for data storage and retrieval similar to the impact the

Internet had on data communication.



Digital Object ArchitectureWhere Are We?

• Handle System• Up and running since the early 90s• Core architecture stable from the late 90s• www.handle.net

• Digital Object Repository• In daily use in multiple projects• Available open-source since the start of 2010• www.dorepository.org• Introductory article in Jan/Feb D-Lib Magazine

• Digital Object Registry• In daily use in multiple projects• Available open-source since May, 2010• www.doregistry.org

http://www.handle.net/

http://www.dorepository.org/

http://www.doregistry.org/

Information Management on Networks

ResolutionClient

Resource Discovery

Search Engines, Metadata Databases, Catalogues, Guides, etc.

<?xml version="1.0"?><description>……. </description>


<?xml version="1.0"?><description>…….

</description>

<?xml version="1.0"?><note> <to>John</to> <from>Jane</from> <heading>Reminder <body>Don't forget me!</note>


Repositories / Collections

Identifier Resolution System



AdministrativeClient




Resource Discovery





</description>




AdministrativeClient




Resource Discovery





</description>



Federation

• Federation in information systems makes sense when– a set of varying features exists across the

federates, which is the reason for multiplicity• Includes organizational boundaries, locations,

content types, etc.

– a set of common features exists across federates, which is usuallly the reason to perform federation

• Shared topics, common audience, etc.


Challenges - Conceptual• Identifying the type of aggregation:

– Aggregate objects ahead of time, before query?– Merge search responses from federates by issuing a distributed

query?– Or, anything in between?

• Identifying the level of semantic interoperability– Enforce complete semantic interoperability across all the data

stored in the federates?– Use only the least common denominator (from a data semantics

point of view) among the federates?• Federate topology

– Are all federates directly connected to each other? (fully-connected mode)

– Is each federate connected to only its neighbor? (peer-peer mode)• These criteria can be visualized as a Federation Spectrum

No Aggregation of Objects(Distributed Query)

Complete Aggregation of Objects

Disconnected

Federates

Fully Connected

Federates

Complete Semantic Interoperability

No Semantic Interoperability(Ad Hoc Mix)




Complete Semantic InteroperabilityComplete Semantic InteroperabilityComplete Semantic Interoperability

Leve

l of d

ata

Inte

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rabi

lity

Format o

f Participation

Level of Aggregation

Leve

l of d

ata

Inte

rope

rabi

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Leve

l of d

ata

Inte

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rabi

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Federation Spectrum


Challenges - Technical• Depending on the criteria chosen for federation,

various technical requirements arise. These may include:– Designing a storage model to aggregate objects into a

common store that identifies the relationship between multiple metadata instances describing a single object

– Designing cross-walking algorithms to translate and map heterogeneous data into a common model

– Designing a query model to gather and rank search results from multiple federates

– Ensuring scalability, reliability, and security without compromising performance


Existing technologies

• Digital Object Registry (basis for ADL-R)– Provides a data model to encapsulate related

metadata instances together– Enables aggregation of objects from fully-

connected mode to peer-peer mode– Uses the Handle System to uniquely identify

objects and metadata instances across all federates

Documents

Digital Object Architecture: Building Information Management Infrastructure for Networks