Friday, October 10, 2008
Friday, October 3, 2008
Reading Notes - Week 6
Hedstrom: Research Challenges in Digital Archiving and Long-term Preservation
Future research capabilities will be seriously compromised without significant investments in research and the development of digital archives.
Digital collections are vast, heterogenuous, and growing at a rate that outpaces our ability to manage and preserve them.
Human labor is the greatest cost factor in digital preservation.
need systems that are: self-sustaining, self-monitoring, self-repairing.
redundancy, replication, security against intentional attacks & technological failures, issues of forward migration: critical
Economic and policy research needs span a wide range of issues such as incentives for organizations to invest in digital archives and incentives for depositores to place content in repositiories.
questions of intellectual property rights, privacy, and trust.
digital preservation will not scale without tools and technologies that automate many aspects of the preservation process and that support human decision-making.
models needed to support: selection, choice of preservation strategies, costs/benfits of vatious levels of description/metadata.
it is important to recognize that metadata, shemas, and ontologies are dynamic
managing schema evolution is a major research issue.
Research issues in the area of naming and authorization nclude development of methods for uniquye and persistent naming of archived digital objects, tools for certification and authentication of preserved digital objects, methodds for version control, and interoperability among naming mechanisms
research is needed on the requirements for a shared and scalable infrastructure to suport digital archiving
a metadat schema registry is also needed
Littman: Actualized Preservation Threats
Chronicling America, three goals for the program are to support the digitization of historically significant newspapers, facilitate public access via a web site, provide for the long-term preservation of these materials by constructing a digital repository.
made the explicit decision not "trust" the repository until some later point; stored and backed up in a completely seperate environment
four preservation threat categories: media failure, hardware failure, software failures, operator errors
a number of hard drive failures; in one case a second problem occurred while storage system was rebuilding; resulted in the loss of a small amount of data from the system. fortunately, file system diagnostics were able to identify & restore corrupted files
first software failure was failure to successfully validate digital objects created by awardees; gaps remained in validation that allowed awardees to to submit METS records that passed validation and were ingested into the repository, but did not conform to the appropriate NDNP profile.
transformation failure: transformation of the METS record has proven to be complex and error prone; the transformation that put the original METS record inline was stripping the XML markup.
XMS file system was corrupted, resulting in the loss of some data
most sifnificant threats to preservation occurred as a result of operator errors. deletion of a large number of files from a section of a file system; lack of auditing capabilities contribured to this problem.
mistakes performed during ingest
already implemented some significant architectural changes to address.
Lavoie: Technology Watch Report
digital preservation – securing the long-term persistence of information in digital form
cultural heritage institutions, businesses, government agencies, etc. – with the need to take steps to secure the long-term viability of the digital materials in their custody. Many of these entities do not perceive an archival function within the scope of their organizational mission.
no perceived consensus on the needs and requirements for maintaining digital information over the long-term. A unifying framework that could fill this gap would be invaluable in terms of encouraging dialog and collaboration among participants in standards-building activities, as well as identifying areas most likely to benefit from standards development.
two primary functions for an archival repository: first, to preserve information – i.e., to secure its long-term persistence – and second, to provide access to the archived information
obtain sufficient intellectual property rights, along with custody of the items, to authorize the procedures necessary to meet preservation objectives. For example, if the OAIS must create a new version of the archived item so that it can be rendered by current technologies, it must have the explicit right to do so.
must not only preserve information, but also a sufficient portion of its associated context to ensure that the information is understandable, and ultimately, useable by future generations. "Contextual information" that might be preserved includes, but is not limited to, a description of the structure or format in which the information is stored, explanations of how and why the information was created, and even its appropriate interpretation.
first functional component is Ingest, the set of processes responsible for accepting information submitted by Producers and preparing it for inclusion in the archival store.
Archival Storage. This is the portion of the archival system that manages the long-term storage and maintenance of digital materials entrusted to the OAIS.
Data Management is the third functional component of an OAIS. The Data Management function maintains databases of descriptive metadata identifying and describing the archived information in support of the OAIS’s finding aids; it also manages the administrative data supporting the OAIS’s internal system operations, such as system performance data or access statistics
Preservation Planning. This service is responsible for mapping out the OAIS’s preservation strategy, as well as recommending appropriate revisions to this strategy in response to evolving conditions in the OAIS environment.
Access is the fifth functional component of an OAIS-type archive. As its name suggests, the Access function manages the processes and services by which Consumers – and especially the Designated Community – locate, request, and receive delivery of items residing in the OAIS’s archival store.
Administration. The Administration function is responsible for managing the day-to-day operations of the OAIS, as well as coordinating the activities of the other five high-level OAIS services
OAIS information model is built around the concept of an information package: a conceptualization of the structure of information as it moves into, through, and out of the archival system. An information package consists of the digital object that is the focus of preservation, along with metadata necessary to support its long-term preservation and access, bound into a single logical package
Submission Information Package, or SIP, is the version of the information package that is transferred from the Producer to the OAIS when information is ingested into the archive.
Archival Information Package, or AIP, is the version of the information package that is stored and preserved by the OAIS.
Dissemination Information Package, or DIP, is the version of the information package delivered to the Consumer in response to an access request.
Taken together, the Content Information and Preservation Description Information represent the archived digital content, the metadata necessary to render and understand it, and the metadata necessary to support its preservation.
Jones/Baegrie: Introduction & Digital Preservation
growing awareness of the significant challenges associated with ensuring continued access to these materials, even in the short term.
The need to create and have widespread access to digital materials has raced ahead of the level of general awareness and understanding of what it takes to manage them effectively.
institutions that have not played a role in preserving traditional collections do not have a strong sense of playing a role in preserving digital materials. Individual researchers were keen to "do the right thing" but frequently lacked the clear guidance and institutional backing to enable them to feel confident of what they should be doing
Digital preservation has many parallels with traditional preservation in matters of broad principle but differs markedly at the operational level and never more so than in the wide range of decision makers who play a crucial role at various stages in the lifecycle of a digital resource
While there is as yet only largely anecdotal evidence, it is certain that many potentially valuable digital materials have already been lost.
Machine Dependency. Digital materials all require specific hardware and software in order to access them
The speed of changes in technology means that the timeframe during which action must be taken is very much shorter than for paper
Fragility of the media.The media digital materials are stored on is inherently unstable and without suitable storage conditions and management can deteriorate very quickly
The ease with which changes can be made and the need to make some changes in order to manage the material means that there are challenges associated with ensuring the continued integrity, authenticity, and history of digital materials.
The implications of allocating priorities are much more severe than for paper.
The nature of the technology requires a life-cycle management approach to be taken to its maintenance
widely acknowledged that the most cost-effective means of ensuring continued access to important digital materials is to consider the preservation implications as early as possible, preferably at creation, and actively to plan for their management throughout their lifecycle.
All public institutions such as archives, libraries, and museums need to be involved in applying their professional skills and expertise to the long-term preservation of digital materials, just as they have taken a role in the preservation of traditional materials.
Preservation costs are expected to be greater in the digital environment than for traditional paper collections
need actively to manage inevitable changes in technology at regular intervals and over a (potentially) infinite timeframe.
lack of standardisation in both the resources themselves and the licensing agreements
as yet unresolved means of reliably and accurately rendering certain digital objects so that they do not lose essential information after technology changes
for some time to come digital preservation may be an additional cost on top of the costs for traditional collections unless cost savings can be realised
Because digital material is machine dependent, it is not possible to access the information unless there is appropriate hardware, and associated software which will make it intelligible.
While it is technically feasible to alter records in a paper environment, the relative ease with which this can be achieved in the digital environment, either deliberately or inadvertently, has given this issue more pressing urgency
Although computer storage is increasing in scale and its relative cost is decreasing constantly, the quantity of data and our ability to capture it with relative ease still matches or exceeds it in a number of areas.
approaches to digital preservation:
-Preserve the original software (and possible hardware) that was used to create and access the information. technology preservation strategy
-Program future powerful computer systems to emulate older, obsolete computer platforms and operating systems as required.This is the technology emulation strategy.
-Ensure that the digital information is re-encoded in new formats before the old format becomes obsolete.This is the digital information migration strategy
The dramatic speed of technological change means that few organisations have been able even fully to articulate what their needs are in this area, much less employ or develop staff with appropriate skills
Roles are also changing within as well as between institutions. Assigning responsibility for preservation of digital materials acquired and/or created by an organisation will inevitably require involvement with personnel from different parts of the organisation working together
Some consideration also needs to be given in the selection to the level of redundancy needed to ensure digital preservation. A level of redundancy with multiple copies held in different repositories is inherent in traditional print materials and has contributed to their preservation over centuries
The IPR issues in digital materials are arguably more complex and significant than for traditional media and if not addressed can impede or even prevent preservation activities. Consideration may need to be given not only to content but to any associated software
Future research capabilities will be seriously compromised without significant investments in research and the development of digital archives.
Digital collections are vast, heterogenuous, and growing at a rate that outpaces our ability to manage and preserve them.
Human labor is the greatest cost factor in digital preservation.
need systems that are: self-sustaining, self-monitoring, self-repairing.
redundancy, replication, security against intentional attacks & technological failures, issues of forward migration: critical
Economic and policy research needs span a wide range of issues such as incentives for organizations to invest in digital archives and incentives for depositores to place content in repositiories.
questions of intellectual property rights, privacy, and trust.
digital preservation will not scale without tools and technologies that automate many aspects of the preservation process and that support human decision-making.
models needed to support: selection, choice of preservation strategies, costs/benfits of vatious levels of description/metadata.
it is important to recognize that metadata, shemas, and ontologies are dynamic
managing schema evolution is a major research issue.
Research issues in the area of naming and authorization nclude development of methods for uniquye and persistent naming of archived digital objects, tools for certification and authentication of preserved digital objects, methodds for version control, and interoperability among naming mechanisms
research is needed on the requirements for a shared and scalable infrastructure to suport digital archiving
a metadat schema registry is also needed
Littman: Actualized Preservation Threats
Chronicling America, three goals for the program are to support the digitization of historically significant newspapers, facilitate public access via a web site, provide for the long-term preservation of these materials by constructing a digital repository.
made the explicit decision not "trust" the repository until some later point; stored and backed up in a completely seperate environment
four preservation threat categories: media failure, hardware failure, software failures, operator errors
a number of hard drive failures; in one case a second problem occurred while storage system was rebuilding; resulted in the loss of a small amount of data from the system. fortunately, file system diagnostics were able to identify & restore corrupted files
first software failure was failure to successfully validate digital objects created by awardees; gaps remained in validation that allowed awardees to to submit METS records that passed validation and were ingested into the repository, but did not conform to the appropriate NDNP profile.
transformation failure: transformation of the METS record has proven to be complex and error prone; the transformation that put the original METS record inline was stripping the XML markup.
XMS file system was corrupted, resulting in the loss of some data
most sifnificant threats to preservation occurred as a result of operator errors. deletion of a large number of files from a section of a file system; lack of auditing capabilities contribured to this problem.
mistakes performed during ingest
already implemented some significant architectural changes to address.
Lavoie: Technology Watch Report
digital preservation – securing the long-term persistence of information in digital form
cultural heritage institutions, businesses, government agencies, etc. – with the need to take steps to secure the long-term viability of the digital materials in their custody. Many of these entities do not perceive an archival function within the scope of their organizational mission.
no perceived consensus on the needs and requirements for maintaining digital information over the long-term. A unifying framework that could fill this gap would be invaluable in terms of encouraging dialog and collaboration among participants in standards-building activities, as well as identifying areas most likely to benefit from standards development.
two primary functions for an archival repository: first, to preserve information – i.e., to secure its long-term persistence – and second, to provide access to the archived information
obtain sufficient intellectual property rights, along with custody of the items, to authorize the procedures necessary to meet preservation objectives. For example, if the OAIS must create a new version of the archived item so that it can be rendered by current technologies, it must have the explicit right to do so.
must not only preserve information, but also a sufficient portion of its associated context to ensure that the information is understandable, and ultimately, useable by future generations. "Contextual information" that might be preserved includes, but is not limited to, a description of the structure or format in which the information is stored, explanations of how and why the information was created, and even its appropriate interpretation.
first functional component is Ingest, the set of processes responsible for accepting information submitted by Producers and preparing it for inclusion in the archival store.
Archival Storage. This is the portion of the archival system that manages the long-term storage and maintenance of digital materials entrusted to the OAIS.
Data Management is the third functional component of an OAIS. The Data Management function maintains databases of descriptive metadata identifying and describing the archived information in support of the OAIS’s finding aids; it also manages the administrative data supporting the OAIS’s internal system operations, such as system performance data or access statistics
Preservation Planning. This service is responsible for mapping out the OAIS’s preservation strategy, as well as recommending appropriate revisions to this strategy in response to evolving conditions in the OAIS environment.
Access is the fifth functional component of an OAIS-type archive. As its name suggests, the Access function manages the processes and services by which Consumers – and especially the Designated Community – locate, request, and receive delivery of items residing in the OAIS’s archival store.
Administration. The Administration function is responsible for managing the day-to-day operations of the OAIS, as well as coordinating the activities of the other five high-level OAIS services
OAIS information model is built around the concept of an information package: a conceptualization of the structure of information as it moves into, through, and out of the archival system. An information package consists of the digital object that is the focus of preservation, along with metadata necessary to support its long-term preservation and access, bound into a single logical package
Submission Information Package, or SIP, is the version of the information package that is transferred from the Producer to the OAIS when information is ingested into the archive.
Archival Information Package, or AIP, is the version of the information package that is stored and preserved by the OAIS.
Dissemination Information Package, or DIP, is the version of the information package delivered to the Consumer in response to an access request.
Taken together, the Content Information and Preservation Description Information represent the archived digital content, the metadata necessary to render and understand it, and the metadata necessary to support its preservation.
Jones/Baegrie: Introduction & Digital Preservation
growing awareness of the significant challenges associated with ensuring continued access to these materials, even in the short term.
The need to create and have widespread access to digital materials has raced ahead of the level of general awareness and understanding of what it takes to manage them effectively.
institutions that have not played a role in preserving traditional collections do not have a strong sense of playing a role in preserving digital materials. Individual researchers were keen to "do the right thing" but frequently lacked the clear guidance and institutional backing to enable them to feel confident of what they should be doing
Digital preservation has many parallels with traditional preservation in matters of broad principle but differs markedly at the operational level and never more so than in the wide range of decision makers who play a crucial role at various stages in the lifecycle of a digital resource
While there is as yet only largely anecdotal evidence, it is certain that many potentially valuable digital materials have already been lost.
Machine Dependency. Digital materials all require specific hardware and software in order to access them
The speed of changes in technology means that the timeframe during which action must be taken is very much shorter than for paper
Fragility of the media.The media digital materials are stored on is inherently unstable and without suitable storage conditions and management can deteriorate very quickly
The ease with which changes can be made and the need to make some changes in order to manage the material means that there are challenges associated with ensuring the continued integrity, authenticity, and history of digital materials.
The implications of allocating priorities are much more severe than for paper.
The nature of the technology requires a life-cycle management approach to be taken to its maintenance
widely acknowledged that the most cost-effective means of ensuring continued access to important digital materials is to consider the preservation implications as early as possible, preferably at creation, and actively to plan for their management throughout their lifecycle.
All public institutions such as archives, libraries, and museums need to be involved in applying their professional skills and expertise to the long-term preservation of digital materials, just as they have taken a role in the preservation of traditional materials.
Preservation costs are expected to be greater in the digital environment than for traditional paper collections
need actively to manage inevitable changes in technology at regular intervals and over a (potentially) infinite timeframe.
lack of standardisation in both the resources themselves and the licensing agreements
as yet unresolved means of reliably and accurately rendering certain digital objects so that they do not lose essential information after technology changes
for some time to come digital preservation may be an additional cost on top of the costs for traditional collections unless cost savings can be realised
Because digital material is machine dependent, it is not possible to access the information unless there is appropriate hardware, and associated software which will make it intelligible.
While it is technically feasible to alter records in a paper environment, the relative ease with which this can be achieved in the digital environment, either deliberately or inadvertently, has given this issue more pressing urgency
Although computer storage is increasing in scale and its relative cost is decreasing constantly, the quantity of data and our ability to capture it with relative ease still matches or exceeds it in a number of areas.
approaches to digital preservation:
-Preserve the original software (and possible hardware) that was used to create and access the information. technology preservation strategy
-Program future powerful computer systems to emulate older, obsolete computer platforms and operating systems as required.This is the technology emulation strategy.
-Ensure that the digital information is re-encoded in new formats before the old format becomes obsolete.This is the digital information migration strategy
The dramatic speed of technological change means that few organisations have been able even fully to articulate what their needs are in this area, much less employ or develop staff with appropriate skills
Roles are also changing within as well as between institutions. Assigning responsibility for preservation of digital materials acquired and/or created by an organisation will inevitably require involvement with personnel from different parts of the organisation working together
Some consideration also needs to be given in the selection to the level of redundancy needed to ensure digital preservation. A level of redundancy with multiple copies held in different repositories is inherent in traditional print materials and has contributed to their preservation over centuries
The IPR issues in digital materials are arguably more complex and significant than for traditional media and if not addressed can impede or even prevent preservation activities. Consideration may need to be given not only to content but to any associated software
Muddiest Point
No muddiest point this week, but I am still unable to install apache on my mac and thus cannot run greenstone.
Sunday, September 28, 2008
Friday, September 26, 2008
Muddiest Point
Will we actually be doing any XML coding for our term projects, or is this something we just need to understand conceptually?
Reading Notes - Week 5
Bryan:
XML is subset of the Standard Generalized Markup Language.
provides a formal syntax for describing the relationships between the entities, elements and attributes that make up an XML document
users must create a Document Type Definition that formally identifies the relationships between the various elements that form their documents
Where elements can have variable forms, or need to be linked together, they can be given suitable attributes to specify the properties to be applied to them
Ogbuji:
XML is based on Standard Generalized Markup Language (SGML), defined in ISO 8879:1986 [ISO Standard]. It represents a significant simplification of SGML, and includes adjustments that make it better suited to the Web environment.
an entity catalog can be used to specify the location from which an XML processor loads a DTD, given the system and public identifiers for that DTD. System identifiers are usually given by Uniform Resource Identifiers (URIs)
**A URI is just an extension of the familiar URLs from use in Web browsers and the like. All URLs are also URIs, but URLs also add URNs** [is this true? i thought the opposite...]
In XML namespaces each vocabulary is called a namespace and there is a special syntax for expressing vocabulary markers. Each element or attribute name can be connected to one namespace
XML Base [W3C Recommendation] provides a means of associating XML elements with URIs in order to more precisely specify how relative URIs are resolved in relevant XML processing actions.
the XML Infoset, defines an abstract way of describing an XML document as a series of objects, called information items, with specialized properties. This abstract data set incorporates aspects of XML documents defined in XML 1.0, XML Namespaces, and XML Base. The XML Infoset is used as the foundation of several other specifications that try to break down XML documents
a physical representation of an XML document, called the canonical form, accounts for the variations allowed in XML syntax without changing meaning
XPointer, language that can be used to refer to fragments of an XML document
XLink offers such links (simple links), as well as more complex links that can have multiple end-points (extended links), and even links that are not expressed in the linked documents, but rather in special hub documents (called linkbases).
XML Tutorial:
Simple elements cannot have attributes. If an element has attributes, it is considered to be of a complex type. But the attribute itself is always declared as a simple type.
Bergholz:
Extensible Markup Language (XML), a semantic language that lets you meaningfully annotate text. Meaningful annotation is, in essence, what XML is all about.
DTDs let users specify the set of tags, the order of tags, and the attributes associated with each
Elements can have zero or more attributes, which are declared using the !ATTLIST tag
Using namespaces avoids name clashes (that is, situations where the same tag name is used in different contexts). For instance, a namespace can identify whether an address is a postal address, an e-mail address, or an IP address
Unfortunately, namespaces and DTDs do not work well together
XML extends HTML’s linking capabilities with three supporting
languages.
Xlink (http://www.w3.org/TR/xlink/), which describes how two documents can be linked;
XPointer, which enables addressing individual parts of an XML document; and
XPath, which is used by XPointer to describe location paths.
The Extensible Stylesheet Language (XSL) is actually two languages: a transformation language (called XSL transformations, or XSLT) and a formatting language (XSL formatting objects). Although DTDs were the first proposal to providefor a standardized data exchange betweenusers, they have disadvantages. Their expressive power seems limited, and their syntax is not XML. Several approaches address these disadvantages by defining a schema language (rather than a grammar) for XML documents:
document definition markup language (DDML), formerly known as XSchema,
document content description (DCD),
schema for object-oriented XML (SOX), and
XML-Data (replaced by DCD). The W3C’s XML Schema activity takes these four proposals into consideration.
XML is subset of the Standard Generalized Markup Language.
XML allows users to:
- bring multiple files together to form compound documents
- identify where illustrations are to be incorporated into text files, and the format used to encode each illustration
- provide processing control information to supporting programs, such as document validators and browsers
- add editorial comments to a file
provides a formal syntax for describing the relationships between the entities, elements and attributes that make up an XML document
users must create a Document Type Definition that formally identifies the relationships between the various elements that form their documents
Where elements can have variable forms, or need to be linked together, they can be given suitable attributes to specify the properties to be applied to them
An XML file normally consists of three types of markup, the first two of which are optional:
- An XML processing instruction identifying the version of XML being used, the way in which it is encoded, and whether it references other files or not, e,g,
- A document type declaration that either contains the formal markup declarations in its internal subset (between square brackets) or references a file containing the relevant markup declarations (the external subset), e.g.:
- A fully-tagged document instance which consists of a root element, whose element type name must match that assigned as the document type name in the document type declaration, within which all other markup is nested.
Ogbuji:
XML is based on Standard Generalized Markup Language (SGML), defined in ISO 8879:1986 [ISO Standard]. It represents a significant simplification of SGML, and includes adjustments that make it better suited to the Web environment.
an entity catalog can be used to specify the location from which an XML processor loads a DTD, given the system and public identifiers for that DTD. System identifiers are usually given by Uniform Resource Identifiers (URIs)
**A URI is just an extension of the familiar URLs from use in Web browsers and the like. All URLs are also URIs, but URLs also add URNs** [is this true? i thought the opposite...]
In XML namespaces each vocabulary is called a namespace and there is a special syntax for expressing vocabulary markers. Each element or attribute name can be connected to one namespace
XML Base [W3C Recommendation] provides a means of associating XML elements with URIs in order to more precisely specify how relative URIs are resolved in relevant XML processing actions.
the XML Infoset, defines an abstract way of describing an XML document as a series of objects, called information items, with specialized properties. This abstract data set incorporates aspects of XML documents defined in XML 1.0, XML Namespaces, and XML Base. The XML Infoset is used as the foundation of several other specifications that try to break down XML documents
a physical representation of an XML document, called the canonical form, accounts for the variations allowed in XML syntax without changing meaning
XPointer, language that can be used to refer to fragments of an XML document
XLink offers such links (simple links), as well as more complex links that can have multiple end-points (extended links), and even links that are not expressed in the linked documents, but rather in special hub documents (called linkbases).
XML Tutorial:
The purpose of an XML Schema is to define the legal building blocks of an XML document, just like a DTD.
An XML Schema:
- defines elements that can appear in a document
- defines attributes that can appear in a document
- defines which elements are child elements
- defines the order of child elements
- defines the number of child elements
- defines whether an element is empty or can include text
- defines data types for elements and attributes
- defines default and fixed values for elements and attributes
One of the greatest strength of XML Schemas is the support for data types.
With support for data types:
- It is easier to describe allowable document content
- It is easier to validate the correctness of data
- It is easier to work with data from a database
- It is easier to define data facets (restrictions on data)
- It is easier to define data patterns (data formats)
- It is easier to convert data between different data types
Simple elements cannot have attributes. If an element has attributes, it is considered to be of a complex type. But the attribute itself is always declared as a simple type.
A complex element is an XML element that contains other elements and/or attributes.
There are four kinds of complex elements:
- empty elements
- elements that contain only other elements
- elements that contain only text
- elements that contain both other elements and text
WSDL is a schema-based language for describing Web services and how to access them.
WSDL describes a web service, along with the message format and protocol details for the web service.
Bergholz:
Extensible Markup Language (XML), a semantic language that lets you meaningfully annotate text. Meaningful annotation is, in essence, what XML is all about.
DTDs let users specify the set of tags, the order of tags, and the attributes associated with each
Elements can have zero or more attributes, which are declared using the !ATTLIST tag
Using namespaces avoids name clashes (that is, situations where the same tag name is used in different contexts). For instance, a namespace can identify whether an address is a postal address, an e-mail address, or an IP address
Unfortunately, namespaces and DTDs do not work well together
XML extends HTML’s linking capabilities with three supporting
languages.
Xlink (http://www.w3.org/TR/xlink/), which describes how two documents can be linked;
XPointer, which enables addressing individual parts of an XML document; and
XPath, which is used by XPointer to describe location paths.
The Extensible Stylesheet Language (XSL) is actually two languages: a transformation language (called XSL transformations, or XSLT) and a formatting language (XSL formatting objects). Although DTDs were the first proposal to providefor a standardized data exchange betweenusers, they have disadvantages. Their expressive power seems limited, and their syntax is not XML. Several approaches address these disadvantages by defining a schema language (rather than a grammar) for XML documents:
document definition markup language (DDML), formerly known as XSchema,
document content description (DCD),
schema for object-oriented XML (SOX), and
XML-Data (replaced by DCD). The W3C’s XML Schema activity takes these four proposals into consideration.
Friday, September 19, 2008
Reading Notes
Setting the Stage
metadata: the sum total of what one can say abotu any information object at any level of aggregation
- content (intrinsic) - what is contained/about
- context (extrinsic) - who what when etc about creation
- structure (either int or ext) - associations b/c or among independent info objects
library metadata: includes indexes, abstracts & catalog records created according to cataloging rules (MARC, LCSH etc)
archival & manuscript metadata: accession records, finding aids, catalog records.
- MARC Archival and Manuscript Control (AMC), no MARC format for bib control
not as much emph on structure for lib/arch, but always important even before digitization.
- growing as comp capabilities increase
- structure can be exploited for searching, etc but need specific metadata
metadata:
- certifies authenticity & degree completeness of content
- establishes & documents context of content
- identifies & exploits structural rel's that exist b/t & w/in info objects
- provides range of intell access points for increasingly diverse range of users
- provides some of info an info prof might have provided in a physical setting
repositories also metadata for admin, accession, preserving, use of coll's
- personal info mgmt, recordkeeping
Dublin Core Metadata Element Set
Table 1 - Types
1) Administrative (acqu info, rights & repro, documentation of legal access req's, location info, selection criteria, version control, audit trails)
2) Descriptive (cat records, finding aids, spec indexes, hyperlink rel's, annotations by users, md for recordkeeping systems)
3) Preservation (documentation of phys condition, actions taken to preserve)
4) Technical (hard/software documentation, digitization info, track sys resp time, auth & sec data)
5) Use (exhibit records, use & user tracking, re-use & multi-version info)
Attributes of metadata:
- Source (Int or Ext)
- Method of creation (auto/comp or manual/human)
- Nature (lay/nonspecialist v. expert - but often orig is lay)
- Status (static, dynamic, long- or short-term)
- Structure (structured or no)
- Semantics (Controlled or no)
- Level (collection or item)
Life-Cycle of Info Object:
1) Creation & Multi-Versioning
2) Organization
3) Searching & Retrieval
4) Utilization
5) Preservation & Disposition
Little-Known facts about metadata:
- doesn't have to be digital
- more than just description
- variety of sources
- continue to accrue during life of info object/sys
- one info obj's metadata can simultaneously be another's data
Why Important?
- Increased accessibility
- retention of context
- expanding use
- multi-versioning
- legal issues
- preservation
- system improvement & economics
Border Crossings
DC: simple, modular, extensible metadata
prob's w/ user-created metadata
structured md important in managing intellectual assets
md for images critical for searchability/discoverability
controlled v. uncontrolled vocab (folksonomy)
- still not sure of future role
"Railroad Gage Dilemma" - why no common formal model?
demand for international/multicultural approach
Witten 2.2
19th c goals for bib sys: finding, collocation, choice
Today: 5 goals
1) locate entities
2) identify
3) select
4) acquire
5) navigate rel's between
principle entities: documents, works, editions, authors, subjects.
- titles & sub classifications are attributes of works, not own entitities
doc's: fundamental hierarchical structure that can more faithfully be reflected in DL than physical
"helpful DLs need to present users an image of stability & continuity" (p.49)
works: disembodied contents of a document
edition - also "version, release, revision"
authority control
subjects: extraction: phrases anlyzed for gram & lexical structure
- key phrase assignment (auto class), easier for scientific than literary
LCSH controlled vocab rel's: equivalence, hierarchical, associative
Witten 5.4 - 5.7
MARC & Dublin Core, BibTeX & Refer
MARC: AACR2R guidelines
- authority files & bib records
Dublin Core: specifically for non-specialist use
- title, creator, subject, description, publisher, contributor, date, type, format, identifier, source, language, relation, coverage, rights
BibTeX: math/sci
Refer: basis of endnote
metadata even more imp for images & multimedia
- image files contain some info
TIFF: tags. integers & ASCII text. dozen or so mandatory.
- most DLs use for images
MPEG-7: multimedia content description interface
- still pics, graphics, 3D models, audio, speech, video, combinations
- stored or streamed
- complex/extensible: DDL (desc def lang) usus XML syntax
- temporal series, spectral vector
- some automatic, some by hand
text-mining: auto metadata extraction
- structured markup s/a XML
Greenstone includes lang ident, extracting acronyms & key phrases, generating phrase hierarchies.
some info easy to extract: url/email, money, date/time, names
- generic entity extraction
bib ref's / citation info can be located & parsed
n-grams procedure for lang ID, can assign language metadata
key-phrase: assignment/extraction
- assignment: compare doc to each entry in list (Y or N)
- extraction: phrases from doc listed & best chosen (easier)
IDing phrases: content word, phrase delimiters, maximal length
metadata: the sum total of what one can say abotu any information object at any level of aggregation
- content (intrinsic) - what is contained/about
- context (extrinsic) - who what when etc about creation
- structure (either int or ext) - associations b/c or among independent info objects
library metadata: includes indexes, abstracts & catalog records created according to cataloging rules (MARC, LCSH etc)
archival & manuscript metadata: accession records, finding aids, catalog records.
- MARC Archival and Manuscript Control (AMC), no MARC format for bib control
not as much emph on structure for lib/arch, but always important even before digitization.
- growing as comp capabilities increase
- structure can be exploited for searching, etc but need specific metadata
metadata:
- certifies authenticity & degree completeness of content
- establishes & documents context of content
- identifies & exploits structural rel's that exist b/t & w/in info objects
- provides range of intell access points for increasingly diverse range of users
- provides some of info an info prof might have provided in a physical setting
repositories also metadata for admin, accession, preserving, use of coll's
- personal info mgmt, recordkeeping
Dublin Core Metadata Element Set
Table 1 - Types
1) Administrative (acqu info, rights & repro, documentation of legal access req's, location info, selection criteria, version control, audit trails)
2) Descriptive (cat records, finding aids, spec indexes, hyperlink rel's, annotations by users, md for recordkeeping systems)
3) Preservation (documentation of phys condition, actions taken to preserve)
4) Technical (hard/software documentation, digitization info, track sys resp time, auth & sec data)
5) Use (exhibit records, use & user tracking, re-use & multi-version info)
Attributes of metadata:
- Source (Int or Ext)
- Method of creation (auto/comp or manual/human)
- Nature (lay/nonspecialist v. expert - but often orig is lay)
- Status (static, dynamic, long- or short-term)
- Structure (structured or no)
- Semantics (Controlled or no)
- Level (collection or item)
Life-Cycle of Info Object:
1) Creation & Multi-Versioning
2) Organization
3) Searching & Retrieval
4) Utilization
5) Preservation & Disposition
Little-Known facts about metadata:
- doesn't have to be digital
- more than just description
- variety of sources
- continue to accrue during life of info object/sys
- one info obj's metadata can simultaneously be another's data
Why Important?
- Increased accessibility
- retention of context
- expanding use
- multi-versioning
- legal issues
- preservation
- system improvement & economics
Border Crossings
DC: simple, modular, extensible metadata
prob's w/ user-created metadata
structured md important in managing intellectual assets
md for images critical for searchability/discoverability
controlled v. uncontrolled vocab (folksonomy)
- still not sure of future role
"Railroad Gage Dilemma" - why no common formal model?
demand for international/multicultural approach
Witten 2.2
19th c goals for bib sys: finding, collocation, choice
Today: 5 goals
1) locate entities
2) identify
3) select
4) acquire
5) navigate rel's between
principle entities: documents, works, editions, authors, subjects.
- titles & sub classifications are attributes of works, not own entitities
doc's: fundamental hierarchical structure that can more faithfully be reflected in DL than physical
"helpful DLs need to present users an image of stability & continuity" (p.49)
works: disembodied contents of a document
edition - also "version, release, revision"
authority control
subjects: extraction: phrases anlyzed for gram & lexical structure
- key phrase assignment (auto class), easier for scientific than literary
LCSH controlled vocab rel's: equivalence, hierarchical, associative
Witten 5.4 - 5.7
MARC & Dublin Core, BibTeX & Refer
MARC: AACR2R guidelines
- authority files & bib records
Dublin Core: specifically for non-specialist use
- title, creator, subject, description, publisher, contributor, date, type, format, identifier, source, language, relation, coverage, rights
BibTeX: math/sci
Refer: basis of endnote
metadata even more imp for images & multimedia
- image files contain some info
TIFF: tags. integers & ASCII text. dozen or so mandatory.
- most DLs use for images
MPEG-7: multimedia content description interface
- still pics, graphics, 3D models, audio, speech, video, combinations
- stored or streamed
- complex/extensible: DDL (desc def lang) usus XML syntax
- temporal series, spectral vector
- some automatic, some by hand
text-mining: auto metadata extraction
- structured markup s/a XML
Greenstone includes lang ident, extracting acronyms & key phrases, generating phrase hierarchies.
some info easy to extract: url/email, money, date/time, names
- generic entity extraction
bib ref's / citation info can be located & parsed
n-grams procedure for lang ID, can assign language metadata
key-phrase: assignment/extraction
- assignment: compare doc to each entry in list (Y or N)
- extraction: phrases from doc listed & best chosen (easier)
IDing phrases: content word, phrase delimiters, maximal length
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