Martin Holmes, Lead Programmer on MoEML, is deeply committed to open-access projects and open documentation of those projects.
He has led the way in making MoEML’s documentation and tagging freely available in a variety of XML forms (including
TEI Lite XML). His CodeSharing Service takes open documentation to a new level. Now, MoEML users can search our complete project and see every instance of every TEI element,
attribute, and value that we have added to MoEML texts. He presented a formal paper at the TEI Conference at Northwestern University in October 2014. With his permission, we share the complete abstract of this paper here (republished from the TEI 2014 site and lightly edited). His paper concludes with an invitation to comment on the tool.
We hope that many other projects will adopt this tool, thus making visible the usually
invisible labour and critical decisions entailed in tagging. (JJ)
Introduction
Although the TEI Guidelines are full of helpful examples, and other initiatives such
as TEI By Example have made great progress in providing more access to samples of text-encoding to
help beginners get started, there is no doubt that one of the biggest obstacles to
encoders at many levels is finding out how other scholars and projects have chosen
to encode a particular feature or use a specific tag or attribute. Burghart and Rehbein tell us that the majority of TEI users are self-taught or learned by doing, and Dee (2014) reports that users need a source for a compendium of examples suitable for inductive learning. Many projects now share their XML code, but that in itself is only marginally helpful.
It can take substantial time to sift through the XML code in a large project to find
what you’re looking for.
This talk presents a simple specification for an Application Programming Interface, along with a sample implementation written in XQuery and designed for the eXist XML database, providing straightforward access both for applications and end-users to sample code
from any TEI project. The API is modelled on the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH), a mechanism designed to allow archival search tools to ingest metadata
from repositories. The CodeSharing protocol and the sample implementation were first
presented at the >Digital.Humanities@Oxford Summer School in July 2013, and a number of improvements have been made to the code and specification based
on feedback from that presentation.
Target audience
The CodeSharing proposal arises out of two separate but intersecting needs: those
of novice encoders and project managers who are not really TEI experts, and those
of people doing research into encoding practices on a large scale across multiple
projects.
Novice encoders
At the time of writing, The Map of Early Modern London (MoEML) project, a typical grant-supported digital humanities project1 with a large encoding component, has a team of around seven or eight encoders working
part-time, with frequent changes of personnel. The project provides regular TEI training,
but there is usually a mix of experienced and rookie encoders, and project managers
have to provide a lot of live help to supplement the documentation. One of the most
difficult things for inexperienced encoders is to find examples of the usage of elements
and attributes they haven’t used before. There are of course lots of resources to
help with this, including the TEI Guidelines examples, the TEI by Example project, and Marjorie Burghart’s Cheatsheets, but it is unusual to find in such external resources enough examples of the use
of a particular element or attribute which exactly match the current use-case. It
is really more effective to search the codebase of your own project.
The MoEML encoders do have access to a lot of the existing codebase, but doing text searches
of this is often ineffective. They are not normally familiar with XPath, XQuery, or regular expressions, and most will never learn them, so in searching for e.g. a <birth> element which has a @notBefore-custom attribute, they will search for <birth notBefore-custom, and therefore miss all the <birth> elements which happen to have their @datingMethod attribute first, or which have two spaces between the tag name and the attribute
name instead of one. Searching the entire codebase may also retrieve examples of encoding
in obsolete or unedited documents, which might provide bad examples. It is more effective,
therefore, to enable them to search the online XML database which contains only documents
which have actually been published.
To serve these needs, we began to think about writing a simple search interface which
would form part of our MoEML web application, and which would provide access to lots of examples of individual
tags and attributes.
The Web interface of the CodeSharing service on the MoEML site.
This straightforward form-based interface enables our encoders to retrieve examples
of encoding quickly and easily from across our text collection.
Research into Encoding Practices
As I worked on the interface above, I also began to think about broader possibilities.
In our work on the TEI Council, we frequently find ourselves asking:
Do people ever actually use this element or attribute?
If so, how do they use it?
We typically resort to posting questions to the TEI-L mailing list to ask for examples from the community, but this is a rather slow, hit-and-miss method
of gathering data. If we could retrieve large numbers of sample usages of particular elements or attributes
and analyse them, this would be very helpful in development of the Guidelines, and in assessing the impact of any change we might make to the schemas or recommendations.
We might also be able to supply fresh examples for the Guidelines text itself by selecting from among thousands of sample usages, rather than drawing
only from our own projects or concocting examples. It would therefore be very helpful
if there were an API that projects could implement to provide access to samples of
their encoding practice in a standardized way, such that the same query could be run
over multiple projects simultaneously and the results combined.
A CodeSharing service can serve the needs of novice encoders as well as encoding researchers.
The Model: OAI-PMH
To answer these needs, I designed a web service that could be provided by large- and
medium-scale encoding projects, enabling anyone to gather examples of their encoding
practice directly from their data. I modelled my protocol on an existing, well-tested
system: the Open Archives Initiative Protocol for Metadata Harvesting, or OAI-PMH, which I had previously implemented for another project.
OAI-PMH is commendably simple and well designed. A participating repository may be
a data provider, which exposes structured metadata through a web service implementing
the OAI-PMH API; or a service provider, which gathers that metadata through requests
to the data providers. The service providers can then act as meta-repositories, or
federated archives, providing search functionality that encompasses the collections
of all the data providers who have exposed their metadata for harvesting. An example
is OCLC’s WorldCat, which aggregates data from a large number of repositories and makes them searchable
from a single interface. The OAI-PMH API is based on HTTP requests using GET or POST. It is designed to allow a harvester to find out what kinds of resources a repository
has, and to gather full metadata records. All responses are in XML, and conform to a standard schema.
OAI-PMH is based around six core verbs:
Identify
ListMetadataFormats
ListIdentifiers
ListSets
ListRecords
GetRecord
A request like this one (made to the OAI-PMH interface provided by the Colonial Correspondence of BC and Vancouver Island project, at http://bcgenesis.uvic.ca):
http://bcgenesis.uvic.ca/oai.xq?verb=Identify
will result in a response in XML which provides identifying information about the
repository:
<OAI-PMH xmlns="http://www.openarchives.org/OAI/2.0/" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/ http://www.openarchives.org/OAI/2.0/OAI-PMH.xsd"> <responseDate>2013-05-08T18:09:31.047Z</responseDate> <request verb="Identify">http://bcgenesis.uvic.ca/oai.xq</request> <Identify> <repositoryName>The colonial despatches of Vancouver Island and British Columbia 1846-1871</repositoryName> <baseURL>http://bcgenesis.uvic.ca/oai.xq</baseURL> <protocolVersion>2.0</protocolVersion> <adminEmail>mholmes@uvic.ca</adminEmail> <adminEmail>cpetter@uvic.ca</adminEmail> <earliestDatestamp>2012-11-19T12:00:00Z</earliestDatestamp> <deletedRecord>no</deletedRecord> <granularity>YYYY-MM-DD</granularity> <description> <oai-identifier xmlns="http://www.openarchives.org/OAI/2.0/oai-identifier" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai-identifier http://www.openarchives.org/OAI/2.0/oai-identifier.xsd"> <scheme>oai</scheme> <repositoryIdentifier>bcgenesis.uvic.ca</repositoryIdentifier> <delimiter>:</delimiter> <sampleIdentifier>oai:bcgenesis.uvic.ca:B63030SP.scx</sampleIdentifier> </oai-identifier> </description> </Identify> </OAI-PMH>
The harvester can use the ListRecords verb to retrieve individual records, which are typically in the form of Dublin Core elements embedded in a larger structure in the OAI namespace:
<record xmlns="http://www.openarchives.org/OAI/2.0/"> <header> <identifier>oai:bcgenesis.uvic.ca:B585TE13.scx</identifier> <datestamp>2013-12-17T14:29:44.553-08:00</datestamp> <setSpec>1858</setSpec> <setSpec>publicOffices</setSpec> <setSpec>B.C.</setSpec> </header> <metadata> <dc xmlns="http://www.openarchives.org/OAI/2.0/oai_dc/" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd"> <title xmlns="http://purl.org/dc/elements/1.1/">The colonial despatches of Vancouver Island and British Columbia 1846-1871: 11566, CO 60/2, p. 291; received 13 November. Trevelyan to Merivale (Permanent Under-Secretary)</title> <date xmlns="http://purl.org/dc/elements/1.1/">1858-11-12</date> </dc> </metadata> </record>
Most repositories will have thousands of records, and retrieving them all at once
would place an unacceptable burden on the server and network infrastructure, so OAI-PMH
has a built-in staging system. Records are supplied in batches, and each batch ends
with a resumption token which acts as a flow-control device:
The format of the resumption token is not defined by the specification; the data provider
may use any suitable format, and the harvester simply has to echo it back to the data
provider to get the next set of records. This gives the data provider complete control
over how rapidly it provides the data, and even in the course of a large transfer,
the provider can throttle or accelerate its provision of records in response to local
conditions such as server load or network bandwidth.
The CodeSharing Service
The complete specification for the CodeSharing API is available at http://mapoflondon.uvic.ca/codesharing_protocol.xhtml, as part of the sample implementation on the MoEML site; in what follows I cover only some key aspects of it.
The Request API
CodeSharing is an XML-based API provided over HTTP, just like OAI-PMH. On the model
of OAI-PMH, it’s also based on a verb parameter, with five possible values:
identify
listElements
listAttributes
listNamespaces
getExamples
The first four are designed to discover the nature of the repository, and what elements,
attributes, and namespaces occur in its document collections. The final value is a
request for actual example encodings; when that value is used, other key-value pairs
provide details about what has been requested:
elementName
attributeName
attributeValue
Each parameter is used to specify what examples are being requested. These can obviously
be combined, so a request for:
elementName=hi&attributeName=rend
will retrieve only hi elements which have @rend attributes;
attributeName=rend&value=italic
will retrieve any elements which have @rend="italic".
Two further parameters are available:
namespace (the namespace for requested elements, defaulting to the TEI namespace)
wrapped (whether or not to return the parent containing the target element)
So a request for:
elementName=hi&wrapped=true
will retrieve <hi> elements in the context of their parent element. Encoders find it helpful to see
not just the target element, but the surrounding context too.
Finally, we have to consider flow control, as in the case of OAI-PMH. It would be
disastrous to attempt to honour a request for all of the <TEI> elements in a large collection; we need to negotiate a reasonable chunk size for
the harvester and the server. In the case of OAI-PMH, the data provider always dictates
the number of records it is prepared to supply. In the case of CodeSharing, I wanted
to allow a little more flexibility, so there is a further parameter the harvester
can provide:
maxItemsPerPage (a positive integer)
The provider service is not required to honour this request; it may decide to send
fewer items. But it may be sensitive enough to know, for instance, that when the request
is for a relatively small element such as <hi>, it might be practical to send 100 examples in one response, whereas it might send
only 20 in the case of requests for <p> or <div> elements.
The Response
What form should the server’s response take? The obvious answer is that it should
be XML, and in fact that it should be TEI P5 XML. The exact format of the response
document is only loosely specified, although some parts of it must follow certain
rules. If the value of the verb parameter is listElements, for instance, then the body of the document must contain the list of all elements
appearing in the collection as a list:
Similar structures are used to list attributes and namespaces.
For returning actual examples, CodeSharing makes use of the <egXML> element,
which is also used for example code in the TEI Guidelines. The <egXML> element is in its own special namespace, http://www.tei-c.org/ns/Examples, and all the elements that are children of it, in the example code, are also by default
in that namespace. This is useful, because it means that we can easily distinguish
example code from other parts of the TEI file. (It also means we can use the API to
retrieve examples of code which themselves are intended as examples in their original context.)
In addition to the results of the query, the protocol specification also requires
that the parameters of the original request be returned to the requestor; this means
that the result document is a complete and self-contained record of the query and
results. Full details are available in the protocol documentation.
A Sample Implementation
A sample implementation of the CodeSharing protocol, including an HTML front-end,
as shown in Figure 1, is available at http://mapoflondon.uvic.ca/codesharing.htm. It is written in XQuery 3.0 and runs in the eXist XML database which hosts the MoEML web application. The open-source code is available on SourceForge at https://sourceforge.net/projects/codesharing/, and includes these files:
codesharing.xql (the XQuery implementation providing responses to queries in XML)
codesharing_config.xql (a simple settings file that tailors the service to your own project)
codesharing.xsl (a transformation which produces the HTML search page you see on the MoEML site)
codesharing_protocol.xhtml (a semi-formal description of the API)
codesharing.odd (an ODD file from which a schema can be generated to validate CodeSharing API responses)
I would welcome any contributions in the form of improvements, suggestions, and implementations
in other languages.
Burghart, Marjorie, and Malte
Rehbein. The Present and Future of the TEI Community for
Manuscript Encoding.Journal of the Text Encoding
Initiative 2 (2012). doi:10.4000/jtei.372.
Holmes, Martin D.CodeSharing:
A Simple API for Disseminating
our TEI Encoding.The Map of Early Modern London, edited by Janelle Jenstad, U of Victoria, 26 Jun. 2020, mapoflondon.uvic.ca/BLOG10.htm.
Chicago citation
Holmes, Martin D.CodeSharing:
A Simple API for Disseminating
our TEI Encoding.The Map of Early Modern London. Ed. Janelle Jenstad. Victoria: University of Victoria. Accessed June 26, 2020. https://mapoflondon.uvic.ca/BLOG10.htm.
APA citation
Holmes, M. D. 2020. CodeSharing:
A Simple API for Disseminating
our TEI Encoding. In J. Jenstad (Ed), The Map of Early Modern London. Victoria: University of Victoria. Retrieved from https://mapoflondon.uvic.ca/BLOG10.htm.
RIS file (for RefMan, EndNote etc.)
Provider: University of Victoria
Database: The Map of Early Modern London
Content: text/plain; charset="utf-8"
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T1 - CodeSharing:
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T2 - The Map of Early Modern London
PY - 2020
DA - 2020/06/26
CY - Victoria
PB - University of Victoria
LA - English
UR - https://mapoflondon.uvic.ca/BLOG10.htm
UR - https://mapoflondon.uvic.ca/xml/standalone/BLOG10.xml
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TEI citation
<bibl type="mla"><author><name ref="#HOLM3"><surname>Holmes</surname>, <forename>Martin</forename>
<forename>D.</forename></name></author> <title level="a">CodeSharing:
A Simple API for Disseminating
our TEI Encoding</title>. <title level="m">The Map of Early Modern London</title>,
edited by <editor><name ref="#JENS1"><forename>Janelle</forename> <surname>Jenstad</surname></name></editor>,
<publisher>U of Victoria</publisher>, <date when="2020-06-26">26 Jun. 2020</date>,
<ref target="https://mapoflondon.uvic.ca/BLOG10.htm">mapoflondon.uvic.ca/BLOG10.htm</ref>.</bibl>
Programmer, 2018-present. Junior Programmer, 2015-2017. Research Assistant, 2014-2017.
Joey Takeda was a graduate student at the University of British Columbia in the Department
of English (Science and Technology research stream). He completed his BA honours in
English
(with a minor in Women’s Studies) at the University of Victoria in 2016. His primary
research interests included diasporic and indigenous Canadian and American literature,
critical theory, cultural studies, and the digital humanities.
Data Manager, 2015-2016. Research Assistant, 2013-2015. Tye completed his undergraduate
honours degree in English at the University of Victoria in 2015.
Director of Pedagogy and Outreach, 2015–present. Associate Project Director, 2015–present.
Assistant Project Director, 2013-2014. MoEML Research Fellow, 2013. Kim McLean-Fiander
comes
to The Map of Early Modern London from the Cultures of Knowledge
digital humanities project at the University of
Oxford, where she was the editor of Early Modern Letters Online, an open-access union
catalogue and editorial interface for correspondence from the sixteenth to eighteenth
centuries. She is currently Co-Director of a sister project to EMLO called Women’s Early Modern Letters Online (WEMLO). In the past, she held an internship with the
curator of manuscripts at the Folger Shakespeare
Library, completed a doctorate at Oxford on
paratext and early modern women writers, and worked a number of years for the Bodleian Libraries and as a freelance editor.
She has a passion for rare books and manuscripts as social and material artifacts,
and is
interested in the development of digital resources that will improve access to these
materials while ensuring their ongoing preservation and conservation. An avid traveler,
Kim
has always loved both London and maps, and so is particularly delighted to be able
to bring
her early modern scholarly expertise to bear on the MoEML project.
Janelle Jenstad is Associate Professor of English at the University of Victoria, Director
of The Map of Early Modern London, and PI of Linked Early Modern Drama Online. She has taught at Queen’s University, the Summer
Academy at the Stratford Festival, the University of Windsor, and the University of
Victoria. With Jennifer Roberts-Smith and Mark Kaethler, she co-edited Shakespeare’s Language in Digital Media (Routledge). She has prepared a documentary edition of John Stow’s A
Survey of London (1598 text) for MoEML and is currently editing The Merchant of Venice (with Stephen Wittek) and Heywood’s 2 If
You Know Not Me You Know Nobody for DRE. Her articles have appeared in Digital Humanities Quarterly, Renaissance and
Reformation,Journal of Medieval and Early Modern Studies,
Early Modern Literary Studies, Elizabethan
Theatre, Shakespeare Bulletin: A Journal of Performance
Criticism, and The Silver Society Journal. Her book
chapters have appeared (or will appear) in Institutional Culture in Early
Modern Society (Brill, 2004), Shakespeare, Language and the Stage,
The Fifth Wall: Approaches to Shakespeare from Criticism, Performance and Theatre
Studies (Arden/Thomson Learning, 2005), Approaches to Teaching
Othello (Modern Language Association, 2005), Performing Maternity
in Early Modern England (Ashgate, 2007), New Directions in the
Geohumanities: Art, Text, and History at the Edge of Place (Routledge, 2011), Early
Modern Studies and the Digital Turn (Iter, 2016), Teaching Early Modern
English Literature from the Archives (MLA, 2015), Placing Names:
Enriching and Integrating Gazetteers (Indiana, 2016), Making
Things and Drawing Boundaries (Minnesota, 2017), and Rethinking
Shakespeare’s Source Study: Audiences, Authors, and Digital Technologies
(Routledge, 2018).
Janelle Jenstad authored or edited the following items in MoEML’s bibliography:
Jenstad, Janelle. Building a Gazetteer for Early Modern London, 1550-1650.Placing Names. Ed. Merrick Lex Berman, Ruth
Mostern, and Humphrey Southall. Bloomington and
Indianapolis: Indiana UP, 2016. 129-145.
Jenstad, Janelle. The
Burse and the Merchant’s Purse: Coin, Credit, and the Nation in Heywood’s 2 If You Know Not Me You Know Nobody.The
Elizabethan Theatre XV. Ed. C.E. McGee and A.L.
Magnusson. Toronto: P.D. Meany, 2002. 181–202.
Print.
Jenstad, Janelle. The City Cannot Hold You: Social Conversion in the Goldsmith’s
Shop.Early Modern Literary Studies 8.2 (2002): 5.1–26..
Jenstad, Janelle. The Gouldesmythes Storehowse: Early Evidence for
Specialisation.The Silver Society Journal 10 (1998): 40–43.
Jenstad, Janelle. Lying-in Like a Countess: The Lisle Letters, the Cecil
Family, and A Chaste Maid in Cheapside.Journal of Medieval and Early Modern Studies 34 (2004): 373–403. doi:10.1215/10829636–34–2–373.
Jenstad, Janelle. Public
Glory, Private Gilt: The Goldsmiths’ Company and the Spectacle of Punishment.Institutional Culture in Early Modern Society. Ed.
Anne Goldgar and Robert Frost. Leiden: Brill, 2004. 191–217. Print.
Jenstad, Janelle. Smock
Secrets: Birth and Women’s Mysteries on the Early Modern Stage.Performing Maternity in Early Modern England. Ed. Katherine
Moncrief and Kathryn McPherson. Aldershot: Ashgate, 2007. 87–99. Print.
Jenstad, Janelle. Using
Early Modern Maps in Literary Studies: Views and Caveats from London.GeoHumanities: Art, History, Text at the Edge of Place. Ed.
Michael Dear, James Ketchum, Sarah
Luria, and Doug Richardson. London: Routledge, 2011. Print.
Stow, John. A SVRVAY OF
LONDON. Contayning the Originall, Antiquity, Increase, Moderne estate, and description
of that Citie, written in the yeare 1598. by Iohn Stow Citizen of London. Also an
Apologie (or defence) against the opinion of some men, concerning that Citie, the
greatnesse thereof. With an Appendix, containing in Latine, Libellum de situ &
nobilitate Londini: written by William Fitzstephen, in the raigne of Henry the
second. Ed. Janelle Jenstad and
the MoEML Team. MoEML. Transcribed. Web.
Programmer at the University of Victoria Humanities Computing and Media Centre (HCMC).
Martin ported the MOL project from its original PHP incarnation to a pure eXist database
implementation in the fall of 2011. Since then, he has been lead programmer on the
project
and has also been responsible for maintaining the project schemas. He was a co-applicant
on
MoEML’s 2012 SSHRC Insight Grant.
