The components of a digital asset management system components of a digital asset management system David Austerberry has worked in the world of asset management since 1997. He was

The components of a digital assetmanagement systemDavid Austerberryhas worked in the world of asset management since 1997. He was product manager for Pro-Bel’s television playout automation and

media asset management product lines. The next step was into systems integration for a content management service provider utilizing

streaming media technologies. He has written two books: Digital Asset Management (Focal Press, 2004) and The Technology of Video

and Audio Streaming, 2nd edition (Focal Press, 2004). He has presented papers on interactive television and digital asset management

at many conferences including the National Association of Broadcasters Convention and the International Broadcasting Convention. He

is now a director of Informed Sauce, a provider of training services to the television industry, and Editor of Broadcast Engineering world

edition.

Keywords: software architecture, modular approach, multi-tier model, object-oriented, third-

party applications, scalable

Abstract This paper looks at the components of digital asset management (DAM). Two views

are taken of the system, one is the software architecture and the other is content-centric. The

evolution of software architectures is covered from the days of mainframe computers to the

multi-tiered systems used by DAM. The components of asset management systems are

detailed, followed by an overview of the distributed software systems used to deploy these

systems. This paper is based on one of the introductory chapters of the author’s book Digital

Asset Management (Focal Press, 2004).

INTRODUCTIONA DAM system uses a suite of applicationslinked together to provide a seamless experienceto the user. It is not just a piece of shrink-wrapped software that can be used straight outof the box. Rather, it is a collection of manycomponents that have been carefully selected tomeet the needs and budgets of the enterprise.

The system should also have links toexisting software applications: accounts,customer records, and planning systems. Tomaximize the operational benefits, it isadvantageous for these applications to exchangedata with the DAM system. Like anyenterprise-wide deployment of software, muchof the installation costs will be for theprofessional services. These are usually requiredto merge the many stand-alone applicationsinto a seamless operating environment, and tocustomize the business logic to suit the needsof the customer.

This list details some of the components thatmay be found in a typical installation:

. content repository;

. digital asset management application;

. databases;

. search engine;

. indexing workstations;

. rights management application;

. web portal.

The complete DAM system is rarely the productof a single vendor. Most partner with specialistsfor services like the search engine, video logging,speech recognition and the underlying databasemanagement system. The core DAM acts likeglue, it binds all these functions together usingthe business rules. The users see a unitary viewof all the systems which is created by thepresentation layer.

This modular approach allows the best-of-breed solutions to be used, and should retainflexibility for the customer to stick with theirfavored databases and operating platforms.Clearly with all these different products, acorporation will need a prime contractor(usually the systems integrator) to ensure thatultimately, the solution operates satisfactorily asa whole and meets the original, agreedrequirements.

The system architecture can be viewed in anumber of ways. One view is that of thesoftware system architecture. This is usually

Henry Stewart Publications 1743–6559 (2005) Vol. 1, 2 131–145 JOURNAL OF DIGITAL ASSET MANAGEMENT 131

David Austerberry

Informed Sauce,

10 Marsh Farm Road,

Twickenham TW2 6SH,

UK

Tel: +44 (0)20 8288 0513

Email:

[email protected]

multi-tiered, with presentation, business and datalayers. Another view is content-centric, with thesystem in shells around the core assets andmodifying the view the user sees.

One of the primary functions of any DAMsystem is to relieve the users of the need toperform repetitive tasks. This frees them toconcentrate on the more creative side of mediaauthoring and publishing. The design of the userinterface (UI) is key to the success of the product.The other issue of great importance to the user isthe way that the system fits with the existingcorporate processes. If too many changes aremade to the ways of working, the users can feelalienated from the asset management. Limitedscale trials are very useful for the shakedown ofworkflow issues. The goal is for the users to feelexcited by the opportunities presented by thesystem, not to resent what could be viewed as asystem imposed to reduce manning levels. Thegoal is a win-win for the corporate managementand the knowledge workers.

MAINFRAMES TO MULTI-TIERLooking back through the history of enterprisecomputing, it all started with the mainframe andsimple clients based upon the video terminal orvisual display unit (VDU). Smaller mainframes(the minicomputer) were developed to suit theneeds of medium-sized businesses, and then IBMlaunched the personal computer (PC). Thisallowed even the smallest business to produceprofessional-looking correspondence and to runaccounts software.

As the power of the PC increased, it becamefeasible to run graphics-rich programs. Althoughthe early PCs had clunky text interfaces withboxy graphics, Apple pioneered the way withmouse-driven windows. These led to theWYSIWYG (what you see is what you get) UIthat we all demand today.

As the costs of the desktop PC dropped tolittle more than the desks they sat on, businessusers demanded the same UI as the personalcomputer. A good example is the wordprocessor. The first products used the mainframecomputer to run the application. To see the finallayout, the operator had to print out a copy. Toproduce a complex layout was an iterativeprocess involving many intermediate printouts.The WYSIWYG word processor application did

away with this, dramatically improvingproductivity. At the same time, it enabled theuser to be more creative with their layout. Thisability to offer new possibilities extends to assetmanagement.

After the replacement of the video terminalswith PCs, the minicomputer that ran the word-processing became redundant; the central fileserver replaced it.

Client-serverThis new architecture was called client-server.The user now had the power of the new officeapplication suites. The combination of wordprocessing, spreadsheets and basic drawingfacilities met most of the average office worker’sneeds. Alongside this, the old mainframe systemsstill ran the company databases for onlinetransaction processing, the sales order processing,inventory control and manufacturing resourceplanning — everything that makes the enterprisetick.

Some asset management products adopted theclient-server approach. The client includes thebusiness logic and a presentation layer for theUI. The server is essentially just a relationaldatabase. The clients interact with each otherthrough the database management system(DBMS) using stored procedures and triggers.Client-server is fine for small systems, but inpractice, it does not scale well beyond 100clients.

Initially everybody was happy with thewonders of modern computers throughout thebusiness. However, it soon became apparent thatrunning thousands of PCs, with thousands ofinstances of the applications, was very expensive.First, there were the costs of the per-seatlicensing. Then there were the costs involved inupdating machines when new software releasescame out (all too frequently). But the real killerwas the ease with which the average officeworker could reduce his or her own computerto a state of malfunction. Either bymisconfiguring the applications, or by illicitlyloading unofficial software, the machine wouldgrind to a halt, ready for rescue by the ITdepartment.

The cost of all this downtime, and the staffinglevels required in IT, began to be of greatconcern to senior management. There had to bebetter ways.

JOURNAL OF DIGITAL ASSET MANAGEMENT Vol. 1, 2 131–145 Henry Stewart Publications 1743–6559 (2005)132

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CLIENT/SERVER WORKSTATION

MAINFRAME

MULTI-TIER COMPUTING

mainframe

dataserver

file server database

imageprocessing

minicomputer

videoterminal

videoterminal

file server/database

webserver

applicationserver

minicomputer

workstation

workstationclientserver-side

webbrowser

graphics compositing3-D modeling

video graphics

transaction processingword processing

transaction processingword processing

image processingpersonal computer

Figure 1: The evolution of multi-tier computing

The components of a digital asset management system


One approach was to use the ‘network’ PC.This had no removable storage; no CD orfloppy drives, so it was difficult to loadunauthorized software. Modern operatingsystems allow remote access by a systemadministrator, so that software updates could beperformed from a central point over thecorporate network. This is fine in a controlledworld, but what about the marketingcommunications department? How do theyexchange files with external designers? How dopersonnel staff backup confidential information?Most enterprises accept that distributedapplications are not going away. The networkPC has a place, but it is not the answer for thetypical distributed asset management application.

IT professionals have taken two paths tocounteract these problems. One path is to retainthe advantages of the client-server environment;the other is the thin client. The solution in theclient-server environment is to use a desktopmanagement system. This allows the IT

managers to have complete control oversoftware distribution to the clients. Theoperating system access is configured to forbidlocal software installation and configuration.Applications, patches and updates are all loadedfrom a central point. The system also offersremote troubleshooting, and can usually self-heallocal software faults. Such a system removesmost of the problematic maintenance issues thathave dogged client-server and distributedinstallations.

The thin clientThe other route is the thin client. This could beseen as a return to the simple terminal of the oldmainframes. Today’s user has many expectationsfrom a UI that the VT100-style terminals couldnot offer. Perhaps the most important aresupport for graphics and mouse-driven userinteraction.

The current implementation of a thin client isto use a web browser on a standard PC. One

network

serversclient

media

player

reports

plugin

user

interface

submit

forms

media

serverbusiness

logic

database

presentation layer business layerdata

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Figure 2: The client-server model


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option is to add additional functionality to theweb environment by adding a Java virtualmachine. This supports applets to run smallprograms on the client. The business logic isthen transferred from the client to a third tier,the application server.

The two paths are best suited to differentapplications. The client-server is ideal for officeapplications, where the work is file-based. Theuser loads a file from a central server, edits itlocally, and then saves back to the server. Theuser has all the advantages of a powerfulapplication running locally. Imagine the latenciesof using a spell checker while typing, if theword processor were running on a remoteserver.

Data-record oriented applications are moresuited to the central data server. Information isviewed and updated from the client, but the dataresides on the central server.

DAM has elements of both. There is muchdata processing, relating to metadata queries andupdates. There is also file processing, the creativeprocesses applied to the content: editing, formatconversion and compositing.

The outcome is a hybrid approach. Many ofthe productivity tools run locally on the clientmachines. They can be centrally maintainedusing a desktop management system. Theseinclude Word, Excel, Quark and PhotoShop.The craft-oriented applications like the non-linear editor may still run stand-aloneapplications (eg Avid, Final Cut Pro andPremier Pro) but will be maintained locally atthe workstation. The database intensiveapplications, with workflow management andpeer-to-peer collaboration, can use a webbrowser to view a presentation layer in theapplication server.

Three tierThe complex business logic of asset managementleads naturally to a central application server.This can support the collaborative workflow andcommunications between the users’ workstationswith central business logic to managecommunication between the software clients.This logic forms a third layer between thedatabase and the client.

Many enterprises planning to purchase DAM

network

serversclient

media

player

reports

plugin

user

interface

submit

forms

applic

ation s

erv

er

media

server

database

presentation layer business layerdata

layer

Figure 3: The three-tier model



systems will want to minimize the cost of eachclient seat. Many users only want to search, thenpreview files. Such an application does notwarrant the cost of a fully-featured clientrunning a local application. The enterprise maywell want to share asset information withsuppliers and customers.

The requirement to minimize cost dictates athin client, especially for remote users. Suppliersof creative services may well use Apple Macs.Other partners may use Linux. An enterprisemay use Windows for office applications andUNIX for transaction processing. All thisdemands a client that is agnostic to operating

systems, and that can use widely availablecommunications protocols. Well there is onesuch client — the web browser.

Rather than running the two tiers of theclient-server model, the web browser requires atleast three tiers with a web server generating thepresentation.

Multi-tierThe multiple or n-tiered approach to computingsplits an application into manageable chunks.Typically, there is a data layer, a presentationlayer, and a layer of business logic linking thetwo. This has many advantages for the IT

networkservers

‘thick’ client

Web client

userinterface

mediaplayer

reports

plugin

webbrowser

forms

web

ser

ver

appl

icat

ion

serv

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mediaserver

database

presentation layer business layer

data layer

Figure 4: Multi- or n-tier computing


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department. The data layer can be a standardrelational database; DB2, Oracle, SQL Server, itdoes not matter. These are mature products,with predictable behavior, and formalmaintenance procedures. The presentation layeris just a web server, again no great problem tooperate and maintain. With this architecture theDAM can be broken away into a separate boxcalled the business logic. Here the rules formanipulating the data, and the connections tothird-party applications, can all reside on aseparate application server that runs the coreasset management software.

The central server has now becomefragmented into functional blocks: data server,web server and application server.

Application serverThe business logic runs on the application server.This provides the services and framework to runthe software objects that implement the businesslogic. The framework has two sub-systems. Oneis to implement the rules of the business logic,the processes like the workflow andcategorization. The second is the transactionmanagement for updating metadata records inthe database.

The data tierThe data tier is usually a relational database,although this is for administrative conveniencerather than elegance of design. It couldalternatively be an object database. The DBMScontrols the connections for the generalmaintenance of the database. The applicationserver is a client to the database. The DBMSmanages the transactions to enter and updatedata, and the information retrieval to generateviews and reports of the data. In addition, thedatabase administrator will have a number oftools to maintain the database.

Originally, each database product required adifferent driver for the applications to performoperations on the data. Microsoft developed thelanguage-independent Open DatabaseConnectivity (ODBC) interface that rationalizedthe database connections into a single standard.This was later joined by Java DataBaseConnectivity (JDBC), which exposes a Javaapplication program interface to the databasedrivers. These technologies have muchsimplified the connection between the businesslogic and the database. There are limitationsto ODBC; it was designed to use structuredquery language (SQL) for access to relational

structuralmaintenance

transactionprocessing

informationretrieval

databaseadministration

DBMS

Figure 5: Elements of the database management



databases. There are now many data sourcesthat are not relational — mail systems, objectdatabases, file servers. There have been newerand more efficient components that canprovide a more universal data access thanODBC.

Limitations of the web tierSome clients need more functionality than canbe provided by the basic web browser. Forexample, media ingest requires PCs equippedwith specialist video encoding cards and extraprocessing power for the speech analysis. ManyDAM products use a hybrid approach. Simplesearch and retrieve operations can be made froma web browser, but more complex ingest andediting operations use a full client application.

So far, this paper has described closedsystems — a corporate network. Mostcollaboration in asset management extendsoutside the enterprise. Customers and partnerswill need controlled access to the assetmanagement. Again, the web browser providesa simple option. The remote user needs nospecial software application; the technology isfamiliar and ubiquitous.

THE CONTENT MODELThe Society of Motion Picture and TelevisionEngineers/European Broadcasting Union TaskForce on Harmonized Standards (1998)developed a system model to represent therelationships between signals, processes andcontrol systems. This report has become a very

cont

rol a

nd m

onito

ring

plane

metadata

dataataataa

aududioud o

Distribution FulfillmentPro ctionn Post ttorage

videdeodeo Archive

Linear Production Flow

Communication layersModel axes

Planes

Com

mun

icat

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laye

rs

Activities

Application

Network

Data Link

Physical

Figure 6: System model for television production


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popular starting point for building object modelsof content.

The model has three orthogonal axes:activities, content planes and communicationlayers. The communication layers represent theintercommunication between peer entities. Thelayers are similar to the ISO open systemsinterface: application, network, data link andphysical. A control and monitoring planeunderlies the planes for activities and content.

This model focused on television content, sosplits content into audio, video and data (knownas essence) and metadata, but the principle couldbe applied to other forms of content. Essence isthe raw content that represents the pictures,sound and text that are delivered to the user.Data essence can be graphics, animation, textfiles and still images. An example of data essenceis the closed caption.

The activities are those typical of the processesin the workflow of television production. Theproduction phase represents planning andshooting. Post is the post-production, where theoriginal footage is edited into a final program,the graphics are added and the sound designimplemented. Distribution is the disseminationof the finished program to the publishers. Thesecould be broadcasters or DVD distributors. Thestorage operation is optional, as the product maybe aired immediately. Fulfillment is the deliveryto the consumer. This could be as broadcasttelevision transmission, or as sell-through media:DVD and VHS. Finally, the program is archivedto a vault.

This flow is linear, but many programs arebrought out of the vault and returned to thepost stage for repurposing and reuse in a cyclicalprocess. We see more of this today to meet thedemands of multi-channel broadcasting plus newmedia distribution channels.

THE ASSETMANAGEMENT SYSTEMThe asset management can be looked at as anumber of blocks. This view is somewhat flexible,what is content, what is data? In this view, contentthat is stored in a file system (like Network FileSystem) is called data, content that is stored asvideo on tape or in special video servers is treatedseparately as content and managed through themedia management component.

Most products are modular, and sit like a hub

at the center of media operations and processes.The core asset management should offer anumber of different functions:

. indexing and categorization;

. search;

. content editing;

. workflow management;

. task and project management;

. resource management;

. user management;

. storage management.

The asset management functions will besupported by a number of services:

. load balancing and fault tolerance;

. access control;

. security;

. configuration.

Indexing and categorization

The index module uses metadata generated atthe ingest stage to create an index and catalogthat can be used by the search engine. Theindexing can be fairly simple using a few keyfields: file name, tile, author, and keywords. Fora large repository, a more sophisticated indexwill be required. This will avoid the commonproblem of huge result sets with little relevanceto the search criteria. In order to return smallerand more relevant result sets one technique is touse concepts rather than keywords.

Search

Search is an essential facility for any assetmanagement. The user can use the search engineto find content within the repository. Searchengines vary from a basic keyword searchthrough to natural language search. Conceptsearches may well suggest allied content thatmay be relevant.

Content editing

Many asset management applications includebasic video editing facilities. A user can assemblea number of scenes or clips into a contiguoussequence. This assembly of clips generates an editdecision list (EDL). This list can be used laterwith a non-linear editor to conform the sourcemedia at broadcast resolution to finished videocontent.



Workflow management

One of the big advantages of asset managementis the workflow management. The systemprovides a platform to automate the businessprocesses. It should have basic features like emailalerts. It may include more comprehensivefacilities. These can help the project teamcollaborate and share content.

Task and project management

Much of the use for DAM is for projects tocreate or repurpose content. A module for taskmanagement can aid the smooth running of aproject.

Resource management

Facilities like video ingest will usually have alimited number of encoding ports and associatedvideotape recorders. A resource managementmodule can manage the allocation of suchhardware to a prepared schedule. There may alsobe the need to manage human resources, like thetape operators.

User management

This module manages the users of the system,with facilities to personalize the web interface,associate with projects, and modify personalconfiguration settings.

Storage management

The asset management application should offer anumber of services to support the storagemanagement. These will include storagenetworks, hierarchical storage management tomanage the disk, near-line and off-line, andmedia management for removable and analogstorage.

System servicesThe core services of asset management can varyfrom platform to platform but certain elementswill be essential.

Load balancing and fault tolerance

Much like a mainframe computer, theapplication server that runs the asset

Digital Asset Management

DAM clients

Persistent Storage

onsumerCooComedia

Rightsmanage

creativeartists c

Digital rightsmanagement

encryptionwatermarkruleskeys

Ingest

CD, DVD

A/V encode

speechrecognitionOCR

documentsmetadata

Files

A-V media

Livevideo

RDBMS fileserver

videoserver

near-linestorage

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.NET

load balance

access controlconfigurationsecurity

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ngesticategorisceditingesearchs

Functional modulesF

workfloww

resource managementruser managementu

storage managementsHSM

storage network

Media Management

Web server

WeebTP

Desktop videonon-linear edit

Publishing

er

streamingdownload

ch

Back-office

accountsecommerceCRM

Figure 7: A typical DAM system


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management is potentially a single point offailure. A successful asset management system isgoing to become key to the efficient operation ofthe business, so high availability will be veryimportant. The object broker platforms areusually designed to be distributed across anumber of server devices. The load from theusers is automatically balanced across the servers.In the event of device failure, the load can berebalanced across the remaining facilities to givefault tolerance.

Access control

Access control is much like a database; users willbe allocated a set of privileges to access folders,projects and files. These privileges may be role-based as well as user-based. There may also beaccess to a project team or workgroup. Theaccess control offered should be as flexible aspossible to support different corporate structures.

Security

The content assets present an attractive target forunauthorized access or malicious damage. Thesecurity policies to protect the system should bemuch the same as the existing IT systems withinthe corporation. Security has to operate at manylevels. Although access control will authorizeusers through the client portals of the assetmanagement, it does not protect the persistentstorage against direct access. The total securitywill include perimeter security, electronic andphysical, operating system security, accesscontrol, and possibly encryption andwatermarking of content within the repository.

Configuration

Just like any other large IT installation, thesystem will need constant configuration andmaintenance.

PeripheralsOutside the core asset management application,there are a number of satellites. Some will belegacy systems, like rights management and theback-office systems. Others will be third-partyapplications that form part of the complete assetmanagement.

Web serverThis is the presentation layer of the DAMsystem. It is usually a conventional dynamic web

server, much like a regular website. The webserver creates the UI as an HTML page. It willoffer the opportunity to brand the pages. Thiscould be for external clients, or for use withdepartmental intranets. Audio-video previewsmay require additional specialized media serversto stream the proxy files. Although most userscan connect to the system via the web server,craft workstations may connect directly to theapplication server.

IngestThis is where some heavy number crunchingtakes place. For this reason it takes place onseparate workstations. This is where the audio-video content is parsed to make it searchable.The video is analyzed to create a storyboard ofrepresentative still frames. At the same time, alow-resolution copy can be made that can beused as a proxy of the content for previewpurposes.

Speech analysis

The soundtrack of a video clip can be analyzed.With varying degrees of success, speechrecognition software can extract the meaning ofthe spoken word. The resulting text transcriptwill be synchronized to the video and can beused to search and navigate through the clip.Some systems are also able to recognize differentspeakers and mark up the transcript accordingly.

Scanning and optical character recognition

Content such as paper documents can bescanned, and then read by optical characterrecognition (OCR) software. This will convertthe content into a text file. OCR technology canalso be used to read video graphics. An exampleof this would be the lower-third graphics usedfor television news broadcasts. These can bedecoded and stored as textual data.

File transfer

Much content may already exist in a digitalform. Files can be ingested by FTP or other filetransfer from clients or partners. An ingestworkstation can be used to register the contentwith the system and to add essential metadata:title, copyright owner, subject, and keywords.Some files may include comprehensive metadata;that can be ingested at the same time and used topopulate the data tables.



Digital rights managementDigital rights management (DRM) can be usedto protect content from unauthorized access orviewing. It can be used to protect confidentialityor for the delivery of paid-for content. DAMcan be used to manage the original encryption,setting the appropriate decryption rules to meetthe business requirements.

PublishingThis will possibly be the most non-standard partof any system. The channels for the publishingof content may range from high-definitiontelevision and digital cinema, through webdelivery of streaming media to the PC, all theway down to lightweight content for wirelessapplications. Fulfillment may also includephysical media, CD-ROMs, DVDs orvideotape.

Third-party applicationsDAM can provide search, workflow and libraryfacilities to many third-party applications withinthe enterprise.

Video editing

Non-linear editing is the primary applicationused for video post-production. The assetmanagement can serve the editors as a repositoryfor the raw elements of the production, and forthe storage and archiving of finished material.

Desktop publishing

Many asset management products offer powerfullinks to Quark XPress, so that the desktoppublisher can use the asset repository to storeoriginal text and graphics, as well as theirfinished work.

Back-office

There are many possible back-office applicationsthat may be linked to the DAM system. Forexample, the workflow management could linkto the accounts department to trigger the issue ofinvoices. The publishing side of the assetmanagement may need links to e-commercesystems.

Rights management

This is the management of the contracts andagreements with content creators and owners. Itis quite separate from digital rights. The rights

are vital metadata for those involved in contentcreation and repurposing. It would prove veryuseful for the rights management to exchangemetadata with the DAM.

Persistent storageThis is the main repository for content, asessence and metadata. The metadata are usuallystored in a third-party relational database.Popular products include Oracle and MicrosoftSQL Server. A regular file server can be used forcontent that can be stored in a standard filesystem like NFS, or NTFS. Such content maybe documents and image files, or media filessuch as AVI, streaming media or QuickTime.Video is often stored on specialized videoservers, but there are many developments thatare allowing video — uncompressed, MPEG orDV — to be stored on normal file systems.

The persistent storage can be disk-based, orany combination of disk, data tape or opticalstorage. If removable storage is used, thenmedia management will be needed to track thecontent. There are many possible architecturesfor the storage system. These include thestorage networks (Storage Area Network andNetwork Attached Storage), hierarchical storagemanagement (HSM), and the basic librarysystems used to manage tapes onshelves.

Content strataContent is stored in strata to improve theefficiency of the overall system. Each stratumrepresents a layer of detail, with file sizes scalingappropriately:

. metadata;

. thumbnails;

. low-resolution preview;

. high resolution for production use.

A search can be made using small text files. Thesearch can be refined using thumbnail images,perhaps a 50 kB file. For video preview, a low-resolution proxy using one of the popularstreaming formats gives efficient networkutilization with data rates less than 1 Mb/s. If thecontent is then required for editing ordistribution then the very large high-resolutionfiles can be accessed.


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Application platformThe asset management system will run on anumber of different server devices. Althoughit could all run on one machine, that wouldonly be feasible for product demonstrations orsmall workgroups. To provide a system that canscale to support many users, the functions of the

presentation layer, application server anddatabase can be separated across different servers.These may even use different operating systems.The database could run on UNIX,the media server could run Windows Mediaservices for streaming low-resolution videopreviews.

web server

application server

database server

netw

ork

media preview server

content server

Query Fulfillment

webbrowser

client

Preview

metadata

businesslogic

presentationlayer

contentrepository

Digital AssetManagement

System

ContentUser

Figure 8: Clusters of servers



DISTRIBUTED COMPUTINGThe smallest asset management application maywell be the single-user photo library. Theapplication, database, and user interface are allrolled up into a single application. Put thephotographer into a workgroup, and theapplication must become distributed. Therequirement changes, in that the members of aworkgroup want to share files and possiblycollaborate on the editing of individual images.

The architecture changes to a workgroupserver, and a number of clients that can viewfiles on the server, and check out files for imageprocessing. As the system scales up to largenumbers of clients, the asset managementdatabase may well reach the limits of the integraldatabase. To scale the system the data are brokenout and stored on a separate relational database.

No database application is installed on theclient; all data queries are performed by the assetmanagement software on the workgroup server.When the client wants to make a query, thecommand is sent to the server, from where thedatabase query is generated. The result set is thenreturned to the client. The client is making aremote call on the server to run a function ormethod; there is no need for the client to loadthe server application. This is the basis ofdistributed computing. Quite clearly, it hasmuch in common with the multi-tier model.

In a large asset management system, a requestfor the metadata on a content file may require aquery across a federation of different databases.The DAM database may store the coremetadata, but other information could be heldon a rights management system, or within theaccounts department records. The assetmanagement application server can make remotecalls for reports from the other systems, thencollate and format the information for return tothe client. Note that the client does not have anyaccounting or rights management softwareloaded. The information is all retrieved throughremote function calls.

The client can edit this information andreturn the dataset, and then the distributeddatabases are updated. This distribution is notwithout its problems. Traditional databasesretain a persistent connection between the clientand the database. The client can lock tablesduring data updates. The number of connectionscan be limited. It is not unknown for a potential

user to phone round several co-workers to findone that could log-off the database in order tofree up a connection.

Web clients are very different, in that they arestateless. A connection is made to download apage, and then it is closed. Persistent informationabout a client has to be maintained by the serverusing devices like cookies. There is anexpectation of constant access to data, with no‘‘busy tone.’’ Since most users are not makingconstant access, the idea of effectively time-sharing the connections makes sense.

The communication between the distributedapplications is becoming more loosely coupledthan the traditional real-time applications liketransaction processing. This places a new set ofdemands upon the software architecture. Thecommunication becomes based more onmessages, almost a return to the days before theonline database. This stateless messaging hasother advantages. A fail-safe system can be puttogether. If one server fails, the client can simplycommunicate with another. So the systembecomes truly distributed. This makes it veryeasy to scale a system to the point where it couldbe distributed across sites in different cities, oreven to different continents. It is not without itsdrawbacks, one issue is the maintenance of datasecurity — protecting the access to data stores toauthorized users.

The development of distributed services isleaning towards the technology of XML webservices. In this architecture each application —media management, rights management, e-commerce — exposes functionality usinginternet protocols. To be specific, HTTP is usedas a transport and XML as the data wrapper.Some vendors have started to adopt webservices, and it promises to lower the costs ofbuilding complex distributed systems by usingshrink wrap products for much of theinfrastructure.

SUMMARYMost asset management vendors have adoptedthe multi-tier model for their systemarchitecture. The client can run a localapplication, or for basic search and previewfunctions, can be a normal web browser. Themetadata are stored in a conventional relationaldatabase. The main asset management softwareruns on an application server.


Austerberry

This architecture is very flexible; it can scalefrom a handful of users up to a large enterprise.It also simplifies software maintenance. TheDBMS, web server and web clients are all veryfamiliar products for the IT personnel tomanage. The asset management software istypically object-oriented, using J2EE orCORBA, so with a suitable application server,can run on most operating systems, and willfeature essential services like fail-over and load-balancing that allows large and highly availablesystems to be assembled.

There is a talent pool of databaseadministrators (DBAs) and web serveradministrators that can be called on to managethe bulk of a multi-tier system. Specialist staff

are only required for the application server.The asset management can be seen as the hub

of a wheel. The spokes extend to third-partyapplications, either to share metadata, or toprovide services to the asset management. Thebusiness logic integrates all these applications togive the user a federated view of media withinthe enterprise.

Distributed systems can scale to support ageographically dispersed business. Web servicespromise a new way to design the systemarchitecture that offers scalable and robustsystems, yet reduces the cost of ownership.

# David Austerberry



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The components of a digital asset management system components of a digital asset management system David Austerberry has worked in the world of asset management since 1997. He was