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python scripts parsing the Europe PMC interchange format JATS using the lxml library

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JATS parsing

This is a repository of the BiTeM group of the HES-SO of Geneva, see http://bitem.hesge.ch/

The project contains python scripts parsing the Europe PMC interchange format JATS using the lxml library

See https://jats.nlm.nih.gov/archiving/tag-library

See also https://lxml.de/parsing.html

License

This project is licensed under the terms of the GNU General Public License, version 3 or any later version (see file LICENSE.txt)

How to use

process_xml.py

Turns a PMC publication file (in XML JATS format) into json file written on the disk and sends some stats on stdout

The data diectory contains some XML JATS publication files copied from Europe PMC for test purpose

The json output is written in the out subirectory

Usage

Parsing a single file

python ./process_xml.py ./data/3_Biotech/PMC3339582.xml
less ./out/33/pmc3339582.json

Parsing a list of files

find data -name "*.xml" -exec python ./process_xml.py {} \;

jsonpmc_httpserver.py

Simple http server providing a json version of a publication given a pmcid.

The server listen http requests on port 8088 and responds ro requests like /parse/pmc/{som pmcid} .

The server retrieves the XML JATS version of the corresponding publication by calling the ebi API.

It then uses process_xml.py to parse the XML. The response is a json version of the publication.

Usage

python ./jsonpmc_httpserver.py > mylog 2>&1 &
# wait 5 seconds
curl http://localhost:8088/parse/pmc/3507161

How to install the utility

How to activate python3 environment:

https://wsvincent.com/install-python3-mac/

# activate:
source ~/.virtualenvs/myvenv/bin/activate

# deactivate:
deactivate

How to install and use beautiful soup and lxml:

https://www.crummy.com/software/BeautifulSoup/bs4/doc/

pip install beautifulsoup4e
pip install lxml

Notes about the parser

Main object structure

The parsing of the publication produces a json object. It is a dictionary with the following fields:

  • _id : the numeric part of the PMC identifier
  • pmcid, pmid, doi : publication identifiers when available
  • journal, issue, volume, start_page, end_page, medline_pgn, medline_ta : journal infos
  • affiliations, authors
  • publication_date, publication_date_alt, publication_year
  • article_type
  • keywords : an array of keywords
  • full_title
  • abstract
  • body_sections : an array of elements with the publication content, the publication title and the abstract are the first two sections in the array (if they exist)
  • back_sections : sections related to the back content of the document (appendices, supplementary material, ...)
  • float_sections : sections which are included in the publication but not in flow ot the body text (i.e. boxed-text)

Section structure

The objects to be found in the body, back and float sections can be aither sections, appendices, or boxed-text.

id

A string identifying the section generated during the parsing process. Sections found in the XML can embed each other. But in the generated json they are all siblings, flattened in a sequence (in the body_section array for example). The hierarchical structure of the section and of any of its content is reflected in its id. For instance, a section with id 1.3.2 comes just after section with id 1.3.1 and both are subparts of section with id 1.3 in the original XML.

tag

Usually the value is sec but since we also handle appendices app and boxed text boxed-text the same way, the value of this tag may vary.

level

Reflects the embedding level of the section in the original XML file. Sections that are children of the body element in the XML have level 1. A section that is a child of another section that is a child of the body element of the XML will have level 2.

implicit

The XML of many publications do not use sections of use paragraphs ( p element ) outside of any section just below the body element. In this case, we create an implicit section (equivalent to the body) to keep the json structure consistent. The title and abstract sections are set as implicit.

label

The label of a section as given in the original XML. For instance, a section number. Often empty.

title

The title of a section as given in the original XML. Often empty.

contents

A list of textual elements that are part of the section. Like sections, the content elements also have an id reflecting their hierachical position in the XML tree. The tag is the name of the XML element containing the textual element. The most common tags are paragraphs p , list list_item , figures fig and tables table . The field caption contains the text for fig boxed_text and table elements. The field text contains the text for paragraphs p and other elements.

Other tags (not p nor fig nor table nor list-item) may appear but no particular effort was made to handle their textual content specifically.

Handling figures

Figures (elements with tag = fig) have specific fields:

  • label : the figure label as given in the XML
  • caption : the figure caption as given in the XML
  • graphics, media and pmcid : identifiers allowing to build an URL containing an image of the figure

In XML, fig may appear in:

  • body, sec : the most usual cases
  • p : in this case, the paragraph is split in several subparts, the figure becoming one of them
  • fig-group : is removed from the XML, its tables are handled normally, see Endosc_Int_Open/PMC4423251.xml , Curr_Health_Sci_J/PMC3945237.xml
  • boxed-text : IGNORED. Are out of main body text flow: ignored by removing them
  • disp-quote : uses the default handler if not included in p or sec

Handling tables

Tables (elements with tag = table) have specific fields:

  • label : the table label as given in the XML
  • caption : the table caption as given in the XML
  • tableColumns : the name of the table column as text
  • tableValues : the values of the table cells as text
  • graphics, media and pmcid : identifiers allowing to build an URL containing an image of the table
  • xml : the XML to be used to display the table in an HTML page

In XML, table-wrap may appear in:

  • sec : section is the most usual container of a table
  • body : in this case, the body is treated as a section
  • boxed-text : is removed from the XML, its tables are handled normally
  • p : in this case, the paragraph is split in several subparts, the table becoming one of them. i.e. 3_Biotech/PMC3324826.xml
  • supplementary-material : is removed from the XML, its tables are handled normally, implicit fig elements in it are also handled, see Biomark_Cancer/PMC3122269.nxml , Eur_J_Rheumatol/PMC6267743.nxml , Adv_Appl_Bioinform_Chem/PMC3459542.nxml
  • table-wrap-group : is removed from the XML, its tables are handled normally. Common label and caption tags are dispatched in each table in there. See Front_Genet/PMC3202977.nxml , Hum_Gene_Ther/PMC4442602.nxml , Intern_Med/PMC5088533.nxml , J_Hum_Reprod_Sci/PMC2700667.nxml
  • disp-quote : An extract or extended quoted passage from another work, usually made typographically distinct from surrounding text. The table caption appears as the text value of the content element with tag disp-quote(default handler). See J_Entrep_Educ/PMC5985942.nxml , Qual_Saf_Health_Care/PMC2602740.nxml
  • fig : IGNORED. A rare case. The table content only appears in the detailed figure popup but not in full text viewer on PMC website, so the table-wrap content ignored in this case. See Pharmaceutics/PMC2997712.nxml

Encoding

alpha - α is seen as "\u03b1" in shell but as α in browser. The unidecode method used pubmed_oa_parser.py could also be used to turn greek letters and other special ones into their ascii closest equivalent.

Info and changes published on 2019, Oct 8th

pub_date elements

pub-date elements are searched in this order: date-type = pmc-release, then epub, ppub, collection, and finally any kind. We return a full date (month is 1, day is 1 if missing) If we had to set a default day or month, publication_date_status = 'incomplete' Example: publication_date: "05-4-2011", publication_date_alt: "2011 Apr 05", publication_date_status: "ok", pubyear: "2011",

box-text elements Missing paragraph in boxed-text Check PMC3887505 Now boxed text are handled like sections and inserted in the text flow

table-wrap-foot elements table wrap footer can be multiple, we now handle that too Check 5810844

figures embedded in a list element Figures embedded in a list (itself in a paragraph in a section) are not parsed. Check 5797209, 5729785 NOT FIXED

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